Create wt-odlux directory

Include odlux apps, helpserver and readthedocs

Issue-ID: CCSDK-3970
Change-Id: I1aee1327e7da12e8f658185b9a985a5204ad6065
Signed-off-by: Ravi Pendurty <ravi.pendurty@highstreet-technologies.com>

1 files changed, 1625 insertions, 0 deletions

diff --git a/sdnr/wt-odlux/odlux/apps/configurationApp/src/yang/yangParser.ts b/sdnr/wt-odlux/odlux/apps/configurationApp/src/yang/yangParser.ts
new file mode 100644
index 000000000..2dbbae274
--- /dev/null
+++ b/sdnr/wt-odlux/odlux/apps/configurationApp/src/yang/yangParser.ts
@@ -0,0 +1,1625 @@
+/* eslint-disable @typescript-eslint/no-loss-of-precision */
+/* eslint-disable @typescript-eslint/no-unused-expressions */
+/* eslint-disable @typescript-eslint/naming-convention */
+/**
+ * ============LICENSE_START========================================================================
+ * ONAP : ccsdk feature sdnr wt odlux
+ * =================================================================================================
+ * Copyright (C) 2019 highstreet technologies GmbH Intellectual Property. All rights reserved.
+ * =================================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ * ============LICENSE_END==========================================================================
+ */
+import { Token, Statement, Module, Identity, ModuleState } from '../models/yang';
+import {
+  Expression,
+  ViewElement,
+  ViewElementBase,
+  ViewSpecification,
+  ViewElementNumber,
+  ViewElementString,
+  ViewElementChoice,
+  ViewElementUnion,
+  ViewElementRpc,
+  isViewElementObjectOrList,
+  isViewElementNumber,
+  isViewElementString,
+  isViewElementRpc,
+  ResolveFunction,
+  YangRange,
+} from '../models/uiModels';
+import { yangService } from '../services/yangService';
+
+const LOGLEVEL = +(localStorage.getItem('log.odlux.app.configuration.yang.yangParser') || 0);
+
+import { LogLevel } from '../../../../framework/src/utilities/logLevel';
+import { parseWhen, WhenAST, WhenTokenType } from './whenParser';
+
+export const splitVPath = (vPath: string, vPathParser: RegExp): RegExpMatchArray[] => {
+  const pathParts: RegExpMatchArray[] = [];
+  let partMatch: RegExpExecArray | null;
+  if (vPath) do {
+    partMatch = vPathParser.exec(vPath);
+    if (partMatch) {
+      pathParts.push(partMatch);
+    }
+  } while (partMatch);
+  return pathParts;
+};
+
+class YangLexer {
+
+  private pos: number = 0;
+
+  private buf: string = '';
+
+  constructor(input: string) {
+    this.pos = 0;
+    this.buf = input;
+  }
+
+  private _opTable: { [key: string]: string } = {
+    ';': 'SEMI',
+    '{': 'L_BRACE',
+    '}': 'R_BRACE',
+  };
+
+  private _isNewline(char: string): boolean {
+    return char === '\r' || char === '\n';
+  }
+
+  private _isWhitespace(char: string): boolean {
+    return char === ' ' || char === '\t' || this._isNewline(char);
+  }
+
+  private _isDigit(char: string): boolean {
+    return char >= '0' && char <= '9';
+  }
+
+  private _isAlpha(char: string): boolean {
+    return (char >= 'a' && char <= 'z') ||
+      (char >= 'A' && char <= 'Z');
+  }
+
+  private _isAlphanum(char: string): boolean {
+    return this._isAlpha(char) || this._isDigit(char) ||
+      char === '_' || char === '-' || char === '.';
+  }
+
+  private _skipNonTokens() {
+    while (this.pos < this.buf.length) {
+      const char = this.buf.charAt(this.pos);
+      if (this._isWhitespace(char)) {
+        this.pos++;
+      } else {
+        break;
+      }
+    }
+  }
+
+  private _processString(terminator: string | null): Token {
+    // this.pos points at the opening quote. Find the ending quote.
+    let end_index = this.pos + 1;
+    while (end_index < this.buf.length) {
+      const char = this.buf.charAt(end_index);
+      if (char === '\\') {
+        end_index += 2;
+        continue;
+      }
+      if (terminator === null && (this._isWhitespace(char) || this._opTable[char] !== undefined) || char === terminator) {
+        break;
+      }
+      end_index++;
+    }
+
+    if (end_index >= this.buf.length) {
+      throw Error('Unterminated quote at ' + this.pos);
+    } else {
+      const start = this.pos + (terminator ? 1 : 0);
+      const end = end_index;
+      const tok = {
+        name: 'STRING',
+        value: this.buf.substring(start, end),
+        start,
+        end,
+      };
+      this.pos = terminator ? end + 1 : end;
+      return tok;
+    }
+  }
+
+  private _processIdentifier(): Token {
+    let endpos = this.pos + 1;
+    while (endpos < this.buf.length && this._isAlphanum(this.buf.charAt(endpos))) {
+      ++endpos;
+    }
+
+    let name = 'IDENTIFIER';
+    if (this.buf.charAt(endpos) === ':') {
+      name = 'IDENTIFIERREF';
+      ++endpos;
+      while (endpos < this.buf.length && this._isAlphanum(this.buf.charAt(endpos))) {
+        ++endpos;
+      }
+    }
+
+    const tok = {
+      name: name,
+      value: this.buf.substring(this.pos, endpos),
+      start: this.pos,
+      end: endpos,
+    };
+
+    this.pos = endpos;
+    return tok;
+  }
+
+  private _processNumber(): Token {
+    let endpos = this.pos + 1;
+    while (endpos < this.buf.length &&
+      this._isDigit(this.buf.charAt(endpos))) {
+      endpos++;
+    }
+
+    const tok = {
+      name: 'NUMBER',
+      value: this.buf.substring(this.pos, endpos),
+      start: this.pos,
+      end: endpos,
+    };
+    this.pos = endpos;
+    return tok;
+  }
+
+  private _processLineComment() {
+    var endpos = this.pos + 2;
+    // Skip until the end of the line
+    while (endpos < this.buf.length && !this._isNewline(this.buf.charAt(endpos))) {
+      endpos++;
+    }
+    this.pos = endpos + 1;
+  }
+
+  private _processBlockComment() {
+    var endpos = this.pos + 2;
+    // Skip until the end of the line
+    while (endpos < this.buf.length && !((this.buf.charAt(endpos) === '/' && this.buf.charAt(endpos - 1) === '*'))) {
+      endpos++;
+    }
+    this.pos = endpos + 1;
+  }
+
+  public tokenize(): Token[] {
+    const result: Token[] = [];
+    this._skipNonTokens();
+    while (this.pos < this.buf.length) {
+
+      const char = this.buf.charAt(this.pos);
+      const op = this._opTable[char];
+
+      if (op !== undefined) {
+        result.push({ name: op, value: char, start: this.pos, end: ++this.pos });
+      } else if (this._isAlpha(char)) {
+        result.push(this._processIdentifier());
+        this._skipNonTokens();
+        const peekChar = this.buf.charAt(this.pos);
+        if (this._opTable[peekChar] === undefined) {
+          result.push((peekChar !== '\'' && peekChar !== '"')
+            ? this._processString(null)
+            : this._processString(peekChar));
+        }
+      } else if (char === '/' && this.buf.charAt(this.pos + 1) === '/') {
+        this._processLineComment();
+      } else if (char === '/' && this.buf.charAt(this.pos + 1) === '*') {
+        this._processBlockComment();
+      } else {
+        throw Error('Token error at ' + this.pos + ' ' + this.buf[this.pos]);
+      }
+      this._skipNonTokens();
+    }
+    return result;
+  }
+
+  public tokenize2(): Statement {
+    let stack: Statement[] = [{ key: 'ROOT', sub: [] }];
+    let current: Statement | null = null;
+
+    this._skipNonTokens();
+    while (this.pos < this.buf.length) {
+
+      const char = this.buf.charAt(this.pos);
+      const op = this._opTable[char];
+
+      if (op !== undefined) {
+        if (op === 'L_BRACE') {
+          current && stack.unshift(current);
+          current = null;
+        } else if (op === 'R_BRACE') {
+          current = stack.shift() || null;
+        }
+        this.pos++;
+      } else if (this._isAlpha(char) || char === '_') {
+        const key = this._processIdentifier().value;
+        this._skipNonTokens();
+        let peekChar = this.buf.charAt(this.pos);
+        let arg = undefined;
+        if (this._opTable[peekChar] === undefined) {
+          arg = (peekChar === '"' || peekChar === '\'')
+            ? this._processString(peekChar).value
+            : this._processString(null).value;
+        }
+        do {
+          this._skipNonTokens();
+          peekChar = this.buf.charAt(this.pos);
+          if (peekChar !== '+') break;
+          this.pos++;
+          this._skipNonTokens();
+          peekChar = this.buf.charAt(this.pos);
+          arg += (peekChar === '"' || peekChar === '\'')
+            ? this._processString(peekChar).value
+            : this._processString(null).value;
+        } while (true);
+        current = { key, arg, sub: [] };
+        stack[0].sub!.push(current);
+      } else if (char === '/' && this.buf.charAt(this.pos + 1) === '/') {
+        this._processLineComment();
+      } else if (char === '/' && this.buf.charAt(this.pos + 1) === '*') {
+        this._processBlockComment();
+      } else {
+        throw Error('Token error at ' + this.pos + ' ' + this.buf.slice(this.pos - 10, this.pos + 10));
+      }
+      this._skipNonTokens();
+    }
+    if (stack[0].key !== 'ROOT' || !stack[0].sub![0]) {
+      throw new Error('Internal Perser Error');
+    }
+    return stack[0].sub![0];
+  }
+}
+
+export class YangParser {
+  private _groupingsToResolve: ViewSpecification[] = [];
+
+  private _typeRefToResolve: (() => void)[] = [];
+
+  private _identityToResolve: (() => void)[] = [];
+
+  private _unionsToResolve: (() => void)[] = [];
+
+  private _modulesToResolve: (() => void)[] = [];
+
+  private _modules: { [name: string]: Module } = {};
+
+  private _views: ViewSpecification[] = [{
+    id: '0',
+    name: 'root',
+    language: 'en-US',
+    canEdit: false,
+    config: true,
+    parentView: '0',
+    title: 'root',
+    elements: {},
+  }];
+
+  public static ResolveStack = Symbol('ResolveStack');
+
+  constructor(
+    private nodeId: string,
+    private _capabilityRevisionMap: { [capability: string]: string } = {},
+    private _unavailableCapabilities: { failureReason: string; capability: string }[] = [],
+    private _importOnlyModules: { name: string; revision: string }[] = [],
+  ) {
+
+  }
+
+  public get modules() {
+    return this._modules;
+  }
+
+  public get views() {
+    return this._views;
+  }
+
+  public async addCapability(capability: string, version?: string, parentImportOnlyModule?: boolean) {
+    // do not add twice
+    const existingCapability = this._modules[capability];
+    const latestVersionExisting = existingCapability && Object.keys(existingCapability.revisions).sort().reverse()[0];
+    if ((latestVersionExisting && version) && (version <= latestVersionExisting)) {
+      if (LOGLEVEL == LogLevel.Warning) {
+        console.warn(`Skipped capability: ${capability}:${version || ''} since already contained.`);
+      }
+      return;
+    }
+
+    // // do not add unavailable capabilities
+    // if (this._unavailableCapabilities.some(c => c.capability === capability)) {
+    //   // console.warn(`Skipped capability: ${capability} since it is marked as unavailable.` );
+    //   return;
+    // }
+
+    const data = await yangService.getCapability(capability, this.nodeId, version);
+    if (!data) {
+      throw new Error(`Could not load yang file for ${capability}:${version || ''}.`);
+    }
+
+    const rootStatement = new YangLexer(data).tokenize2();
+
+    if (rootStatement.key !== 'module') {
+      throw new Error(`Root element of ${capability} is not a module.`);
+    }
+    if (rootStatement.arg !== capability) {
+      throw new Error(`Root element capability ${rootStatement.arg} does not requested ${capability}.`);
+    }
+
+    const isUnavailable = this._unavailableCapabilities.some(c => c.capability === capability);
+    const isImportOnly = parentImportOnlyModule === true || this._importOnlyModules.some(c => c.name === capability);
+
+    // extract revisions
+    const revisions = this.extractNodes(rootStatement, 'revision').reduce<{ [version: string]: {} }>((acc, revision) => {
+      if (!revision.arg) {
+        throw new Error(`Module [${rootStatement.arg}] has a version w/o version number.`);
+      }
+      const description = this.extractValue(revision, 'description');
+      const reference = this.extractValue(revision, 'reference');
+      acc[revision.arg] = {
+        description,
+        reference,
+      };
+      return acc;
+    }, {});
+
+    const latestVersionLoaded = Object.keys(revisions).sort().reverse()[0];
+    if (existingCapability && latestVersionExisting >= latestVersionLoaded) {
+      if (LOGLEVEL == LogLevel.Warning) {
+        console.warn(`Skipped capability: ${capability}:${latestVersionLoaded} since ${capability}:${latestVersionExisting} already contained.`);
+      }
+      return;
+    }
+    
+    const module = this._modules[capability] = {
+      name: rootStatement.arg,
+      revisions,
+      imports: {},
+      features: {},
+      identities: {},
+      augments: {},
+      groupings: {},
+      typedefs: {},
+      views: {},
+      elements: {},
+      state: isUnavailable
+        ? ModuleState.unavailable
+        : isImportOnly
+          ? ModuleState.importOnly
+          : ModuleState.stable,
+    };
+
+    await this.handleModule(module, rootStatement, capability);
+  }
+
+  private async handleModule(module: Module, rootStatement: Statement, capability: string) {
+
+    // extract namespace && prefix
+    module.namespace = this.extractValue(rootStatement, 'namespace');
+    module.prefix = this.extractValue(rootStatement, 'prefix');
+    if (module.prefix) {
+      module.imports[module.prefix] = capability;
+    }
+
+    // extract features
+    const features = this.extractNodes(rootStatement, 'feature');
+    module.features = {
+      ...module.features,
+      ...features.reduce<{ [version: string]: {} }>((acc, feature) => {
+        if (!feature.arg) {
+          throw new Error(`Module [${module.name}] has a feature w/o name.`);
+        }
+        const description = this.extractValue(feature, 'description');
+        acc[feature.arg] = {
+          description,
+        };
+        return acc;
+      }, {}),
+    };
+
+    // extract imports
+    const imports = this.extractNodes(rootStatement, 'import');
+    module.imports = {
+      ...module.imports,
+      ...imports.reduce<{ [key: string]: string }>((acc, imp) => {
+        const prefix = imp.sub && imp.sub.filter(s => s.key === 'prefix');
+        if (!imp.arg) {
+          throw new Error(`Module [${module.name}] has an import with neither name nor prefix.`);
+        }
+        acc[prefix && prefix.length === 1 && prefix[0].arg || imp.arg] = imp.arg;
+        return acc;
+      }, {}),
+    };
+
+    // import all required files and set module state 
+    if (imports) for (let ind = 0; ind < imports.length; ++ind) {
+      const moduleName = imports[ind].arg!;
+
+      const revision = this._capabilityRevisionMap[moduleName] || undefined;
+      await this.addCapability(moduleName, revision, module.state === ModuleState.importOnly);
+      const importedModule = this._modules[imports[ind].arg!];
+      if (importedModule && importedModule.state > ModuleState.stable) {
+        module.state = Math.max(module.state, ModuleState.instable);
+      }
+    }
+
+    this.extractTypeDefinitions(rootStatement, module, '');
+
+    this.extractIdentities(rootStatement, 0, module, '');
+
+    const groupings = this.extractGroupings(rootStatement, 0, module, '');
+    this._views.push(...groupings);
+
+    const augments = this.extractAugments(rootStatement, 0, module, '');
+    this._views.push(...augments);
+
+    // the default for config on module level is config = true;
+    const [currentView, subViews] = this.extractSubViews(rootStatement, 0, module, '');
+    this._views.push(currentView, ...subViews);
+
+    // create the root elements for this module
+    module.elements = currentView.elements;
+    this._modulesToResolve.push(() => {
+      Object.keys(module.elements).forEach(key => {
+        const viewElement = module.elements[key];
+        if (!(isViewElementObjectOrList(viewElement) || isViewElementRpc(viewElement))) {
+          console.error(new Error(`Module: [${module}]. Only Object, List or RPC are allowed on root level.`));
+        }
+        if (isViewElementObjectOrList(viewElement)) {
+          const viewIdIndex = Number(viewElement.viewId);
+          module.views[key] = this._views[viewIdIndex];
+        }
+
+        // add only the UI View if the module is available
+        if (module.state === ModuleState.stable || module.state === ModuleState.instable) this._views[0].elements[key] = module.elements[key];
+      });
+    });
+    return module;
+  }
+
+  public postProcess() {
+
+    // execute all post processes like resolving in proper order
+    this._unionsToResolve.forEach(cb => {
+      try { cb(); } catch (error) {
+        console.warn(error.message);
+      }
+    });
+
+    // process all groupings
+    this._groupingsToResolve.filter(vs => vs.uses && vs.uses[ResolveFunction]).forEach(vs => {
+      try { vs.uses![ResolveFunction] !== undefined && vs.uses![ResolveFunction]!('|'); } catch (error) {
+        console.warn(`Error resolving: [${vs.name}] [${error.message}]`);
+      }
+    });
+
+    /**
+     * This is to fix the issue for sequential execution of modules based on their child and parent relationship
+     * We are sorting the module object based on their augment status
+     */
+    Object.keys(this.modules)
+      .map(elem => {
+        if (this.modules[elem].augments && Object.keys(this.modules[elem].augments).length > 0) {
+          const { augments, ..._rest } = this.modules[elem];
+          const partsOfKeys = Object.keys(augments).map((key) => (key.split('/').length - 1));
+          this.modules[elem].executionOrder = Math.max(...partsOfKeys);
+        } else {
+          this.modules[elem].executionOrder = 0;
+        }
+      });
+
+    // process all augmentations / sort by namespace changes to ensure proper order 
+    Object.keys(this.modules).sort((a, b) => this.modules[a].executionOrder! - this.modules[b].executionOrder!).forEach(modKey => {
+      const module = this.modules[modKey];
+      const augmentKeysWithCounter = Object.keys(module.augments).map((key) => {
+        const pathParts = splitVPath(key, /(?:(?:([^\/\:]+):)?([^\/]+))/g);  // 1 = opt: namespace / 2 = property 
+        let nameSpaceChangeCounter = 0;
+        let currentNS = module.name; // init namespace
+        pathParts.forEach(([ns, _]) => {
+          if (ns === currentNS) {
+            currentNS = ns;
+            nameSpaceChangeCounter++;
+          }
+        });
+        return {
+          key,
+          nameSpaceChangeCounter,
+        };
+      });
+
+      const augmentKeys = augmentKeysWithCounter
+        .sort((a, b) => a.nameSpaceChangeCounter > b.nameSpaceChangeCounter ? 1 : a.nameSpaceChangeCounter === b.nameSpaceChangeCounter ? 0 : -1)
+        .map((a) => a.key);
+
+      augmentKeys.forEach(augKey => {
+        const augments = module.augments[augKey];
+        const viewSpec = this.resolveView(augKey);
+        if (!viewSpec) console.warn(`Could not find view to augment [${augKey}] in [${module.name}].`);
+        if (augments && viewSpec) {
+          augments.forEach(augment => Object.keys(augment.elements).forEach(key => {
+            const elm = augment.elements[key];
+            
+            const when = elm.when && augment.when
+              ? {
+                type: WhenTokenType.AND,
+                left: elm.when,
+                right: augment.when,
+              }
+              : elm.when || augment.when;
+            
+            const ifFeature = elm.ifFeature
+              ? `(${augment.ifFeature}) and (${elm.ifFeature})`
+              : augment.ifFeature;
+            
+            viewSpec.elements[key] = {
+              ...augment.elements[key],
+              when,
+              ifFeature,
+            };
+          }));
+        }
+      });
+    });
+
+    // process Identities
+    const traverseIdentity = (identities: Identity[]) => {
+      const result: Identity[] = [];
+      for (let identity of identities) {
+        if (identity.children && identity.children.length > 0) {
+          result.push(...traverseIdentity(identity.children));
+        } else {
+          result.push(identity);
+        }
+      }
+      return result;
+    };
+
+    const baseIdentities: Identity[] = [];
+    Object.keys(this.modules).forEach(modKey => {
+      const module = this.modules[modKey];
+      Object.keys(module.identities).forEach(idKey => {
+        const identity = module.identities[idKey];
+        if (identity.base != null) {
+          const base = this.resolveIdentity(identity.base, module);
+          base.children?.push(identity);
+        } else {
+          baseIdentities.push(identity);
+        }
+      });
+    });
+    baseIdentities.forEach(identity => {
+      identity.values = identity.children && traverseIdentity(identity.children) || [];
+    });
+
+    this._identityToResolve.forEach(cb => {
+      try { cb(); } catch (error) {
+        console.warn(error.message);
+      }
+    });
+
+    this._typeRefToResolve.forEach(cb => {
+      try { cb(); } catch (error) {
+        console.warn(error.message);
+      }
+    });
+
+    this._modulesToResolve.forEach(cb => {
+      try { cb(); } catch (error) {
+        console.warn(error.message);
+      }
+    });
+
+    // resolve readOnly
+    const resolveReadOnly = (view: ViewSpecification, parentConfig: boolean) => {
+
+      // update view config
+      view.config = view.config && parentConfig;
+
+      Object.keys(view.elements).forEach((key) => {
+        const elm = view.elements[key];
+
+        // update element config
+        elm.config = elm.config && view.config;
+
+        // update all sub-elements of objects
+        if (elm.uiType === 'object') {
+          resolveReadOnly(this.views[+elm.viewId], elm.config);
+        }
+
+      });
+    };
+
+    const dump = resolveReadOnly(this.views[0], true);
+    if (LOGLEVEL > 2) {
+      console.log('Resolved views:', dump);
+    }
+  }
+
+  private _nextId = 1;
+
+  private get nextId() {
+    return this._nextId++;
+  }
+
+  private extractNodes(statement: Statement, key: string): Statement[] {
+    return statement.sub && statement.sub.filter(s => s.key === key) || [];
+  }
+
+  private extractValue(statement: Statement, key: string): string | undefined;
+  private extractValue(statement: Statement, key: string, parser: RegExp): RegExpExecArray | undefined;
+  private extractValue(statement: Statement, key: string, parser?: RegExp): string | RegExpExecArray | undefined {
+    const typeNodes = this.extractNodes(statement, key);
+    const rawValue = typeNodes.length > 0 && typeNodes[0].arg || undefined;
+    return parser
+      ? rawValue && parser.exec(rawValue) || undefined
+      : rawValue;
+  }
+
+  private extractTypeDefinitions(statement: Statement, module: Module, currentPath: string): void {
+    const typedefs = this.extractNodes(statement, 'typedef');
+    typedefs && typedefs.forEach(def => {
+      if (!def.arg) {
+        throw new Error(`Module: [${module.name}]. Found typedef without name.`);
+      }
+      module.typedefs[def.arg] = this.getViewElement(def, module, 0, currentPath, false);
+    });
+  }
+
+  /** Handles groupings like named Container */
+  private extractGroupings(statement: Statement, parentId: number, module: Module, currentPath: string): ViewSpecification[] {
+    const subViews: ViewSpecification[] = [];
+    const groupings = this.extractNodes(statement, 'grouping');
+    if (groupings && groupings.length > 0) {
+      subViews.push(...groupings.reduce<ViewSpecification[]>((acc, cur) => {
+        if (!cur.arg) {
+          throw new Error(`Module: [${module.name}][${currentPath}]. Found grouping without name.`);
+        }
+        const grouping = cur.arg;
+
+        // the default for config on module level is config = true;
+        const [currentView, currentSubViews] = this.extractSubViews(cur, /* parentId */ -1, module, currentPath);
+        grouping && (module.groupings[grouping] = currentView);
+        acc.push(currentView, ...currentSubViews);
+        return acc;
+      }, []));
+    }
+
+    return subViews;
+  }
+
+  /** Handles augments also like named container */
+  private extractAugments(statement: Statement, parentId: number, module: Module, currentPath: string): ViewSpecification[] {
+    const subViews: ViewSpecification[] = [];
+    const augments = this.extractNodes(statement, 'augment');
+    if (augments && augments.length > 0) {
+      subViews.push(...augments.reduce<ViewSpecification[]>((acc, cur) => {
+        if (!cur.arg) {
+          throw new Error(`Module: [${module.name}][${currentPath}]. Found augment without path.`);
+        }
+        const augment = this.resolveReferencePath(cur.arg, module);
+
+        // the default for config on module level is config = true;
+        const [currentView, currentSubViews] = this.extractSubViews(cur, parentId, module, currentPath);
+        if (augment) {
+          module.augments[augment] = module.augments[augment] || [];
+          module.augments[augment].push(currentView);
+        }
+        acc.push(currentView, ...currentSubViews);
+        return acc;
+      }, []));
+    }
+
+    return subViews;
+  }
+
+  /** Handles identities  */
+  private extractIdentities(statement: Statement, parentId: number, module: Module, currentPath: string) {
+    const identities = this.extractNodes(statement, 'identity');
+    module.identities = identities.reduce<{ [name: string]: Identity }>((acc, cur) => {
+      if (!cur.arg) {
+        throw new Error(`Module: [${module.name}][${currentPath}]. Found identity without name.`);
+      }
+      acc[cur.arg] = {
+        id: `${module.name}:${cur.arg}`,
+        label: cur.arg,
+        base: this.extractValue(cur, 'base'),
+        description: this.extractValue(cur, 'description'),
+        reference: this.extractValue(cur, 'reference'),
+        children: [],
+      };
+      return acc;
+    }, {});
+  }
+
+  // Hint: use 0 as parentId for rootElements and -1 for rootGroupings.
+  private extractSubViews(statement: Statement, parentId: number, module: Module, currentPath: string): [ViewSpecification, ViewSpecification[]] {
+    // used for scoped definitions
+    const context: Module = {
+      ...module,
+      typedefs: {
+        ...module.typedefs,
+      },
+    };
+
+    const currentId = this.nextId;
+    const subViews: ViewSpecification[] = [];
+    let elements: ViewElement[] = [];
+
+    const configValue = this.extractValue(statement, 'config');
+    const config = configValue == null ? true : configValue.toLocaleLowerCase() !== 'false';
+
+    // extract conditions
+    const ifFeature = this.extractValue(statement, 'if-feature');
+    const whenCondition = this.extractValue(statement, 'when');
+    if (whenCondition) console.warn('Found in [' + context.name + ']' + currentPath + ' when: ' + whenCondition);
+
+    // extract all scoped typedefs
+    this.extractTypeDefinitions(statement, context, currentPath);
+
+    // extract all scoped groupings
+    subViews.push(
+      ...this.extractGroupings(statement, parentId, context, currentPath),
+    );
+
+    // extract all container
+    const container = this.extractNodes(statement, 'container');
+    if (container && container.length > 0) {
+      subViews.push(...container.reduce<ViewSpecification[]>((acc, cur) => {
+        if (!cur.arg) {
+          throw new Error(`Module: [${context.name}]${currentPath}. Found container without name.`);
+        }
+        const [currentView, currentSubViews] = this.extractSubViews(cur, currentId, context, `${currentPath}/${context.name}:${cur.arg}`);
+        elements.push({
+          id: parentId === 0 ? `${context.name}:${cur.arg}` : cur.arg,
+          label: cur.arg,
+          path: currentPath,
+          module: context.name || module.name || '',
+          uiType: 'object',
+          viewId: currentView.id,
+          config: currentView.config,
+        });
+        acc.push(currentView, ...currentSubViews);
+        return acc;
+      }, []));
+    }
+
+    // process all lists
+    // a list is a list of containers with the leafs contained in the list
+    const lists = this.extractNodes(statement, 'list');
+    if (lists && lists.length > 0) {
+      subViews.push(...lists.reduce<ViewSpecification[]>((acc, cur) => {
+        let elmConfig = config;
+        if (!cur.arg) {
+          throw new Error(`Module: [${context.name}]${currentPath}. Found list without name.`);
+        }
+        const key = this.extractValue(cur, 'key') || undefined;
+        if (elmConfig && !key) {
+          console.warn(`Module: [${context.name}]${currentPath}. Found configurable list without key. Assume config shell be false.`);
+          elmConfig = false;
+        }
+        const [currentView, currentSubViews] = this.extractSubViews(cur, currentId, context, `${currentPath}/${context.name}:${cur.arg}`);
+        elements.push({
+          id: parentId === 0 ? `${context.name}:${cur.arg}` : cur.arg,
+          label: cur.arg,
+          path: currentPath,
+          module: context.name || module.name || '',
+          isList: true,
+          uiType: 'object',
+          viewId: currentView.id,
+          key: key,
+          config: elmConfig && currentView.config,
+        });
+        acc.push(currentView, ...currentSubViews);
+        return acc;
+      }, []));
+    }
+
+    // process all leaf-lists
+    // a leaf-list is a list of some type
+    const leafLists = this.extractNodes(statement, 'leaf-list');
+    if (leafLists && leafLists.length > 0) {
+      elements.push(...leafLists.reduce<ViewElement[]>((acc, cur) => {
+        const element = this.getViewElement(cur, context, parentId, currentPath, true);
+        element && acc.push(element);
+        return acc;
+      }, []));
+    }
+
+    // process all leafs
+    // a leaf is mainly a property of an object
+    const leafs = this.extractNodes(statement, 'leaf');
+    if (leafs && leafs.length > 0) {
+      elements.push(...leafs.reduce<ViewElement[]>((acc, cur) => {
+        const element = this.getViewElement(cur, context, parentId, currentPath, false);
+        element && acc.push(element);
+        return acc;
+      }, []));
+    }
+
+
+    const choiceStms = this.extractNodes(statement, 'choice');
+    if (choiceStms && choiceStms.length > 0) {
+      elements.push(...choiceStms.reduce<ViewElementChoice[]>((accChoice, curChoice) => {
+        if (!curChoice.arg) {
+          throw new Error(`Module: [${context.name}]${currentPath}. Found choise without name.`);
+        }
+        // extract all cases like containers
+        const cases: { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } }[] = [];
+        const caseStms = this.extractNodes(curChoice, 'case');
+        if (caseStms && caseStms.length > 0) {
+          cases.push(...caseStms.reduce((accCase, curCase) => {
+            if (!curCase.arg) {
+              throw new Error(`Module: [${context.name}]${currentPath}/${curChoice.arg}. Found case without name.`);
+            }
+            const description = this.extractValue(curCase, 'description') || undefined;
+            const [caseView, caseSubViews] = this.extractSubViews(curCase, parentId, context, `${currentPath}/${context.name}:${curChoice.arg}`);
+            subViews.push(caseView, ...caseSubViews);
+
+            const caseDef: { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } } = {
+              id: parentId === 0 ? `${context.name}:${curCase.arg}` : curCase.arg,
+              label: curCase.arg,
+              description: description,
+              elements: caseView.elements,
+            };
+            accCase.push(caseDef);
+            return accCase;
+          }, [] as { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } }[]));
+        }
+
+        // extract all simple cases (one case per leaf, container, etc.)
+        const [choiceView, choiceSubViews] = this.extractSubViews(curChoice, parentId, context, `${currentPath}/${context.name}:${curChoice.arg}`);
+        subViews.push(choiceView, ...choiceSubViews);
+        cases.push(...Object.keys(choiceView.elements).reduce((accElm, curElm) => {
+          const elm = choiceView.elements[curElm];
+          const caseDef: { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } } = {
+            id: elm.id,
+            label: elm.label,
+            description: elm.description,
+            elements: { [elm.id]: elm },
+          };
+          accElm.push(caseDef);
+          return accElm;
+        }, [] as { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } }[]));
+
+        const choiceDescription = this.extractValue(curChoice, 'description') || undefined;
+        const choiceConfigValue = this.extractValue(curChoice, 'config');
+        const choiceConfig = choiceConfigValue == null ? true : choiceConfigValue.toLocaleLowerCase() !== 'false';
+
+        const mandatory = this.extractValue(curChoice, 'mandatory') === 'true' || false;
+
+        const element: ViewElementChoice = {
+          uiType: 'choice',
+          id: parentId === 0 ? `${context.name}:${curChoice.arg}` : curChoice.arg,
+          label: curChoice.arg,
+          path: currentPath,
+          module: context.name || module.name || '',
+          config: choiceConfig,
+          mandatory: mandatory,
+          description: choiceDescription,
+          cases: cases.reduce((acc, cur) => {
+            acc[cur.id] = cur;
+            return acc;
+          }, {} as { [name: string]: { id: string; label: string; description?: string; elements: { [name: string]: ViewElement } } }),
+        };
+
+        accChoice.push(element);
+        return accChoice;
+      }, []));
+    }
+
+    const rpcStms = this.extractNodes(statement, 'rpc');
+    if (rpcStms && rpcStms.length > 0) {
+      elements.push(...rpcStms.reduce<ViewElementRpc[]>((accRpc, curRpc) => {
+        if (!curRpc.arg) {
+          throw new Error(`Module: [${context.name}]${currentPath}. Found rpc without name.`);
+        }
+
+        const rpcDescription = this.extractValue(curRpc, 'description') || undefined;
+        const rpcConfigValue = this.extractValue(curRpc, 'config');
+        const rpcConfig = rpcConfigValue == null ? true : rpcConfigValue.toLocaleLowerCase() !== 'false';
+
+        let inputViewId: string | undefined = undefined;
+        let outputViewId: string | undefined = undefined;
+
+        const input = this.extractNodes(curRpc, 'input') || undefined;
+        const output = this.extractNodes(curRpc, 'output') || undefined;
+
+        if (input && input.length > 0) {
+          const [inputView, inputSubViews] = this.extractSubViews(input[0], parentId, context, `${currentPath}/${context.name}:${curRpc.arg}`);
+          subViews.push(inputView, ...inputSubViews);
+          inputViewId = inputView.id;
+        }
+
+        if (output && output.length > 0) {
+          const [outputView, outputSubViews] = this.extractSubViews(output[0], parentId, context, `${currentPath}/${context.name}:${curRpc.arg}`);
+          subViews.push(outputView, ...outputSubViews);
+          outputViewId = outputView.id;
+        }
+
+        const element: ViewElementRpc = {
+          uiType: 'rpc',
+          id: parentId === 0 ? `${context.name}:${curRpc.arg}` : curRpc.arg,
+          label: curRpc.arg,
+          path: currentPath,
+          module: context.name || module.name || '',
+          config: rpcConfig,
+          description: rpcDescription,
+          inputViewId: inputViewId,
+          outputViewId: outputViewId,
+        };
+
+        accRpc.push(element);
+
+        return accRpc;
+      }, []));
+    }
+
+    if (!statement.arg) {
+      console.error(new Error(`Module: [${context.name}]. Found statement without name.`));
+    }
+
+    let whenParsed: WhenAST | undefined = undefined;
+    try {
+      whenParsed = whenCondition && parseWhen(whenCondition) || undefined;
+    } catch (e) {
+      console.error(new Error(`Module: [${context.name}]. Found invalid when condition: ${whenCondition}`));
+    }
+
+    const viewSpec: ViewSpecification = {
+      id: String(currentId),
+      parentView: String(parentId),
+      ns: context.name,
+      name: statement.arg != null ? statement.arg : undefined,
+      title: statement.arg != null ? statement.arg : undefined,
+      language: 'en-us',
+      canEdit: false,
+      config: config,
+      ifFeature: ifFeature,
+      when: whenParsed,
+      elements: elements.reduce<{ [name: string]: ViewElement }>((acc, cur) => {
+        acc[cur.id] = cur;
+        return acc;
+      }, {}),
+    };
+
+    // evaluate canEdit depending on all conditions
+    Object.defineProperty(viewSpec, 'canEdit', {
+      get: () => {
+        return Object.keys(viewSpec.elements).some(key => {
+          const elm = viewSpec.elements[key];
+          return (!isViewElementObjectOrList(elm) && elm.config);
+        });
+      },
+    });
+
+    // merge in all uses references and resolve groupings
+    const usesRefs = this.extractNodes(statement, 'uses');
+    if (usesRefs && usesRefs.length > 0) {
+
+      viewSpec.uses = (viewSpec.uses || []);
+      const resolveFunctions: ((parentElementPath: string) => void)[] = [];
+
+      for (let i = 0; i < usesRefs.length; ++i) {
+        const groupingName = usesRefs[i].arg;
+        if (!groupingName) {
+          throw new Error(`Module: [${context.name}]. Found an uses statement without a grouping name.`);
+        }
+
+        viewSpec.uses.push(this.resolveReferencePath(groupingName, context));
+
+        resolveFunctions.push((parentElementPath: string) => {
+          const groupingViewSpec = this.resolveGrouping(groupingName, context);
+          if (groupingViewSpec) {
+
+            // resolve recursive
+            const resolveFunc = groupingViewSpec.uses && groupingViewSpec.uses[ResolveFunction];
+            resolveFunc && resolveFunc(parentElementPath);
+
+            Object.keys(groupingViewSpec.elements).forEach(key => {
+              const elm = groupingViewSpec.elements[key];
+              // a useRef on root level need a namespace
+              const resolvedWhen = elm.when && groupingViewSpec.when
+                ? {
+                  type: WhenTokenType.AND,
+                  left: elm.when,
+                  right: groupingViewSpec.when,
+                }
+                : elm.when || groupingViewSpec.when;  
+              
+              const resolvedIfFeature = elm.ifFeature
+                ? `(${groupingViewSpec.ifFeature}) and (${elm.ifFeature})`
+                : groupingViewSpec.ifFeature;
+
+              viewSpec.elements[parentId === 0 ? `${module.name}:${key}` : key] = {
+                ...elm,
+                when: resolvedWhen,
+                ifFeature: resolvedIfFeature,
+              };
+            });
+          }
+        });
+      }
+
+      viewSpec.uses[ResolveFunction] = (parentElementPath: string) => {
+        const currentElementPath = `${parentElementPath} -> ${viewSpec.ns}:${viewSpec.name}`;
+        resolveFunctions.forEach(resolve => {
+          try {
+            resolve(currentElementPath);
+          } catch (error) {
+            console.error(error);
+          }
+        });
+        // console.log("Resolved "+currentElementPath, viewSpec);
+        if (viewSpec?.uses) {
+          viewSpec.uses[ResolveFunction] = undefined;
+        }
+      };
+
+      this._groupingsToResolve.push(viewSpec);
+    }
+
+    return [viewSpec, subViews];
+  }
+
+  // https://tools.ietf.org/html/rfc7950#section-9.3.4
+  private static decimalRange = [
+    { min: -9223372036854775808, max: 9223372036854775807 },
+    { min: -922337203685477580.8, max: 922337203685477580.7 },
+    { min: -92233720368547758.08, max: 92233720368547758.07 },
+    { min: -9223372036854775.808, max: 9223372036854775.807 },
+    { min: -922337203685477.5808, max: 922337203685477.5807 },
+    { min: -92233720368547.75808, max: 92233720368547.75807 },
+    { min: -9223372036854.775808, max: 9223372036854.775807 },
+    { min: -922337203685.4775808, max: 922337203685.4775807 },
+    { min: -92233720368.54775808, max: 92233720368.54775807 },
+    { min: -9223372036.854775808, max: 9223372036.854775807 },
+    { min: -922337203.6854775808, max: 922337203.6854775807 },
+    { min: -92233720.36854775808, max: 92233720.36854775807 },
+    { min: -9223372.036854775808, max: 9223372.036854775807 },
+    { min: -922337.2036854775808, max: 922337.2036854775807 },
+    { min: -92233.72036854775808, max: 92233.72036854775807 },
+    { min: -9223.372036854775808, max: 9223.372036854775807 },
+    { min: -922.3372036854775808, max: 922.3372036854775807 },
+    { min: -92.23372036854775808, max: 92.23372036854775807 },
+    { min: -9.223372036854775808, max: 9.223372036854775807 },
+  ];
+
+  /** Extracts the UI View from the type in the cur statement. */
+  private getViewElement(cur: Statement, module: Module, parentId: number, currentPath: string, isList: boolean): ViewElement {
+
+    const type = this.extractValue(cur, 'type');
+    const defaultVal = this.extractValue(cur, 'default') || undefined;
+    const description = this.extractValue(cur, 'description') || undefined;
+
+    const configValue = this.extractValue(cur, 'config');
+    const config = configValue == null ? true : configValue.toLocaleLowerCase() !== 'false';
+
+    const extractRange = (min: number, max: number, property: string = 'range'): { expression: Expression<YangRange> | undefined; min: number; max: number } => {
+      const ranges = this.extractValue(this.extractNodes(cur, 'type')[0]!, property) || undefined;
+      const range = ranges?.replace(/min/i, String(min)).replace(/max/i, String(max)).split('|').map(r => {
+        let minValue: number;
+        let maxValue: number;
+
+        if (r.indexOf('..') > -1) {
+          const [minStr, maxStr] = r.split('..');
+          minValue = Number(minStr);
+          maxValue = Number(maxStr);
+        } else if (!isNaN(maxValue = Number(r && r.trim()))) {
+          minValue = maxValue;
+        } else {
+          minValue = min,
+          maxValue = max;
+        }
+
+        if (minValue > min) min = minValue;
+        if (maxValue < max) max = maxValue;
+
+        return {
+          min: minValue,
+          max: maxValue,
+        };
+      });
+      return {
+        min: min,
+        max: max,
+        expression: range && range.length === 1
+          ? range[0]
+          : range && range.length > 1
+            ? { operation: 'OR', arguments: range }
+            : undefined,
+      };
+    };
+
+    const extractPattern = (): Expression<RegExp> | undefined => {
+    // 2023.01.26 decision MF & SKO: we will no longer remove the backslashes from the pattern, seems to be a bug in the original code
+      const pattern = this.extractNodes(this.extractNodes(cur, 'type')[0]!, 'pattern').map(p => p.arg!).filter(p => !!p).map(p => `^${p/*.replace(/(?:\\(.))/g, '$1')*/}$`);
+      return pattern && pattern.length == 1
+        ? new RegExp(pattern[0])
+        : pattern && pattern.length > 1
+          ? { operation: 'AND', arguments: pattern.map(p => new RegExp(p)) }
+          : undefined;
+    };
+
+    const mandatory = this.extractValue(cur, 'mandatory') === 'true' || false;
+
+    if (!cur.arg) {
+      throw new Error(`Module: [${module.name}]. Found element without name.`);
+    }
+
+    if (!type) {
+      throw new Error(`Module: [${module.name}].[${cur.arg}]. Found element without type.`);
+    }
+
+    const element: ViewElementBase = {
+      id: parentId === 0 ? `${module.name}:${cur.arg}` : cur.arg,
+      label: cur.arg,
+      path: currentPath,
+      module: module.name || '',
+      config: config,
+      mandatory: mandatory,
+      isList: isList,
+      default: defaultVal,
+      description: description,
+    };
+
+    if (type === 'string') {
+      const length = extractRange(0, +18446744073709551615, 'length');
+      return ({
+        ...element,
+        uiType: 'string',
+        length: length.expression,
+        pattern: extractPattern(),
+      });
+    } else if (type === 'boolean') {
+      return ({
+        ...element,
+        uiType: 'boolean',
+      });
+    } else if (type === 'uint8') {
+      const range = extractRange(0, +255);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'uint16') {
+      const range = extractRange(0, +65535);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'uint32') {
+      const range = extractRange(0, +4294967295);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'uint64') {
+      const range = extractRange(0, +18446744073709551615);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'int8') {
+      const range = extractRange(-128, +127);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'int16') {
+      const range = extractRange(-32768, +32767);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'int32') {
+      const range = extractRange(-2147483648, +2147483647);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'int64') {
+      const range = extractRange(-9223372036854775808, +9223372036854775807);
+      return ({
+        ...element,
+        uiType: 'number',
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'decimal64') {
+      // decimalRange
+      const fDigits = Number(this.extractValue(this.extractNodes(cur, 'type')[0]!, 'fraction-digits')) || -1;
+      if (fDigits === -1) {
+        throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Found decimal64 with invalid fraction-digits.`);
+      }
+      const range = extractRange(YangParser.decimalRange[fDigits].min, YangParser.decimalRange[fDigits].max);
+      return ({
+        ...element,
+        uiType: 'number',
+        fDigits: fDigits,
+        range: range.expression,
+        min: range.min,
+        max: range.max,
+        units: this.extractValue(cur, 'units') || undefined,
+        format: this.extractValue(cur, 'format') || undefined,
+      });
+    } else if (type === 'enumeration') {
+      const typeNode = this.extractNodes(cur, 'type')[0]!;
+      const enumNodes = this.extractNodes(typeNode, 'enum');
+      return ({
+        ...element,
+        uiType: 'selection',
+        options: enumNodes.reduce<{ key: string; value: string; description?: string }[]>((acc, enumNode) => {
+          if (!enumNode.arg) {
+            throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Found option without name.`);
+          }
+          // const ifClause = this.extractValue(enumNode, 'if-feature');
+          const value = this.extractValue(enumNode, 'value');
+          const enumOption = {
+            key: enumNode.arg,
+            value: value != null ? value : enumNode.arg,
+            description: this.extractValue(enumNode, 'description') || undefined,
+          };
+          // todo: ❗ handle the if clause ⚡
+          acc.push(enumOption);
+          return acc;
+        }, []),
+      });
+    } else if (type === 'leafref') {
+      const typeNode = this.extractNodes(cur, 'type')[0]!;
+      const vPath = this.extractValue(typeNode, 'path');
+      if (!vPath) {
+        throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Found leafref without path.`);
+      }
+      const refPath = this.resolveReferencePath(vPath, module);
+      const resolve = this.resolveReference.bind(this);
+      const res: ViewElement = {
+        ...element,
+        uiType: 'reference',
+        referencePath: refPath,
+        ref(this: ViewElement, basePath: string) {
+          const elementPath = `${basePath}/${cur.arg}`;
+
+          const result = resolve(refPath, elementPath);
+          if (!result) return undefined;
+
+          const [resolvedElement, resolvedPath] = result;
+          return resolvedElement && [{
+            ...resolvedElement,
+            id: this.id,
+            label: this.label,
+            config: this.config,
+            mandatory: this.mandatory,
+            isList: this.isList,
+            default: this.default,
+            description: this.description,
+          } as ViewElement, resolvedPath] || undefined;
+        },
+      };
+      return res;
+    } else if (type === 'identityref') {
+      const typeNode = this.extractNodes(cur, 'type')[0]!;
+      const base = this.extractValue(typeNode, 'base');
+      if (!base) {
+        throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Found identityref without base.`);
+      }
+      const res: ViewElement = {
+        ...element,
+        uiType: 'selection',
+        options: [],
+      };
+      this._identityToResolve.push(() => {
+        const identity: Identity = this.resolveIdentity(base, module);
+        if (!identity) {
+          throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Could not resolve identity [${base}].`);
+        }
+        if (!identity.values || identity.values.length === 0) {
+          throw new Error(`Identity: [${base}] has no values.`);
+        }
+        res.options = identity.values.map(val => ({
+          key: val.id,
+          value: val.id,
+          description: val.description,
+        }));
+      });
+      return res;
+    } else if (type === 'empty') {
+      // todo: ❗ handle empty ⚡
+      /*  9.11.  The empty Built-In Type
+          The empty built-in type represents a leaf that does not have any
+          value, it conveys information by its presence or absence. */
+      return {
+        ...element,
+        uiType: 'empty',
+      };
+    } else if (type === 'union') {
+      // todo: ❗ handle union ⚡
+      /* 9.12.  The union Built-In Type */
+      const typeNode = this.extractNodes(cur, 'type')[0]!;
+      const typeNodes = this.extractNodes(typeNode, 'type');
+
+      const resultingElement = {
+        ...element,
+        uiType: 'union',
+        elements: [],
+      } as ViewElementUnion;
+
+      const resolveUnion = () => {
+        resultingElement.elements.push(...typeNodes.map(node => {
+          const stm: Statement = {
+            ...cur,
+            sub: [
+              ...(cur.sub?.filter(s => s.key !== 'type') || []),
+              node,
+            ],
+          };
+          return {
+            ...this.getViewElement(stm, module, parentId, currentPath, isList),
+            id: node.arg!,
+          };
+        }));
+      };
+
+      this._unionsToResolve.push(resolveUnion);
+
+      return resultingElement;
+    } else if (type === 'bits') {
+      const typeNode = this.extractNodes(cur, 'type')[0]!;
+      const bitNodes = this.extractNodes(typeNode, 'bit');
+      return {
+        ...element,
+        uiType: 'bits',
+        flags: bitNodes.reduce<{ [name: string]: number | undefined }>((acc, bitNode) => {
+          if (!bitNode.arg) {
+            throw new Error(`Module: [${module.name}][${currentPath}][${cur.arg}]. Found bit without name.`);
+          }
+          // const ifClause = this.extractValue(bitNode, 'if-feature');
+          const pos = Number(this.extractValue(bitNode, 'position'));
+          acc[bitNode.arg] = pos === pos ? pos : undefined;
+          return acc;
+        }, {}),
+      };
+    } else if (type === 'binary') {
+      return {
+        ...element,
+        uiType: 'binary',
+        length: extractRange(0, +18446744073709551615, 'length'),
+      };
+    } else if (type === 'instance-identifier') {
+      // https://tools.ietf.org/html/rfc7950#page-168
+      return {
+        ...element,
+        uiType: 'string',
+        length: extractRange(0, +18446744073709551615, 'length'),
+      };
+    } else {
+      // not a build in type, need to resolve type
+      let typeRef = this.resolveType(type, module);
+      if (typeRef == null) console.error(new Error(`Could not resolve type ${type} in [${module.name}][${currentPath}].`));
+
+      if (isViewElementString(typeRef)) {
+        typeRef = this.resolveStringType(typeRef, extractPattern(), extractRange(0, +18446744073709551615));
+      } else if (isViewElementNumber(typeRef)) {
+        typeRef = this.resolveNumberType(typeRef, extractRange(typeRef.min, typeRef.max));
+      }
+
+      const res = {
+        id: element.id,
+      } as ViewElement;
+
+      this._typeRefToResolve.push(() => {
+        // spoof date type here from special string type
+        if ((type === 'date-and-time' || type.endsWith(':date-and-time')) && typeRef.module === 'ietf-yang-types') {
+          Object.assign(res, {
+            ...typeRef,
+            ...element,
+            description: description,
+            uiType: 'date',
+          });
+        } else {
+          Object.assign(res, {
+            ...typeRef,
+            ...element,
+            description: description,
+          });
+        }
+      });
+      
+      return res;
+    }
+  }
+
+  private resolveStringType(parentElement: ViewElementString, pattern: Expression<RegExp> | undefined, length: { expression: Expression<YangRange> | undefined; min: number; max: number }) {
+    return {
+      ...parentElement,
+      pattern: pattern != null && parentElement.pattern
+        ? { operation: 'AND', arguments: [pattern, parentElement.pattern] }
+        : parentElement.pattern
+          ? parentElement.pattern
+          : pattern,
+      length: length.expression != null && parentElement.length
+        ? { operation: 'AND', arguments: [length.expression, parentElement.length] }
+        : parentElement.length
+          ? parentElement.length
+          : length?.expression,
+    } as ViewElementString;
+  }
+
+  private resolveNumberType(parentElement: ViewElementNumber, range: { expression: Expression<YangRange> | undefined; min: number; max: number }) {
+    return {
+      ...parentElement,
+      range: range.expression != null && parentElement.range
+        ? { operation: 'AND', arguments: [range.expression, parentElement.range] }
+        : parentElement.range
+          ? parentElement.range
+          : range,
+      min: range.min,
+      max: range.max,
+    } as ViewElementNumber;
+  }
+
+  private resolveReferencePath(vPath: string, module: Module) {
+    const vPathParser = /(?:(?:([^\/\:]+):)?([^\/]+))/g; // 1 = opt: namespace / 2 = property
+    return vPath.replace(vPathParser, (_, ns, property) => {
+      const nameSpace = ns && module.imports[ns] || module.name;
+      return `${nameSpace}:${property}`;
+    });
+  }
+
+  private resolveReference(vPath: string, currentPath: string) {
+    const vPathParser = /(?:(?:([^\/\[\]\:]+):)?([^\/\[\]]+)(\[[^\]]+\])?)/g; // 1 = opt: namespace / 2 = property / 3 = opt: indexPath
+    let element: ViewElement | null = null;
+    let moduleName = '';
+
+    const vPathParts = splitVPath(vPath, vPathParser).map(p => ({ ns: p[1], property: p[2], ind: p[3] }));
+    const resultPathParts = !vPath.startsWith('/')
+      ? splitVPath(currentPath, vPathParser).map(p => { moduleName = p[1] || moduleName; return { ns: moduleName, property: p[2], ind: p[3] }; })
+      : [];
+
+    for (let i = 0; i < vPathParts.length; ++i) {
+      const vPathPart = vPathParts[i];
+      if (vPathPart.property === '..') {
+        resultPathParts.pop();
+      } else if (vPathPart.property !== '.') {
+        resultPathParts.push(vPathPart);
+      }
+    }
+
+    // resolve element by path
+    for (let j = 0; j < resultPathParts.length; ++j) {
+      const pathPart = resultPathParts[j];
+      if (j === 0) {
+        moduleName = pathPart.ns;
+        const rootModule = this._modules[moduleName];
+        if (!rootModule) throw new Error('Could not resolve module [' + moduleName + '].\r\n' + vPath);
+        element = rootModule.elements[`${pathPart.ns}:${pathPart.property}`];
+      } else if (element && isViewElementObjectOrList(element)) {
+        const view: ViewSpecification = this._views[+element.viewId];
+        if (moduleName !== pathPart.ns) {
+          moduleName = pathPart.ns;
+        }
+        element = view.elements[pathPart.property] || view.elements[`${moduleName}:${pathPart.property}`];
+      } else {
+        throw new Error('Could not resolve reference.\r\n' + vPath);
+      }
+      if (!element) throw new Error('Could not resolve path [' + pathPart.property + '] in [' + currentPath + '] \r\n' + vPath);
+    }
+
+    moduleName = ''; // create the vPath for the resolved element, do not add the element itself this will be done later in the res(...) function
+    return [element, resultPathParts.slice(0, -1).map(p => `${moduleName !== p.ns ? `${moduleName = p.ns}:` : ''}${p.property}${p.ind || ''}`).join('/')];
+  }
+
+  private resolveView(vPath: string) {
+    const vPathParser = /(?:(?:([^\/\[\]\:]+):)?([^\/\[\]]+)(\[[^\]]+\])?)/g; // 1 = opt: namespace / 2 = property / 3 = opt: indexPath
+    let element: ViewElement | null = null;
+    let partMatch: RegExpExecArray | null;
+    let view: ViewSpecification | null = null;
+    let moduleName = '';
+    if (vPath) do {
+      partMatch = vPathParser.exec(vPath);
+      if (partMatch) {
+        if (element === null) {
+          moduleName = partMatch[1]!;
+          const rootModule = this._modules[moduleName];
+          if (!rootModule) return null;
+          element = rootModule.elements[`${moduleName}:${partMatch[2]!}`];
+        } else if (isViewElementObjectOrList(element)) {
+          view = this._views[+element.viewId];
+          if (moduleName !== partMatch[1]) {
+            moduleName = partMatch[1];
+            element = view.elements[`${moduleName}:${partMatch[2]}`];
+          } else {
+            element = view.elements[partMatch[2]];
+          }
+        } else {
+          return null;
+        }
+        if (!element) return null;
+      }
+    } while (partMatch);
+    return element && isViewElementObjectOrList(element) && this._views[+element.viewId] || null;
+  }
+
+  private resolveType(type: string, module: Module) {
+    const colonInd = type.indexOf(':');
+    const preFix = colonInd > -1 ? type.slice(0, colonInd) : '';
+    const typeName = colonInd > -1 ? type.slice(colonInd + 1) : type;
+
+    const res = preFix
+      ? this._modules[module.imports[preFix]].typedefs[typeName]
+      : module.typedefs[typeName];
+    return res;
+  }
+
+  private resolveGrouping(grouping: string, module: Module) {
+    const collonInd = grouping.indexOf(':');
+    const preFix = collonInd > -1 ? grouping.slice(0, collonInd) : '';
+    const groupingName = collonInd > -1 ? grouping.slice(collonInd + 1) : grouping;
+
+    return preFix
+      ? this._modules[module.imports[preFix]].groupings[groupingName]
+      : module.groupings[groupingName];
+
+  }
+
+  private resolveIdentity(identity: string, module: Module) {
+    const collonInd = identity.indexOf(':');
+    const preFix = collonInd > -1 ? identity.slice(0, collonInd) : '';
+    const identityName = collonInd > -1 ? identity.slice(collonInd + 1) : identity;
+
+    return preFix
+      ? this._modules[module.imports[preFix]].identities[identityName]
+      : module.identities[identityName];
+
+  }
+}
\ No newline at end of file