/* -*- Mode: js; js-indent-level: 2; -*- */
/*
 * Copyright 2011 Mozilla Foundation and contributors
 * Licensed under the New BSD license. See LICENSE or:
 * http://opensource.org/licenses/BSD-3-Clause
 */
if (typeof define !== 'function') {
    var define = require('amdefine')(module);
}
define(function (require, exports, module) {

  var util = require('./util');
  var binarySearch = require('./binary-search');
  var ArraySet = require('./array-set').ArraySet;
  var base64VLQ = require('./base64-vlq');

  /**
   * A SourceMapConsumer instance represents a parsed source map which we can
   * query for information about the original file positions by giving it a file
   * position in the generated source.
   *
   * The only parameter is the raw source map (either as a JSON string, or
   * already parsed to an object). According to the spec, source maps have the
   * following attributes:
   *
   *   - version: Which version of the source map spec this map is following.
   *   - sources: An array of URLs to the original source files.
   *   - names: An array of identifiers which can be referrenced by individual mappings.
   *   - sourceRoot: Optional. The URL root from which all sources are relative.
   *   - mappings: A string of base64 VLQs which contain the actual mappings.
   *   - file: The generated file this source map is associated with.
   *
   * Here is an example source map, taken from the source map spec[0]:
   *
   *     {
   *       version : 3,
   *       file: "out.js",
   *       sourceRoot : "",
   *       sources: ["foo.js", "bar.js"],
   *       names: ["src", "maps", "are", "fun"],
   *       mappings: "AA,AB;;ABCDE;"
   *     }
   *
   * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit?pli=1#
   */
  function SourceMapConsumer(aSourceMap) {
    var sourceMap = aSourceMap;
    if (typeof aSourceMap === 'string') {
      sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
    }

    var version = util.getArg(sourceMap, 'version');
    var sources = util.getArg(sourceMap, 'sources');
    var names = util.getArg(sourceMap, 'names');
    var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
    var mappings = util.getArg(sourceMap, 'mappings');
    var file = util.getArg(sourceMap, 'file');

    if (version !== this._version) {
      throw new Error('Unsupported version: ' + version);
    }

    this._names = ArraySet.fromArray(names);
    this._sources = ArraySet.fromArray(sources);
    this._sourceRoot = sourceRoot;
    this.file = file;

    // `this._generatedMappings` and `this._originalMappings` hold the parsed
    // mapping coordinates from the source map's "mappings" attribute. Each
    // object in the array is of the form
    //
    //     {
    //       generatedLine: The line number in the generated code,
    //       generatedColumn: The column number in the generated code,
    //       source: The path to the original source file that generated this
    //               chunk of code,
    //       originalLine: The line number in the original source that
    //                     corresponds to this chunk of generated code,
    //       originalColumn: The column number in the original source that
    //                       corresponds to this chunk of generated code,
    //       name: The name of the original symbol which generated this chunk of
    //             code.
    //     }
    //
    // All properties except for `generatedLine` and `generatedColumn` can be
    // `null`.
    //
    // `this._generatedMappings` is ordered by the generated positions.
    //
    // `this._originalMappings` is ordered by the original positions.
    this._generatedMappings = [];
    this._originalMappings = [];
    this._parseMappings(mappings, sourceRoot);
  }

  /**
   * The version of the source mapping spec that we are consuming.
   */
  SourceMapConsumer.prototype._version = 3;

  /**
   * The list of original sources.
   */
  Object.defineProperty(SourceMapConsumer.prototype, 'sources', {
    get: function () {
      return this._sources.toArray().map(function (s) {
        return this._sourceRoot ? util.join(this._sourceRoot, s) : s;
      }, this);
    }
  });

  /**
   * Parse the mappings in a string in to a data structure which we can easily
   * query (an ordered list in this._generatedMappings).
   */
  SourceMapConsumer.prototype._parseMappings =
    function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
      var generatedLine = 1;
      var previousGeneratedColumn = 0;
      var previousOriginalLine = 0;
      var previousOriginalColumn = 0;
      var previousSource = 0;
      var previousName = 0;
      var mappingSeparator = /^[,;]/;
      var str = aStr;
      var mapping;
      var temp;

      while (str.length > 0) {
        if (str.charAt(0) === ';') {
          generatedLine++;
          str = str.slice(1);
          previousGeneratedColumn = 0;
        }
        else if (str.charAt(0) === ',') {
          str = str.slice(1);
        }
        else {
          mapping = {};
          mapping.generatedLine = generatedLine;

          // Generated column.
          temp = base64VLQ.decode(str);
          mapping.generatedColumn = previousGeneratedColumn + temp.value;
          previousGeneratedColumn = mapping.generatedColumn;
          str = temp.rest;

          if (str.length > 0 && !mappingSeparator.test(str.charAt(0))) {
            // Original source.
            temp = base64VLQ.decode(str);
            if (aSourceRoot) {
              mapping.source = util.join(aSourceRoot, this._sources.at(previousSource + temp.value));
            }
            else {
              mapping.source = this._sources.at(previousSource + temp.value);
            }
            previousSource += temp.value;
            str = temp.rest;
            if (str.length === 0 || mappingSeparator.test(str.charAt(0))) {
              throw new Error('Found a source, but no line and column');
            }

            // Original line.
            temp = base64VLQ.decode(str);
            mapping.originalLine = previousOriginalLine + temp.value;
            previousOriginalLine = mapping.originalLine;
            // Lines are stored 0-based
            mapping.originalLine += 1;
            str = temp.rest;
            if (str.length === 0 || mappingSeparator.test(str.charAt(0))) {
              throw new Error('Found a source and line, but no column');
            }

            // Original column.
            temp = base64VLQ.decode(str);
            mapping.originalColumn = previousOriginalColumn + temp.value;
            previousOriginalColumn = mapping.originalColumn;
            str = temp.rest;

            if (str.length > 0 && !mappingSeparator.test(str.charAt(0))) {
              // Original name.
              temp = base64VLQ.decode(str);
              mapping.name = this._names.at(previousName + temp.value);
              previousName += temp.value;
              str = temp.rest;
            }
          }

          this._generatedMappings.push(mapping);
          this._originalMappings.push(mapping);
        }
      }

      this._originalMappings.sort(this._compareOriginalPositions);
    };

  /**
   * Comparator between two mappings where the original positions are compared.
   */
  SourceMapConsumer.prototype._compareOriginalPositions =
    function SourceMapConsumer_compareOriginalPositions(mappingA, mappingB) {
      if (mappingA.source > mappingB.source) {
        return 1;
      }
      else if (mappingA.source < mappingB.source) {
        return -1;
      }
      else {
        var cmp = mappingA.originalLine - mappingB.originalLine;
        return cmp === 0
          ? mappingA.originalColumn - mappingB.originalColumn
          : cmp;
      }
    };

  /**
   * Comparator between two mappings where the generated positions are compared.
   */
  SourceMapConsumer.prototype._compareGeneratedPositions =
    function SourceMapConsumer_compareGeneratedPositions(mappingA, mappingB) {
      var cmp = mappingA.generatedLine - mappingB.generatedLine;
      return cmp === 0
        ? mappingA.generatedColumn - mappingB.generatedColumn
        : cmp;
    };

  /**
   * Find the mapping that best matches the hypothetical "needle" mapping that
   * we are searching for in the given "haystack" of mappings.
   */
  SourceMapConsumer.prototype._findMapping =
    function SourceMapConsumer_findMapping(aNeedle, aMappings, aLineName,
                                           aColumnName, aComparator) {
      // To return the position we are searching for, we must first find the
      // mapping for the given position and then return the opposite position it
      // points to. Because the mappings are sorted, we can use binary search to
      // find the best mapping.

      if (aNeedle[aLineName] <= 0) {
        throw new TypeError('Line must be greater than or equal to 1, got '
                            + aNeedle[aLineName]);
      }
      if (aNeedle[aColumnName] < 0) {
        throw new TypeError('Column must be greater than or equal to 0, got '
                            + aNeedle[aColumnName]);
      }

      return binarySearch.search(aNeedle, aMappings, aComparator);
    };

  /**
   * Returns the original source, line, and column information for the generated
   * source's line and column positions provided. The only argument is an object
   * with the following properties:
   *
   *   - line: The line number in the generated source.
   *   - column: The column number in the generated source.
   *
   * and an object is returned with the following properties:
   *
   *   - source: The original source file, or null.
   *   - line: The line number in the original source, or null.
   *   - column: The column number in the original source, or null.
   *   - name: The original identifier, or null.
   */
  SourceMapConsumer.prototype.originalPositionFor =
    function SourceMapConsumer_originalPositionFor(aArgs) {
      var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };
      }

      return {
        source: null,
        line: null,
        column: null,
        name: null
      };
    };

  /**
   * Returns the generated line and column information for the original source,
   * line, and column positions provided. The only argument is an object with
   * the following properties:
   *
   *   - source: The filename of the original source.
   *   - line: The line number in the original source.
   *   - column: The column number in the original source.
   *
   * and an object is returned with the following properties:
   *
   *   - line: The line number in the generated source, or null.
   *   - column: The column number in the generated source, or null.
   */
  SourceMapConsumer.prototype.generatedPositionFor =
    function SourceMapConsumer_generatedPositionFor(aArgs) {
      var needle = {
        source: util.getArg(aArgs, 'source'),
        originalLine: util.getArg(aArgs, 'line'),
        originalColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._originalMappings,
                                      "originalLine",
                                      "originalColumn",
                                      this._compareOriginalPositions)

      if (mapping) {
        return {
          line: util.getArg(mapping, 'generatedLine', null),
          column: util.getArg(mapping, 'generatedColumn', null)
        };
      }

      return {
        line: null,
        column: null
      };
    };

  SourceMapConsumer.GENERATED_ORDER = 1;
  SourceMapConsumer.ORIGINAL_ORDER = 2;

  /**
   * Iterate over each mapping between an original source/line/column and a
   * generated line/column in this source map.
   *
   * @param Function aCallback
   *        The function that is called with each mapping. This function should
   *        not mutate the mapping.
   * @param Object aContext
   *        Optional. If specified, this object will be the value of `this` every
   *        time that `aCallback` is called.
   * @param aOrder
   *        Either `SourceMapConsumer.GENERATED_ORDER` or
   *        `SourceMapConsumer.ORIGINAL_ORDER`. Specifies whether you want to
   *        iterate over the mappings sorted by the generated file's line/column
   *        order or the original's source/line/column order, respectively. Defaults to
   *        `SourceMapConsumer.GENERATED_ORDER`.
   */
  SourceMapConsumer.prototype.eachMapping =
    function SourceMapConsumer_eachMapping(aCallback, aContext, aOrder) {
      var context = aContext || null;
      var order = aOrder || SourceMapConsumer.GENERATED_ORDER;

      var mappings;
      switch (order) {
      case SourceMapConsumer.GENERATED_ORDER:
        mappings = this._generatedMappings;
        break;
      case SourceMapConsumer.ORIGINAL_ORDER:
        mappings = this._originalMappings;
        break;
      default:
        throw new Error("Unknown order of iteration.");
      }

      mappings.forEach(aCallback, context);
    };

  exports.SourceMapConsumer = SourceMapConsumer;

});
