/// <reference path="PAImage.ts" />
/// <reference path="PathAnimator.ts" />

/**
 * Functionality to handle browser io
 */
class BrowserHandler {
  /**
   * Drop area for file uploads
   */
  private dropArea: HTMLElement;
  /**
   * Main instace of application
   */
  private instance: PathAnimator;
  /**
   * Indicator flag if the drop area is highlighted
   */
  private isHighlighted: boolean;
  /**
   * Algrothm selection dropdown element
   */
  private algorithmElem: HTMLSelectElement;

  /**
   * Constructor
   */
  constructor(instance: PathAnimator) {
    this.instance = instance;
    this.isHighlighted = false;
    this.dropArea = document.getElementById('drop-area');
    ['dragenter', 'dragover', 'dragleave', 'drop'].forEach(eventName => {
      this.dropArea.addEventListener(eventName, this.preventDefaults, false);
    });
    this.dropArea.addEventListener('dragover', this.dragOver.bind(this), false)
    this.dropArea.addEventListener('drop', this.dragDrop.bind(this), false)
    this.algorithmElem = <HTMLSelectElement>document.getElementById("alsel");
    this.algorithmElem.addEventListener("change", this.algorithmChanged.bind(this));
    this.algorithmChanged();
    document.getElementById("fileElem").addEventListener("change", this.handleSourceFile.bind(this));
    document.getElementById("run").addEventListener("click", this.run.bind(this));
    document.getElementById("save").addEventListener("click", this.save.bind(this));
  }

  /**
   * Prevent default action for given event
   * @param e incoming event
   */
  preventDefaults (e: Event) {
    e.preventDefault()
    e.stopPropagation()
  }

  /**
   * Event when something is dragged over out drag/drop area
   */
  dragOver() {
    if (!this.isHighlighted) {
      this.dropArea.classList.add("highlight");
      this.isHighlighted = true;
    }
  }

  /**
   * Something was droppen on our drag/drop area
   * @param e Incoming event
   */
  dragDrop(e: DragEvent) {
    let dt = e.dataTransfer
    let files = dt.files
    this.setSourceFile(files);
    if (this.isHighlighted) {
      this.dropArea.classList.remove("highlight");
      this.isHighlighted = false;
    }
  }

  /**
   * A file was selected via upload file button
   * @param e: Incoming event
   */
  handleSourceFile(e: Event) {
    var fs = <HTMLInputElement>e.target;
    this.setSourceFile(fs.files);
  }

  /**
   * Set the source file and trigger processing with given file list. Only the first file will be used
   * @param fileList the file list generated by the browser on drop or file selection
   */
  setSourceFile(fileList: FileList) {
    // we only support one image
    if (fileList.length > 0) {
      var file = fileList.item(0);
      this.processFile(file);
    }
  }

  /**
   * Process (load) given file, calls fileLoaded when read
   * @param file file to process
   */
  processFile(file: File) {
    let reader = new FileReader()
    reader.readAsDataURL(file)
    reader.addEventListener("loadend", this.fileLoaded.bind(this));
  }

  /**
   * The file loading from processFile has been finished.
   * fileParsed will be called after image was rendered
   * @param e progress event (normally file loaded)
   */
  fileLoaded(e:ProgressEvent) {
    if (e.type === "loadend") { // sanity check
      var reader = <FileReader>e.target;
      let img = <HTMLImageElement>document.createElement('img');
      img.src = <string>reader.result;
      img.addEventListener("load", this.fileParsed.bind(this));
    }
  }

  /**
   * The image data from file is ready.
   * The canvas is filled with the image and the pixel data is extracted
   * and set for the main processing instance.
   * @param e incoming event
   */
  fileParsed(e: Event) {
    var img = <HTMLImageElement>e.target;
    const canvas = <HTMLCanvasElement>document.getElementById("inputcanvas");
    const ctx = canvas.getContext('2d');
    canvas.width = img.width;
    canvas.height = img.height;
    ctx.drawImage(img, 0, 0);
    const rgba = ctx.getImageData(0, 0, img.width, img.height).data;
    var image = new PAImage(img.width, img.height, 4);
    image.setPixels(rgba);
    this.instance.setInputImage(image);
    document.getElementById("run").classList.remove("hidden");
  }

  /**
   * The algrothm select dropdown was changed.
   * Show and hide algrothm specific inputs
   */
  algorithmChanged() {
    var div = document.getElementById("algorithm").getElementsByTagName("div");
    for (var i = 0; i < div.length; ++i) {
      if (div[i].hasAttribute("id")) {
        if (div[i].getAttribute("id") === this.algorithmElem.value) {
          div[i].classList.remove("hidden");
        } else {
          div[i].classList.add("hidden");
        }
      }
    }
  }

  /**
   * The run button was pressed.
   * The algorithm specific setting are collected and an async timeout call is triggered to run the PathAnimator run function
   * @param e incoming Event
   */
  run(e: Event) {
    e.preventDefault();
    e.stopPropagation();
    // collect algorithm param
    var config = {
      algorithm: this.algorithmElem.value
    }
    var div = document.getElementById(this.algorithmElem.value);
    var fields = div.getElementsByTagName("input");
    for (var i = 0; i < fields.length; ++i) {
      config[fields[i].getAttribute("name")] = fields[i].value;
    }
    document.getElementById("output").classList.add("running");
    document.getElementById("run").classList.add("hidden");
    document.getElementById("save").classList.add("hidden");
    window.setTimeout(this.instance.run.bind(this.instance, config), 10);
  }

  /**
   * Clear logging output
   */
  clearOutput() {
    document.getElementById("output").innerHTML = "";
  }

  /**
   * Append message to logging output
   * @param data string to display
   */
  appendOutput(data: string) {
    var p = document.createElement("p");
    p.innerText = data;
    document.getElementById("output").append(p);
  }

  /**
   * Replace old logging output by new data
   * @param data new string to display
   */
  replaceOutput(data: string) {
    this.clearOutput();
    this.appendOutput(data);
  }

  /**
   * Processing has completed
   * Show buttons and hide running animation
   */
  completed() {
    document.getElementById("output").classList.remove("running");
    document.getElementById("run").classList.remove("hidden");
    document.getElementById("save").classList.remove("hidden");
  }

  /**
   * Show output of the algorithm
   * The Canvas is filled with the output of the algorithm.
   * Preprocessing is needed, the algorithm exports RGB data, the canvas wants RGBA.
   * @param image image to show
   */
  showOutput(image: PAImage) {
    var output = <HTMLCanvasElement>document.getElementById("outputcanvas");
    output.classList.remove("hidden");
    var width = image.getWidth();
    var height = image.getHeight();
    output.width = width;
    output.height = height;
    var end =  width* height * 3;
    const ctx = output.getContext('2d');
    var outCanvas = ctx.getImageData(0,0, width, height);
    const outCanvasPixel = outCanvas.data;
    var imagePixel = image.getPixels8();
    var offsetCanvas = 0;
    var offsetImage = 0;
    for (var i = 0; i < end; ++i) {
      outCanvasPixel[offsetCanvas++] = imagePixel[offsetImage++];
      outCanvasPixel[offsetCanvas++] = imagePixel[offsetImage++];
      outCanvasPixel[offsetCanvas++] = imagePixel[offsetImage++];
      outCanvasPixel[offsetCanvas++] = 255;
    }
    ctx.putImageData(outCanvas, 0, 0);
  }

  /**
   * User has clicked the save button
   * Trigger download
   * @param e incoming Event
   */
  save(e: Event) {
    var output = <HTMLCanvasElement>document.getElementById("outputcanvas");
    var dataURL = output.toDataURL("image/png");
    var a = document.createElement('a');
    a.href = dataURL;
    a.download = "output.png";
    document.body.appendChild(a);
    a.click();
  }
}