sugar/common/internal/createFormatMatcher.js

A Javascript utility library for working with native objects.

'use strict';

var STRING_FORMAT_REG = require('../var/STRING_FORMAT_REG'),
    CommonChars = require('../var/CommonChars'),
    memoizeFunction = require('./memoizeFunction');

var OPEN_BRACE = CommonChars.OPEN_BRACE,
    CLOSE_BRACE = CommonChars.CLOSE_BRACE;

function createFormatMatcher(bracketMatcher, percentMatcher, precheck) {

  var reg = STRING_FORMAT_REG;
  var compileMemoized = memoizeFunction(compile);

  function getToken(format, match) {
    var get, token, literal, fn;
    var bKey = match[2];
    var pLit = match[3];
    var pKey = match[5];
    if (match[4] && percentMatcher) {
      token = pKey;
      get = percentMatcher;
    } else if (bKey) {
      token = bKey;
      get = bracketMatcher;
    } else if (pLit && percentMatcher) {
      literal = pLit;
    } else {
      literal = match[1] || match[0];
    }
    if (get) {
      assertPassesPrecheck(precheck, bKey, pKey);
      fn = function(obj, opt) {
        return get(obj, token, opt);
      };
    }
    format.push(fn || getLiteral(literal));
  }

  function getSubstring(format, str, start, end) {
    if (end > start) {
      var sub = str.slice(start, end);
      assertNoUnmatched(sub, OPEN_BRACE);
      assertNoUnmatched(sub, CLOSE_BRACE);
      format.push(function() {
        return sub;
      });
    }
  }

  function getLiteral(str) {
    return function() {
      return str;
    };
  }

  function assertPassesPrecheck(precheck, bt, pt) {
    if (precheck && !precheck(bt, pt)) {
      throw new TypeError('Invalid token '+ (bt || pt) +' in format string');
    }
  }

  function assertNoUnmatched(str, chr) {
    if (str.indexOf(chr) !== -1) {
      throw new TypeError('Unmatched '+ chr +' in format string');
    }
  }

  function compile(str) {
    var format = [], lastIndex = 0, match;
    reg.lastIndex = 0;
    while(match = reg.exec(str)) {
      getSubstring(format, str, lastIndex, match.index);
      getToken(format, match);
      lastIndex = reg.lastIndex;
    }
    getSubstring(format, str, lastIndex, str.length);
    return format;
  }

  return function(str, obj, opt) {
    var format = compileMemoized(str), result = '';
    for (var i = 0; i < format.length; i++) {
      result += format[i](obj, opt);
    }
    return result;
  };
}

module.exports = createFormatMatcher;