import Foundation

// MARK: - Service Protocol

protocol RaceServiceProtocol: Sendable {
    func listRaces(filter: RaceFilter) async throws -> [Race]
    func getRace(id: String) async throws -> Race
    func saveRace(id: String, isSaved: Bool) async throws
    func registerForRace(id: String) async throws
}

// MARK: - Default Service

class RaceService: RaceServiceProtocol {
    private let baseURL: URL
    private let session: URLSession
    private let authToken: String?

    init(
        baseURL: URL = URL(string: "http://localhost:3000")!,
        session: URLSession = .shared,
        authToken: String? = nil
    ) {
        self.baseURL = baseURL
        self.session = session
        self.authToken = authToken
    }

    func listRaces(filter: RaceFilter = RaceFilter()) async throws -> [Race] {
        var components = URLComponents(url: baseURL.appendingPathComponent("/api/races"), resolvingAgainstBaseURL: true)!
        var queryItems: [URLQueryItem] = [
            URLQueryItem(name: "limit", value: String(filter.limit)),
            URLQueryItem(name: "offset", value: String(filter.offset))
        ]
        if let distance = filter.distanceKm { queryItems.append(URLQueryItem(name: "distance", value: String(distance))) }
        if let type = filter.raceType { queryItems.append(URLQueryItem(name: "type", value: type.rawValue)) }
        if let terrain = filter.terrainType { queryItems.append(URLQueryItem(name: "terrain", value: terrain.rawValue)) }
        if let startDate = filter.startDate { queryItems.append(URLQueryItem(name: "startDate", value: ISO8601DateFormatter().string(from: startDate))) }
        if let endDate = filter.endDate { queryItems.append(URLQueryItem(name: "endDate", value: ISO8601DateFormatter().string(from: endDate))) }
        if let location = filter.location { queryItems.append(URLQueryItem(name: "location", value: location)) }
        if let radius = filter.radiusKm { queryItems.append(URLQueryItem(name: "radius", value: String(radius))) }
        components.queryItems = queryItems

        let request = try buildRequest(url: components.url!)
        let (data, response) = try await session.data(for: request)
        try validateResponse(response)

        let decoded = try JSONDecoder().decode(RaceListResponse.self, from: data)
        return decoded.races
    }

    func getRace(id: String) async throws -> Race {
        let url = baseURL.appendingPathComponent("/api/races/\(id)")
        let request = try buildRequest(url: url)
        let (data, response) = try await session.data(for: request)
        try validateResponse(response)

        let decoded = try JSONDecoder().decode(RaceDetailResponse.self, from: data)
        return decoded.race
    }

    func saveRace(id: String, isSaved: Bool) async throws {
        let method: HTTPMethod = isSaved ? .post : .delete
        let url = baseURL.appendingPathComponent("/api/races/\(id)/save")
        let request = try buildRequest(url: url, method: method)
        let (_, response) = try await session.data(for: request)
        try validateResponse(response)
    }

    func registerForRace(id: String) async throws {
        let url = baseURL.appendingPathComponent("/api/races/\(id)/register")
        let request = try buildRequest(url: url, method: .post)
        let (_, response) = try await session.data(for: request)
        try validateResponse(response)
    }

    // MARK: - Helpers

    private func buildRequest(url: URL, method: HTTPMethod = .get, body: Data? = nil) throws -> URLRequest {
        var request = URLRequest(url: url)
        request.httpMethod = method.rawValue
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")

        if let token = authToken {
            request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        }

        if let body = body {
            request.httpBody = body
        }

        return request
    }

    private func validateResponse(_ response: URLResponse) throws {
        guard let httpResponse = response as? HTTPURLResponse else {
            throw RaceError.invalidResponse
        }

        guard (200...299).contains(httpResponse.statusCode) else {
            switch httpResponse.statusCode {
            case 401: throw RaceError.unauthorized
            case 403: throw RaceError.forbidden
            case 404: throw RaceError.notFound
            case 429: throw RaceError.rateLimited
            case 500...599: throw RaceError.serverError(httpResponse.statusCode)
            default: throw RaceError.httpError(httpResponse.statusCode)
            }
        }
    }
}

// MARK: - Error Types

enum RaceError: LocalizedError {
    case invalidResponse
    case unauthorized
    case forbidden
    case notFound
    case rateLimited
    case serverError(Int)
    case httpError(Int)

    var errorDescription: String {
        switch self {
        case .invalidResponse: return "Invalid server response"
        case .unauthorized: return "Unauthorized — please log in again"
        case .forbidden: return "Forbidden — check permissions"
        case .notFound: return "Race not found"
        case .rateLimited: return "Too many requests — try again shortly"
        case .serverError(let code): return "Server error (\(code))"
        case .httpError(let code): return "HTTP error (\(code))"
        }
    }
}