<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Http\JsonResponse;

class GridController extends Controller
{
    // Grid size in degrees (~1km at equator)
    const GRID_SIZE = 0.009;

    /**
     * Calculate grid ID from coordinates
     */
    private function getGridId(float $lat, float $lng): string
    {
        $gridLat = floor($lat / self::GRID_SIZE);
        $gridLng = floor($lng / self::GRID_SIZE);
        return "grid_{$gridLat}_{$gridLng}";
    }

    /**
     * Calculate grid bounds from grid ID
     */
    private function getGridBounds(string $gridId): array
    {
        $parts = explode('_', $gridId);
        $gridLat = (int) $parts[1];
        $gridLng = (int) $parts[2];

        return [
            'south' => $gridLat * self::GRID_SIZE,
            'north' => ($gridLat + 1) * self::GRID_SIZE,
            'west' => $gridLng * self::GRID_SIZE,
            'east' => ($gridLng + 1) * self::GRID_SIZE
        ];
    }

    /**
     * GET /api/grids
     * Get all grids within viewport bounds
     */
    public function index(Request $request): JsonResponse
    {
        $bounds = $request->query('bounds');

        // For now, return empty since we don't have MongoDB
        // In production, this would query the database
        return response()->json([]);
    }

    /**
     * GET /api/grids/generate
     * Generate grid cells for a viewport (doesn't save to DB, just returns structure)
     */
    public function generate(Request $request): JsonResponse
    {
        $bounds = $request->query('bounds');

        if (!$bounds) {
            return response()->json([
                'error' => 'bounds parameter required (south,west,north,east)'
            ], 400);
        }

        $coords = array_map('floatval', explode(',', $bounds));
        $south = $coords[0];
        $west = $coords[1];
        $north = $coords[2];
        $east = $coords[3];

        $grids = [];

        // Generate grid cells for the viewport
        for ($lat = floor($south / self::GRID_SIZE) * self::GRID_SIZE; $lat < $north; $lat += self::GRID_SIZE) {
            for ($lng = floor($west / self::GRID_SIZE) * self::GRID_SIZE; $lng < $east; $lng += self::GRID_SIZE) {
                $centerLat = $lat + self::GRID_SIZE / 2;
                $centerLng = $lng + self::GRID_SIZE / 2;
                $gridId = $this->getGridId($centerLat, $centerLng);

                $grids[] = [
                    'gridId' => $gridId,
                    'bounds' => [
                        'south' => $lat,
                        'north' => $lat + self::GRID_SIZE,
                        'west' => $lng,
                        'east' => $lng + self::GRID_SIZE
                    ],
                    'centerLat' => $centerLat,
                    'centerLng' => $centerLng,
                    'status' => 'pending',
                    'downloadedTypes' => [],
                    'placesCount' => 0
                ];
            }
        }

        return response()->json([
            'gridSize' => self::GRID_SIZE,
            'gridCount' => count($grids),
            'grids' => $grids
        ]);
    }

    /**
     * POST /api/grids/{gridId}/download
     * Mark a grid for download (actual download happens from frontend via Google Places API)
     */
    public function download(Request $request, string $gridId): JsonResponse
    {
        $types = $request->input('types', []);
        $places = $request->input('places', []);

        $bounds = $this->getGridBounds($gridId);
        $centerLat = ($bounds['north'] + $bounds['south']) / 2;
        $centerLng = ($bounds['east'] + $bounds['west']) / 2;

        // In production, this would save to database
        // For now, just return success response
        $grid = [
            'gridId' => $gridId,
            'bounds' => $bounds,
            'centerLat' => $centerLat,
            'centerLng' => $centerLng,
            'status' => 'downloaded',
            'downloadedTypes' => $types,
            'placesCount' => count($places),
            'downloadedAt' => now()->toISOString(),
            'lastUpdated' => now()->toISOString()
        ];

        return response()->json([
            'success' => true,
            'grid' => $grid,
            'savedPlaces' => count($places)
        ]);
    }

    /**
     * GET /api/grids/stats
     * Get download statistics
     */
    public function stats(): JsonResponse
    {
        // In production, this would query the database
        // For now, return mock stats
        return response()->json([
            'totalGrids' => 0,
            'downloadedGrids' => 0,
            'totalPlaces' => 0,
            'placesByType' => []
        ]);
    }
}