<?php

declare(strict_types=1);

namespace App\Libraries;

/**
 * Art-directed cover thumbnails served from /thumb/{W}x{H}/{id}.jpg.
 * Generated on demand from the cached original cover into
 * writable/cache/covers/thumbs/{W}x{H}/ and served from disk afterwards.
 */
class CoverArt
{
    /** Allowed thumbnail sizes — requests snap to the nearest one. */
    public const SIZES = [
        'small'  => [240, 320],   // grade previews, dense grids
        'medium' => [360, 480],   // catalog cards
        'large'  => [540, 720],   // detail sidebar / og:image
    ];

    public static function sizes(): array
    {
        return self::SIZES;
    }

    public static function thumb(string $id, string $fullFile, array $book = [], int $w = 360, int $h = 480): ?string
    {
        [$w, $h] = self::closestSize($w, $h);

        $dir  = dirname($fullFile) . '/thumbs/' . $w . 'x' . $h;
        $file = $dir . '/' . basename($fullFile);

        if (is_file($file) && filemtime($file) >= filemtime($fullFile)) {
            return $file;
        }

        $src = @imagecreatefromstring((string) file_get_contents($fullFile));
        if (! $src) {
            return $book ? self::fallback($dir, $file, $book, $w, $h) : null;
        }

        $sw = imagesx($src);
        $sh = imagesy($src);

        // landscape low-res = upstream placeholder → designed fallback
        if ($sw <= 400 && $sh <= 200) {
            imagedestroy($src);
            return $book ? self::fallback($dir, $file, $book, $w, $h) : null;
        }

        // flatten alpha (upstream PNGs have transparency) onto light background
        $flat = imagecreatetruecolor($sw, $sh);
        imagefill($flat, 0, 0, imagecolorallocate($flat, 232, 236, 244));
        imagecopy($flat, $src, 0, 0, 0, 0, $sw, $sh);
        imagedestroy($src);
        $src = $flat;

        // center-crop to target ratio (favor top 40% when cropping height:
        // Vietnamese textbook covers carry their title in the upper part)
        $targetRatio = $w / $h;
        $ratio = $sw / $sh;
        if ($ratio > $targetRatio) {
            $cw = (int) round($sh * $targetRatio);
            $cx = (int) (($sw - $cw) / 2);
            $cy = 0;
            $ch = $sh;
        } else {
            $ch = (int) round($sw / $targetRatio);
            $cy = (int) max(0, ($sh - $ch) * 0.40);
            $cx = 0;
            $cw = $sw;
        }

        $dst = imagecreatetruecolor($w, $h);
        imagefill($dst, 0, 0, imagecolorallocate($dst, 232, 236, 244));
        imagecopyresampled($dst, $src, 0, 0, $cx, $cy, $w, $h, $cw, $ch);
        self::sharpen($dst);

        self::save($dst, $dir, $file, 86);
        imagedestroy($src);
        imagedestroy($dst);

        return $file;
    }

    private static function closestSize(int $w, int $h): array
    {
        $best = null;
        $bestDiff = PHP_INT_MAX;
        foreach (self::SIZES as [$tw, $th]) {
            $diff = abs($tw - $w) + abs($th - $h);
            if ($diff < $bestDiff) {
                $bestDiff = $diff;
                $best = [$tw, $th];
            }
        }
        return $best;
    }

    private static function save($img, string $dir, string $file, int $quality): void
    {
        if (! is_dir($dir)) {
            @mkdir($dir, 0775, true);
        }
        $tmp = $file . '.tmp' . getmypid();
        imagejpeg($img, $tmp, $quality);
        rename($tmp, $file);
    }

    /**
     * Designed fallback cover: vertical brand gradient, SGK badge,
     * subject, wrapped title, grade + publisher footer.
     */
    private static function fallback(string $dir, string $file, array $book, int $w, int $h): ?string
    {
        $dst = imagecreatetruecolor($w, $h);

        // vertical gradient: deep blue → azure
        $r0 = 30; $g0 = 58; $b0 = 138;
        $r1 = 59; $g1 = 130; $b1 = 246;
        for ($y = 0; $y < $h; $y++) {
            $t = $y / $h;
            imageline($dst, 0, $y, $w, $y, imagecolorallocate($dst,
                (int) ($r0 + ($r1 - $r0) * $t),
                (int) ($g0 + ($g1 - $g0) * $t),
                (int) ($b0 + ($b1 - $b0) * $t)));
        }

        // decorative translucent circles (scale with size)
        $s = $w / 360;
        $acc = imagecolorallocatealpha($dst, 255, 255, 255, 100);
        imagefilledellipse($dst, (int) (400 * $s), (int) (90 * $s), (int) (220 * $s), (int) (220 * $s), $acc);
        imagefilledellipse($dst, (int) (80 * $s), (int) (560 * $s), (int) (260 * $s), (int) (260 * $s), $acc);

        $white = imagecolorallocate($dst, 255, 255, 255);
        $soft  = imagecolorallocate($dst, 219, 231, 254);
        $gold  = imagecolorallocate($dst, 245, 158, 11);

        // SGK brand badge
        imagefilledrectangle($dst, (int) (24 * $s), (int) (28 * $s), (int) (122 * $s), (int) (66 * $s),
            imagecolorallocatealpha($dst, 255, 255, 255, 88));
        imagestring($dst, 5, (int) (38 * $s), (int) (39 * $s), 'SGK.ORG', $gold);

        // subject
        $subject = mb_strtoupper($book['subject'] !== '' ? $book['subject'] : 'Giao khoa');
        imagestring($dst, 5, (int) (26 * $s), (int) (120 * $s), self::ascii($subject), $soft);

        // wrapped title
        $lines = self::wrapAscii((string) ($book['title'] ?? ''), (int) ($w - 52 * $s), 5);
        $y = (int) (170 * $s);
        foreach ($lines as $line) {
            imagestring($dst, 5, (int) (26 * $s), $y, self::ascii($line), $white);
            $y += (int) (24 * $s);
            if ($y > $h - 110 * $s) break;
        }

        // footer: grade + publisher
        $bottom = trim(($book['grade'] ? 'LOP ' . $book['grade'] . '  .  ' : '') . $book['publisher']);
        imageline($dst, (int) (26 * $s), (int) ($h - 86 * $s), (int) ($w - 26 * $s), (int) ($h - 86 * $s), $gold);
        imagestring($dst, 4, (int) (26 * $s), (int) ($h - 72 * $s), self::ascii($bottom), $gold);

        self::save($dst, $dir, $file, 88);
        imagedestroy($dst);

        return $file;
    }

    /** Vietnamese diacritics → ASCII for GD built-in fonts. */
    private static function ascii(string $s): string
    {
        $map = [
            'à'=>'a','á'=>'a','ạ'=>'a','ả'=>'a','ã'=>'a','â'=>'a','ầ'=>'a','ấ'=>'a','ậ'=>'a','ẩ'=>'a','ẫ'=>'a',
            'ă'=>'a','ằ'=>'a','ắ'=>'a','ặ'=>'a','ẳ'=>'a','ẵ'=>'a','À'=>'A','Á'=>'A','Ạ'=>'A','Ả'=>'A','Ã'=>'A',
            'Â'=>'A','Ă'=>'A','è'=>'e','é'=>'e','ẹ'=>'e','ẻ'=>'e','ẽ'=>'e','ê'=>'e','ề'=>'e','ế'=>'e','ệ'=>'e',
            'ể'=>'e','ễ'=>'e','È'=>'E','É'=>'E','Ẹ'=>'E','Ẻ'=>'E','Ẽ'=>'E','Ê'=>'E','ì'=>'i','í'=>'i','ị'=>'i',
            'ỉ'=>'i','ĩ'=>'i','Ì'=>'I','Í'=>'I','Ị'=>'I','Ỉ'=>'I','Ĩ'=>'I','ò'=>'o','ó'=>'o','ọ'=>'o','ỏ'=>'o',
            'õ'=>'o','ô'=>'o','ồ'=>'o','ố'=>'o','ộ'=>'o','ổ'=>'o','ỗ'=>'o','ơ'=>'o','ờ'=>'o','ớ'=>'o','ợ'=>'o',
            'ở'=>'o','ỡ'=>'o','Ò'=>'O','Ó'=>'O','Ọ'=>'O','Ỏ'=>'O','Õ'=>'O','Ô'=>'O','Ơ'=>'O','ù'=>'u','ú'=>'u',
            'ụ'=>'u','ủ'=>'u','ũ'=>'u','ư'=>'u','ừ'=>'u','ứ'=>'u','ự'=>'u','ử'=>'u','ữ'=>'u','Ù'=>'U','Ú'=>'U',
            'Ụ'=>'U','Ủ'=>'U','Ũ'=>'U','Ư'=>'U','ỳ'=>'y','ý'=>'y','ỵ'=>'y','ỷ'=>'y','ỹ'=>'y','Ỳ'=>'Y',
            'Ý'=>'Y','Ỵ'=>'Y','Ỷ'=>'Y','Ỹ'=>'Y','đ'=>'d','Đ'=>'D','Ừ'=>'U','Ữ'=>'U',
        ];
        $s = strtr($s, $map);
        return preg_replace('/[^\x20-\x7E]/', '', $s) ?: 'SGK';
    }

    /** Word-wrap for GD font 5 (~9px/char). */
    private static function wrapAscii(string $text, int $maxW, int $maxLines): array
    {
        $maxChars = max(8, (int) ($maxW / 9));
        $words = preg_split('/\s+/', trim($text)) ?: [];
        $lines = [];
        $cur = '';
        foreach ($words as $wd) {
            $try = $cur === '' ? $wd : "$cur $wd";
            if (strlen($try) <= $maxChars) {
                $cur = $try;
                continue;
            }
            if ($cur !== '') $lines[] = $cur;
            $cur = strlen($wd) > $maxChars ? substr($wd, 0, $maxChars - 1) . '-' : $wd;
            if (count($lines) >= $maxLines) {
                $cur = '';
                break;
            }
        }
        if ($cur !== '' && count($lines) < $maxLines) $lines[] = $cur;
        if (count($lines) === $maxLines) {
            $lines[$maxLines - 1] = rtrim($lines[$maxLines - 1]) . '...';
        }
        return $lines ?: ['SGK'];
    }

    private static function sharpen($img): void
    {
        // mild unsharp mask
        imageconvolution($img, [
            [0.0, -0.6, 0.0],
            [-0.6, 3.4, -0.6],
            [0.0, -0.6, 0.0],
        ], 1.0, 0.0);
    }
}