var startTime = new Date().getTime();

var fs = require("fs");
var pngjs = require("pngjs").PNG;

/**
 *
 */
var Pixels = function() {};

/**
 *
 */
Pixels.prototype = {
    source: null,
    confirm: null,
    target: null,
    result: {},
};

/**
 * Heavy lifting done here.
 */
Pixels.prototype.repalettize = function() {
    // Indices is count from 0 to LxW, used to reference pixels in the tgtPalette, which are 8? bits wide.
    var indices = [];
    for (var y = 0; y < P.target.height; y++) {
        for (var x = 0; x < P.target.width; x++) {
            indices.push((P.target.width * y + x) << 2);
        }
    }

    var len = indices.length;
    P.result.asBuffer = new Buffer(P.target.height * P.target.width * 4);
    P.result.asArray = [];

    var i, ii;

    while (len) {
        i = Math.floor(Math.random() * len);
        ii = indices[i];

        // Find RGB in source, no need for alpha channel.
        matchIndex = P.findMatch(
            zeropad(P.target.asBuffer[ii], 3) +
            zeropad(P.target.asBuffer[ii + 1], 3) +
            zeropad(P.target.asBuffer[ii + 2], 3)
        );

        matchRgb = P.source.asArray[matchIndex];

        P.result.asArray.push(matchRgb);

        P.result.asBuffer[ii] = matchRgb.substr(0, 3) * 1;
        P.result.asBuffer[ii + 1] = matchRgb.substr(3, 3) * 1;
        P.result.asBuffer[ii + 2] = matchRgb.substr(6, 3) * 1;
        P.result.asBuffer[ii + 3] = 255;

        indices.splice(i, 1);
        P.source.asArray.splice(matchIndex, 1);
        len = indices.length;
    }

    var resultImg = new pngjs({
        filterType: 4
    });

    resultImg.data = P.result.asBuffer;
    resultImg.width = P.target.width;
    resultImg.height = P.target.height;
    resultImg.pack().pipe(fs.createWriteStream('result.png'));

    var endTime = new Date().getTime();
    console.log((endTime - startTime) / 1000 + " seconds, confirming");

    P.doConfirm(P.confirm.asArray, P.result.asArray) ?
        console.log('OK - Source array and result array match.') :
        console.log('ERROR! Source array and result array do not match!');
};

/**
 * Slightly modified binary search tree.
 */
Pixels.prototype.findMatch = function(rgb0) {
    var start = 0;
    var end = P.source.asArray.length;
    var mid;

    while (start + 1 < end) {
        mid = Math.floor((end - start) / 2 + start);
        if (P.source.asArray[mid] < rgb0) {
            start = mid;
        }
        else {
            end = mid;
        }
    }

    return start;
};

/**
 *
 */
Pixels.prototype.doConfirm = function(arr1, arr2) {
    var len1 = arr1.length;
    var len2 = arr2.length;

    if (len1 !== len2) {
        return false;
    }

    arr1.sort();
    arr2.sort();

    for (var i = 0; i < len1; i++) {
        if (arr1[i] !== arr2[i]) {
            return false;
        }
    }

    return true;
};

/**
 * Reads an image from a path, generates required information, and passes information to callback.
 */
Pixels.prototype.read = function(path0, callback0) {
    var width = 0;
    var height = 0;
    var asBuffer = null;
    var asArray = null;

    fs.createReadStream(path0).pipe(new pngjs({ filterType: 4 }))
    .on('metadata', function(meta0) {
        width = meta0.width;
        height = meta0.height;
    })
    .on('parsed', function(buffer0) {
        var x, y, i;
        var arr = [];
        for (y = 0; y < height; y++) {
            for (x = 0; x < width; x++) {
                i = y * width + x << 2;

                arr.push(zeropad(buffer0[i], 3) + zeropad(buffer0[i + 1], 3) + zeropad(buffer0[i + 2], 3));
            }
        }

        callback0({
            width: width,
            height: height,
            asBuffer: buffer0,
            asArray: arr,
        });
    });
};

/**
 * sprintf implementation to ensure 9-digit pixels for sorting.
 */
var zeropad = function(str0, len0) {
    str0 = str0.toString();
    while (str0.length < len0) {
        str0 = "0" + str0;
    }
    return str0;
};

/**
 * Ansynchronous file reads will execute and call this function. After they're all finished, the processing can begin.
 */
var filesRead = 0;
var thenContinue = function(data0) {
    filesRead++;

    if (filesRead === 3) {
        P.source.asArray.sort();
        P.repalettize();
    }
}

/**
 * Information for the source image, where the pixels are taken from.
 */
var thenSaveSource = function(obj0) {
    P.source = obj0;
    thenContinue();
}

/**
 * A copy of the source data used after processing to ensure source pixels match result pixels.
 */
var thenSaveConfirm = function(obj0) {
    P.confirm = obj0;
    thenContinue();
}

/**
 * Information for the target images, which the pixels are matched to.
 */
var thenSaveTarget = function(obj0) {
    P.target = obj0;
    thenContinue();
}

//===== Entry point
var P = new Pixels();
P.read('scream.png', thenSaveSource);
P.read('scream.png', thenSaveConfirm);
P.read('starry.png', thenSaveTarget);