<?php
class DocumentProcessor {
    private $srcImage;
    private $processedImage;
    private $outputPath;
    
    public function __construct() {
        if (!extension_loaded('gd')) {
            throw new Exception('GD extension is required');
        }
    }

    public function processDocument($imagePath, $outputPath) {
        $this->outputPath = $outputPath;
        
        // Detecta o tipo da imagem e carrega
        $imageInfo = getimagesize($imagePath);
        if ($imageInfo === false) {
            throw new Exception('Failed to load image');
        }

        switch ($imageInfo[2]) {
            case IMAGETYPE_JPEG:
                $this->srcImage = imagecreatefromjpeg($imagePath);
                break;
            case IMAGETYPE_PNG:
                $this->srcImage = imagecreatefrompng($imagePath);
                break;
            default:
                throw new Exception('Unsupported image type');
        }

        if ($this->srcImage === false) {
            throw new Exception('Failed to create image resource');
        }

        // Novo pipeline de processamento mais completo
        $this->detectAndCropDocument()
             ->convertToGrayscale()
             ->enhanceContrast()
             ->sharpenImage()
             ->removeNoise()
             ->adjustBrightnessContrast()
             ->normalizeBackground()
             ->saveResult();

        return $this->outputPath;
    }

    private function detectAndCropDocument() {
        $width = imagesx($this->srcImage);
        $height = imagesy($this->srcImage);
        
        // Cria imagem temporária em escala de cinza
        $gray = imagecreatetruecolor($width, $height);
        imagecopy($gray, $this->srcImage, 0, 0, 0, 0, $width, $height);
        imagefilter($gray, IMG_FILTER_GRAYSCALE);
        
        // Aplica threshold adaptativo para binarização
        $threshold = $this->getAdaptiveThreshold($gray);
        $binary = imagecreatetruecolor($width, $height);
        
        for ($x = 0; $x < $width; $x++) {
            for ($y = 0; $y < $height; $y++) {
                $rgb = imagecolorat($gray, $x, $y);
                $colors = imagecolorsforindex($gray, $rgb);
                $value = ($colors['red'] + $colors['green'] + $colors['blue']) / 3;
                
                if ($value > $threshold) {
                    imagesetpixel($binary, $x, $y, 0xFFFFFF);
                } else {
                    imagesetpixel($binary, $x, $y, 0x000000);
                }
            }
        }
        
        // Encontra os contornos do documento
        $bounds = $this->findDocumentBounds($binary);
        
        if ($bounds) {
            // Adiciona margem de segurança
            $margin = 10;
            $cropX = max(0, $bounds['left'] - $margin);
            $cropY = max(0, $bounds['top'] - $margin);
            $cropWidth = min($width - $cropX, $bounds['right'] - $bounds['left'] + 2 * $margin);
            for ($y = 0; $y < $height; $y += 10) {
                $rgb = imagecolorat($img, $x, $y);
                $colors = imagecolorsforindex($img, $rgb);
                
                // Detecta mudanças bruscas de intensidade
                if ($this->isEdgePoint($img, $x, $y)) {
                    $points[] = [$x, $y];
                }
            }
        }
        
        // Encontra os 4 cantos do documento
        if (count($points) >= 4) {
            return $this->findCornerPoints($points);
        }
        
        return null;
    }

    private function isEdgePoint($img, $x, $y) {
        $threshold = 30;
        
        // Verifica pixels vizinhos
        $center = $this->getPixelIntensity($img, $x, $y);
        $left = $this->getPixelIntensity($img, $x - 1, $y);
        $right = $this->getPixelIntensity($img, $x + 1, $y);
        $top = $this->getPixelIntensity($img, $x, $y - 1);
        $bottom = $this->getPixelIntensity($img, $x, $y + 1);
        
        return (abs($center - $left) > $threshold ||
                abs($center - $right) > $threshold ||
                abs($center - $top) > $threshold ||
                abs($center - $bottom) > $threshold);
    }

    private function getPixelIntensity($img, $x, $y) {
        if ($x < 0 || $y < 0 || $x >= imagesx($img) || $y >= imagesy($img)) {
            return 0;
        }
        
        $rgb = imagecolorat($img, $x, $y);
        $colors = imagecolorsforindex($img, $rgb);
        return ($colors['red'] + $colors['green'] + $colors['blue']) / 3;
    }

    private function findCornerPoints($points) {
        // Encontra os pontos mais extremos
        $topLeft = null;
        $topRight = null;
        $bottomLeft = null;
        $bottomRight = null;
        $minSum = PHP_FLOAT_MAX;
        $maxSum = PHP_FLOAT_MIN;
        $minDiff = PHP_FLOAT_MAX;
        $maxDiff = PHP_FLOAT_MIN;
        
        foreach ($points as $point) {
            $sum = $point[0] + $point[1];
            $diff = $point[0] - $point[1];
            
            if ($sum < $minSum) {
                $minSum = $sum;
                $topLeft = $point;
            }
            if ($sum > $maxSum) {
                $maxSum = $sum;
                $bottomRight = $point;
            }
            if ($diff < $minDiff) {
                $minDiff = $diff;
                $bottomLeft = $point;
            }
            if ($diff > $maxDiff) {
                $maxDiff = $diff;
                $topRight = $point;
            }
        }
        
        if ($topLeft && $topRight && $bottomLeft && $bottomRight) {
            return [$topLeft, $topRight, $bottomRight, $bottomLeft];
        }
        
        return null;
    }

    private function cropAndTransform($img, $corners) {
        $width = abs($corners[1][0] - $corners[0][0]);
        $height = abs($corners[3][1] - $corners[0][1]);
        
        $dest = imagecreatetruecolor($width, $height);
        
        // Preserva transparência
        imagealphablending($dest, false);
        imagesavealpha($dest, true);
        
        // Define pontos de destino
        $dest_points = [
            0, 0,
            $width - 1, 0,
            $width - 1, $height - 1,
            0, $height - 1
        ];
        
        // Define pontos de origem
        $src_points = [];
        foreach ($corners as $corner) {
            $src_points[] = $corner[0];
            $src_points[] = $corner[1];
        }
        
        // Aplica transformação perspectiva
        imagecopyresampled(
            $dest, $img,
            0, 0, min($src_points[0], $src_points[6]), min($src_points[1], $src_points[3]),
            $width, $height,
            max($src_points[2], $src_points[4]) - min($src_points[0], $src_points[6]),
            max($src_points[5], $src_points[7]) - min($src_points[1], $src_points[3])
        );
        
        return $dest;
    }

    private function convertToGrayscale() {
        if (!isset($this->processedImage)) {
            $this->processedImage = $this->srcImage;
        }
        
        imagefilter($this->processedImage, IMG_FILTER_GRAYSCALE);
        return $this;
    }

    private function enhanceContrast() {
        // Aplica equalização de histograma adaptativa
        $width = imagesx($this->processedImage);
        $height = imagesy($this->processedImage);
        
        // Divide a imagem em blocos e aplica equalização local
        $blockSize = 32;
        for ($x = 0; $x < $width; $x += $blockSize) {
            for ($y = 0; $y < $height; $y += $blockSize) {
                $this->equalizeHistogramBlock($x, $y, min($blockSize, $width - $x), min($blockSize, $height - $y));
            }
        }
        
        return $this;
    }

    private function equalizeHistogramBlock($startX, $startY, $blockWidth, $blockHeight) {
        $histogram = array_fill(0, 256, 0);
        $total = 0;
        
        // Calcula histograma do bloco
        for ($x = $startX; $x < $startX + $blockWidth; $x++) {
            for ($y = $startY; $y < $startY + $blockHeight; $y++) {
                $rgb = imagecolorat($this->processedImage, $x, $y);
                $colors = imagecolorsforindex($this->processedImage, $rgb);
                $gray = $colors['red']; // Já está em escala de cinza
                $histogram[$gray]++;
                $total++;
            }
        }
        
        // Calcula LUT de equalização
        $lut = array();
        $sum = 0;
        for ($i = 0; $i < 256; $i++) {
            $sum += $histogram[$i];
            $lut[$i] = round(($sum * 255) / $total);
        }
        
        // Aplica equalização
        for ($x = $startX; $x < $startX + $blockWidth; $x++) {
            for ($y = $startY; $y < $startY + $blockHeight; $y++) {
                $rgb = imagecolorat($this->processedImage, $x, $y);
                $colors = imagecolorsforindex($this->processedImage, $rgb);
                $newGray = $lut[$colors['red']];
                $color = imagecolorallocate($this->processedImage, $newGray, $newGray, $newGray);
                imagesetpixel($this->processedImage, $x, $y, $color);
            }
        }
    }

    private function sharpenImage() {
        // Matriz de convolução para sharpening
        $sharpenMatrix = [
            [-1, -1, -1],
            [-1,  9, -1],
            [-1, -1, -1]
        ];
        
        $this->applyConvolution($sharpenMatrix);
        return $this;
    }

    private function removeNoise() {
        // Aplica filtro mediano
        $temp = imagecreatetruecolor(imagesx($this->processedImage), imagesy($this->processedImage));
        imagecopy($temp, $this->processedImage, 0, 0, 0, 0, imagesx($this->processedImage), imagesy($this->processedImage));
        
        for ($x = 1; $x < imagesx($this->processedImage) - 1; $x++) {
            for ($y = 1; $y < imagesy($this->processedImage) - 1; $y++) {
                $values = array();
                // Coleta valores dos pixels vizinhos
                for ($i = -1; $i <= 1; $i++) {
                    for ($j = -1; $j <= 1; $j++) {
                        $rgb = imagecolorat($temp, $x + $i, $y + $j);
                        $colors = imagecolorsforindex($temp, $rgb);
                        $values[] = $colors['red'];
                    }
                }
                sort($values);
                $median = $values[4]; // Valor mediano
                $color = imagecolorallocate($this->processedImage, $median, $median, $median);
                imagesetpixel($this->processedImage, $x, $y, $color);
            }
        }
        
        imagedestroy($temp);
        return $this;
    }

    private function adjustBrightnessContrast() {
        // Ajusta brilho automaticamente
        imagefilter($this->processedImage, IMG_FILTER_BRIGHTNESS, 10);
        imagefilter($this->processedImage, IMG_FILTER_CONTRAST, -10);
        return $this;
    }

    private function normalizeBackground() {
        $width = imagesx($this->processedImage);
        $height = imagesy($this->processedImage);
        
        // Detecta cor do fundo (assume que os cantos são fundo)
        $cornerColors = array();
        $cornerColors[] = imagecolorat($this->processedImage, 0, 0);
        $cornerColors[] = imagecolorat($this->processedImage, $width-1, 0);
        $cornerColors[] = imagecolorat($this->processedImage, 0, $height-1);
        $cornerColors[] = imagecolorat($this->processedImage, $width-1, $height-1);
        
        // Calcula cor média do fundo
        $avgBackground = 255; // Assumimos fundo branco
        
        // Normaliza fundo
        for ($x = 0; $x < $width; $x++) {
            for ($y = 0; $y < $height; $y++) {
                $rgb = imagecolorat($this->processedImage, $x, $y);
                $colors = imagecolorsforindex($this->processedImage, $rgb);
                
                if ($colors['red'] > $avgBackground - 30) { // Se for próximo do fundo
                    $color = imagecolorallocate($this->processedImage, 255, 255, 255);
                    imagesetpixel($this->processedImage, $x, $y, $color);
                }
            }
        }
        
        return $this;
    }

    private function saveResult() {
        if (!isset($this->processedImage)) {
            throw new Exception('No processed image to save');
        }

        $extension = strtolower(pathinfo($this->outputPath, PATHINFO_EXTENSION));
        
        switch ($extension) {
            case 'jpg':
            case 'jpeg':
                imagejpeg($this->processedImage, $this->outputPath, 90);
                break;
            case 'png':
                imagepng($this->processedImage, $this->outputPath, 9);
                break;
            default:
                throw new Exception('Unsupported output image type');
        }

        if (is_resource($this->srcImage)) {
            imagedestroy($this->srcImage);
        }
        if (is_resource($this->processedImage)) {
            imagedestroy($this->processedImage);
        }

        return $this;
    }
}