<?php

namespace App\Services;

use App\Models\User;
use App\Models\Transaction;
use App\Models\KpiTarget;
use App\Models\KpiAchievement;
use Carbon\Carbon;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Log;

class KpiService
{
    /**
     * Calculate KPI achievement for a user
     *
     * @param User $user
     * @param int $year
     * @param int $month
     * @return KpiAchievement|null
     */
    public function calculateKpiAchievement(User $user, $year = null, $month = null)
    {
        $year = $year ?? now()->year;
        $month = $month ?? now()->month;
        
        // Get current KPI target (no longer filtered by year/month)
        $kpiTarget = $user->kpiTargets()
            ->where('is_active', true)
            ->first();
        
        if (!$kpiTarget) {
            Log::info("No KPI target found for user {$user->id}");
            return null;
        }

        // Calculate actual value based on month
        $actualValue = $this->getActualWorkCount($user, $year, $month);
        
        // Calculate percentage
        $achievementPercentage = $kpiTarget->target_value > 0 
            ? ($actualValue / $kpiTarget->target_value) * 100 
            : 0;

        // Save or update achievement with target value stored directly
        return KpiAchievement::updateOrCreate(
            [
                'user_id' => $user->id,
                'year' => $year,
                'month' => $month
            ],
            [
                'kpi_target_id' => $kpiTarget->id,
                'target_value' => $kpiTarget->target_value, // Store target value directly for historical tracking
                'actual_value' => $actualValue,
                'achievement_percentage' => $achievementPercentage
            ]
        );
    }

    /**
     * Get actual work count for a user in specific month
     *
     * @param User $user
     * @param int $year
     * @param int $month
     * @return int
     */
    private function getActualWorkCount(User $user, $year, $month)
    {
        return Transaction::where('user_id', $user->id)
            ->where('status', 'completed')
            ->whereYear('date', $year)
            ->whereMonth('date', $month)
            ->sum('qty');
    }

    /**
     * Generate KPI report for a user
     *
     * @param User $user
     * @param int|null $year
     * @param int|null $month
     * @return array
     */
    public function generateKpiReport(User $user, $year = null, $month = null)
    {
        $year = $year ?? now()->year;
        $month = $month ?? now()->month;

        $achievements = $user->kpiAchievements()
            ->where('year', $year)
            ->where('month', $month)
            ->orderBy('month')
            ->get();

        $target = $user->kpiTargets()
            ->where('is_active', true)
            ->first();

        return [
            'user' => $user,
            'target' => $target,
            'achievements' => $achievements,
            'summary' => $this->calculateSummary($achievements),
            'period' => [
                'year' => $year,
                'month' => $month,
                'period_name' => $this->getMonthName($month) . ' ' . $year
            ]
        ];
    }

    /**
     * Calculate summary statistics for achievements
     *
     * @param \Illuminate\Database\Eloquent\Collection $achievements
     * @return array
     */
    private function calculateSummary($achievements)
    {
        if ($achievements->isEmpty()) {
            return [
                'total_target' => 0,
                'total_actual' => 0,
                'average_achievement' => 0,
                'best_period' => null,
                'worst_period' => null,
                'total_periods' => 0,
                'achievement_rate' => 0
            ];
        }

        $totalTarget = $achievements->sum('target_value');
        $totalActual = $achievements->sum('actual_value');
        $averageAchievement = $achievements->avg('achievement_percentage');
        $totalPeriods = $achievements->count();
        $achievementRate = $totalPeriods > 0 ? ($achievements->where('achievement_percentage', '>=', 100)->count() / $totalPeriods) * 100 : 0;

        $bestPeriod = $achievements->sortByDesc('achievement_percentage')->first();
        $worstPeriod = $achievements->sortBy('achievement_percentage')->first();

        return [
            'total_target' => $totalTarget,
            'total_actual' => $totalActual,
            'average_achievement' => round($averageAchievement, 2),
            'best_period' => $bestPeriod,
            'worst_period' => $worstPeriod,
            'total_periods' => $totalPeriods,
            'achievement_rate' => round($achievementRate, 2)
        ];
    }

    /**
     * Get KPI statistics for all mechanics
     *
     * @param int|null $year
     * @param int|null $month
     * @return array
     */
    public function getMechanicsKpiStats($year = null, $month = null)
    {
        $year = $year ?? now()->year;
        $month = $month ?? now()->month;

        $mechanics = User::whereHas('role', function($query) {
            $query->where('name', 'mechanic');
        })->get();

        $stats = [];
        foreach ($mechanics as $mechanic) {
            $report = $this->generateKpiReport($mechanic, $year, $month);
            $stats[] = [
                'user' => $mechanic,
                'summary' => $report['summary'],
                'target' => $report['target']
            ];
        }

        return $stats;
    }

    /**
     * Auto-calculate KPI achievements for all mechanics
     *
     * @param int|null $year
     * @param int|null $month
     * @return array
     */
    public function autoCalculateAllMechanics($year = null, $month = null)
    {
        $year = $year ?? now()->year;
        $month = $month ?? now()->month;
        
        $mechanics = User::whereHas('role', function($query) {
            $query->where('name', 'mechanic');
        })->get();

        $results = [];
        foreach ($mechanics as $mechanic) {
            try {
                $achievement = $this->calculateKpiAchievement($mechanic, $year, $month);
                $results[] = [
                    'user_id' => $mechanic->id,
                    'user_name' => $mechanic->name,
                    'success' => true,
                    'achievement' => $achievement
                ];
            } catch (\Exception $e) {
                Log::error("Failed to calculate KPI for user {$mechanic->id}: " . $e->getMessage());
                $results[] = [
                    'user_id' => $mechanic->id,
                    'user_name' => $mechanic->name,
                    'success' => false,
                    'error' => $e->getMessage()
                ];
            }
        }

        return $results;
    }

    /**
     * Get KPI trend data for chart
     *
     * @param User $user
     * @param int $months
     * @return array
     */
    public function getKpiTrendData(User $user, $months = 12)
    {
        $endDate = now();
        $startDate = $endDate->copy()->subMonths($months);

        $achievements = $user->kpiAchievements()
            ->where(function($query) use ($startDate, $endDate) {
                $query->where(function($q) use ($startDate, $endDate) {
                    $q->where('year', '>', $startDate->year)
                      ->orWhere(function($subQ) use ($startDate, $endDate) {
                          $subQ->where('year', $startDate->year)
                               ->where('month', '>=', $startDate->month);
                      });
                })
                ->where(function($q) use ($endDate) {
                    $q->where('year', '<', $endDate->year)
                      ->orWhere(function($subQ) use ($endDate) {
                          $subQ->where('year', $endDate->year)
                               ->where('month', '<=', $endDate->month);
                      });
                });
            })
            ->orderBy('year')
            ->orderBy('month')
            ->get();

        $trendData = [];
        foreach ($achievements as $achievement) {
            $trendData[] = [
                'period' => $achievement->getPeriodDisplayName(),
                'target' => $achievement->target_value,
                'actual' => $achievement->actual_value,
                'percentage' => $achievement->achievement_percentage,
                'status' => $achievement->status
            ];
        }

        return $trendData;
    }

    /**
     * Get month name in Indonesian
     *
     * @param int $month
     * @return string
     */
    private function getMonthName($month)
    {
        $monthNames = [
            1 => 'Januari', 2 => 'Februari', 3 => 'Maret', 4 => 'April',
            5 => 'Mei', 6 => 'Juni', 7 => 'Juli', 8 => 'Agustus',
            9 => 'September', 10 => 'Oktober', 11 => 'November', 12 => 'Desember'
        ];
        
        return $monthNames[$month] ?? 'Unknown';
    }

    /**
     * Get KPI summary for dashboard
     *
     * @param User $user
     * @return array
     */
    public function getKpiSummary(User $user)
    {
        $currentYear = now()->year;
        $currentMonth = now()->month;

        // Get current month achievement
        $currentAchievement = $user->kpiAchievements()
            ->where('year', $currentYear)
            ->where('month', $currentMonth)
            ->first();

        // Get current month target (no longer filtered by year/month)
        $currentTarget = $user->kpiTargets()
            ->where('is_active', true)
            ->first();

        // Get last 6 months achievements
        $recentAchievements = $user->kpiAchievements()
            ->where(function($query) use ($currentYear, $currentMonth) {
                $query->where('year', '>', $currentYear - 1)
                      ->orWhere(function($q) use ($currentYear, $currentMonth) {
                          $q->where('year', $currentYear)
                            ->where('month', '>=', max(1, $currentMonth - 5));
                      });
            })
            ->orderBy('year', 'desc')
            ->orderBy('month', 'desc')
            ->limit(6)
            ->get();

        return [
            'current_achievement' => $currentAchievement,
            'current_target' => $currentTarget,
            'recent_achievements' => $recentAchievements,
            'current_percentage' => $currentAchievement ? $currentAchievement->achievement_percentage : 0,
            'is_on_track' => $currentAchievement ? $currentAchievement->achievement_percentage >= 100 : false
        ];
    }
}