<?php

namespace App\Support;

use App\Models\User;
use App\Models\WorkoutSession;
use App\Models\WorkoutSessionItem;
use Carbon\Carbon;

class Gamification
{
    /**
     * @return array{current_streak: int, longest_streak: int, badges: array<int, array{key: string, name: string, description: string, earned: bool}>}
     */
    public static function forUser(User $user): array
    {
        $completedDates = WorkoutSession::where('user_id', $user->id)
            ->whereNotNull('completed_at')
            ->pluck('completed_at')
            ->map(fn ($dt) => $dt->toDateString())
            ->unique()
            ->sort()
            ->values();

        $currentStreak = self::currentStreak($completedDates);
        $longestStreak = self::longestStreak($completedDates);

        $completedSessions = $completedDates->isNotEmpty()
            ? WorkoutSession::where('user_id', $user->id)->whereNotNull('completed_at')->count()
            : 0;

        $hasCenturyLift = WorkoutSessionItem::whereHas('session', fn ($q) => $q->where('user_id', $user->id))
            ->where('done', true)
            ->where('actual_weight', '>=', 100)
            ->exists();

        $badges = [
            [
                'key' => 'first_steps',
                'name' => 'First Steps',
                'description' => 'Complete your first workout session.',
                'earned' => $completedSessions >= 1,
            ],
            [
                'key' => 'consistent',
                'name' => 'Consistent',
                'description' => 'Complete 10 workout sessions.',
                'earned' => $completedSessions >= 10,
            ],
            [
                'key' => 'dedicated',
                'name' => 'Dedicated',
                'description' => 'Complete 50 workout sessions.',
                'earned' => $completedSessions >= 50,
            ],
            [
                'key' => 'week_warrior',
                'name' => 'Week Warrior',
                'description' => 'Reach a 7-day training streak.',
                'earned' => $longestStreak >= 7,
            ],
            [
                'key' => 'iron_will',
                'name' => 'Iron Will',
                'description' => 'Reach a 30-day training streak.',
                'earned' => $longestStreak >= 30,
            ],
            [
                'key' => 'century_club',
                'name' => 'Century Club',
                'description' => 'Log 100kg or more on a completed set.',
                'earned' => $hasCenturyLift,
            ],
        ];

        return [
            'current_streak' => $currentStreak,
            'longest_streak' => $longestStreak,
            'badges' => $badges,
        ];
    }

    /**
     * @param \Illuminate\Support\Collection<int, string> $completedDates Sorted, unique Y-m-d strings.
     */
    private static function currentStreak($completedDates): int
    {
        if ($completedDates->isEmpty()) {
            return 0;
        }

        $dateSet = $completedDates->flip();
        $cursor = Carbon::today();

        // A missed "today" doesn't break the streak until tomorrow - only walk
        // back from yesterday if today has no completed session yet.
        if (!$dateSet->has($cursor->toDateString())) {
            $cursor = $cursor->copy()->subDay();
        }

        $streak = 0;
        while ($dateSet->has($cursor->toDateString())) {
            $streak++;
            $cursor = $cursor->copy()->subDay();
        }

        return $streak;
    }

    /**
     * @param \Illuminate\Support\Collection<int, string> $completedDates Sorted, unique Y-m-d strings.
     */
    private static function longestStreak($completedDates): int
    {
        $longest = 0;
        $run = 0;
        $previous = null;

        foreach ($completedDates as $dateStr) {
            $date = Carbon::parse($dateStr);
            $run = ($previous && (int) abs($date->diffInDays($previous)) === 1) ? $run + 1 : 1;
            $longest = max($longest, $run);
            $previous = $date;
        }

        return $longest;
    }
}