/**
 * Holds the entire state of the diagram as a 2D array of cells
 * and provides methods to modify the current state.
 *
 * @constructor
 */
ascii.State = function() {
  /** @type {Array.<Array.<ascii.Cell>>} */
  this.cells = new Array(MAX_GRID_SIZE);
  /** @type {Array.<ascii.MappedCell>} */
  this.scratchCells = new Array();

  /** @type {Array.<Array.<ascii.MappedValue>>} */
  this.undoStates = new Array();

  for (var i = 0; i < this.cells.length; i++) {
    this.cells[i] = new Array(MAX_GRID_SIZE);
    for (var j = 0; j < this.cells[i].length; j++) {
      this.cells[i][j] = new ascii.Cell();
    }
  }
};

/**
 * Returns the cell at the given coordinates.
 *
 * @param {ascii.Vector} vector
 * @return {ascii.Cell}
 */
ascii.State.prototype.getCell = function(vector) {
  return this.cells[vector.x][vector.y];
};

/**
 * Sets the cells value at the given position. Probably shouldn't
 * be used directly in many cases. Used drawValue instead.
 *
 * @param {ascii.Vector} position
 * @param {?string} value
 */
ascii.State.prototype.setValue = function(position, value) {
  this.getCell(position).value = value;
};

/**
 * Sets the cells scratch (uncommitted) value at the given position.
 *
 * @param {ascii.Vector} position
 * @param {?string} value
 */
ascii.State.prototype.drawValue = function(position, value) {
  var cell = this.getCell(position);
  this.scratchCells.push(new ascii.MappedCell(position, cell));
  cell.scratchValue = value;
};

/**
 * Clears the current drawing scratchpad.
 */
ascii.State.prototype.clearDraw = function() {
  for (var i in this.scratchCells) {
    this.scratchCells[i].cell.scratchValue = null;
  }
  this.scratchCells.length = 0;
};

/**
 * Returns the draw value of a cell at the given position.
 *
 * @param {ascii.Vector} position
 * @return {?string}
 */
ascii.State.prototype.getDrawValue = function(position) {
  var cell = this.getCell(position);
  var value = cell.scratchValue != null ? cell.scratchValue : cell.value;
  if (value != SPECIAL_VALUE) {
    return value;
  }

  // Magic time.
  var context = this.getContext(position);

  if (context.left && context.right && !context.up && !context.down) {
    return SPECIAL_LINE_H;
  }
  if (!context.left && !context.right && context.up && context.down) {
    return SPECIAL_LINE_V;
  }
  if (context.left && context.right && context.up && context.down) {
    return SPECIAL_LINE_H;
  }
  return SPECIAL_VALUE;
};

/**
 * @param {ascii.Vector} position
 * @return {ascii.CellContext}
 */
ascii.State.prototype.getContext = function(position) {
  var left = this.getCell(position.add(new ascii.Vector(-1, 0))).isSpecial();
  var right = this.getCell(position.add(new ascii.Vector(1, 0))).isSpecial();
  var up = this.getCell(position.add(new ascii.Vector(0, -1))).isSpecial();
  var down = this.getCell(position.add(new ascii.Vector(0, 1))).isSpecial();
  return new ascii.CellContext(left, right, up, down);
};

/**
 * Ends the current draw, commiting anything currently drawn the scratchpad.
 * @param {boolean=} opt_skipSave
 */
ascii.State.prototype.commitDraw = function(opt_skipSave) {
  var oldValues = [];

  // Dedupe the scratch values, or this causes havoc for history management.
  var positions = this.scratchCells.map(function (value) {
    return value.position.x.toString() + value.position.y.toString();
  });
  var scratchCellsUnique = this.scratchCells.filter(function (value, index, arr) {
    return positions.indexOf(positions[index]) == index;
  });

  this.scratchCells.length = 0;

  for (var i in scratchCellsUnique) {
    var position = scratchCellsUnique[i].position;
    var cell = scratchCellsUnique[i].cell;

    // Push the effective old value unto the array.
    oldValues.push(new ascii.MappedValue(position, cell.value != null ? cell.value : ' '));

    var newValue = cell.getRawValue();
    // Cheeky little hack for making erase play nicely.
    if (newValue == ' ') {
      newValue = null;
    }
    cell.scratchValue = null;
    cell.value = newValue;
  }

  // If we have too many undo states, clear one out.
  if(this.undoStates.length > MAX_UNDO) {
    this.undoStates.shift();
  }
  // Don't save a new state if we are undoing an old one.
  if (!opt_skipSave && oldValues.length > 0) {
    this.undoStates.push(oldValues);
  }
};

/**
 * Undoes the last committed state.
 */
ascii.State.prototype.undo = function() {
  if (this.undoStates.length == 0) { return; }

  var lastState = this.undoStates.pop();
  for (var i in lastState) {
    var mappedValue = lastState[i];
    this.drawValue(mappedValue.position, mappedValue.value);
  }
  this.commitDraw(true);
};

/**
 * Outputs the entire contents of the diagram as text.
 * @return {string}
 */
ascii.State.prototype.outputText = function() {
  // Find the first/last cells in the diagram so we don't output everything.
  var start = new ascii.Vector(Number.MAX_VALUE, Number.MAX_VALUE);
  var end = new ascii.Vector(-1, -1);

  for (var i = 0; i < this.cells.length; i++)  {
    for (var j = 0; j < this.cells[i].length; j++) {
      if (this.cells[i][j].getRawValue() != null) {
        if (i < start.x) { start.x = i; }
        if (j < start.y) { start.y = j; }
        if (i > end.x) { end.x = i; }
        if (j > end.y) { end.y = j; }
      }
    }
  }
  if (end.x < 0) { return '' };

  var output = '';
  for (var j = start.y; j <= end.y; j++) {
    var line = '';
    for (var i = start.x; i <= end.x; i++) {
      var val = this.getDrawValue(new ascii.Vector(i, j));
      line += (val == null ? ' ' : val);
    }
    // Trim end whitespace.
    output += line.replace('\\s+$/g', '') + '\n';
  }
  return output;
};