import Foundation

enum APIError: Error, LocalizedError {
    case badStatus(Int)
    case invalidUrl
    case noData

    var errorDescription: String? {
        switch self {
        case .badStatus(let code): "Server returned \(code)"
        case .invalidUrl: "Invalid server URL"
        case .noData: "No data received"
        }
    }
}

actor LinkdingAPI {
    private let config: ServerConfig
    private let session: URLSession
    private let decoder: JSONDecoder

    init(config: ServerConfig) {
        self.config = config
        self.session = URLSession.shared
        let d = JSONDecoder()
        d.dateDecodingStrategy = .custom { decoder in
            let s = try decoder.singleValueContainer().decode(String.self)
            let f = ISO8601DateFormatter()
            f.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
            if let date = f.date(from: s) { return date }
            f.formatOptions = [.withInternetDateTime]
            if let date = f.date(from: s) { return date }
            throw DecodingError.dataCorrupted(.init(codingPath: decoder.codingPath, debugDescription: "Bad date: \(s)"))
        }
        self.decoder = d
    }

    private func makeUrl(path: String, queryItems: [URLQueryItem] = []) throws -> URL {
        var components = URLComponents()
        components.scheme = config.useHttps ? "https" : "http"
        components.host = config.host
        components.port = config.port
        components.path = config.path.isEmpty ? path : config.path + path
        if !queryItems.isEmpty { components.queryItems = queryItems }
        guard let url = components.url else { throw APIError.invalidUrl }
        return url
    }

    private func authorizedRequest(url: URL, method: String = "GET", body: Data? = nil) -> URLRequest {
        var req = URLRequest(url: url)
        req.httpMethod = method
        req.setValue("Token \(config.token)", forHTTPHeaderField: "Authorization")
        if let body {
            req.setValue("application/json", forHTTPHeaderField: "Content-Type")
            req.httpBody = body
        }
        return req
    }

    func fetchBookmarks(search: String = "", offset: Int = 0, limit: Int = 50) async throws -> BookmarkResponse {
        var items: [URLQueryItem] = [
            .init(name: "limit", value: "\(limit)"),
            .init(name: "offset", value: "\(offset)")
        ]
        if !search.isEmpty { items.append(.init(name: "q", value: search)) }
        let url = try makeUrl(path: "/api/bookmarks/", queryItems: items)
        let (data, response) = try await session.data(for: authorizedRequest(url: url))
        guard (response as? HTTPURLResponse)?.statusCode == 200 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
        return try decoder.decode(BookmarkResponse.self, from: data)
    }

    func fetchBookmarksFromUrl(_ urlString: String) async throws -> BookmarkResponse {
        guard let url = URL(string: urlString) else { throw APIError.invalidUrl }
        let (data, _) = try await session.data(for: authorizedRequest(url: url))
        return try decoder.decode(BookmarkResponse.self, from: data)
    }

    func createBookmark(_ create: BookmarkCreate) async throws -> Bookmark {
        let body = try JSONEncoder().encode(create)
        let url = try makeUrl(path: "/api/bookmarks/")
        let (data, response) = try await session.data(for: authorizedRequest(url: url, method: "POST", body: body))
        guard (response as? HTTPURLResponse)?.statusCode == 201 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
        return try decoder.decode(Bookmark.self, from: data)
    }

    func updateBookmark(id: Int, tagNames: [String]) async throws -> Bookmark {
        let body = try JSONEncoder().encode(["tag_names": tagNames])
        let url = try makeUrl(path: "/api/bookmarks/\(id)/")
        let (data, response) = try await session.data(for: authorizedRequest(url: url, method: "PATCH", body: body))
        guard (response as? HTTPURLResponse)?.statusCode == 200 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
        return try decoder.decode(Bookmark.self, from: data)
    }

    func deleteBookmark(id: Int) async throws {
        let url = try makeUrl(path: "/api/bookmarks/\(id)/")
        let (_, response) = try await session.data(for: authorizedRequest(url: url, method: "DELETE"))
        guard (response as? HTTPURLResponse)?.statusCode == 204 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
    }

    func archiveBookmark(id: Int) async throws {
        let url = try makeUrl(path: "/api/bookmarks/\(id)/archive/")
        let (_, response) = try await session.data(for: authorizedRequest(url: url, method: "POST"))
        guard let code = (response as? HTTPURLResponse)?.statusCode, code == 200 || code == 204 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
    }

    func verifyConnection() async throws {
        let url = try makeUrl(path: "/api/bookmarks/", queryItems: [.init(name: "limit", value: "1")])
        let (_, response) = try await session.data(for: authorizedRequest(url: url))
        guard (response as? HTTPURLResponse)?.statusCode == 200 else {
            throw APIError.badStatus((response as? HTTPURLResponse)?.statusCode ?? 0)
        }
    }
}