<?php

namespace TFGraphics\SmartImport\DomainEngine;

use TFGraphics\SmartImport\Domain\Search\MediaType;

/**
 * Classifies a raw input string according to DISCOVERY-001 tassonomia.
 *
 * Classe A  — deterministic regex → HIGH confidence
 * Classe B  — contextual pattern   → MEDIUM confidence
 * Classe C  — free text / unknown  → null (Domain Engine handles)
 */
final class IdentifierClassifier
{
    // ------------------------------------------------------------------ Classe A

    /** ISBN-13 (starts with 978 or 979) */
    private const RE_ISBN13 = '/^97[89]\d{10}$/';

    /** ISBN-10 (9 digits + digit or X) */
    private const RE_ISBN10 = '/^\d{9}[\dX]$/i';

    /** ISSN  XXXX-XXXX */
    private const RE_ISSN = '/^\d{4}-?\d{3}[\dX]$/i';

    /** MusicBrainz UUID */
    private const RE_MBID = '/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i';

    /** IMDb ID */
    private const RE_IMDB = '/^tt\d{7,8}$/i';

    /** Italian AIFA authorisation identifiers (medicine or package). */
    private const RE_AIC6 = '/^\d{6}$/';
    private const RE_AIC9 = '/^\d{9}$/';

    /** WHO ATC code (levels 2–5), for example A10BA02. */
    private const RE_ATC = '/^[A-V]\d{2}(?:[A-Z]{1,2}(?:\d{2})?)?$/i';

    // EAN-13 / UPC-A / EAN-8 / GTIN-14
    private const RE_EAN13   = '/^\d{13}$/';
    private const RE_UPCA    = '/^\d{12}$/';
    private const RE_EAN8    = '/^\d{8}$/';
    private const RE_GTIN14  = '/^\d{14}$/';

    // ------------------------------------------------------------------ Classe B keywords

    private const MUSIC_KEYWORDS = [
        'vinyl', 'lp', 'cd', 'ep', 'album', 'single', 'release',
        'remaster', 'remastered', '45rpm', '33rpm',
    ];

    private const GAME_KEYWORDS = [
        'ps5', 'ps4', 'ps3', 'xbox', 'nintendo', 'switch', 'wii',
        'playstation', 'steam', 'pc game', 'game',
    ];

    private const MOVIE_KEYWORDS = [
        'dvd', 'blu-ray', 'bluray', '4k uhd', 'uhd', 'movie', 'film',
        'serie', 'series', 'stagione', 'season',
    ];

    // ------------------------------------------------------------------ public API

    /**
     * Classify $input and return a resolution, or null if input is free text (Classe C).
     *
     * @param string      $input  raw user input (query field)
     * @param string|null $hint   optional operator hint (e.g. explicit mediaType from UI)
     */
    public function classify(string $input, ?string $hint = null): ?IdentifierResolution
    {
        $normalized = $this->normalize($input);

        // Explicit prefixes remove the ambiguity between an AIC and a retail
        // barcode. A bare six/nine-digit value is also a deterministic AIC
        // candidate: those lengths are not retail EAN/UPC lengths, and
        // forcing the operator to type `AIC:` made the identifier path fail
        // in the default/auto domain.
        $explicit = strtoupper(trim($input));
        if (preg_match('/^AIC(?:6|9)?(?:\s*[:\-]\s*|\s+)(\d{6}|\d{9})$/', $explicit, $matches) === 1) {
            $aic = $matches[1];
            return new IdentifierResolution(
                MediaType::MEDICINE,
                strlen($aic) === 9 ? 'aic9' : 'aic6',
                $aic,
                IdentifierResolution::CONFIDENCE_HIGH,
                'explicit AIC notation'
            );
        }
        // Some Italian pharmacy systems print AIC values with a leading
        // letter (for example A028511095). Treat that notation as the same
        // six/nine-digit AIC used by the AIFA archive.
        if (preg_match('/^A(\d{6}|\d{9})$/', $explicit, $matches) === 1) {
            $aic = $matches[1];
            return new IdentifierResolution(
                MediaType::MEDICINE,
                strlen($aic) === 9 ? 'aic9' : 'aic6',
                $aic,
                IdentifierResolution::CONFIDENCE_HIGH,
                'A-prefixed AIC notation'
            );
        }
        if (preg_match('/^ATC\s*:\s*([A-V]\d{2}(?:[A-Z]{1,2}(?:\d{2})?)?)$/', $explicit, $matches) === 1) {
            return new IdentifierResolution(
                MediaType::MEDICINE,
                'atc',
                strtoupper($matches[1]),
                IdentifierResolution::CONFIDENCE_HIGH,
                'explicit ATC prefix'
            );
        }

        $hintNorm = MediaType::normalize($hint);
        if ($hintNorm === MediaType::MEDICINE) {
            if (preg_match(self::RE_AIC9, $normalized) === 1) {
                return new IdentifierResolution(MediaType::MEDICINE, 'aic9', $normalized, IdentifierResolution::CONFIDENCE_HIGH, 'operator hint: medicine');
            }
            if (preg_match(self::RE_AIC6, $normalized) === 1) {
                return new IdentifierResolution(MediaType::MEDICINE, 'aic6', $normalized, IdentifierResolution::CONFIDENCE_HIGH, 'operator hint: medicine');
            }
            if (preg_match(self::RE_ATC, $normalized) === 1) {
                return new IdentifierResolution(MediaType::MEDICINE, 'atc', $normalized, IdentifierResolution::CONFIDENCE_HIGH, 'operator hint: medicine');
            }
        }

        // In AUTO, six/nine digits are AIC candidates because they are not
        // retail EAN/UPC lengths. A concrete non-medical operator hint keeps
        // precedence and continues through its normal identifier rules.
        if (in_array($hintNorm, [MediaType::AUTO, MediaType::UNKNOWN], true)) {
            if (preg_match(self::RE_AIC9, $normalized) === 1) {
                return new IdentifierResolution(MediaType::MEDICINE, 'aic9', $normalized, IdentifierResolution::CONFIDENCE_HIGH, 'bare AIC-9 identifier');
            }
            if (preg_match(self::RE_AIC6, $normalized) === 1) {
                return new IdentifierResolution(MediaType::MEDICINE, 'aic6', $normalized, IdentifierResolution::CONFIDENCE_HIGH, 'bare AIC-6 identifier');
            }
        }

        if (preg_match(self::RE_ATC, $normalized) === 1) {
            return new IdentifierResolution(MediaType::MEDICINE, 'atc', $normalized, IdentifierResolution::CONFIDENCE_HIGH);
        }

        // ---- Classe A: structured identifiers ----

        if (preg_match(self::RE_MBID, $input)) {
            return new IdentifierResolution(
                MediaType::MUSIC, 'mbid', $input,
                IdentifierResolution::CONFIDENCE_HIGH
            );
        }

        if (preg_match(self::RE_IMDB, $input)) {
            return new IdentifierResolution(
                MediaType::MOVIE, 'imdb_id', strtolower($input),
                IdentifierResolution::CONFIDENCE_HIGH
            );
        }

        // Eight bare digits are also GTIN-8. Prefer ISSN only when the standard
        // hyphen is present, or when its checksum is valid and GTIN's is not.
        if (preg_match(self::RE_ISSN, $normalized)
            && (str_contains(trim($input), '-') || ($this->isIssnValid($normalized) && ! $this->isGtinValid($normalized)))) {
            $valid = $this->isIssnValid($normalized);
            return new IdentifierResolution(
                MediaType::BOOK, 'issn', $normalized,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? null : 'ISSN checksum invalid'
            );
        }

        if (preg_match(self::RE_ISBN13, $normalized)) {
            $valid = $this->isGtinValid($normalized);
            return new IdentifierResolution(
                MediaType::BOOK, 'isbn13', $normalized,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? null : 'ISBN-13 checksum invalid'
            );
        }

        if (preg_match(self::RE_ISBN10, $normalized)) {
            $valid = $this->isIsbn10Valid($normalized);
            // Invalid ISBN-like input stays normalized but is never promoted by
            // conversion to a seemingly valid, high-confidence ISBN-13.
            $isbn13 = $this->isbn10to13($normalized);
            return new IdentifierResolution(
                MediaType::BOOK, $valid ? 'isbn13' : 'isbn10', $valid ? $isbn13 : $normalized,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? 'Converted from ISBN-10: ' . $normalized : 'ISBN-10 checksum invalid'
            );
        }

        if (preg_match(self::RE_GTIN14, $normalized)) {
            $valid = $this->isGtinValid($normalized);
            return new IdentifierResolution(
                MediaType::GENERIC, 'gtin14', $normalized,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? null : 'GTIN-14 checksum invalid'
            );
        }

        if (preg_match(self::RE_EAN13, $normalized)) {
            return $this->classifyEan13($normalized, $hint);
        }

        if (preg_match(self::RE_UPCA, $normalized)) {
            return $this->classifyUpcA($normalized, $hint);
        }

        if (preg_match(self::RE_EAN8, $normalized)) {
            $valid = $this->isGtinValid($normalized);
            return new IdentifierResolution(
                MediaType::FOOD, 'ean8', $normalized,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? null : 'GTIN-8 checksum invalid'
            );
        }

        // ---- Classe B: contextual keywords ----

        $lower = strtolower($input);

        if ($this->containsKeyword($lower, self::MUSIC_KEYWORDS)) {
            return new IdentifierResolution(
                MediaType::MUSIC, 'title_hint', $input,
                IdentifierResolution::CONFIDENCE_MEDIUM, 'music keyword detected'
            );
        }

        if ($this->containsKeyword($lower, self::GAME_KEYWORDS)) {
            return new IdentifierResolution(
                MediaType::GAME, 'title_hint', $input,
                IdentifierResolution::CONFIDENCE_MEDIUM, 'game keyword detected'
            );
        }

        if ($this->containsKeyword($lower, self::MOVIE_KEYWORDS)) {
            return new IdentifierResolution(
                MediaType::MOVIE, 'title_hint', $input,
                IdentifierResolution::CONFIDENCE_MEDIUM, 'movie keyword detected'
            );
        }

        // Classe C: free text, no domain determinable
        return null;
    }

    // ------------------------------------------------------------------ private helpers

    private function normalize(string $input): string
    {
        return strtoupper(str_replace(['-', ' '], '', trim($input)));
    }

    /**
     * EAN-13 routing based on GS1 prefix:
     *  978/979 → Books
     *  200-299 → internal/variable-measure
     *  default → Food/Generic
     */
    private function classifyEan13(string $ean13, ?string $hint): IdentifierResolution
    {
        $valid = $this->isGtinValid($ean13);
        $prefix3 = substr($ean13, 0, 3);

        if ($prefix3 === '978' || $prefix3 === '979') {
            return new IdentifierResolution(
                MediaType::BOOK, 'isbn13', $ean13,
                $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                $valid ? null : 'ISBN-13 checksum invalid'
            );
        }

        // Hint from operator (UI domain selector)
        if ($hint !== null) {
            $hintNorm = MediaType::normalize($hint);
            if ($hintNorm !== MediaType::UNKNOWN && $hintNorm !== MediaType::AUTO) {
                return new IdentifierResolution(
                    $hintNorm, 'ean13', $ean13,
                    $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                    'operator hint: ' . $hint . ($valid ? '' : '; EAN-13 checksum invalid')
                );
            }
        }

        // Default: treat as food/generic product
        return new IdentifierResolution(
            MediaType::FOOD, 'ean13', $ean13,
            $valid ? IdentifierResolution::CONFIDENCE_MEDIUM : IdentifierResolution::CONFIDENCE_LOW,
            $valid ? null : 'EAN-13 checksum invalid'
        );
    }

    /**
     * UPC-A (12 digits) — typically music CDs/vinyl or generic products.
     * Routing uses operator hint if present.
     */
    private function classifyUpcA(string $upc, ?string $hint): IdentifierResolution
    {
        $valid = $this->isGtinValid($upc);
        if ($hint !== null) {
            $hintNorm = MediaType::normalize($hint);
            if ($hintNorm === MediaType::MUSIC) {
                return new IdentifierResolution(
                    MediaType::MUSIC, 'upc', $upc,
                    $valid ? IdentifierResolution::CONFIDENCE_HIGH : IdentifierResolution::CONFIDENCE_LOW,
                    'operator hint: music' . ($valid ? '' : '; UPC-A checksum invalid')
                );
            }
        }

        return new IdentifierResolution(
            MediaType::GENERIC, 'upc', $upc,
            $valid ? IdentifierResolution::CONFIDENCE_MEDIUM : IdentifierResolution::CONFIDENCE_LOW,
            $valid ? null : 'UPC-A checksum invalid'
        );
    }

    private function isGtinValid(string $value): bool
    {
        $sum = 0;
        for ($i = strlen($value) - 2, $position = 1; $i >= 0; $i--, $position++) {
            $sum += (int) $value[$i] * ($position % 2 === 1 ? 3 : 1);
        }
        return (10 - ($sum % 10)) % 10 === (int) $value[strlen($value) - 1];
    }

    private function isIsbn10Valid(string $value): bool
    {
        $sum = 0;
        for ($i = 0; $i < 10; $i++) {
            $digit = strtoupper($value[$i]) === 'X' ? 10 : (int) $value[$i];
            if ($digit === 10 && $i !== 9) { return false; }
            $sum += (10 - $i) * $digit;
        }
        return $sum % 11 === 0;
    }

    private function isIssnValid(string $value): bool
    {
        $value = str_replace('-', '', strtoupper($value));
        $sum = 0;
        for ($i = 0; $i < 8; $i++) {
            $digit = $value[$i] === 'X' ? 10 : (int) $value[$i];
            if ($digit === 10 && $i !== 7) { return false; }
            $sum += (8 - $i) * $digit;
        }
        return $sum % 11 === 0;
    }

    private function containsKeyword(string $lower, array $keywords): bool
    {
        foreach ($keywords as $kw) {
            if (str_contains($lower, $kw)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Convert ISBN-10 to ISBN-13 (add 978 prefix, recompute check digit).
     */
    private function isbn10to13(string $isbn10): string
    {
        $isbn10 = strtoupper($isbn10);
        $base   = '978' . substr($isbn10, 0, 9);
        $sum    = 0;
        for ($i = 0; $i < 12; $i++) {
            $d    = (int) $base[$i];
            $sum += ($i % 2 === 0) ? $d : $d * 3;
        }
        $check = (10 - ($sum % 10)) % 10;
        return $base . $check;
    }
}