<?php

namespace App\Services\Ai;

/**
 * Deterministic VIN decoder. Extracts year, country and manufacturer from the
 * 17-character Vehicle Identification Number per ISO 3779/3780. No external API.
 *
 * Reliable signals:
 *   - position 1     → world region (geographic prefix)
 *   - positions 1-3  → WMI (world manufacturer identifier)
 *   - position 10    → model year (cyclical 30-year mapping)
 *   - position 11    → assembly plant code
 *   - position 9     → check digit (NA-spec checksum, optional verification)
 *
 * Granular model/trim info requires a licensed database (TecDoc / NHTSA API);
 * those are out of scope here. We return a "best-effort" identification.
 */
class VinDecoder
{
    private const YEAR_CODES = [
        'A' => [1980, 2010], 'B' => [1981, 2011], 'C' => [1982, 2012], 'D' => [1983, 2013],
        'E' => [1984, 2014], 'F' => [1985, 2015], 'G' => [1986, 2016], 'H' => [1987, 2017],
        'J' => [1988, 2018], 'K' => [1989, 2019], 'L' => [1990, 2020], 'M' => [1991, 2021],
        'N' => [1992, 2022], 'P' => [1993, 2023], 'R' => [1994, 2024], 'S' => [1995, 2025],
        'T' => [1996, 2026], 'V' => [1997, 2027], 'W' => [1998, 2028], 'X' => [1999, 2029],
        'Y' => [2000, 2030], '1' => [2001, 2031], '2' => [2002, 2032], '3' => [2003, 2033],
        '4' => [2004, 2034], '5' => [2005, 2035], '6' => [2006, 2036], '7' => [2007, 2037],
        '8' => [2008, 2038], '9' => [2009, 2039],
    ];

    // Region by first char (ISO 3779 broad regions).
    private const REGIONS = [
        'A' => 'Africa', 'B' => 'Africa', 'C' => 'Africa', 'D' => 'Africa',
        'E' => 'Africa', 'F' => 'Africa', 'G' => 'Africa', 'H' => 'Africa',
        'J' => 'Asia', 'K' => 'Asia', 'L' => 'Asia', 'M' => 'Asia',
        'N' => 'Asia', 'P' => 'Asia', 'R' => 'Asia',
        'S' => 'Europe', 'T' => 'Europe', 'U' => 'Europe', 'V' => 'Europe',
        'W' => 'Europe', 'X' => 'Europe', 'Y' => 'Europe', 'Z' => 'Europe',
        '1' => 'North America', '2' => 'North America', '3' => 'North America',
        '4' => 'North America', '5' => 'North America',
        '6' => 'Oceania', '7' => 'Oceania',
        '8' => 'South America', '9' => 'South America',
    ];

    // Selected WMI → manufacturer/country. Covers most common European/Asian/US
    // brands relevant for a Moldova service shop.
    private const WMI = [
        // Volkswagen group
        'WVW' => ['VW', 'Germany'], 'WV1' => ['VW Commercial', 'Germany'], 'WV2' => ['VW Bus', 'Germany'],
        'WAU' => ['Audi', 'Germany'], 'WA1' => ['Audi SUV', 'Germany'],
        'TRU' => ['Audi', 'Hungary'], 'WUA' => ['Audi Sport', 'Germany'],
        'VWV' => ['VW', 'Spain'], 'VSS' => ['SEAT', 'Spain'], 'TMB' => ['Škoda', 'Czechia'],
        // BMW
        'WBA' => ['BMW', 'Germany'], 'WBS' => ['BMW M', 'Germany'], 'WBY' => ['BMW i', 'Germany'],
        'WBX' => ['BMW X SUV', 'USA'], 'NM0' => ['BMW Mini', 'Turkey'],
        // Mercedes
        'WDB' => ['Mercedes-Benz', 'Germany'], 'WDC' => ['Mercedes-Benz SUV', 'USA'],
        'WDD' => ['Mercedes-Benz', 'Germany'], 'WDF' => ['Mercedes-Benz Van', 'Germany'],
        // Porsche
        'WP0' => ['Porsche', 'Germany'], 'WP1' => ['Porsche SUV', 'Germany'],
        // Opel / Vauxhall
        'W0L' => ['Opel', 'Germany'], 'W0V' => ['Opel/Vauxhall', 'Germany'],
        // Ford
        '1FA' => ['Ford', 'USA'], '1FT' => ['Ford Truck', 'USA'], '1FM' => ['Ford SUV', 'USA'],
        'WF0' => ['Ford Europe', 'Germany'],
        // Honda
        '1HG' => ['Honda', 'USA'], 'JHM' => ['Honda', 'Japan'], 'JHL' => ['Honda SUV', 'Japan'],
        // Toyota
        'JT2' => ['Toyota', 'Japan'], 'JTD' => ['Toyota', 'Japan'], 'JTE' => ['Toyota', 'Japan'],
        '4T1' => ['Toyota', 'USA'], '5TD' => ['Toyota', 'USA'],
        // Hyundai/Kia
        'KMH' => ['Hyundai', 'Korea'], 'KNA' => ['Kia', 'Korea'], 'KND' => ['Kia SUV', 'Korea'],
        // Renault/Dacia
        'VF1' => ['Renault', 'France'], 'VF6' => ['Renault Trucks', 'France'],
        'UU1' => ['Dacia', 'Romania'], 'UU3' => ['Dacia Pickup', 'Romania'],
        // Peugeot/Citroën
        'VF3' => ['Peugeot', 'France'], 'VF7' => ['Citroën', 'France'],
        // Fiat group
        'ZFA' => ['Fiat', 'Italy'], 'ZAR' => ['Alfa Romeo', 'Italy'], 'ZFF' => ['Ferrari', 'Italy'],
        // Volvo
        'YV1' => ['Volvo Cars', 'Sweden'], 'YV4' => ['Volvo SUV', 'Sweden'],
        // Nissan
        'JN1' => ['Nissan', 'Japan'], 'JN8' => ['Nissan SUV', 'Japan'], '1N4' => ['Nissan', 'USA'],
        // Mazda
        'JM1' => ['Mazda', 'Japan'], 'JMZ' => ['Mazda', 'Japan'],
        // Subaru
        'JF1' => ['Subaru', 'Japan'], 'JF2' => ['Subaru SUV', 'Japan'],
        // Mitsubishi
        'JMB' => ['Mitsubishi', 'Japan'], 'JA3' => ['Mitsubishi', 'Japan'],
        // Lada / Russian
        'XTA' => ['Lada/AvtoVAZ', 'Russia'], 'X4X' => ['UAZ', 'Russia'],
        // Tesla
        '5YJ' => ['Tesla', 'USA'], 'LRW' => ['Tesla', 'China'],
        // Chinese brands
        'LGW' => ['Great Wall', 'China'], 'LJV' => ['JAC', 'China'], 'LSJ' => ['MG/SAIC', 'China'],
        'LB1' => ['Geely', 'China'],
    ];

    public function decode(string $raw): array
    {
        $vin = preg_replace('/[^A-HJ-NPR-Z0-9]/', '', strtoupper($raw));
        if (strlen($vin) !== 17) {
            return [
                'vin' => $vin,
                'valid_length' => false,
                'reason' => 'VIN must be exactly 17 characters (no I, O, Q allowed).',
            ];
        }

        $wmi = substr($vin, 0, 3);
        $yearCode = $vin[9];
        $plant = $vin[10];

        [$manufacturer, $country] = self::WMI[$wmi] ?? [null, null];
        $region = self::REGIONS[$vin[0]] ?? null;

        $year = $this->resolveYear($yearCode, $vin);

        return [
            'vin' => $vin,
            'valid_length' => true,
            'wmi' => $wmi,
            'region' => $region,
            'country' => $country,
            'manufacturer' => $manufacturer,
            'year' => $year,
            'plant' => $plant,
            'checksum_valid' => $this->validateChecksum($vin),
        ];
    }

    /**
     * Position 10 encodes year cyclically. Use position 7 as A-Z → 2010+, 0-9 → pre-2010
     * disambiguator for new-spec VINs (since 2010 NHTSA spec).
     */
    private function resolveYear(string $code, string $vin): ?int
    {
        if (! isset(self::YEAR_CODES[$code])) return null;
        [$old, $new] = self::YEAR_CODES[$code];

        // Position 7 alpha → post-2010 cycle; numeric → pre-2010
        $p7 = $vin[6];
        return ctype_alpha($p7) ? $new : $old;
    }

    /**
     * ISO 3779 / NA-spec checksum. Position 9 = mod-11 check digit (X = 10).
     * Optional — many European/Asian manufacturers don't follow the spec.
     */
    private function validateChecksum(string $vin): bool
    {
        $weights = [8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2];
        $values = [
            'A' => 1, 'B' => 2, 'C' => 3, 'D' => 4, 'E' => 5, 'F' => 6, 'G' => 7, 'H' => 8,
            'J' => 1, 'K' => 2, 'L' => 3, 'M' => 4, 'N' => 5, 'P' => 7, 'R' => 9,
            'S' => 2, 'T' => 3, 'U' => 4, 'V' => 5, 'W' => 6, 'X' => 7, 'Y' => 8, 'Z' => 9,
        ];

        $sum = 0;
        for ($i = 0; $i < 17; $i++) {
            $c = $vin[$i];
            $v = ctype_digit($c) ? (int) $c : ($values[$c] ?? null);
            if ($v === null) return false;
            $sum += $v * $weights[$i];
        }
        $check = $sum % 11;
        $expected = $check === 10 ? 'X' : (string) $check;
        return $vin[8] === $expected;
    }
}