var cameraGrid = {};

cameraGrid.CameraGrid = function(container, sourceUrls, resolutions, getUrl) {
  this.container_ = container;
  this.sourceUrls_ = sourceUrls;
  this.resolutions_ = resolutions || this.defaultResolutions_;
  this.getUrl_ = getUrl || this.defaultGetUrl_;

  this.tileScaleWidth_ = this.resolutions_[0][0];
  this.tileScaleHeight_ = this.resolutions_[0][1];

  this.gridWidthCells_ = 0;
  this.gridHeightCells_ = 0;

  this.imgWidthPx_ = 0;
  this.imgHeightPx_ = 0;
  this.constraint_ = null;

  this.containerImgWidthPx_ = 0;
  this.ctonainerImgHeightPx_ = 0;
  this.containerConstraint_ = null;

  this.selected_ = null;
  this.scanning_ = false;

  this.buildCells_();
  this.buildStylesheet_();

  this.container_.tabIndex = 0;
  this.container_.focus();
  this.container_.addEventListener('keypress', this.onKeyPress_.bind(this), false);
  this.container_.addEventListener('keydown', this.onKeyDown_.bind(this), false);

  window.addEventListener('resize', this.rebuildIfNeeded_.bind(this), false);
  this.rebuildIfNeeded_();

  window.setInterval(this.onScanTimer_.bind(this), 3000);
};

// Resolution list must be sorted ascending.
// All resolutions must be the same aspect ratio.
cameraGrid.CameraGrid.prototype.defaultResolutions_ = [
  [ 160, 120 ],
  [ 240, 180 ],
  [ 320, 240 ],
  [ 480, 360 ],
  [ 640, 480 ],
  [ 800, 600 ],
  [ 1024, 768 ],
  [ 1280, 960 ],
];

cameraGrid.CameraGrid.prototype.defaultGetUrl_ = function(sourceUrl, width, height) {
  return sourceUrl + 'mjpg/video.mjpg?resolution=' + width + 'x' + height;
};

cameraGrid.CameraGrid.prototype.disableScanning_ = function() {
  if (this.scanning_) {
    this.scanning_ = false;
    // Images might all be higher res than needed, so we refresh.
    this.buildImages_();
  }
};

cameraGrid.CameraGrid.prototype.setSelectedNoScan_ = function(index) {
  this.setSelected_(index);
  this.disableScanning_();
};

cameraGrid.CameraGrid.prototype.setSelected_ = function(index) {
  var old_index;

  if (this.selected_ == index) {
    this.removeCSSClass_(this.cells_[this.selected_], 'cameraGridFullScreen');
    old_index = this.selected_;
    this.selected_ = null;
  } else {
    if (this.selected_ != null) {
      this.removeCSSClass_(this.cells_[this.selected_], 'cameraGridFullScreen');
      old_index = this.selected_;
    }
    this.addCSSClass_(this.cells_[index], 'cameraGridFullScreen');
    this.selected_ = index;
  }

  if (this.containerImgWidthPx_ != this.imgWidthPx_ ||
      this.containerImgHeightPx_ != this.imgHeightPx_) {
    // Image stream should change when toggling full screen.
    if (old_index != null) {
      this.buildImage_(old_index);
    }
    if (this.selected_ != null) {
      this.buildImage_(this.selected_);
    }
  }
};

cameraGrid.CameraGrid.prototype.buildCells_ = function() {
  this.cells_ = [];
  for (var i = 0; i < this.sourceUrls_.length; i++) {
    var cell = document.createElement('cameraGridCell');
    this.cells_.push(cell);
  }
};

cameraGrid.CameraGrid.prototype.addCSSClass_ = function(node, className) {
  var classes = node.className.split(' ').filter(function(className) { return className; });
  if (classes.indexOf(className) != -1) {
    // Already has class.
    return;
  }
  classes.push(className);
  node.className = classes.join(' ');
}

cameraGrid.CameraGrid.prototype.removeCSSClass_ = function(node, className) {
  var classes = node.className.split(' ').filter(function(className) { return className; });
  var i = classes.indexOf(className);
  if (i == -1) {
    // Already doesn't have class.
    return;
  }
  delete classes[i];
  node.className = classes.join(' ');
}

cameraGrid.CameraGrid.prototype.buildStylesheet_ = function() {
  var style = document.createElement('style');
  document.head.appendChild(style);

  style.sheet.insertRule('cameraGridRow {}', 0);
  this.rowHeightRule_ = style.sheet.cssRules[0];
  style.sheet.insertRule('cameraGridCell {}', 0);
  this.cellWidthRule_ = style.sheet.cssRules[0];
  style.sheet.insertRule('cameraGridImgContainer img {}', 0);
  this.imageScaleRule_ = style.sheet.cssRules[0];
  style.sheet.insertRule('cameraGridCell.cameraGridFullScreen cameraGridImgContainer img {}', 0);
  this.containerImageScaleRule_ = style.sheet.cssRules[0];

  style.sheet.insertRule('cameraGridRow { display: block; width: 100% }', 0);
  style.sheet.insertRule('cameraGridCell { display: inline-block; height: 100%; position: relative }', 0);
  style.sheet.insertRule('cameraGridImgContainer { position: absolute; top: 0; left: 0; bottom: 0; right: 0; text-align: center }', 0);
  style.sheet.insertRule('cameraGridImgContainer img { max-height: 100%; max-width: 100% }', 0);
  style.sheet.insertRule('.cameraGridContainer { font-size: 0; text-align: center; -webkit-user-select: none; -moz-user-select: none; }', 0);
  style.sheet.insertRule('cameraGridCell.cameraGridFullScreen { position: static }', 0);
  style.sheet.insertRule('cameraGridCell.cameraGridFullScreen cameraGridImgContainer { z-index: 1 }', 0);

  this.addCSSClass_(this.container_, 'cameraGridContainer');
};

cameraGrid.CameraGrid.prototype.calculateGrid_ = function() {
  var containerWidth = this.container_.offsetWidth;
  var containerHeight = this.container_.offsetHeight;
  var numTiles = this.sourceUrls_.length;

  var scaleFactor = ((containerHeight / this.tileScaleHeight_)
                     / (containerWidth / this.tileScaleWidth_));

  var gridHeight = Math.sqrt(scaleFactor * numTiles);
  var gridWidth = Math.sqrt(numTiles / scaleFactor);

  var gridOptions = [
    [ Math.ceil(gridWidth), Math.floor(gridHeight) ],
    [ Math.floor(gridWidth), Math.ceil(gridHeight) ],
    [ Math.ceil(gridWidth), Math.ceil(gridHeight) ],
  ];

  // Check all possible options.
  // We are optimizing for several dimensions (decreasing priority):
  // 1) Be able to fit all the tiles.
  // 2) Maximum scale for an image in each cell.
  // 3) Minimize number of cells.
  var minCells = Number.MAX_VALUE;
  var maxScale = 0.0;
  var chosenHeight, chosenWidth, chosenConstraint;
  for (var i = 0; i < gridOptions.length; i++) {
    var gridOption = gridOptions[i];
    var numCells = gridOption[0] * gridOption[1];
    if (numCells < numTiles) {
      // Can't fit all the tiles in (we've rounded down too far).
      continue;
    }
    var widthScale = (containerWidth / gridOption[0]) / this.tileScaleWidth_;
    var heightScale = (containerHeight / gridOption[1]) / this.tileScaleHeight_;
    var scale, constraint;
    if (widthScale < heightScale) {
      scale = widthScale;
      constraint = 'width';
    } else {
      scale = heightScale;
      constraint = 'height';
    }
    if (scale < maxScale) {
      // This would make cells smaller than another viable solution.
      continue;
    }
    if (scale == maxScale && numCells > minCells) {
      // Same cell size as another viable solution, but ours has more cells.
      continue;
    }
    chosenWidth = gridOption[0];
    chosenHeight = gridOption[1];
    chosenConstraint = constraint;
    minCells = numCells;
    maxScale = scale;
  }

  return {
    gridWidthCells: chosenWidth,
    gridHeightCells: chosenHeight,
    constraint: chosenConstraint,
    containerConstraint: scaleFactor > 1 ? 'width' : 'height',
    cellWidthPx: this.tileScaleWidth_ * maxScale,
    cellHeightPx: this.tileScaleHeight_ * maxScale,
  };
};

cameraGrid.CameraGrid.prototype.findMinimumResolution_ = function(tileWidth, tileHeight) {
  for (var i = 0; i < this.resolutions_.length; i++) {
    var resolution = this.resolutions_[i];
    if (i + 1 < this.resolutions_.length &&
        (resolution[0] < tileWidth && resolution[1] < tileHeight)) {
      continue;
    }
    return {
      imgWidthPx: resolution[0],
      imgHeightPx: resolution[1],
    };
  }
};

cameraGrid.CameraGrid.prototype.deletePreviousSiblings_ = function(element) {
  while (element.previousSibling) {
    element.parentNode.removeChild(element.previousSibling);
  }
};

cameraGrid.CameraGrid.prototype.buildImage_ = function(index) {
  var sourceUrl = this.sourceUrls_[index];
  var imgUrl = (
      (this.scanning_ || index == this.selected_) ?
      this.getUrl_(sourceUrl, this.containerImgWidthPx_, this.containerImgHeightPx_) :
      this.getUrl_(sourceUrl, this.imgWidthPx_, this.imgHeightPx_));
  var cell = this.cells_[index];

  // cell > imgContainer(s) > img
  // Last imgContainer will eventually win.
  if (cell.lastChild && cell.lastChild.firstChild.src == imgUrl) {
    // We'd be re-adding the same image; skip.
    return;
  }

  var img = document.createElement('img');
  img.src = imgUrl;
  var imgContainer = document.createElement('cameraGridImgContainer');
  imgContainer.addEventListener('click', this.setSelected_.bind(this, index), false);
  img.addEventListener('load', this.deletePreviousSiblings_.bind(this, imgContainer), false);
  imgContainer.appendChild(img);
  cell.appendChild(imgContainer);
};

cameraGrid.CameraGrid.prototype.buildImages_ = function() {
  for (var i = 0; i < this.sourceUrls_.length; i++) {
    this.buildImage_(i);
  }
};

cameraGrid.CameraGrid.prototype.buildGrid_ = function() {
  this.container_.innerHTML = '';

  this.rowHeightRule_.style.height = 100 / this.gridHeightCells_ + '%';
  this.cellWidthRule_.style.width = 100 / this.gridWidthCells_ + '%';

  var i = 0;
  for (var y = 0; y < this.gridHeightCells_; y++) {
    var row = document.createElement('cameraGridRow');
    for (var x = 0; x < this.gridWidthCells_; x++) {
      if (i < this.cells_.length) {
        var cell = this.cells_[i];
        row.appendChild(cell);
        i++;
      }
    }
    this.container_.appendChild(row);
  }
};

cameraGrid.CameraGrid.prototype.setUpscaleRule_ = function(constraint, rule) {
  if (constraint == 'height') {
    rule.style.minWidth = 0;
    rule.style.minHeight = '100%';
  } else {
    rule.style.minWidth = '100%';
    rule.style.minHeight = 0;
  }
};

cameraGrid.CameraGrid.prototype.rebuildIfNeeded_ = function() {
  var grid = this.calculateGrid_();
  var resolution = this.findMinimumResolution_(grid.cellWidthPx, grid.cellHeightPx);
  var containerResolution = this.findMinimumResolution_(this.container_.offsetWidth, this.container_.offsetHeight);

  if (grid.constraint != this.constraint_) {
    this.constraint_ = grid.constraint;
    this.setUpscaleRule_(this.constraint_, this.imageScaleRule_);
  }

  if (grid.containerConstraint != this.containerConstraint_) {
    this.containerConstraint_ = grid.containerConstraint;
    this.setUpscaleRule_(this.containerConstraint_, this.containerImageScaleRule_);
  }

  if (resolution.imgWidthPx != this.imgWidthPx_ ||
      resolution.imgHeightPx != this.imgHeightPx_) {
    // Need to recache images.
    this.imgWidthPx_ = resolution.imgWidthPx;
    this.imgHeightPx_ = resolution.imgHeightPx;
    this.buildImages_();
  }

  if (containerResolution.imgWidthPx != this.containerImgWidthPx_ ||
      containerResolution.imgHeightPx != this.containerImgHeightPx_) {
    this.containerImgWidthPx_ = containerResolution.imgWidthPx;
    this.containerImgHeightPx_ = containerResolution.imgHeightPx;
    if (this.selected_ != null) {
      this.buildImage_(this.selected_);
    }
  }

  if (grid.gridWidthCells != this.gridWidthCells_ ||
      grid.gridHeightCells != this.gridHeightCells_) {
    this.gridWidthCells_ = grid.gridWidthCells;
    this.gridHeightCells_ = grid.gridHeightCells;
    this.buildGrid_();
  }
};

cameraGrid.CameraGrid.prototype.onKeyPress_ = function(e) {
  var character = String.fromCharCode(e.charCode);
  switch (character) {
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
    case '0':
      var index = e.charCode - '1'.charCodeAt(0);
      if (index == -1) {
        index = 10;
      }
      if (index < this.cells_.length) {
        this.setSelectedNoScan_(index);
      }
      break;
    case 's':
      if (this.scanning_ && this.selected_ != null) {
        // Toggle off
        this.setSelectedNoScan_(this.selected_);
        return;
      }
      this.scanning_ = true;
      if (this.selected_ == null) {
        this.setSelected_(0);
      }
      break;
    case ' ':
      this.scanning_ = !this.scanning_;
      break;
  }
};

cameraGrid.CameraGrid.prototype.scanLeft_ = function() {
  this.setSelected_(this.selected_ > 0 ? this.selected_ - 1 : this.cells_.length - 1);
};

cameraGrid.CameraGrid.prototype.scanRight_ = function() {
  this.setSelected_((this.selected_ + 1) % this.cells_.length);
};

cameraGrid.CameraGrid.prototype.onKeyDown_ = function(e) {
  switch (e.keyCode) {
    case 27: // Esc
      if (this.selected_ != null) {
        // Toggle selected feed off.
        this.setSelectedNoScan_(this.selected_);
      }
      break;
    case 37: // Left arrow
      if (this.selected_ != null) {
        this.scanLeft_();
        this.disableScanning_();
      }
      break;
    case 39: // Right arrow
      if (this.selected_ != null) {
        this.scanRight_();
        this.disableScanning_();
      }
      break;
  }
};

cameraGrid.CameraGrid.prototype.onScanTimer_ = function() {
  if (!this.scanning_ || this.selected_ == null) {
    return;
  }
  this.scanRight_();
};