<?php

namespace App\Services\Route;

use App\Models\Route;
use Illuminate\Support\Facades\DB;

class RouteCalculator
{
    public const DEFAULT_AVG_SPEED_KMH = 25.0;
    public const DUMPSITE_DWELL_MINUTES = 20;

    /**
     * Recompute total_distance_km and estimated_duration_minutes for the
     * given route based on its current ordered stops + default dumpsite.
     */
    public function recompute(Route $route): void
    {
        $route->load(['stops.dropOffPoint', 'defaultDumpsite']);

        $points = $route->stops
            ->map(fn ($s) => $s->dropOffPoint?->coordinates)
            ->filter()
            ->values();

        if ($route->defaultDumpsite?->coordinates) {
            $points->push($route->defaultDumpsite->coordinates);
        }

        $distanceKm = 0.0;
        for ($i = 0; $i < $points->count() - 1; $i++) {
            $distanceKm += $this->haversineKm(
                $points[$i]->latitude,
                $points[$i]->longitude,
                $points[$i + 1]->latitude,
                $points[$i + 1]->longitude,
            );
        }

        $dwellAtStops = (int) $route->stops->sum('estimated_duration_at_stop_minutes');
        $avgSpeed = (float) config('routes.avg_speed_kmh', self::DEFAULT_AVG_SPEED_KMH);
        $travelMinutes = $avgSpeed > 0 ? (int) round(($distanceKm / $avgSpeed) * 60) : 0;
        $dumpsiteDwell = $route->defaultDumpsite ? self::DUMPSITE_DWELL_MINUTES : 0;

        $route->forceFill([
            'total_distance_km' => round($distanceKm, 3),
            'estimated_duration_minutes' => $dwellAtStops + $travelMinutes + $dumpsiteDwell,
        ])->save();
    }

    private function haversineKm(float $lat1, float $lng1, float $lat2, float $lng2): float
    {
        // Use MySQL ST_Distance_Sphere directly for consistency with the
        // database geofence math.
        $row = DB::selectOne(
            'SELECT ST_Distance_Sphere(ST_SRID(POINT(?, ?), 4326), ST_SRID(POINT(?, ?), 4326)) AS m',
            [$lng1, $lat1, $lng2, $lat2],
        );

        return ((float) $row->m) / 1000.0;
    }
}