#!/usr/bin/env python

# Generates (or updates) a unit test image mask, which is used to specify whether
# a pixel in the control image should be checked (black pixel in mask) or not (white
# pixel in mask). For non black or white pixels, the pixels lightness is used to
# specify a maximum delta for each color component

import os
import sys
import argparse
from PyQt4.QtGui import QImage, QColor, qRed, qBlue, qGreen, qAlpha, qRgb
import struct
import urllib2
import glob


def error(msg):
    print msg
    sys.exit(1)


def colorDiff(c1, c2):
    redDiff = abs(qRed(c1) - qRed(c2))
    greenDiff = abs(qGreen(c1) - qGreen(c2))
    blueDiff = abs(qBlue(c1) - qBlue(c2))
    alphaDiff = abs(qAlpha(c1) - qAlpha(c2))
    return max(redDiff, greenDiff, blueDiff, alphaDiff)


def imageFromPath(path):
    if (path[:7] == 'http://' or path[:7] == 'file://'):
        #fetch remote image
        data = urllib2.urlopen(path).read()
        image = QImage()
        image.loadFromData(data)
    else:
        image = QImage(path)
    return image


def getControlImagePath(path):
    if os.path.isfile(path):
        return path

    #else try and find matching test image
    script_folder = os.path.dirname(os.path.realpath(sys.argv[0]))
    control_images_folder = os.path.join(script_folder, '../tests/testdata/control_images')

    matching_control_images = [x[0] for x in os.walk(control_images_folder) if path in x[0]]
    if len(matching_control_images) > 1:
        error('Found multiple matching control images for {}'.format(path))
    elif len(matching_control_images) == 0:
        error('No matching control images found for {}'.format(path))

    found_control_image_path = matching_control_images[0]

    #check for a single matching expected image
    images = glob.glob(os.path.join(found_control_image_path, '*.png'))
    filtered_images = [i for i in images if not i[-9:] == '_mask.png']
    if len(filtered_images) > 1:
        error('Found multiple matching control images for {}'.format(path))
    elif len(filtered_images) == 0:
        error('No matching control images found for {}'.format(path))

    found_image = filtered_images[0]
    print 'Found matching control image: {}'.format(found_image)
    return found_image


def updateMask(control_image_path, rendered_image_path, mask_image_path):
    control_image = imageFromPath(control_image_path)
    if not control_image:
        error('Could not read control image {}'.format(control_image_path))

    rendered_image = imageFromPath(rendered_image_path)
    if not rendered_image:
        error('Could not read rendered image {}'.format(rendered_image_path))
    if not rendered_image.width() == control_image.width() or not rendered_image.height() == control_image.height():
        print ('Size mismatch - control image is {}x{}, rendered image is {}x{}'.format(control_image.width(),
                                                                                        control_image.height(),
                                                                                        rendered_image.width(),
                                                                                        rendered_image.height()))

    max_width = min(rendered_image.width(), control_image.width())
    max_height = min(rendered_image.height(), control_image.height())

    #read current mask, if it exist
    mask_image = imageFromPath(mask_image_path)
    if mask_image.isNull():
        print 'Mask image does not exist, creating {}'.format(mask_image_path)
        mask_image = QImage(control_image.width(), control_image.height(), QImage.Format_ARGB32)
        mask_image.fill(QColor(0, 0, 0))

    #loop through pixels in rendered image and compare
    mismatch_count = 0
    linebytes = max_width * 4
    for y in xrange(max_height):
        control_scanline = control_image.constScanLine(y).asstring(linebytes)
        rendered_scanline = rendered_image.constScanLine(y).asstring(linebytes)
        mask_scanline = mask_image.scanLine(y).asstring(linebytes)

        for x in xrange(max_width):
            currentTolerance = qRed(struct.unpack('I', mask_scanline[x * 4:x * 4 + 4])[0])

            if currentTolerance == 255:
                #ignore pixel
                continue

            expected_rgb = struct.unpack('I', control_scanline[x * 4:x * 4 + 4])[0]
            rendered_rgb = struct.unpack('I', rendered_scanline[x * 4:x * 4 + 4])[0]
            difference = colorDiff(expected_rgb, rendered_rgb)

            if difference > currentTolerance:
                #update mask image
                mask_image.setPixel(x, y, qRgb(difference, difference, difference))
                mismatch_count += 1

    if mismatch_count:
        #update mask
        mask_image.save(mask_image_path, "png")
        print 'Updated {} pixels in {}'.format(mismatch_count, mask_image_path)
    else:
        print 'No mismatches in {}'.format(mask_image_path)

parser = argparse.ArgumentParser() # OptionParser("usage: %prog control_image rendered_image mask_image")
parser.add_argument('control_image')
parser.add_argument('rendered_image')
parser.add_argument('mask_image', nargs='?', default=None)
args = parser.parse_args()

args.control_image = getControlImagePath(args.control_image)

if not args.mask_image:
    args.mask_image = args.control_image[:-4] + '_mask.png'

updateMask(args.control_image, args.rendered_image, args.mask_image)