libphonenumber-js/es6-modern/AsYouTypeFormatter.PatternParser.js

A simpler (and smaller) rewrite of Google Android's libphonenumber library in javascript

export default class PatternParser {
  parse(pattern) {
    this.context = [{
      or: true,
      instructions: []
    }];
    this.parsePattern(pattern);
    if (this.context.length !== 1) {
      throw new Error('Non-finalized contexts left when pattern parse ended');
    }
    const {
      branches,
      instructions
    } = this.context[0];
    if (branches) {
      return {
        op: '|',
        args: branches.concat([expandSingleElementArray(instructions)])
      };
    }

    /* istanbul ignore if */
    if (instructions.length === 0) {
      throw new Error('Pattern is required');
    }
    if (instructions.length === 1) {
      return instructions[0];
    }
    return instructions;
  }
  startContext(context) {
    this.context.push(context);
  }
  endContext() {
    this.context.pop();
  }
  getContext() {
    return this.context[this.context.length - 1];
  }
  parsePattern(pattern) {
    if (!pattern) {
      throw new Error('Pattern is required');
    }
    const match = pattern.match(OPERATOR);
    if (!match) {
      if (ILLEGAL_CHARACTER_REGEXP.test(pattern)) {
        throw new Error(`Illegal characters found in a pattern: ${pattern}`);
      }
      this.getContext().instructions = this.getContext().instructions.concat(pattern.split(''));
      return;
    }
    const operator = match[1];
    const before = pattern.slice(0, match.index);
    const rightPart = pattern.slice(match.index + operator.length);
    switch (operator) {
      case '(?:':
        if (before) {
          this.parsePattern(before);
        }
        this.startContext({
          or: true,
          instructions: [],
          branches: []
        });
        break;
      case ')':
        if (!this.getContext().or) {
          throw new Error('")" operator must be preceded by "(?:" operator');
        }
        if (before) {
          this.parsePattern(before);
        }
        if (this.getContext().instructions.length === 0) {
          throw new Error('No instructions found after "|" operator in an "or" group');
        }
        const {
          branches
        } = this.getContext();
        branches.push(expandSingleElementArray(this.getContext().instructions));
        this.endContext();
        this.getContext().instructions.push({
          op: '|',
          args: branches
        });
        break;
      case '|':
        if (!this.getContext().or) {
          throw new Error('"|" operator can only be used inside "or" groups');
        }
        if (before) {
          this.parsePattern(before);
        }
        // The top-level is an implicit "or" group, if required.
        if (!this.getContext().branches) {
          // `branches` are not defined only for the root implicit "or" operator.
          /* istanbul ignore else */
          if (this.context.length === 1) {
            this.getContext().branches = [];
          } else {
            throw new Error('"branches" not found in an "or" group context');
          }
        }
        this.getContext().branches.push(expandSingleElementArray(this.getContext().instructions));
        this.getContext().instructions = [];
        break;
      case '[':
        if (before) {
          this.parsePattern(before);
        }
        this.startContext({
          oneOfSet: true
        });
        break;
      case ']':
        if (!this.getContext().oneOfSet) {
          throw new Error('"]" operator must be preceded by "[" operator');
        }
        this.endContext();
        this.getContext().instructions.push({
          op: '[]',
          args: parseOneOfSet(before)
        });
        break;

      /* istanbul ignore next */
      default:
        throw new Error(`Unknown operator: ${operator}`);
    }
    if (rightPart) {
      this.parsePattern(rightPart);
    }
  }
}
function parseOneOfSet(pattern) {
  const values = [];
  let i = 0;
  while (i < pattern.length) {
    if (pattern[i] === '-') {
      if (i === 0 || i === pattern.length - 1) {
        throw new Error(`Couldn't parse a one-of set pattern: ${pattern}`);
      }
      const prevValue = pattern[i - 1].charCodeAt(0) + 1;
      const nextValue = pattern[i + 1].charCodeAt(0) - 1;
      let value = prevValue;
      while (value <= nextValue) {
        values.push(String.fromCharCode(value));
        value++;
      }
    } else {
      values.push(pattern[i]);
    }
    i++;
  }
  return values;
}
const ILLEGAL_CHARACTER_REGEXP = /[\(\)\[\]\?\:\|]/;
const OPERATOR = new RegExp(
// any of:
'(' +
// or operator
'\\|' +
// or
'|' +
// or group start
'\\(\\?\\:' +
// or
'|' +
// or group end
'\\)' +
// or
'|' +
// one-of set start
'\\[' +
// or
'|' +
// one-of set end
'\\]' + ')');
function expandSingleElementArray(array) {
  if (array.length === 1) {
    return array[0];
  }
  return array;
}
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