<?php
namespace app\common\logic;

use app\common\model\VehVehicleSku;

/**
 * SKU 生成器
 * - 输入: 车辆规格数组(以 *_code 为主)
 * - 输出: 稳定、人读友好的 sku_code (<= 40 默认)
 */
final class SkuCodeBuilder
{
    /** 压缩映射（可按需扩充） */
    private const ABBR = [
        // level
        'FLAGSHIP' => 'FLG',
        'PREMIUM'  => 'PRM',
        'STANDARD' => 'STD',
        'DELUXE'   => 'DLX',
        // edition
        'HONOR'    => 'HNR',
        'CHAMPION' => 'CHP',
        'ANNIV'    => 'ANV',
        // trans
        '1SPEED'   => '1SP',
        // drive/fuel/body 等一般已短，不必压缩
    ];

    /** 入口：生成 sku_code */
    public static function build(array $s, array $opts = []): string
    {
        $maxLen       = $opts['max_len']        ?? 40;
        $ensureUnique = $opts['ensure_unique']  ?? true;

        $tokens = [
            'brand'   => self::tok($s['brand_code']  ?? ''),
            'series'  => self::tok($s['series_code'] ?? ''),
            'year'    => isset($s['model_year']) ? (string)intval($s['model_year']) : '',
            'fuel'    => self::tok($s['fuel_type_code'] ?? ''),
            'drive'   => self::tok($s['drive_type_code'] ?? ''),
            'spec'    => self::buildSpec($s, self::tok($s['fuel_type_code'] ?? '')),
            'level'   => self::abbr(self::tok($s['trim_level_code'] ?? '')),
            'edition' => self::abbr(self::tok($s['edition_code']    ?? '')),
        ];

        // 过滤空段并按既定顺序拼接
        $order = ['brand','series','year','fuel','drive','spec','level','edition'];
        $parts = [];
        foreach ($order as $k) {
            if (!empty($tokens[$k])) $parts[$k] = $tokens[$k];
        }

        $sku = self::normalizeSku(implode('-', $parts));

        if (strlen($sku) > $maxLen) {
            $sku = self::shrink($parts, $maxLen); // 传入“带键名的 parts”
        }

        if ($ensureUnique) {
            $sku = self::ensureUnique($sku, $maxLen);
        }
        return $sku;
    }

    /** 构造规格位(SPEC)，按能源类型差异化 */
    private static function buildSpec(array $s, string $fuel): string
    {
        $fuel = strtoupper($fuel);
        if ($fuel === 'EV') {
            if (!empty($s['range_km'])) {
                $r = (int)$s['range_km'];
                $r10 = (int)round($r / 10) * 10; // 到 10 位
                return (string)$r10;
            }
            if (!empty($s['battery_kwh'])) {
                return self::numToken($s['battery_kwh']) . 'KWH';
            }
            return '';
        }

        if ($fuel === 'GAS') {
            $bits = [];
            if (!empty($s['engine_disp_l'])) {
                $bits[] = self::dispToken($s['engine_disp_l']); // 1.5L -> 15L
            }
            if (!empty($s['engine_turbo']) && intval($s['engine_turbo']) === 1) {
                $bits[] = 'T';
            }
            if (!empty($s['transmission_code'])) {
                $bits[] = self::abbr(self::tok($s['transmission_code']));
            }
            return implode('', $bits); // 如 15LTCVT
        }

        // HEV/PHEV/EREV 等
        $bits = [];
        if (!empty($s['engine_disp_l'])) {
            $bits[] = self::dispToken($s['engine_disp_l']); // 可空
        }
        if (!empty($s['motor_layout_code'])) {
            $bits[] = self::tok($s['motor_layout_code']);   // 如 AWD / DM-I / DM-P
        }
        return implode('', $bits);
    }

    /** 冲突检测并追加短校验（全局唯一） */
    private static function ensureUnique(string $sku, int $maxLen): string
    {
        if (!VehVehicleSku::where('sku_code', $sku)->exists()) {
            return $sku;
        }
        // 用 crc32 生成 5~6 位 base36 校验（稳定且短）
        $crc = self::base36Crc($sku);
        $suffix = '-X' . $crc;

        if (strlen($sku . $suffix) > $maxLen) {
            $sku = substr($sku, 0, max(0, $maxLen - strlen($suffix)));
            $sku = rtrim($sku, '-'); // 避免尾部 '-'
        }
        $sku .= $suffix;

        // 若极端情况下仍冲突，追加递增计数
        $i = 2;
        $candidate = $sku;
        while (VehVehicleSku::where('sku_code', $candidate)->exists()) {
            $extra = '-'.$i;
            $cut = max(0, $maxLen - strlen($extra));
            $candidate = substr($sku, 0, $cut) . $extra;
            $i++;
        }
        return $candidate;
    }

    /** 把 token 数组尽量压到 maxLen（逐步压缩策略） */
    private static function shrink(array $partsByKey, int $maxLen): string
    {
        // 1) 先对 series/level/edition 做激进压缩
        $p = $partsByKey;
        foreach (['series','level','edition'] as $k) {
            if (!empty($p[$k])) $p[$k] = self::heavyAbbr($p[$k]);
        }
        $sku = self::normalizeSku(implode('-', $p));
        if (strlen($sku) <= $maxLen) return $sku;

        // 2) 依次移除不太关键的信息：edition → level（若存在）
        if (!empty($p['edition'])) { unset($p['edition']); }
        $sku = self::normalizeSku(implode('-', $p));
        if (strlen($sku) <= $maxLen) return $sku;

        if (!empty($p['level'])) { unset($p['level']); }
        $sku = self::normalizeSku(implode('-', $p));
        if (strlen($sku) <= $maxLen) return $sku;

        // 3) 压缩 spec（如去 KM/KWH，仅保留核心）
        if (!empty($p['spec'])) { $p['spec'] = self::compactSpec($p['spec']); }
        $sku = self::normalizeSku(implode('-', $p));
        if (strlen($sku) <= $maxLen) return $sku;

        // 4) 仍超长：从右向左截断次要段（spec/drive/year），保留前三段（brand/series/fuel）优先
        $dropOrder = ['spec','drive','year'];
        $q = $p;
        foreach ($dropOrder as $k) {
            if (!empty($q[$k])) { unset($q[$k]); }
            $sku = self::normalizeSku(implode('-', $q));
            if (strlen($sku) <= $maxLen) return $sku;
        }

        // 5) 最后兜底：硬截到 maxLen，后续 ensureUnique 会追加 -X 校验并避免冲突
        return substr(self::normalizeSku(implode('-', $p)), 0, $maxLen);
    }

    /* ===== Helpers ===== */

    private static function tok($v): string
    {
        $v = strtoupper((string)$v);
        return preg_replace('/[^A-Z0-9_]/', '', $v ?? '');
    }

    private static function abbr(string $t): string
    {
        return self::ABBR[$t] ?? $t;
    }

    private static function heavyAbbr(string $t): string
    {
        // 更激进：去除元音，连字符化
        $t = str_replace(['STANDARD','FLAGSHIP','PREMIUM','DELUXE'], ['STD','FLG','PRM','DLX'], $t);
        $t = preg_replace('/[AEIOU]/', '', $t);
        return $t;
    }

    private static function compactSpec(string $s): string
    {
        // 规则：去 KM/KWH 等单位，只保留数字与核心字母
        $s = strtoupper($s);
        $s = str_replace(['KM','KWH'], '', $s);
        return $s;
    }

    private static function numToken($v): string
    {
        return preg_replace('/[^0-9]/', '', (string)$v);
    }

    /** 1.5L -> 15L；2.0L -> 20L */
    private static function dispToken($l): string
    {
        $x = (float)$l;
        return (string)round($x * 10) . 'L';
    }

    private static function base36Crc(string $s): string
    {
        $crc = sprintf('%u', crc32($s));           // 无符号
        $n = (int)$crc;
        $chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $res = '';
        do {
            $res = $chars[$n % 36] . $res;
            $n = intdiv($n, 36);
        } while ($n > 0);
        return substr($res, -6); // 取后6位足够
    }

    private static function normalizeSku(string $s): string
    {
        // 连续的 '-' 合并，首尾修剪
        $s = preg_replace('/-+/', '-', $s);
        $s = trim($s, '-');
        return $s;
    }
}