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'use strict'; |
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import { Lexer, Token } from '../Lexer'; |
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/** |
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* The botlang parser for creating the abstract syntax tree. |
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*/ |
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class Parser { |
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/** |
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* Create a Parser. |
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* @param {Lexer} lexer |
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* @throws {TypeError} |
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*/ |
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constructor(lexer) { |
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if (!(lexer instanceof Lexer)) { |
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throw new TypeError('Argument "lexer" must be an instance of type "Lexer".'); |
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} |
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/** |
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* @private |
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* @type {Lexer} |
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*/ |
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this.lexer = lexer; |
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/** |
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* @private |
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* @type {Array} |
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*/ |
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this.syntaxTree = []; |
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/** |
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* @private |
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* @type {Integer} |
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*/ |
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this.syntaxTreeIndex = 0; |
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} |
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/** |
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* @private |
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* @return {Object|null} |
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*/ |
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getLastNode() { |
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return 'undefined' !== typeof this.syntaxTree[this.syntaxTreeIndex - 1] |
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? this.syntaxTree[this.syntaxTreeIndex - 1] |
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: null; |
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} |
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/** |
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* @private |
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* @param {Token} token |
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* @return {Boolean} |
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*/ |
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static isResponse(token) { |
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return token instanceof Token && 'operation' === token.getType() && '-' === token.getValue(); |
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} |
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/** |
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* @private |
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* @param {Token} token |
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* @return {Boolean} |
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*/ |
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static isTrigger(token) { |
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return token instanceof Token && 'operation' === token.getType() && '+' === token.getValue(); |
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} |
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/** |
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* Parse input and return abstract syntax tree (AST) |
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* @return {Object} |
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*/ |
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parse() { |
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while (!this.lexer.eof()) { |
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const token = this.lexer.next(); |
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if (!(token instanceof Token)) { |
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continue; |
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} |
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if (Parser.isTrigger(token)) { |
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this.pushNodeToSyntaxTree(this.parseTrigger()); |
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} |
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if (Parser.isResponse(token) && 'trigger' === this.getLastNode().type) { |
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this.getLastNode().responses.push(this.parseResponse()); |
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} |
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} |
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return { |
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type : 'program', |
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body : this.syntaxTree |
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}; |
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} |
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/** |
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* @private |
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* @return {Object} |
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*/ |
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parseTrigger() { |
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const trigger = this.lexer.next(); |
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let pattern = ''; |
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if ('string' !== trigger.getType()) { |
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return this.lexer.inputError('Expected trigger pattern after trigger identifier.'); |
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} |
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pattern = Parser.replaceWildcard(trigger.getValue()); |
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pattern = Parser.replaceStringSubstitution(pattern); |
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return { |
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type : 'trigger', |
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src : trigger.getValue(), |
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pattern, |
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responses : [] |
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}; |
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} |
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/** |
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* @private |
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* @return {Object} |
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*/ |
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parseResponse() { |
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const response = this.lexer.next(); |
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if ('string' !== response.getType()) { |
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this.lexer.inputError('Expected string after response identifier.'); |
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} |
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return { |
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type : 'response', |
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value : response.getValue() |
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}; |
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} |
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/** |
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* @private |
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* @param {Object} node |
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* @return {void} |
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*/ |
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pushNodeToSyntaxTree(node) { |
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this.syntaxTreeIndex += 1; |
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this.syntaxTree.push(node); |
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} |
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/** |
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* Replace string substitution [$] character |
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* @param {String} string |
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* @return {String} |
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*/ |
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static replaceStringSubstitution(string) { |
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return string.replace(/(\s?)\$(\s?)/g, '\\s?(\\w+?)\\s?'); |
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} |
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150
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/** |
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* Replace wildcard [*] character |
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152
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* @param {String} string |
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* @return {String} |
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*/ |
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static replaceWildcard(string) { |
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return string.replace(/(\s?)\*(\s?)/g, '(\\w?)'); |
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} |
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} |
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160
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export default Parser; |
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161
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botlang /
botlang-js
