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"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = Diff;

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function Diff() {}

Diff.prototype = {
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  diff: function diff(oldString, newString) {
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    var
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    options = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {};
    var callback = options.callback;

    if (typeof options === 'function') {
      callback = options;
      options = {};
    }

    this.options = options;
    var self = this;

    function done(value) {
      if (callback) {
        setTimeout(function () {
          callback(undefined, value);
        }, 0);
        return true;
      } else {
        return value;
      }
    } // Allow subclasses to massage the input prior to running


    oldString = this.castInput(oldString);
    newString = this.castInput(newString);
    oldString = this.removeEmpty(this.tokenize(oldString));
    newString = this.removeEmpty(this.tokenize(newString));
    var newLen = newString.length,
        oldLen = oldString.length;
    var editLength = 1;
    var maxEditLength = newLen + oldLen;
    var bestPath = [{
      newPos: -1,
      components: []
    }]; // Seed editLength = 0, i.e. the content starts with the same values

    var oldPos = this.extractCommon(bestPath[0], newString, oldString, 0);

    if (bestPath[0].newPos + 1 >= newLen && oldPos + 1 >= oldLen) {
      // Identity per the equality and tokenizer
      return done([{
        value: this.join(newString),
        count: newString.length
      }]);
    } // Main worker method. checks all permutations of a given edit length for acceptance.


    function execEditLength() {
      for (var diagonalPath = -1 * editLength; diagonalPath <= editLength; diagonalPath += 2) {
        var basePath =
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        void 0
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        ;

        var addPath = bestPath[diagonalPath - 1],
            removePath = bestPath[diagonalPath + 1],
            _oldPos = (removePath ? removePath.newPos : 0) - diagonalPath;

        if (addPath) {
          // No one else is going to attempt to use this value, clear it
          bestPath[diagonalPath - 1] = undefined;
        }

        var canAdd = addPath && addPath.newPos + 1 < newLen,
            canRemove = removePath && 0 <= _oldPos && _oldPos < oldLen;

        if (!canAdd && !canRemove) {
          // If this path is a terminal then prune
          bestPath[diagonalPath] = undefined;
          continue;
        } // Select the diagonal that we want to branch from. We select the prior
        // path whose position in the new string is the farthest from the origin
        // and does not pass the bounds of the diff graph


        if (!canAdd || canRemove && addPath.newPos < removePath.newPos) {
          basePath = clonePath(removePath);
          self.pushComponent(basePath.components, undefined, true);
        } else {
          basePath = addPath; // No need to clone, we've pulled it from the list

          basePath.newPos++;
          self.pushComponent(basePath.components, true, undefined);
        }

        _oldPos = self.extractCommon(basePath, newString, oldString, diagonalPath); // If we have hit the end of both strings, then we are done

        if (basePath.newPos + 1 >= newLen && _oldPos + 1 >= oldLen) {
          return done(buildValues(self, basePath.components, newString, oldString, self.useLongestToken));
        } else {
          // Otherwise track this path as a potential candidate and continue.
          bestPath[diagonalPath] = basePath;
        }
      }

      editLength++;
    } // Performs the length of edit iteration. Is a bit fugly as this has to support the
    // sync and async mode which is never fun. Loops over execEditLength until a value
    // is produced.


    if (callback) {
      (function exec() {
        setTimeout(function () {
          // This should not happen, but we want to be safe.

          /* istanbul ignore next */
          if (editLength > maxEditLength) {
            return callback();
          }

          if (!execEditLength()) {
            exec();
          }
        }, 0);
      })();
    } else {
      while (editLength <= maxEditLength) {
        var ret = execEditLength();

        if (ret) {
          return ret;
        }
      }
    }
  },

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  pushComponent: function pushComponent(components, added, removed) {
    var last = components[components.length - 1];

    if (last && last.added === added && last.removed === removed) {
      // We need to clone here as the component clone operation is just
      // as shallow array clone
      components[components.length - 1] = {
        count: last.count + 1,
        added: added,
        removed: removed
      };
    } else {
      components.push({
        count: 1,
        added: added,
        removed: removed
      });
    }
  },

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  extractCommon: function extractCommon(basePath, newString, oldString, diagonalPath) {
    var newLen = newString.length,
        oldLen = oldString.length,
        newPos = basePath.newPos,
        oldPos = newPos - diagonalPath,
        commonCount = 0;

    while (newPos + 1 < newLen && oldPos + 1 < oldLen && this.equals(newString[newPos + 1], oldString[oldPos + 1])) {
      newPos++;
      oldPos++;
      commonCount++;
    }

    if (commonCount) {
      basePath.components.push({
        count: commonCount
      });
    }

    basePath.newPos = newPos;
    return oldPos;
  },

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  equals: function equals(left, right) {
    if (this.options.comparator) {
      return this.options.comparator(left, right);
    } else {
      return left === right || this.options.ignoreCase && left.toLowerCase() === right.toLowerCase();
    }
  },

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  removeEmpty: function removeEmpty(array) {
    var ret = [];

    for (var i = 0; i < array.length; i++) {
      if (array[i]) {
        ret.push(array[i]);
      }
    }

    return ret;
  },

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  castInput: function castInput(value) {
    return value;
  },

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  tokenize: function tokenize(value) {
    return value.split('');
  },

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  join: function join(chars) {
    return chars.join('');
  }
};

function buildValues(diff, components, newString, oldString, useLongestToken) {
  var componentPos = 0,
      componentLen = components.length,
      newPos = 0,
      oldPos = 0;

  for (; componentPos < componentLen; componentPos++) {
    var component = components[componentPos];

    if (!component.removed) {
      if (!component.added && useLongestToken) {
        var value = newString.slice(newPos, newPos + component.count);
        value = value.map(function (value, i) {
          var oldValue = oldString[oldPos + i];
          return oldValue.length > value.length ? oldValue : value;
        });
        component.value = diff.join(value);
      } else {
        component.value = diff.join(newString.slice(newPos, newPos + component.count));
      }

      newPos += component.count; // Common case

      if (!component.added) {
        oldPos += component.count;
      }
    } else {
      component.value = diff.join(oldString.slice(oldPos, oldPos + component.count));
      oldPos += component.count; // Reverse add and remove so removes are output first to match common convention
      // The diffing algorithm is tied to add then remove output and this is the simplest
      // route to get the desired output with minimal overhead.

      if (componentPos && components[componentPos - 1].added) {
        var tmp = components[componentPos - 1];
        components[componentPos - 1] = components[componentPos];
        components[componentPos] = tmp;
      }
    }
  } // Special case handle for when one terminal is ignored (i.e. whitespace).
  // For this case we merge the terminal into the prior string and drop the change.
  // This is only available for string mode.


  var lastComponent = components[componentLen - 1];

  if (componentLen > 1 && typeof lastComponent.value === 'string' && (lastComponent.added || lastComponent.removed) && diff.equals('', lastComponent.value)) {
    components[componentLen - 2].value += lastComponent.value;
    components.pop();
  }

  return components;
}

function clonePath(path) {
  return {
    newPos: path.newPos,
    components: path.components.slice(0)
  };
}
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