<?php

namespace App\Services;

use App\Models\TicketGrabEvent;
use App\Models\TicketGrabEventVenue;
use App\Models\TicketGrabVenueReleaseDay;
use Carbon\Carbon;
use Carbon\CarbonPeriod;
use Illuminate\Support\Facades\DB;
use Illuminate\Validation\ValidationException;

class TicketGrabReleaseDayService
{
    /**
     * 将 total 均分至 n 天，不能整除时余量依次分给前 n 个日期各 +1，等价于前 remainder 天多 1 张（此处按「多给前面日期」与需求「多的分配到第一日」一致为：余数 r 个日期各 +1，从第 0 天开始；即 [ceil, floor, floor, ...]）。
     *
     * @return int[]
     */
    public static function equalSplit(int $total, int $n): array
    {
        if ($n <= 0) {
            return [];
        }
        if ($total < 0) {
            $total = 0;
        }
        $base = intdiv($total, $n);
        $r = $total % $n;
        $out = array_fill(0, $n, $base);
        for ($i = 0; $i < $r; $i++) {
            $out[$i]++;
        }

        return $out;
    }

    public static function syncCarryInChain(int $eventId, ?int $venueId = null): void
    {
        $q = TicketGrabEventVenue::query()->where('ticket_grab_event_id', $eventId);
        if ($venueId !== null) {
            $q->where('venue_id', $venueId);
        }
        $pivots = $q->get();
        foreach ($pivots as $p) {
            $days = TicketGrabVenueReleaseDay::query()
                ->where('ticket_grab_event_id', $eventId)
                ->where('venue_id', $p->venue_id)
                ->orderBy('release_date')
                ->get();

            $tz = (string) config('app.timezone');
            $today = Carbon::now($tz)->toDateString();
            $run = 0;
            foreach ($days as $d) {
                $d->carry_in = $run;
                $raw = (int) $d->carry_in + (int) $d->day_quota - (int) $d->booked_count;
                $rem = max(0, $raw);
                $rd = $d->release_date instanceof Carbon
                    ? $d->release_date->format('Y-m-d')
                    : Carbon::parse($d->release_date)->format('Y-m-d');
                // 仅当该放票日已早于「今天」才把当日余量滚入下一天；当日与未来的日期不提前把余量算进次日
                if ($rd < $today) {
                    $run = $rem;
                } else {
                    $run = 0;
                }
                $d->save();
            }
        }
    }

    /**
     * 根据活动与预约起止、场馆及配额，重建每日放票行（会删除该活动下未删除场馆对应的旧行并插入新行，booked 清零 —— 见调用方在更新时的保护）.
     */
    public static function rebuildAllReleaseDaysForEvent(int $eventId, bool $preserveBooked = false): void
    {
        $event = TicketGrabEvent::query()->with('eventVenuePivots')->find($eventId);
        if (! $event || ! $event->booking_start_at || ! $event->booking_end_at) {
            return;
        }

        $start = $event->booking_start_at->copy();
        $end = $event->booking_end_at->copy();
        if ($end->lt($start)) {
            return;
        }

        $dates = [];
        foreach (CarbonPeriod::create($start, $end) as $d) {
            $dates[] = $d->toDateString();
        }
        $n = count($dates);
        if ($n === 0) {
            return;
        }

        DB::transaction(function () use ($eventId, $dates, $n, $preserveBooked) {
            if (! $preserveBooked) {
                TicketGrabVenueReleaseDay::query()
                    ->where('ticket_grab_event_id', $eventId)
                    ->delete();
            }
            $pivots = TicketGrabEventVenue::query()->where('ticket_grab_event_id', $eventId)->get();
            foreach ($pivots as $p) {
                $alloc = self::equalSplit((int) $p->venue_total_quota, $n);
                if (! $preserveBooked) {
                    foreach ($dates as $i => $dateStr) {
                        TicketGrabVenueReleaseDay::query()->create([
                            'ticket_grab_event_id' => $eventId,
                            'venue_id' => $p->venue_id,
                            'release_date' => $dateStr,
                            'day_quota' => (int) ($alloc[$i] ?? 0),
                            'booked_count' => 0,
                            'carry_in' => 0,
                        ]);
                    }
                }
            }
            self::syncCarryInChain($eventId);
        });

        if (! $preserveBooked) {
            $sum = (int) TicketGrabEventVenue::query()
                ->where('ticket_grab_event_id', $eventId)
                ->sum('venue_total_quota');
            TicketGrabEvent::query()->where('id', $eventId)->update(['total_quota' => $sum]);
        }
    }

    /**
     * 预约起止变更后同步每日放票行：已有预约时不可整表重建，改为按新窗口增删日期并重新均分配额。
     *
     * @throws ValidationException 缩短窗口导致「窗口外」仍有已预约放票日时
     */
    public static function syncReleaseDaysToBookingWindow(int $eventId): void
    {
        $event = TicketGrabEvent::query()->with('eventVenuePivots')->find($eventId);
        if (! $event || ! $event->booking_start_at || ! $event->booking_end_at) {
            return;
        }

        $tz = (string) config('app.timezone');
        $start = Carbon::parse($event->booking_start_at, $tz)->copy()->startOfDay();
        $end = Carbon::parse($event->booking_end_at, $tz)->copy()->startOfDay();
        if ($end->lt($start)) {
            return;
        }

        $dates = [];
        foreach (CarbonPeriod::create($start, $end) as $d) {
            $dates[] = $d->toDateString();
        }
        $n = count($dates);
        if ($n === 0) {
            return;
        }

        $invalid = TicketGrabVenueReleaseDay::query()
            ->where('ticket_grab_event_id', $eventId)
            ->whereNotIn('release_date', $dates)
            ->where('booked_count', '>', 0)
            ->exists();
        if ($invalid) {
            throw ValidationException::withMessages([
                'booking_end_at' => ['所选预约窗口之外仍有已预约人数对应的放票日，无法缩小至此范围。可先扩大结束日或处理相关预约后再调整。'],
            ]);
        }

        DB::transaction(function () use ($eventId, $dates, $n) {
            $pivots = TicketGrabEventVenue::query()->where('ticket_grab_event_id', $eventId)->get();
            foreach ($pivots as $p) {
                $total = (int) $p->venue_total_quota;
                $alloc = self::equalSplit($total, $n);

                foreach ($dates as $i => $dateStr) {
                    $target = (int) ($alloc[$i] ?? 0);
                    $row = TicketGrabVenueReleaseDay::query()
                        ->where('ticket_grab_event_id', $eventId)
                        ->where('venue_id', $p->venue_id)
                        ->whereDate('release_date', $dateStr)
                        ->first();

                    if (! $row) {
                        TicketGrabVenueReleaseDay::query()->create([
                            'ticket_grab_event_id' => $eventId,
                            'venue_id' => $p->venue_id,
                            'release_date' => $dateStr,
                            'day_quota' => $target,
                            'booked_count' => 0,
                            'carry_in' => 0,
                        ]);
                    } else {
                        $booked = (int) $row->booked_count;
                        $row->day_quota = max($target, $booked);
                        $row->save();
                    }
                }

                TicketGrabVenueReleaseDay::query()
                    ->where('ticket_grab_event_id', $eventId)
                    ->where('venue_id', $p->venue_id)
                    ->whereNotIn('release_date', $dates)
                    ->delete();

                self::rebalanceVenueReleaseDays($eventId, $p->venue_id, $total);
            }

            self::syncCarryInChain($eventId);
        });

        $sum = (int) TicketGrabEventVenue::query()
            ->where('ticket_grab_event_id', $eventId)
            ->sum('venue_total_quota');
        TicketGrabEvent::query()->where('id', $eventId)->update(['total_quota' => $sum]);
    }

    /**
     * 将某馆各日 day_quota 之和收敛为 venue_total_quota（已尊重 booked_count 下限）。
     *
     * @throws ValidationException 无法在不跌破已预约数的前提下收敛时
     */
    private static function rebalanceVenueReleaseDays(int $eventId, int $venueId, int $targetTotal): void
    {
        $rows = TicketGrabVenueReleaseDay::query()
            ->where('ticket_grab_event_id', $eventId)
            ->where('venue_id', $venueId)
            ->orderBy('release_date')
            ->get();

        if ($rows->isEmpty()) {
            return;
        }

        $sum = (int) $rows->sum('day_quota');
        $diff = $targetTotal - $sum;
        if ($diff === 0) {
            return;
        }

        if ($diff > 0) {
            $keys = $rows->keys()->all();
            $k = count($keys);
            $i = 0;
            while ($diff > 0) {
                $idx = $keys[$i % $k];
                $row = $rows[$idx];
                $row->day_quota = (int) $row->day_quota + 1;
                $row->save();
                $diff--;
                $i++;
            }

            return;
        }

        $need = -$diff;
        $sorted = $rows->sortByDesc(fn ($r) => (int) $r->day_quota - (int) $r->booked_count)->values();
        foreach ($sorted as $row) {
            if ($need <= 0) {
                break;
            }
            $slack = max(0, (int) $row->day_quota - (int) $row->booked_count);
            $dec = min($slack, $need);
            if ($dec > 0) {
                $row->day_quota = (int) $row->day_quota - $dec;
                $row->save();
                $need -= $dec;
            }
        }

        if ($need > 0) {
            throw ValidationException::withMessages([
                'booking_end_at' => ['各日已预约数量较多，无法在给定预约窗口与放票总数下平衡每日配额，请检查后再试。'],
            ]);
        }
    }

    public static function updateDayQuotasFromAdmin(int $eventId, int $venueId, array $dateToQuota): void
    {
        $pivot = TicketGrabEventVenue::query()
            ->where('ticket_grab_event_id', $eventId)
            ->where('venue_id', $venueId)
            ->firstOrFail();

        $total = (int) $pivot->venue_total_quota;

        if ($total === 0) {
            foreach ($dateToQuota as $q) {
                if ((int) $q !== 0) {
                    throw ValidationException::withMessages([
                        'day_quota' => ['该馆放票总数为 0 时，各日放票数须均为 0。'],
                    ]);
                }
            }
            TicketGrabVenueReleaseDay::query()
                ->where('ticket_grab_event_id', $eventId)
                ->where('venue_id', $venueId)
                ->update(['day_quota' => 0]);
            self::syncCarryInChain($eventId, $venueId);

            return;
        }

        foreach ($dateToQuota as $date => $q) {
            TicketGrabVenueReleaseDay::query()
                ->where('ticket_grab_event_id', $eventId)
                ->where('venue_id', $venueId)
                ->whereDate('release_date', $date)
                ->update(['day_quota' => (int) $q]);
        }

        $dbSum = (int) TicketGrabVenueReleaseDay::query()
            ->where('ticket_grab_event_id', $eventId)
            ->where('venue_id', $venueId)
            ->sum('day_quota');

        if ($dbSum !== $total) {
            throw ValidationException::withMessages([
                'day_quota' => ["各日放票数之和必须等于该馆放票总数（{$total}）。当前合计为 {$dbSum}。"],
            ]);
        }
        self::syncCarryInChain($eventId, $venueId);
    }
}