/**
 * Copyright 2009 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// revision info is a skip list whos entries represent a particular revision
// of the document.  These revisions are connected together by various
// changesets,  or deltas, between any two revisions.
function Revision(revNum) {
  this.rev = revNum;
  this.changesets = [];
}

Revision.prototype.addChangeset = function(destIndex, changeset, timeDelta) {
  var changesetWrapper = {
    deltaRev: destIndex-this.rev,
    deltaTime: timeDelta,
    getValue: function() {
      return changeset;
    }
  };
  this.changesets.push(changesetWrapper);
  this.changesets.sort(function(a, b) {
    return (b.deltaRev - a.deltaRev)
  });
}

revisionInfo = {};
revisionInfo.addChangeset = function(fromIndex, toIndex, changeset, backChangeset, timeDelta) {
  var startRevision = revisionInfo[fromIndex] || revisionInfo.createNew(fromIndex);
  var endRevision = revisionInfo[toIndex] || revisionInfo.createNew(toIndex);
  startRevision.addChangeset(toIndex, changeset, timeDelta);
  endRevision.addChangeset(fromIndex, backChangeset, -1 * timeDelta);
}

revisionInfo.latest = clientVars.totalRevs || -1;

revisionInfo.createNew = function(index) {
  revisionInfo[index] = new Revision(index);
  if(index > revisionInfo.latest) {
    revisionInfo.latest = index;
  }

  return revisionInfo[index];
}

// assuming that there is a path from fromIndex to toIndex, and that the links
// are laid out in a skip-list format
revisionInfo.getPath = function(fromIndex, toIndex) {
  var changesets = [];
  var spans = [];
  var times = [];
  var elem = revisionInfo[fromIndex] || revisionInfo.createNew(fromIndex);
  if(elem.changesets.length != 0 && fromIndex != toIndex) {
    var reverse = !(fromIndex < toIndex)
    while(((elem.rev < toIndex) && !reverse) ||
          ((elem.rev > toIndex) && reverse)) {
      var couldNotContinue = false;
      var oldRev = elem.rev;

      for(var i = reverse ? elem.changesets.length - 1 : 0;
          reverse?i>=0:i<elem.changesets.length;
          i += reverse ? -1 : 1) {
        if(((elem.changesets[i].deltaRev < 0) && !reverse) ||
           ((elem.changesets[i].deltaRev > 0) && reverse)) {
          couldNotContinue = true;
          break;
        }

        if(((elem.rev + elem.changesets[i].deltaRev <= toIndex) && !reverse) ||
           ((elem.rev + elem.changesets[i].deltaRev >= toIndex) && reverse)) {
          var topush = elem.changesets[i];
          changesets.push(topush.getValue());
          spans.push(elem.changesets[i].deltaRev);
          times.push(topush.deltaTime);
          elem = revisionInfo[elem.rev + elem.changesets[i].deltaRev];
          break;
        }
      }

      if(couldNotContinue || oldRev == elem.rev) break;
    }
  }

  var status = 'partial';
  if(elem.rev == toIndex)
    status = 'complete';

  return {
    'fromRev':fromIndex,
    'rev': elem.rev,
    'status': status,
    'changesets': changesets,
    'spans' : spans,
    'times' : times
  };
}

// revisionInfo.addChangeset(0, 5, "abcde")
// revisionInfo.addChangeset(5, 10, "fghij")
// revisionInfo.addChangeset(10, 11, "k")
// revisionInfo.addChangeset(11, 12, "l")
// revisionInfo.addChangeset(12, 13, "m")
// revisionInfo.addChangeset(13, 14, "n")
// revisionInfo.addChangeset(14, 15, "o")
// revisionInfo.addChangeset(15, 20, "pqrst")
//
// print (revisionInfo.getPath(15, 0))