import { asArray as ol_color_asArray } from 'ol/color.js'

/** Helper for loading BIL-32 (Band Interleaved by Line) image
 * @param {string} src
 * @param {function} onload a function that takes a Float32Array and a ol.size.Size (array size)
 * @param {function} onerror
 * @private
 */
var ol_ext_imageLoader_loadBILImage = function(src, onload, onerror) {
  var size = [
    parseInt(src.replace(/.*WIDTH=(\d*).*/i,'$1')), 
    parseInt(src.replace(/.*HEIGHT=(\d*).*/i,'$1'))
  ];
  var xhr = new XMLHttpRequest();
  xhr.responseType = 'blob';
  xhr.addEventListener('loadend', function () {
    var resp = this.response;
    if (resp !== undefined) {
      const reader = new FileReader();
      // Get as array
      reader.addEventListener('loadend', (e) => {
        var data = new Float32Array(e.target.result);
        onload(data, size);
      });
      // Start reading the blob
      reader.readAsArrayBuffer(resp);
      // tile.getImage().src = URL.createObjectURL(blob);
    } else {
      onerror();
    }
  });
  xhr.addEventListener('error', function () {
    onerror();
  });
  xhr.open('GET', src);
  xhr.send();
};

/** Helper for loading image
 * @param {string} src
 * @param {function} onload a function that takes a an image and a ol.size.Size
 * @param {function} onerror
 * @private
 */
var ol_ext_imageLoader_loadImage = function(src, onload, onerror) {
  var xhr = new XMLHttpRequest();
  xhr.responseType = 'blob';
  xhr.addEventListener('loadend', function () {
    var resp = this.response;
    if (resp !== undefined) {
      var img = new Image();
      img.onload = function() {
        onload(img, [img.naturalWidth, img.naturalHeight]);
      }
      img.src = URL.createObjectURL(resp);
    } else {
      onerror();
    }
  });
  xhr.addEventListener('error', function () {
    onerror();
  });
  xhr.open('GET', src);
  xhr.send();
};

/** Get a TileLoadFunction to transform tiles images
 * @param {function} setPixel a function that takes a Uint8ClampedArray and the pixel position to transform
 * @returns {function} an ol/Tile~LoadFunction
 */
var ol_ext_imageLoader_pixelTransform = function(setPixel) {
  return function(tile, src) {
    ol_ext_imageLoader_loadImage(
      src, 
      function(img, size) {
        var canvas = document.createElement('canvas');
        canvas.width = size[0];
        canvas.height = size[1];
        var ctx = canvas.getContext('2d');
        ctx.drawImage(img, 0, 0);
        var imgData = ctx.getImageData(0, 0, size[0], size[1]);
        var pixels = imgData.data;
        for (var i = 0; i < pixels.length; i += 4) {
          setPixel(pixels, i, size);
        }
        ctx.putImageData(imgData, 0, 0);
        tile.setImage(canvas);
      },
      function() {
        tile.setState(3);
      }
    );
  }
};

/** Get a TileLoadFunction to transform tiles into grayscale images
 * @returns {function} an ol/Tile~LoadFunction
 */
var ol_ext_imageLoader_grayscale = function() {
  return ol_ext_imageLoader_pixelTransform(function(pixels, i) {
    pixels[i] = pixels[i + 1] = pixels[i + 2] = parseInt(3*pixels[i] + 4*pixels[i + 1] + pixels[i + 2] >>> 3);
  })
};

/** Get a TileLoadFunction to turn color or a color range transparent
 * @param {ol.color.Color|Array<ol.color.Color>} colors color or color range to turn transparent
 * @returns {function} an ol/Tile~LoadFunction
 */
var ol_ext_imageLoader_transparent = function(colors) {
  var color1, color2;
  if (colors instanceof Array) {
    color1 = colors[0];
    color2 = colors[1];
  }
  var color = color1 = ol_color_asArray(color1);
  if (!color2) {
    return ol_ext_imageLoader_pixelTransform(function(pixels, i) {
      if (pixels[i]===color[0] && pixels[i+1]===color[1] && pixels[i+2]===color[2]) {
        pixels[i+3] = 0;
      }
    })
  } else {
    color2 = ol_color_asArray(color2);
    color = [Math.min(color1[0], color2[0]), Math.min(color1[1], color2[1]), Math.min(color1[2], color2[2])];
    color2 = [Math.max(color1[0], color2[0]), Math.max(color1[1], color2[1]), Math.max(color1[2], color2[2])];
    return ol_ext_imageLoader_pixelTransform(function(pixels, i) {
      if (pixels[i]>=color1[0] && pixels[i]<=color2[0] 
        && pixels[i+1]>=color[1] && pixels[i+1]<=color2[1] 
        && pixels[i+2]>=color[2] && pixels[i+2]<=color2[2]) {
        pixels[i+3] = 0;
      }
    })
  }
};

/** Returns an Imageloader function to load an x-bil-32 image as sea level map 
 * to use as a ol/Tile~LoadFunction or ol/Image~LoadFunction
 * @param { number } level
 * @param {*} options
 *  @param { ol.Color } [options.color] fill color
 *  @param { boolean } [options.opacity=true] smooth color on border
 *  @param { number } [options.minValue=-Infinity] minimum level value
 * @returns {function} an ol/Tile~LoadFunction
 */
var ol_ext_imageLoader_seaLevelMap = function(level, options) {
  options = options || {};
  var h0 = Math.max(level + .01, .01);
  var c = options.color ? ol_color_asArray(options.color) : [135,203,249];
  var min = typeof(options.minValue) === 'number' ? options.minValue : -Infinity;
  var opacity = options.opacity!==false;
  return ol_ext_imageLoader_elevationMap(function(h) {
    if (h < h0 && h > min) {
      return [c[0], c[1], c[2], opacity ? 255 * (h0-h) / h0 : 255];
    } else {
      return [0,0,0,0];
    }
  })
};

/** Shaded relief ? not/bad working yet...
 * @returns {function} an ol/Tile~LoadFunction
 * @private
 */
var ol_ext_imageLoader_shadedRelief = function() {
  var sunElev = Math.PI / 4;
  var sunAzimuth = 2*Math.PI - Math.PI / 4;

  return function (tile, src) {
    ol_ext_imageLoader_loadBILImage(
      src,
      function(data, size) {
        var canvas = document.createElement('canvas');
        var ctx = canvas.getContext('2d');
        var width = canvas.width = size[0];
        var height = canvas.height = size[1];
        var imgData = ctx.getImageData(0, 0, width, height);
        var pixels = imgData.data;

        function getIndexForCoordinates(x, y) {
          return x + y*width;
        }
        for (var x=0; x<width; x++) for(var y=0; y<height; y++) {
          var top = getIndexForCoordinates(x,Math.max(0,y-1))
          var left = getIndexForCoordinates(Math.max(0,x-1),y);
          var right = getIndexForCoordinates(Math.min(width-1,x+1),y);
          var bottom = getIndexForCoordinates(x,Math.min(height,y+1))
          // get slope values
          var topValue = data[top];
          var leftValue = data[left];
          var rightValue = data[right];
          var bottomValue = data[bottom];
          var slx = (rightValue - leftValue)/3;
          var sly = ( bottomValue - topValue )/3;
          var sl0 = Math.sqrt( slx*slx + sly*sly );
          
          // get aspect
          var phi = Math.acos( slx/sl0 );
          if ( sl0 == 0 ) {
            phi = 0;
          }
          var azimuth = 0;
          if ( slx > 0 ) {
            if ( sly > 0 ) azimuth = phi + 1.5*Math.PI;
            else if ( sly < 0 ) azimuth = 1.5*Math.PI - phi;
            else phi = 1.5*Math.PI;
          } else if ( slx < 0 ){
            if ( sly < 0 ) azimuth = phi + .5*Math.PI;
            else if ( sly > 0 ) azimuth = .5*Math.PI - phi;
            else azimuth = .5*Math.PI;
          } else {
            if ( sly < 0 ) azimuth = Math.PI;
            else if ( sly > 0 ) azimuth = 0;
          }
          
          // get luminance
          var lum = Math.cos( azimuth - sunAzimuth )*Math.cos( Math.PI*.5 - Math.atan(sl0) )*Math.cos( sunElev ) +  Math.sin( Math.PI*.5 - Math.atan(sl0) )*Math.sin( sunElev );
          
          if (lum<0) lum = 0;
          lum = Math.sqrt(lum*.8 + .5);
          var p = getIndexForCoordinates(x,y) * 4;
          pixels[p] = pixels[p+1] = pixels[p+2] = 0;
          pixels[p+3] = 255 - lum*255;
        }
        ctx.putImageData(imgData, 0, 0);
        tile.setImage(canvas);
      },
      function () {
        tile.setState(3);
      }
    )
  };
};

/** Get a TileLoadFunction to load an x-bil-32 image as elevation map (ie. pixels colors codes elevations as terrain-RGB)
 * If getPixelColor is not define pixel store elevation as rgb, use {@link ol_ext_getElevationFromPixel} to get elevation from pixel
 * @param {function} [getPixelColor] a function that taket an elevation and return a color array [r,g,b,a], default store elevation as terrain-RGB
 * @returns {function} an ol/Tile~LoadFunction
 */
var ol_ext_imageLoader_elevationMap = function(getPixelColor) {
  if (typeof(getPixelColor) !== 'function') getPixelColor = ol_ext_getPixelFromElevation;
  return function (tile, src) {
    ol_ext_imageLoader_loadBILImage(
      src,
      function(data, size) {
        var canvas = document.createElement('canvas');
        var ctx = canvas.getContext('2d');
        canvas.width = size[0];
        canvas.height = size[1];
        var imgData = ctx.getImageData(0, 0, size[0], size[1]);
        var pixels = imgData.data;
        for (var i=0; i<data.length; i++) {
          var p = getPixelColor(data[i]);
          pixels[4*i] = p[0];
          pixels[4*i+1] = p[1];
          pixels[4*i+2] = p[2];
          pixels[4*i+3] = p[3];
        }
        ctx.putImageData(imgData, 0, 0);
        tile.setImage(canvas);
      },
      function () {
        tile.setState(3);
      }
    )
  };
};

/** Convert elevation to pixel as terrain-RGB
 * Encode elevation data in raster tiles
 * - max deep watter trench min > -12000 m
 * - 2 digits (0.01 m)
 * @param {number} height elevation
 * @returns {Array<number>} pixel value
 */
var ol_ext_getPixelFromElevation =  function(height) {
  var h = Math.round(height*100 + 1200000);
  var pixel = [
    h >> 16, 
    (h % 65536) >> 8, 
    h % 256, 
    255
  ];
  return pixel;
};

/** Convert pixel (terrain-RGB) to elevation 
 * @see ol_ext_getPixelFromElevation
 * @param {Array<number>} pixel the pixel value
 * @returns {number} elevation
 */
var ol_ext_getElevationFromPixel = function(pixel) {
  // return -10000 + (pixel[0] * 65536 + pixel[1] * 256 + pixel[2]) * 0.01;
  return -12000 + ((pixel[0] << 16) + (pixel[1] << 8) + pixel[2]) * 0.01;
};

export { ol_ext_imageLoader_loadBILImage as loadBILImage }
export { ol_ext_imageLoader_seaLevelMap as seaLevelMap, ol_ext_imageLoader_elevationMap as elevationMap }
export { ol_ext_getPixelFromElevation as getPixelFromElevation, ol_ext_getElevationFromPixel as getElevationFromPixel }
export { ol_ext_imageLoader_grayscale as grayscale, ol_ext_imageLoader_transparent as transparent }
export { ol_ext_imageLoader_pixelTransform as pixelTransform }

export { ol_ext_imageLoader_shadedRelief }