<?php
declare(strict_types=1);

namespace Modules\FxRates\Api;

use Modules\FxRates\Domain\FxRatesService;

final class Router
{
    public function __construct(
        private FxRatesService $service
    ) {
    }

    public function handle(string $relativePath): never
    {
        $method = strtoupper((string) ($_SERVER['REQUEST_METHOD'] ?? 'GET'));
        $path = trim($relativePath, '/');

        try {
            if ($path === 'v1/health' && $method === 'GET') {
                $this->respond(['ok' => true, 'module' => 'fx-rates']);
            }

            if ($path === 'v1/endpoints' && $method === 'GET') {
                $this->respond(['data' => $this->endpointCatalog()]);
            }

            if ($path === 'v1/status' && $method === 'GET') {
                $this->respond(['data' => $this->service->latestStatuses()]);
            }

            if ($path === 'v1/recent-fetches' && $method === 'GET') {
                $limit = max(1, min(50, (int) ($_GET['limit'] ?? 12)));
                $this->respond(['data' => $this->service->recentFetches($limit)]);
            }

            if ($path === 'v1/latest' && $method === 'GET') {
                $symbols = $this->parseCsv($_GET['symbols'] ?? null);
                $base = $this->stringOrNull($_GET['base'] ?? null);
                if ($symbols === null) {
                    $settings = module_fn('fx-rates', 'settings');
                    $symbols = is_array($settings['preferred_currencies'] ?? null) ? $settings['preferred_currencies'] : null;
                }
                $snapshot = $this->service->snapshot($base, null, $symbols, null);
                $this->respond(['data' => $snapshot]);
            }

            if ($path === 'v1/fetch' && $method === 'GET') {
                $fetchId = max(0, (int) ($_GET['fetch_id'] ?? 0));
                $base = $this->stringOrNull($_GET['base'] ?? null);
                $symbols = $this->parseCsv($_GET['symbols'] ?? null);
                $snapshot = $this->service->snapshotByFetchId($fetchId, $base, $symbols);
                $this->respond(['data' => $snapshot]);
            }

            if ($path === 'v1/nearest' && $method === 'GET') {
                $base = $this->stringOrNull($_GET['base'] ?? null);
                $symbols = $this->parseCsv($_GET['symbols'] ?? null);
                $at = $this->stringOrNull($_GET['at'] ?? null);
                $windowMinutes = $this->intOrNull($_GET['window_minutes'] ?? null);
                $snapshot = $this->service->nearestSnapshot($base, (string) $at, $symbols, $windowMinutes);
                $this->respond(['data' => $snapshot]);
            }

            if ($path === 'v1/snapshot' && $method === 'GET') {
                $symbols = $this->parseCsv($_GET['symbols'] ?? null);
                $base = $this->stringOrNull($_GET['base'] ?? null);
                $at = $this->stringOrNull($_GET['at'] ?? null);
                $windowMinutes = $this->intOrNull($_GET['window_minutes'] ?? null);
                $snapshot = $this->service->snapshot($base, $at, $symbols, $windowMinutes);
                $this->respond(['data' => $snapshot]);
            }

            if ($path === 'v1/rate' && $method === 'GET') {
                $from = $this->stringOrNull($_GET['from'] ?? null);
                $to = $this->stringOrNull($_GET['to'] ?? null);
                $at = $this->stringOrNull($_GET['at'] ?? null);
                $windowMinutes = $this->intOrNull($_GET['window_minutes'] ?? null);
                $rate = $this->service->findRate($from, $to, $at, $windowMinutes);
                $this->respond(['data' => $rate]);
            }

            if ($path === 'v1/history' && $method === 'GET') {
                $from = $this->stringOrNull($_GET['from'] ?? null);
                $to = $this->stringOrNull($_GET['to'] ?? null);
                $fromAt = $this->stringOrNull($_GET['from_at'] ?? null);
                $toAt = $this->stringOrNull($_GET['to_at'] ?? null);
                $limit = max(1, min(1000, (int) ($_GET['limit'] ?? 200)));
                $history = $this->service->history((string) $from, (string) $to, $fromAt, $toAt, $limit);
                $this->respond(['data' => $history]);
            }

            if ($path === 'v1/refresh' && $method === 'POST') {
                $input = $this->input();
                $base = $this->stringOrNull($input['base'] ?? null);
                $force = !empty($input['force']);
                $maxAgeMinutes = is_numeric($input['max_age_minutes'] ?? null) ? (int) $input['max_age_minutes'] : null;

                $result = $force
                    ? $this->service->refreshLatestRates(null, $base, 'api')
                    : $this->service->autoRefreshLatestRates($base, null, $maxAgeMinutes, 'api');

                $this->respond(['data' => $result], 201);
            }

            if ($path === 'v1/probe' && $method === 'GET') {
                $base = $this->stringOrNull($_GET['base'] ?? null);
                $this->respond(['data' => $this->service->probeLatestRates($base)]);
            }

            if ($path === 'v1/settings' && $method === 'GET') {
                $this->respond(['data' => module_fn('fx-rates', 'settings')]);
            }

            if ($path === 'v1/settings' && $method === 'PUT') {
                $this->respond(['data' => module_fn('fx-rates', 'save_runtime_settings', $this->input())]);
            }

            $this->respond(['error' => 'Unbekannter API-Pfad.'], 404);
        } catch (\Throwable $exception) {
            $this->respond([
                'error' => 'FX-API Fehler.',
                'context' => ['message' => $exception->getMessage()],
            ], 500);
        }
    }

    private function respond(array $payload, int $statusCode = 200): never
    {
        http_response_code($statusCode);
        header('Content-Type: application/json; charset=utf-8');
        echo json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
        exit;
    }

    private function input(): array
    {
        $raw = file_get_contents('php://input');
        $decoded = json_decode((string) $raw, true);
        return is_array($decoded) ? $decoded : [];
    }

    private function parseCsv(mixed $value): ?array
    {
        if (is_array($value)) {
            $items = $value;
        } else {
            $value = trim((string) $value);
            if ($value === '') {
                return null;
            }
            $items = explode(',', $value);
        }

        $result = [];
        foreach ($items as $item) {
            $item = strtoupper(trim((string) $item));
            if ($item !== '') {
                $result[] = $item;
            }
        }

        $result = array_values(array_unique($result));
        return $result !== [] ? $result : null;
    }

    private function stringOrNull(mixed $value): ?string
    {
        $value = trim((string) $value);
        return $value !== '' ? $value : null;
    }

    private function intOrNull(mixed $value): ?int
    {
        return is_numeric($value) ? (int) $value : null;
    }

    private function endpointCatalog(): array
    {
        return [
            'module' => 'fx-rates',
            'version' => 'v1',
            'languages' => ['de', 'en'],
            'endpoints' => [
                [
                    'path' => '/api/fx-rates/v1/endpoints',
                    'method' => 'GET',
                    'description_de' => 'Gibt alle verfuegbaren FX-API-Endpunkte mit deutscher und englischer Erklaerung zurueck.',
                    'description_en' => 'Returns all available FX API endpoints with German and English explanations.',
                ],
                [
                    'path' => '/api/fx-rates/v1/latest',
                    'method' => 'GET',
                    'params' => ['base', 'symbols'],
                    'description_de' => 'Liefert den neuesten gespeicherten Snapshot, optional auf eine Zielbasis umgerechnet und auf ausgewaehlte Waehrungen gefiltert.',
                    'description_en' => 'Returns the latest stored snapshot, optionally rebased to a target currency and filtered to selected symbols.',
                ],
                [
                    'path' => '/api/fx-rates/v1/fetch',
                    'method' => 'GET',
                    'params' => ['fetch_id', 'base', 'symbols'],
                    'description_de' => 'Liefert einen gespeicherten Snapshot anhand der fetch_id, optional umgerechnet auf eine Zielbasis und gefiltert auf einzelne Waehrungen.',
                    'description_en' => 'Returns a stored snapshot by fetch_id, optionally rebased to a target currency and filtered to selected symbols.',
                ],
                [
                    'path' => '/api/fx-rates/v1/nearest',
                    'method' => 'GET',
                    'params' => ['at', 'base', 'symbols', 'window_minutes'],
                    'description_de' => 'Liefert den zeitlich naechsten gespeicherten Snapshot zu einem Datum/Uhrzeit-Wert.',
                    'description_en' => 'Returns the stored snapshot nearest to a given date/time value.',
                ],
                [
                    'path' => '/api/fx-rates/v1/snapshot',
                    'method' => 'GET',
                    'params' => ['at', 'base', 'symbols', 'window_minutes'],
                    'description_de' => 'Liefert einen Snapshot zur Zielbasis und sucht fuer einen Zeitpunkt den naechsten passenden gespeicherten Kurs.',
                    'description_en' => 'Returns a snapshot for the requested base and finds the nearest matching stored rate for a given timestamp.',
                ],
                [
                    'path' => '/api/fx-rates/v1/rate',
                    'method' => 'GET',
                    'params' => ['from', 'to', 'at', 'window_minutes'],
                    'description_de' => 'Liefert einen Einzelkurs zwischen zwei Waehrungen, direkt oder als Kreuzkurs aus gespeicherten Snapshots.',
                    'description_en' => 'Returns a single rate between two currencies, directly or as a cross-rate from stored snapshots.',
                ],
                [
                    'path' => '/api/fx-rates/v1/history',
                    'method' => 'GET',
                    'params' => ['from', 'to', 'from_at', 'to_at', 'limit'],
                    'description_de' => 'Liefert den gespeicherten Kursverlauf zwischen zwei Waehrungen fuer einen Zeitraum.',
                    'description_en' => 'Returns the stored rate history between two currencies for a given time range.',
                ],
                [
                    'path' => '/api/fx-rates/v1/refresh',
                    'method' => 'POST',
                    'body' => ['base', 'force', 'max_age_minutes'],
                    'description_de' => 'Aktualisiert Kurse nur dann neu, wenn der letzte Abruf aelter als die erlaubte Zeitspanne ist. Die Antwort enthaelt immer die fetch_id des verwendeten Snapshots.',
                    'description_en' => 'Refreshes rates only if the last fetch is older than the allowed age. The response always includes the fetch_id of the snapshot used.',
                ],
                [
                    'path' => '/api/fx-rates/v1/status',
                    'method' => 'GET',
                    'description_de' => 'Liefert den neuesten gespeicherten Abruf je Basiswaehrung.',
                    'description_en' => 'Returns the most recent stored fetch per base currency.',
                ],
                [
                    'path' => '/api/fx-rates/v1/recent-fetches',
                    'method' => 'GET',
                    'params' => ['limit'],
                    'description_de' => 'Liefert die zuletzt gespeicherten Abrufe mit fetch_id und Zeitstempel.',
                    'description_en' => 'Returns the most recently stored fetches including fetch_id and timestamp.',
                ],
                [
                    'path' => '/api/fx-rates/v1/probe',
                    'method' => 'GET',
                    'params' => ['base'],
                    'description_de' => 'Prueft, ob der konfigurierte Provider aktuelle Kurse liefern kann.',
                    'description_en' => 'Checks whether the configured provider can return current rates.',
                ],
                [
                    'path' => '/api/fx-rates/v1/settings',
                    'method' => 'GET',
                    'description_de' => 'Liefert die aktuellen Modul-Settings.',
                    'description_en' => 'Returns the current module settings.',
                ],
            ],
        ];
    }
}