<?php

namespace App\Domain\Trip\Services;

use App\Models\Trip;
use App\Models\CalendarSlot;
use Carbon\Carbon;
use Illuminate\Support\Collection;

class CalendarSlotService
{
    public function createOrUpdateSlotsForTrip(Trip $trip): Collection
    {
        if (!$trip->start_date || !$trip->end_date) {
            return collect();
        }

        // Fresh load to avoid stale relationship data
        $trip->refresh();
        $existingSlots = $trip->calendarSlots;
        $existingSlotsMap = $existingSlots->keyBy(function ($slot) {
            return $slot->slot_date instanceof \Carbon\Carbon
                ? $slot->slot_date->toDateString()
                : $slot->slot_date;
        });

        $startDate = Carbon::parse($trip->start_date);
        $endDate = Carbon::parse($trip->end_date);

        $newSlots = collect();
        $currentDate = $startDate->copy();
        $dayNumber = 1;

        while ($currentDate->lte($endDate)) {
            $slotDate = $currentDate->toDateString();

            if (!$existingSlotsMap->has($slotDate)) {
                $slot = CalendarSlot::create([
                    'trip_id' => $trip->id,
                    'name' => 'Day ' . $dayNumber,
                    'slot_date' => $slotDate,
                    'datetime_start' => $currentDate->copy()->startOfDay(),
                    'datetime_end' => $currentDate->copy()->endOfDay(),
                    'slot_order' => $dayNumber,
                ]);
                $newSlots->push($slot);
            } else {
                $existingSlot = $existingSlotsMap->get($slotDate);
                $existingSlot->update([
                    'slot_order' => $dayNumber,
                    'datetime_start' => $currentDate->copy()->startOfDay(),
                    'datetime_end' => $currentDate->copy()->endOfDay(),
                ]);
                $newSlots->push($existingSlot);
            }

            $currentDate->addDay();
            $dayNumber++;
        }

        $trip->calendarSlots()
            ->whereNotIn('slot_date', $newSlots->pluck('slot_date'))
            ->delete();

        return $newSlots;
    }

    public function deleteSlotsForTrip(Trip $trip): void
    {
        $trip->calendarSlots()->delete();
    }

    /**
     * Calculate the slot_order for a new slot based on datetime_start
     * Orders chronologically by start time within the same day
     */
    public function calculateSlotOrder(int $tripId, string $slotDate, Carbon $datetimeStart): int
    {
        $maxOrder = CalendarSlot::where('trip_id', $tripId)
            ->where('slot_date', $slotDate)
            ->where('datetime_start', '<', $datetimeStart)
            ->max('slot_order');

        return ($maxOrder ?? -1) + 1;
    }

    /**
     * Recalculate slot_order for all slots on a given date
     * Orders by datetime_start ASC
     * Uses database transaction with individual updates for safety
     */
    public function recalculateSlotOrdersForDate(int $tripId, string $slotDate): void
    {
        $slots = CalendarSlot::where('trip_id', $tripId)
            ->where('slot_date', $slotDate)
            ->orderBy('datetime_start')
            ->get();

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

        // Update each slot's order within a transaction
        \DB::transaction(function () use ($slots) {
            foreach ($slots as $index => $slot) {
                $slot->slot_order = $index;
                $slot->save();
            }
        });
    }
}