import Foundation
import UIKit

actor APIService {
    static let shared = APIService()

    // Change to your server URL
    private let baseURL = URL(string: "https://api.nightly.app/")!

    private var authToken: String? { KeychainService.shared.getToken() }

    // MARK: - Auth

    func login(username: String, password: String) async throws {
        let r: AuthResponse = try await post("auth/login", body: [
            "username": username, "password": password
        ])
        KeychainService.shared.saveToken(r.token)
    }

    func register(username: String, password: String, displayName: String) async throws {
        let r: AuthResponse = try await post("auth/register", body: [
            "username": username, "password": password, "displayName": displayName
        ])
        KeychainService.shared.saveToken(r.token)
    }

    func getCurrentUser() async throws -> User {
        try await get("users/me")
    }

    // MARK: - Posts

    func getFeed() async throws -> [Post] {
        try await get("posts/feed")
    }

    func createPost(content: String, mood: Mood, isAnonymous: Bool) async throws {
        let _: EmptyResponse = try await post("posts", body: [
            "content": content,
            "mood": mood.rawValue,
            "isAnonymous": isAnonymous
        ])
    }

    func resonate(postId: String) async throws {
        let _: EmptyResponse = try await post("posts/\(postId)/resonate", body: [:])
    }

    func unresoante(postId: String) async throws {
        let _: EmptyResponse = try await delete("posts/\(postId)/resonate")
    }

    func sendWhisper(toUserId: String, content: String) async throws {
        let _: EmptyResponse = try await post("users/\(toUserId)/whisper", body: ["content": content])
    }

    // MARK: - Users

    func getUserPosts(userId: String) async throws -> [Post] {
        try await get("users/\(userId)/posts")
    }

    func getUserStreak(userId: String) async throws -> Int {
        let r: StreakResponse = try await get("users/\(userId)/streak")
        return r.streak
    }

    func registerPushToken(_ token: String) async {
        _ = try? await post("users/me/push-token", body: ["token": token]) as EmptyResponse
    }

    // MARK: - HTTP

    private func get<T: Decodable>(_ path: String) async throws -> T {
        try await perform(makeRequest("GET", path: path))
    }

    @discardableResult
    private func post<T: Decodable>(_ path: String, body: [String: Any]) async throws -> T {
        var req = makeRequest("POST", path: path)
        req.httpBody = try JSONSerialization.data(withJSONObject: body)
        return try await perform(req)
    }

    @discardableResult
    private func delete<T: Decodable>(_ path: String) async throws -> T {
        try await perform(makeRequest("DELETE", path: path))
    }

    private func makeRequest(_ method: String, path: String) -> URLRequest {
        var req = URLRequest(url: baseURL.appendingPathComponent(path))
        req.httpMethod = method
        req.setValue("application/json", forHTTPHeaderField: "Content-Type")
        if let t = authToken { req.setValue("Bearer \(t)", forHTTPHeaderField: "Authorization") }
        return req
    }

    private func perform<T: Decodable>(_ request: URLRequest) async throws -> T {
        let (data, response) = try await URLSession.shared.data(for: request)
        guard let http = response as? HTTPURLResponse else { throw APIError.invalidResponse }
        guard (200...299).contains(http.statusCode) else {
            let msg = (try? JSONDecoder().decode(APIErrorBody.self, from: data))?.message
                ?? HTTPURLResponse.localizedString(forStatusCode: http.statusCode)
            throw APIError.serverError(msg)
        }
        let dec = JSONDecoder()
        dec.dateDecodingStrategy = .iso8601
        return try dec.decode(T.self, from: data)
    }
}

private struct AuthResponse: Decodable { let token: String }
private struct StreakResponse: Decodable { let streak: Int }
private struct APIErrorBody: Decodable { let message: String }
struct EmptyResponse: Decodable {}

enum APIError: LocalizedError {
    case invalidResponse
    case serverError(String)
    var errorDescription: String? {
        switch self {
        case .invalidResponse:     return "Ungültige Serverantwort"
        case .serverError(let m):  return m
        }
    }
}