<?php
declare(strict_types=1);

namespace App;

/**
 * 花销与分摊
 *
 * 表结构：expenses（挂在 trip_nodes 上）+ expense_splits（这笔钱按人分摊，谁承担多少）
 *
 * ⚠️ 历史上 expenses 有 is_budget（预算 / 实际）之分，用户明确反馈「预算没有意义」，
 *    现在只记真实花销：查询一律 is_budget = 0，表单也不再提供「预算」选项。
 *    列本身保留（老数据还在库里，不至于丢），但 UI 与汇总都不再出现预算概念。
 */
class Expenses
{
    public const CATEGORIES = ['餐饮', '门票', '交通', '住宿', '购物', '娱乐', '其他'];

    /** 展示用的货币符号（库里只存三字母代码） */
    public const SYMBOLS = ['CNY' => '¥', 'JPY' => '¥', 'USD' => '$', 'EUR' => '€', 'HKD' => 'HK$'];

    public const MAX_AMOUNT = 99999999.99;

    public static function currencyLabels(): array
    {
        return ['CNY' => '人民币 ¥', 'JPY' => '日元 ¥', 'USD' => '美元 $', 'EUR' => '欧元 €', 'HKD' => '港币 HK$'];
    }

    /** 某个节点下的花销（只看真实花销），带付款人和分摊明细 */
    public static function forNode(int $nodeId): array
    {
        $db = Database::get();
        $stmt = $db->prepare('
            SELECT e.*, u.name AS payer_name, u.avatar AS payer_avatar
            FROM expenses e
            LEFT JOIN users u ON u.id = e.payer_user_id
            WHERE e.trip_node_id = ? AND e.is_budget = 0
            ORDER BY e.created_at ASC, e.id ASC');
        $stmt->execute([$nodeId]);
        $rows = $stmt->fetchAll();
        if (empty($rows)) return [];

        $ids = array_column($rows, 'id');
        $ph  = implode(',', array_fill(0, count($ids), '?'));
        $s = $db->prepare("SELECT es.*, u.name AS user_name
            FROM expense_splits es
            LEFT JOIN users u ON u.id = es.user_id
            WHERE es.expense_id IN ($ph)
            ORDER BY es.id ASC");
        $s->execute($ids);
        $splits = [];
        foreach ($s->fetchAll() as $row) {
            $splits[(int)$row['expense_id']][] = $row;
        }
        foreach ($rows as &$row) {
            $row['splits'] = $splits[(int)$row['id']] ?? [];
        }
        unset($row);
        return $rows;
    }

    /** 活动下的真实花销总计，以及各节点的小计 */
    public static function summaryForActivity(int $activityId): array
    {
        $db = Database::get();
        $stmt = $db->prepare('
            SELECT tn.id AS node_id, SUM(e.total_amount) AS amount, COUNT(*) AS cnt
            FROM expenses e
            JOIN trip_nodes tn ON tn.id = e.trip_node_id
            WHERE tn.activity_id = ? AND e.is_budget = 0
            GROUP BY tn.id');
        $stmt->execute([$activityId]);

        $byNode = [];
        $total = 0.0;
        $count = 0;
        foreach ($stmt->fetchAll() as $row) {
            $amount = (float)$row['amount'];
            $byNode[(int)$row['node_id']] = $amount;
            $total += $amount;
            $count += (int)$row['cnt'];
        }

        return [
            'total'   => $total,
            'count'   => $count,
            'by_node' => $byNode,
        ];
    }

    /**
     * 新增一笔花销，并把金额按人平均分摊（尾差归最后一人，保证分摊之和等于总额）
     * @return array{ok: bool, error?: string, id?: int}
     */
    public static function create(int $nodeId, int $payerId, string $amountRaw, string $currency, string $category, string $description, bool $isBudget, array $splitUserIds): array
    {
        $db = Database::get();

        $amountRaw = str_replace([',', '，', ' '], '', trim($amountRaw));
        if ($amountRaw === '' || !is_numeric($amountRaw)) {
            return ['ok' => false, 'error' => '金额必须是数字'];
        }
        $amount = round((float)$amountRaw, 2);
        if ($amount <= 0) {
            return ['ok' => false, 'error' => '金额必须大于 0'];
        }
        if ($amount > self::MAX_AMOUNT) {
            return ['ok' => false, 'error' => '金额过大'];
        }

        if (!isset(self::currencyLabels()[$currency])) {
            $currency = 'CNY';
        }
        if ($category === '' || !in_array($category, self::CATEGORIES, true)) {
            $category = '其他';
        }
        $description = trim($description);
        if (mb_strlen($description) > 200) {
            return ['ok' => false, 'error' => '描述不能超过 200 个字'];
        }

        // 付款人和分摊人都必须是这个节点所属家庭的成员
        $stmt = $db->prepare('SELECT a.family_id FROM trip_nodes tn JOIN activities a ON a.id = tn.activity_id WHERE tn.id = ?');
        $stmt->execute([$nodeId]);
        $familyId = $stmt->fetchColumn();
        if ($familyId === false) {
            return ['ok' => false, 'error' => '节点不存在'];
        }
        $familyId = (int)$familyId;

        $memberIds = array_column(Members::familyUsers($familyId), 'id');
        $memberIds = array_map('intval', $memberIds);

        if (!in_array($payerId, $memberIds, true)) {
            return ['ok' => false, 'error' => '付款人必须是本家庭成员'];
        }
        $splitUserIds = array_values(array_unique(array_intersect(array_map('intval', $splitUserIds), $memberIds)));
        if (empty($splitUserIds)) {
            // 没选分摊人时默认由付款人自己承担
            $splitUserIds = [$payerId];
        }

        $db->beginTransaction();
        try {
            $stmt = $db->prepare('INSERT INTO expenses
                (trip_node_id, payer_user_id, currency, total_amount, category, description, is_budget)
                VALUES (?, ?, ?, ?, ?, ?, ?)');
            $stmt->execute([
                $nodeId, $payerId, $currency, number_format($amount, 2, '.', ''),
                $category, $description !== '' ? $description : null, $isBudget ? 1 : 0,
            ]);
            $expenseId = (int)$db->lastInsertId();

            // 以「分」为单位平均分，把除不尽的尾差加到最后一个人身上
            $totalCents = (int)round($amount * 100);
            $n    = count($splitUserIds);
            $base = intdiv($totalCents, $n);
            $rest = $totalCents - $base * $n;

            $stmt = $db->prepare('INSERT INTO expense_splits (expense_id, user_id, share_amount) VALUES (?, ?, ?)');
            foreach ($splitUserIds as $i => $uid) {
                $cents = $base + ($i === $n - 1 ? $rest : 0);
                $stmt->execute([$expenseId, $uid, number_format($cents / 100, 2, '.', '')]);
            }

            $db->commit();
        } catch (\Throwable $e) {
            $db->rollBack();
            return ['ok' => false, 'error' => '保存失败：' . $e->getMessage()];
        }

        return ['ok' => true, 'id' => $expenseId];
    }

    public static function delete(int $id): bool
    {
        $db = Database::get();
        $stmt = $db->prepare('SELECT id FROM expenses WHERE id = ?');
        $stmt->execute([$id]);
        if (!$stmt->fetch()) return false;

        // expense_splits 有 ON DELETE CASCADE，这里显式删一遍更直观
        $db->prepare('DELETE FROM expense_splits WHERE expense_id = ?')->execute([$id]);
        $db->prepare('DELETE FROM expenses WHERE id = ?')->execute([$id]);
        return true;
    }

    /** 某个节点的真实花销合计 */
    public static function summaryForNode(int $nodeId): array
    {
        $stmt = Database::get()->prepare('SELECT COALESCE(SUM(total_amount), 0) AS amount, COUNT(*) AS cnt
            FROM expenses WHERE trip_node_id = ? AND is_budget = 0');
        $stmt->execute([$nodeId]);
        $row = $stmt->fetch();
        return ['total' => (float)$row['amount'], 'count' => (int)$row['cnt']];
    }
}