var Changeset = require('./Changeset');
var ChangesetUtils = require('./ChangesetUtils');
var _ = require('./underscore');

var lineMarkerAttribute = 'lmkr';

// If one of these attributes are set to the first character of a
// line it is considered as a line attribute marker i.e. attributes
// set on this marker are applied to the whole line.
// The list attribute is only maintained for compatibility reasons
var lineAttributes = [lineMarkerAttribute,'list'];

/*
  The Attribute manager builds changesets based on a document
  representation for setting and removing range or line-based attributes.

  @param rep the document representation to be used
  @param applyChangesetCallback this callback will be called
    once a changeset has been built.


  A document representation contains
  - an array `alines` containing 1 attributes string for each line
  - an Attribute pool `apool`
  - a SkipList `lines` containing the text lines of the document.
*/

var AttributeManager = function(rep, applyChangesetCallback)
{
  this.rep = rep;
  this.applyChangesetCallback = applyChangesetCallback;
  this.author = '';

  // If the first char in a line has one of the following attributes
  // it will be considered as a line marker
};

AttributeManager.lineAttributes = lineAttributes;

AttributeManager.prototype = _(AttributeManager.prototype).extend({

  applyChangeset: function(changeset){
    if(!this.applyChangesetCallback) return changeset;

    var cs = changeset.toString();
    if (!Changeset.isIdentity(cs))
    {
      this.applyChangesetCallback(cs);
    }

    return changeset;
  },

  /*
    Sets attributes on a range
    @param start [row, col] tuple pointing to the start of the range
    @param end [row, col] tuple pointing to the end of the range
    @param attribs: an array of attributes
  */
  setAttributesOnRange: function(start, end, attribs)
  {
    // instead of applying the attributes to the whole range at once, we need to apply them
    // line by line, to be able to disregard the "*" used as line marker. For more details,
    // see https://github.com/ether/etherpad-lite/issues/2772
    var allChangesets;
    for(var row = start[0]; row <= end[0]; row++) {
      var rowRange = this._findRowRange(row, start, end);
      var startCol = rowRange[0];
      var endCol   = rowRange[1];

      var rowChangeset = this._setAttributesOnRangeByLine(row, startCol, endCol, attribs);

      // compose changesets of all rows into a single changeset, as the range might not be continuous
      // due to the presence of line markers on the rows
      if (allChangesets) {
        allChangesets = Changeset.compose(allChangesets.toString(), rowChangeset.toString(), this.rep.apool);
      } else {
        allChangesets = rowChangeset;
      }
    }

    return this.applyChangeset(allChangesets);
  },

  _findRowRange: function(row, start, end)
  {
    var startCol, endCol;

    var startLineOffset = this.rep.lines.offsetOfIndex(row);
    var endLineOffset   = this.rep.lines.offsetOfIndex(row+1);
    var lineLength      = endLineOffset - startLineOffset;

    // find column where range on this row starts
    if (row === start[0]) { // are we on the first row of range?
      startCol = start[1];
    } else {
      startCol = this.lineHasMarker(row) ? 1 : 0; // remove "*" used as line marker
    }

    // find column where range on this row ends
    if (row === end[0]) { // are we on the last row of range?
      endCol = end[1]; // if so, get the end of range, not end of row
    } else {
      endCol = lineLength - 1; // remove "\n"
    }

    return [startCol, endCol];
  },

  /*
    Sets attributes on a range, by line
    @param row the row where range is
    @param startCol column where range starts
    @param endCol column where range ends
    @param attribs: an array of attributes
  */
  _setAttributesOnRangeByLine: function(row, startCol, endCol, attribs)
  {
    var builder = Changeset.builder(this.rep.lines.totalWidth());
    ChangesetUtils.buildKeepToStartOfRange(this.rep, builder, [row, startCol]);
    ChangesetUtils.buildKeepRange(this.rep, builder, [row, startCol], [row, endCol], attribs, this.rep.apool);
    return builder;
  },

  /*
    Returns if the line already has a line marker
    @param lineNum: the number of the line
  */
  lineHasMarker: function(lineNum){
    var that = this;

    return _.find(lineAttributes, function(attribute){
      return that.getAttributeOnLine(lineNum, attribute) != '';
    }) !== undefined;
  },

  /*
    Gets a specified attribute on a line
    @param lineNum: the number of the line to set the attribute for
    @param attributeKey: the name of the attribute to get, e.g. list
  */
  getAttributeOnLine: function(lineNum, attributeName){
    // get  `attributeName` attribute of first char of line
    var aline = this.rep.alines[lineNum];
    if (aline)
    {
      var opIter = Changeset.opIterator(aline);
      if (opIter.hasNext())
      {
        return Changeset.opAttributeValue(opIter.next(), attributeName, this.rep.apool) || '';
      }
    }
    return '';
  },

  /*
    Gets all attributes on a line
    @param lineNum: the number of the line to get the attribute for
  */
  getAttributesOnLine: function(lineNum){
    // get attributes of first char of line
    var aline = this.rep.alines[lineNum];
    var attributes = []
    if (aline)
    {
      var opIter = Changeset.opIterator(aline)
        , op
      if (opIter.hasNext())
      {
        op = opIter.next()
        if(!op.attribs) return []

        Changeset.eachAttribNumber(op.attribs, function(n) {
          attributes.push([this.rep.apool.getAttribKey(n), this.rep.apool.getAttribValue(n)])
        }.bind(this))
        return attributes;
      }
    }
    return [];
  },

 /*
    Gets a given attribute on a selection
    @param attributeName
    @param prevChar
    returns true or false if an attribute is visible in range
  */
  getAttributeOnSelection: function(attributeName, prevChar){
    var rep = this.rep;
    if (!(rep.selStart && rep.selEnd)) return
    // If we're looking for the caret attribute not the selection
    // has the user already got a selection or is this purely a caret location?
    var isNotSelection = (rep.selStart[0] == rep.selEnd[0] && rep.selEnd[1] === rep.selStart[1]);
    if(isNotSelection){
      if(prevChar){
        // If it's not the start of the line
        if(rep.selStart[1] !== 0){
          rep.selStart[1]--;
        }
      }
    }

    var withIt = Changeset.makeAttribsString('+', [
      [attributeName, 'true']
    ], rep.apool);
    var withItRegex = new RegExp(withIt.replace(/\*/g, '\\*') + "(\\*|$)");
    function hasIt(attribs)
    {
      return withItRegex.test(attribs);
    }

    return rangeHasAttrib(rep.selStart, rep.selEnd)

    function rangeHasAttrib(selStart, selEnd) {
      // if range is collapsed -> no attribs in range
      if(selStart[1] == selEnd[1] && selStart[0] == selEnd[0]) return false

      if(selStart[0] != selEnd[0]) { // -> More than one line selected
        var hasAttrib = true

        // from selStart to the end of the first line
        hasAttrib = hasAttrib && rangeHasAttrib(selStart, [selStart[0], rep.lines.atIndex(selStart[0]).text.length])

        // for all lines in between
        for(var n=selStart[0]+1; n < selEnd[0]; n++) {
          hasAttrib = hasAttrib && rangeHasAttrib([n, 0], [n, rep.lines.atIndex(n).text.length])
        }

        // for the last, potentially partial, line
        hasAttrib = hasAttrib && rangeHasAttrib([selEnd[0], 0], [selEnd[0], selEnd[1]])

        return hasAttrib
      }

      // Logic tells us we now have a range on a single line

      var lineNum = selStart[0]
        , start = selStart[1]
        , end = selEnd[1]
        , hasAttrib = true

      // Iterate over attribs on this line

      var opIter = Changeset.opIterator(rep.alines[lineNum])
        , indexIntoLine = 0

      while (opIter.hasNext()) {
        var op = opIter.next();
        var opStartInLine = indexIntoLine;
        var opEndInLine = opStartInLine + op.chars;
        if (!hasIt(op.attribs)) {
          // does op overlap selection?
          if (!(opEndInLine <= start || opStartInLine >= end)) {
            hasAttrib = false; // since it's overlapping but hasn't got the attrib -> range hasn't got it
            break;
          }
        }
        indexIntoLine = opEndInLine;
      }

      return hasAttrib
    }
  },

  /*
    Gets all attributes at a position containing line number and column
    @param lineNumber starting with zero
    @param column starting with zero
    returns a list of attributes in the format
    [ ["key","value"], ["key","value"], ...  ]
  */
  getAttributesOnPosition: function(lineNumber, column){
    // get all attributes of the line
    var aline = this.rep.alines[lineNumber];

    if (!aline) {
        return [];
    }
    // iterate through all operations of a line
    var opIter = Changeset.opIterator(aline);

    // we need to sum up how much characters each operations take until the wanted position
    var currentPointer = 0;
    var attributes = [];
    var currentOperation;

    while (opIter.hasNext()) {
      currentOperation = opIter.next();
      currentPointer = currentPointer + currentOperation.chars;

      if (currentPointer > column) {
        // we got the operation of the wanted position, now collect all its attributes
        Changeset.eachAttribNumber(currentOperation.attribs, function (n) {
          attributes.push([
            this.rep.apool.getAttribKey(n),
            this.rep.apool.getAttribValue(n)
          ]);
        }.bind(this));

        // skip the loop
        return attributes;
      }
    }
    return attributes;

  },

  /*
    Gets all attributes at caret position
    if the user selected a range, the start of the selection is taken
    returns a list of attributes in the format
    [ ["key","value"], ["key","value"], ...  ]
  */
  getAttributesOnCaret: function(){
    return this.getAttributesOnPosition(this.rep.selStart[0], this.rep.selStart[1]);
  },

  /*
    Sets a specified attribute on a line
    @param lineNum: the number of the line to set the attribute for
    @param attributeKey: the name of the attribute to set, e.g. list
    @param attributeValue: an optional parameter to pass to the attribute (e.g. indention level)

  */
  setAttributeOnLine: function(lineNum, attributeName, attributeValue){
    var loc = [0,0];
    var builder = Changeset.builder(this.rep.lines.totalWidth());
    var hasMarker = this.lineHasMarker(lineNum);

    ChangesetUtils.buildKeepRange(this.rep, builder, loc, (loc = [lineNum, 0]));

    if(hasMarker){
      ChangesetUtils.buildKeepRange(this.rep, builder, loc, (loc = [lineNum, 1]), [
        [attributeName, attributeValue]
      ], this.rep.apool);
    }else{
        // add a line marker
        builder.insert('*', [
          ['author', this.author],
          ['insertorder', 'first'],
          [lineMarkerAttribute, '1'],
          [attributeName, attributeValue]
        ], this.rep.apool);
    }

    return this.applyChangeset(builder);
  },

 /**
   * Removes a specified attribute on a line
   *  @param lineNum the number of the affected line
   *  @param attributeName the name of the attribute to remove, e.g. list
   *  @param attributeValue if given only attributes with equal value will be removed
   */
 removeAttributeOnLine: function(lineNum, attributeName, attributeValue){
   var builder = Changeset.builder(this.rep.lines.totalWidth());
   var hasMarker = this.lineHasMarker(lineNum);
   var found = false;

   var attribs = _(this.getAttributesOnLine(lineNum)).map(function (attrib) {
     if (attrib[0] === attributeName && (!attributeValue || attrib[0] === attributeValue)){
       found = true;
       return [attributeName, ''];
     }else if (attrib[0] === 'author'){
       // update last author to make changes to line attributes on this line
       return [attributeName, this.author];
     }
     return attrib;
   });

   if (!found) {
     return;
   }

   ChangesetUtils.buildKeepToStartOfRange(this.rep, builder, [lineNum, 0]);

   var countAttribsWithMarker = _.chain(attribs).filter(function(a){return !!a[1];})
     .map(function(a){return a[0];}).difference(['author', 'lmkr', 'insertorder', 'start']).size().value();

   //if we have marker and any of attributes don't need to have marker. we need delete it
   if(hasMarker && !countAttribsWithMarker){
     ChangesetUtils.buildRemoveRange(this.rep, builder, [lineNum, 0], [lineNum, 1]);
   }else{
     ChangesetUtils.buildKeepRange(this.rep, builder, [lineNum, 0], [lineNum, 1], attribs, this.rep.apool);
   }

   return this.applyChangeset(builder);
 },

   /*
     Toggles a line attribute for the specified line number
     If a line attribute with the specified name exists with any value it will be removed
     Otherwise it will be set to the given value
     @param lineNum: the number of the line to toggle the attribute for
     @param attributeKey: the name of the attribute to toggle, e.g. list
     @param attributeValue: the value to pass to the attribute (e.g. indention level)
  */
  toggleAttributeOnLine: function(lineNum, attributeName, attributeValue) {
    return this.getAttributeOnLine(lineNum, attributeName) ?
      this.removeAttributeOnLine(lineNum, attributeName) :
      this.setAttributeOnLine(lineNum, attributeName, attributeValue);

  }
});

module.exports = AttributeManager;