'use strict';

var index = require('../../utils/es/index.js');

var blit = (() => ({
  /**
   * Blits a source image on to this image
   * @param {Jimp} src the source Jimp instance
   * @param {number} x the x position to blit the image
   * @param {number} y the y position to blit the image
   * @param {number} srcx (optional) the x position from which to crop the source image
   * @param {number} srcy (optional) the y position from which to crop the source image
   * @param {number} srcw (optional) the width to which to crop the source image
   * @param {number} srch (optional) the height to which to crop the source image
   * @param {function(Error, Jimp)} cb (optional) a callback for when complete
   * @returns {Jimp} this for chaining of methods
   */
  blit(src, x, y, srcx, srcy, srcw, srch, cb) {
    if (!(src instanceof this.constructor)) {
      return index.throwError.call(this, "The source must be a Jimp image", cb);
    }
    if (typeof x !== "number" || typeof y !== "number") {
      return index.throwError.call(this, "x and y must be numbers", cb);
    }
    if (typeof srcx === "function") {
      cb = srcx;
      srcx = 0;
      srcy = 0;
      srcw = src.bitmap.width;
      srch = src.bitmap.height;
    } else if (typeof srcx === typeof srcy && typeof srcy === typeof srcw && typeof srcw === typeof srch) {
      srcx = srcx || 0;
      srcy = srcy || 0;
      srcw = srcw || src.bitmap.width;
      srch = srch || src.bitmap.height;
    } else {
      return index.throwError.call(this, "srcx, srcy, srcw, srch must be numbers", cb);
    }

    // round input
    x = Math.round(x);
    y = Math.round(y);

    // round input
    srcx = Math.round(srcx);
    srcy = Math.round(srcy);
    srcw = Math.round(srcw);
    srch = Math.round(srch);
    const maxWidth = this.bitmap.width;
    const maxHeight = this.bitmap.height;
    const baseImage = this;
    src.scanQuiet(srcx, srcy, srcw, srch, function (sx, sy, idx) {
      const xOffset = x + sx - srcx;
      const yOffset = y + sy - srcy;
      if (xOffset >= 0 && yOffset >= 0 && maxWidth - xOffset > 0 && maxHeight - yOffset > 0) {
        const dstIdx = baseImage.getPixelIndex(xOffset, yOffset);
        const src = {
          r: this.bitmap.data[idx],
          g: this.bitmap.data[idx + 1],
          b: this.bitmap.data[idx + 2],
          a: this.bitmap.data[idx + 3]
        };
        const dst = {
          r: baseImage.bitmap.data[dstIdx],
          g: baseImage.bitmap.data[dstIdx + 1],
          b: baseImage.bitmap.data[dstIdx + 2],
          a: baseImage.bitmap.data[dstIdx + 3]
        };
        baseImage.bitmap.data[dstIdx] = (src.a * (src.r - dst.r) - dst.r + 255 >> 8) + dst.r;
        baseImage.bitmap.data[dstIdx + 1] = (src.a * (src.g - dst.g) - dst.g + 255 >> 8) + dst.g;
        baseImage.bitmap.data[dstIdx + 2] = (src.a * (src.b - dst.b) - dst.b + 255 >> 8) + dst.b;
        baseImage.bitmap.data[dstIdx + 3] = this.constructor.limit255(dst.a + src.a);
      }
    });
    if (index.isNodePattern(cb)) {
      cb.call(this, null, this);
    }
    return this;
  }
}));

module.exports = blit;
