/**
 * @constructor
 * @implements {ascii.DrawFunction}
 * @param {ascii.State} state
 */
ascii.DrawSelect = function(state) {
  this.state = state;
  /** @type {ascii.Vector} */
  this.startPosition = null;
  /** @type {ascii.Vector} */
  this.endPosition = null;
  /** @type {ascii.Vector} */
  this.dragStart = null;
  /** @type {ascii.Vector} */
  this.dragEnd = null;

  /** @type {boolean} */
  this.finished = true;

  /** @type {Array.<ascii.MappedValue>} */
  this.selectedCells = null;
};

/** @inheritDoc */
ascii.DrawSelect.prototype.start = function(position) {
  // Must be dragging.
  if (this.startPosition != null &&
      this.endPosition != null &&
      this.getSelectedBox().contains(position)) {
    this.dragStart = position;
    this.copyArea();
    this.dragMove(position);
  } else {
    this.startPosition = position;
    this.endPosition = null;
    this.finished = false;
    this.move(position);
  }
};

ascii.DrawSelect.prototype.getSelectedBox = function() {
  return new ascii.Box(this.startPosition, this.endPosition);
};

ascii.DrawSelect.prototype.copyArea = function() {
  var nonEmptyCells = this.state.scratchCells.filter(function(value) {
    var rawValue = value.cell.getRawValue();
    return value.cell.getRawValue() != null && value.cell.getRawValue() != ERASE_CHAR;
  });
  var topLeft = this.getSelectedBox().topLeft();
  this.selectedCells = nonEmptyCells.map(function(value) {
    return new ascii.MappedValue(value.position.subtract(topLeft), value.cell.getRawValue());
  });
};

/** @inheritDoc */
ascii.DrawSelect.prototype.move = function(position) {
  if (this.dragStart != null) {
    this.dragMove(position);
    return;
  }

  if (this.finished == true) {
    return;
  }
  this.endPosition = position;
  this.state.clearDraw();

  var box = new ascii.Box(this.startPosition, position);

  for (var i = box.startX; i <= box.endX; i++) {
    for (var j = box.startY; j <= box.endY; j++) {
      var current = new ascii.Vector(i, j);
      // Effectively highlights the cell.
      var currentValue = this.state.getCell(current).getRawValue();
      this.state.drawValue(current,
          currentValue == null ? ERASE_CHAR : currentValue);
    }
  }
};

ascii.DrawSelect.prototype.dragMove = function(position) {
  this.dragEnd = position;
  this.state.clearDraw();
  var eraser = new ascii.DrawErase(this.state);
  eraser.start(this.startPosition);
  eraser.move(this.endPosition);
  var startPos = this.dragEnd.subtract(this.dragStart).add(this.getSelectedBox().topLeft());
  this.drawSelected(startPos);
};

ascii.DrawSelect.prototype.drawSelected = function(startPos) {
 for (var i in this.selectedCells) {
    this.state.drawValue(this.selectedCells[i].position.add(startPos), this.selectedCells[i].value);
  }
};

/** @inheritDoc */
ascii.DrawSelect.prototype.end = function() {
  if (this.dragStart != null) {
    this.state.commitDraw();
    this.startPosition = null;
    this.endPosition = null;
  }
  this.dragStart = null;
  this.dragEnd = null;
  this.finished = true;
};

/** @inheritDoc */
ascii.DrawSelect.prototype.getCursor = function(position) {
  if (this.startPosition != null &&
      this.endPosition != null &&
      new ascii.Box(this.startPosition, this.endPosition).contains(position)) {
    return 'pointer';
  }
  return 'default';
};

/** @inheritDoc */
ascii.DrawSelect.prototype.handleKey = function(value) {
  if (this.startPosition != null &&
      this.endPosition != null) {
    if (value == KEY_COPY || value == KEY_CUT) {
      this.copyArea();
    }
    if (value == KEY_CUT) {
      var eraser = new ascii.DrawErase(this.state);
      eraser.start(this.startPosition);
      eraser.move(this.endPosition);
      this.state.commitDraw();
    }
  }
  if (value == KEY_PASTE) {
    this.drawSelected(this.startPosition);
    this.state.commitDraw();
  }
};