<?php

namespace App\Services;

use App\Models\Outcode;
use App\Models\Postcode;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

class PostcodeService
{
    private const string BASE_URL = 'https://api.postcodes.io';

    private const int CACHE_TTL = 60 * 60 * 24 * 30; // 30 days

    public function __construct(
        private readonly ApiLogger $apiLogger,
    ) {}

    /**
     * Resolve a UK location query (full postcode, outcode, or place name) to coordinates.
     * Returns null if the location cannot be resolved.
     */
    public function resolve(string $query): ?LocationResult
    {
        $query = trim($query);

        if ($this->isFullPostcode($query)) {
            return $this->lookupLocalPostcode($query) ?? $this->lookupPostcode($query);
        }

        if ($this->isOutcode($query)) {
            return $this->lookupLocalOutcode($query) ?? $this->lookupOutcode($query);
        }

        $cacheKey = 'place:'.strtolower(preg_replace('/\s+/', '', $query));

        $cached = Cache::get($cacheKey);

        if ($cached instanceof LocationResult) {
            return $cached;
        }

        $result = $this->lookupPlace($query);

        if ($result !== null) {
            Cache::put($cacheKey, $result, self::CACHE_TTL);
        }

        return $result;
    }

    /**
     * Reverse-geocode coordinates to a general UK area label (e.g. "Peterborough").
     *
     * Coordinates are bucketed to ~1km (2dp) before lookup so the cache is shared
     * across nearby searches and nothing more precise than the stored bucket is
     * ever queried. Returns null if the area cannot be determined.
     */
    public function reverseResolve(float $lat, float $lng): ?string
    {
        $latBucket = round($lat, 2);
        $lngBucket = round($lng, 2);
        $cacheKey = "revgeo:{$latBucket},{$lngBucket}";

        $cached = Cache::get($cacheKey);

        if (is_string($cached)) {
            return $cached;
        }

        $label = $this->lookupArea($latBucket, $lngBucket);

        if ($label !== null) {
            Cache::put($cacheKey, $label, self::CACHE_TTL);
        }

        return $label;
    }

    private function lookupArea(float $lat, float $lng): ?string
    {
        $url = self::BASE_URL.'/postcodes';
        // radius=2000 (postcodes.io max): we query the ~1km bucket centroid, which
        // can sit up to ~780m from any real point in the bucket. The default 100m
        // radius misses in low-density areas, so widen it to guarantee a hit.
        $logUrl = $url.'?lon='.$lng.'&lat='.$lat.'&radius=2000&limit=1';

        try {
            $response = $this->apiLogger->send('postcodes_io', 'GET', $logUrl, fn () => Http::timeout(5)
                ->get($url, ['lon' => $lng, 'lat' => $lat, 'radius' => 2000, 'limit' => 1]));

            if (! $response->successful()) {
                return null;
            }

            $results = $response->json('result');

            if (! is_array($results) || ! isset($results[0]) || ! is_array($results[0])) {
                return null;
            }

            // Prefer the most human "town/district" field, falling back to broader areas.
            foreach (['admin_district', 'parish', 'admin_ward', 'region', 'country'] as $field) {
                $value = $results[0][$field] ?? null;

                if (is_string($value) && $value !== '') {
                    return $value;
                }
            }

            return null;
        } catch (Throwable $e) {
            Log::error('PostcodeService: reverse geocode failed', [
                'lat' => $lat,
                'lng' => $lng,
                'error' => $e->getMessage(),
            ]);

            return null;
        }
    }

    private function normalisePostcode(string $value): string
    {
        return strtoupper(preg_replace('/\s+/', '', $value));
    }

    private function isFullPostcode(string $query): bool
    {
        return (bool) preg_match('/^[A-Z]{1,2}[0-9][0-9A-Z]?\s*[0-9][A-Z]{2}$/i', $query);
    }

    private function isOutcode(string $query): bool
    {
        return (bool) preg_match('/^[A-Z]{1,2}[0-9][0-9A-Z]?$/i', $query);
    }

    private function lookupLocalPostcode(string $postcode): ?LocationResult
    {
        $normalised = $this->normalisePostcode($postcode);

        $row = Postcode::find($normalised);

        if ($row === null) {
            return null;
        }

        return new LocationResult(
            query: $postcode,
            displayName: $this->formatPostcode($normalised),
            lat: $row->lat,
            lng: $row->lng,
        );
    }

    private function lookupLocalOutcode(string $outcode): ?LocationResult
    {
        $normalised = strtoupper(trim($outcode));

        $row = Outcode::find($normalised);

        if ($row === null) {
            return null;
        }

        return new LocationResult(
            query: $outcode,
            displayName: $normalised,
            lat: $row->lat,
            lng: $row->lng,
        );
    }

    private function formatPostcode(string $normalised): string
    {
        // Insert the single space before the last 3 chars ("SW1A1AA" -> "SW1A 1AA").
        if (strlen($normalised) < 5) {
            return $normalised;
        }

        return substr($normalised, 0, -3).' '.substr($normalised, -3);
    }

    private function lookupPostcode(string $postcode): ?LocationResult
    {
        $normalised = $this->normalisePostcode($postcode);
        $url = self::BASE_URL.'/postcodes/'.$normalised;

        try {
            $response = $this->apiLogger->send('postcodes_io', 'GET', $url, fn () => Http::timeout(10)->get($url));

            if (! $response->successful()) {
                return null;
            }

            $data = $response->json('result');

            if (! is_array($data) || ! isset($data['postcode'], $data['latitude'], $data['longitude'])) {
                return null;
            }

            $result = new LocationResult(
                query: $postcode,
                displayName: $data['postcode'],
                lat: $data['latitude'],
                lng: $data['longitude'],
            );

            try {
                Postcode::updateOrCreate(
                    ['postcode' => $normalised],
                    [
                        'outcode' => substr($normalised, 0, strlen($normalised) - 3),
                        'lat' => $data['latitude'],
                        'lng' => $data['longitude'],
                    ],
                );
            } catch (Throwable $e) {
                Log::warning('PostcodeService: failed to persist postcode after HTTP fallback', [
                    'postcode' => $normalised,
                    'error' => $e->getMessage(),
                ]);
            }

            return $result;
        } catch (Throwable $e) {
            Log::error('PostcodeService: postcode lookup failed', [
                'postcode' => $postcode,
                'error' => $e->getMessage(),
            ]);

            return null;
        }
    }

    private function lookupOutcode(string $outcode): ?LocationResult
    {
        $normalised = strtoupper(trim($outcode));
        $url = self::BASE_URL.'/outcodes/'.$normalised;

        try {
            $response = $this->apiLogger->send('postcodes_io', 'GET', $url, fn () => Http::timeout(10)->get($url));

            if (! $response->successful()) {
                return null;
            }

            $data = $response->json('result');

            if (! is_array($data) || ! isset($data['outcode'], $data['latitude'], $data['longitude'])) {
                return null;
            }

            $result = new LocationResult(
                query: $outcode,
                displayName: $data['outcode'],
                lat: $data['latitude'],
                lng: $data['longitude'],
            );

            try {
                Outcode::updateOrCreate(
                    ['outcode' => $normalised],
                    [
                        'lat' => $data['latitude'],
                        'lng' => $data['longitude'],
                    ],
                );
            } catch (Throwable $e) {
                Log::warning('PostcodeService: failed to persist outcode after HTTP fallback', [
                    'outcode' => $normalised,
                    'error' => $e->getMessage(),
                ]);
            }

            return $result;
        } catch (Throwable $e) {
            Log::error('PostcodeService: outcode lookup failed', [
                'outcode' => $outcode,
                'error' => $e->getMessage(),
            ]);

            return null;
        }
    }

    private function lookupPlace(string $place): ?LocationResult
    {
        $url = self::BASE_URL.'/places';
        $logUrl = $url.'?q='.urlencode($place).'&limit=1';

        try {
            $response = $this->apiLogger->send('postcodes_io', 'GET', $logUrl, fn () => Http::timeout(10)
                ->get($url, ['q' => $place, 'limit' => 1]));

            if (! $response->successful()) {
                return null;
            }

            $results = $response->json('result');

            if (empty($results)) {
                return null;
            }

            $data = $results[0];

            return new LocationResult(
                query: $place,
                displayName: $data['name_1'],
                lat: $data['latitude'],
                lng: $data['longitude'],
            );
        } catch (Throwable $e) {
            Log::error('PostcodeService: place lookup failed', [
                'place' => $place,
                'error' => $e->getMessage(),
            ]);

            return null;
        }
    }
}