import Foundation
import ManaCore

/// Cards-spezifischer API-Client. Wrapper um `AuthenticatedTransport`
/// aus ManaCore, der die Cardecky-Endpoints kennt.
actor CardsAPI {
    private let transport: AuthenticatedTransport
    private let decoder: JSONDecoder

    init(auth: AuthClient) {
        transport = AuthenticatedTransport(baseURL: AppConfig.apiBaseURL, auth: auth)
        decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .iso8601withFractional
    }

    /// Health-Probe — verifiziert dass cardecky-api erreichbar ist
    /// und der eigene JWT akzeptiert wird.
    func healthCheck() async throws -> Bool {
        let (_, http) = try await transport.request(path: "/healthz")
        return http.statusCode == 200
    }

    // MARK: - Decks

    /// `GET /api/v1/decks?archived=false` — alle aktiven Decks des Users.
    /// Optional: `forkedFromMarketplaceOnly` filtert auf Inbox-Decks
    /// (für den Inbox-Banner).
    func listDecks(forkedFromMarketplaceOnly: Bool = false) async throws -> [Deck] {
        var path = "/api/v1/decks"
        if forkedFromMarketplaceOnly {
            path += "?forked_from_marketplace=true"
        }
        let (data, http) = try await transport.request(path: path)
        try ensureOK(http, data: data)
        let body = try decoder.decode(DeckListResponse.self, from: data)
        return body.decks
    }

    /// `GET /api/v1/cards?deck_id=...` — Anzahl Karten in einem Deck.
    /// Web macht das pro Deck einzeln; identisches Pattern hier.
    func cardCount(deckId: String) async throws -> Int {
        let (data, http) = try await transport.request(path: "/api/v1/cards?deck_id=\(deckId)")
        try ensureOK(http, data: data)
        return try decoder.decode(CardListResponse.self, from: data).total
    }

    /// `GET /api/v1/cards?deck_id=...` — komplette Liste der Karten
    /// für den Browse-Modus im DeckDetailView.
    func listCards(deckId: String) async throws -> [Card] {
        let (data, http) = try await transport.request(path: "/api/v1/cards?deck_id=\(deckId)")
        try ensureOK(http, data: data)
        return try decoder.decode(CardListResponse.self, from: data).cards
    }

    /// `GET /api/v1/reviews/due?deck_id=...&limit=500` — Anzahl fälliger
    /// Reviews in einem Deck.
    func dueCount(deckId: String) async throws -> Int {
        let (data, http) = try await transport.request(
            path: "/api/v1/reviews/due?deck_id=\(deckId)&limit=500"
        )
        try ensureOK(http, data: data)
        return try decoder.decode(DueReviewsResponse.self, from: data).total
    }

    // MARK: - Marketplace

    /// `GET /api/v1/marketplace/explore` — Featured + Trending.
    func explore() async throws -> ExploreResponse {
        let (data, http) = try await transport.request(path: "/api/v1/marketplace/explore")
        try ensureOK(http, data: data)
        return try decoder.decode(ExploreResponse.self, from: data)
    }

    /// `GET /api/v1/marketplace/decks` — Browse mit Filtern.
    func browseMarketplace(
        query: String? = nil,
        sort: MarketplaceSort = .recent,
        language: String? = nil,
        limit: Int = 20,
        offset: Int = 0
    ) async throws -> BrowseResponse {
        var items: [URLQueryItem] = [
            .init(name: "sort", value: sort.rawValue),
            .init(name: "limit", value: "\(limit)"),
            .init(name: "offset", value: "\(offset)"),
        ]
        if let query, !query.trimmingCharacters(in: .whitespaces).isEmpty {
            items.append(.init(name: "q", value: query))
        }
        if let language {
            items.append(.init(name: "language", value: language))
        }
        var components = URLComponents()
        components.queryItems = items
        let queryString = components.percentEncodedQuery ?? ""
        let path = "/api/v1/marketplace/decks?\(queryString)"

        let (data, http) = try await transport.request(path: path)
        try ensureOK(http, data: data)
        return try decoder.decode(BrowseResponse.self, from: data)
    }

    /// `GET /api/v1/marketplace/decks/:slug`.
    func publicDeck(slug: String) async throws -> PublicDeckDetail {
        let (data, http) = try await transport.request(path: "/api/v1/marketplace/decks/\(slug)")
        try ensureOK(http, data: data)
        return try decoder.decode(PublicDeckDetail.self, from: data)
    }

    /// `POST /api/v1/marketplace/decks/:slug/subscribe` — Auto-Fork
    /// passiert serverseitig, Response liefert `private_deck_id`.
    @discardableResult
    func subscribe(slug: String) async throws -> SubscribeResponse {
        let (data, http) = try await transport.request(
            path: "/api/v1/marketplace/decks/\(slug)/subscribe",
            method: "POST"
        )
        try ensureOK(http, data: data)
        return try decoder.decode(SubscribeResponse.self, from: data)
    }

    /// `DELETE /api/v1/marketplace/decks/:slug/subscribe`.
    func unsubscribe(slug: String) async throws {
        let (data, http) = try await transport.request(
            path: "/api/v1/marketplace/decks/\(slug)/subscribe",
            method: "DELETE"
        )
        try ensureOK(http, data: data)
    }

    // MARK: - Media

    /// `POST /api/v1/media/upload` — Multipart-Upload. Max 25 MiB.
    /// Erlaubte MIMEs: image/*, audio/*, video/*.
    func uploadMedia(data: Data, filename: String, mimeType: String) async throws -> MediaUploadResponse {
        let boundary = "cards-native-\(UUID().uuidString)"
        let body = makeMultipartBody(
            file: data,
            filename: filename,
            mimeType: mimeType,
            boundary: boundary
        )
        let (response, http) = try await transport.request(
            path: "/api/v1/media/upload",
            method: "POST",
            body: body,
            contentType: "multipart/form-data; boundary=\(boundary)"
        )
        try ensureOK(http, data: response)
        return try decoder.decode(MediaUploadResponse.self, from: response)
    }

    /// `GET /api/v1/media/:id` — streamt das Media-File. Antwortet mit
    /// raw bytes (kein JSON), Caller schreibt das auf Disk via MediaCache.
    func fetchMedia(id: String) async throws -> Data {
        let (data, http) = try await transport.request(path: "/api/v1/media/\(id)")
        guard (200 ..< 300).contains(http.statusCode) else {
            throw AuthError.serverError(status: http.statusCode, message: "media fetch failed")
        }
        return data
    }

    /// `DELETE /api/v1/media/:id` — Soft-Forget. (Endpoint heute nicht
    /// implementiert serverseitig; Stub bleibt für späteren Use.)
    func deleteMedia(id _: String) async throws {
        throw AuthError.serverError(status: 501, message: "media delete not implemented on server")
    }

    // MARK: - Deck-Mutations

    /// `POST /api/v1/decks` — Deck anlegen.
    @discardableResult
    func createDeck(_ body: DeckCreateBody) async throws -> Deck {
        let data = try makeJSON(body)
        let (responseData, http) = try await transport.request(
            path: "/api/v1/decks",
            method: "POST",
            body: data
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(Deck.self, from: responseData)
    }

    /// `PATCH /api/v1/decks/:id` — Deck-Felder ändern.
    @discardableResult
    func updateDeck(id: String, body: DeckUpdateBody) async throws -> Deck {
        let data = try makeJSON(body)
        let (responseData, http) = try await transport.request(
            path: "/api/v1/decks/\(id)",
            method: "PATCH",
            body: data
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(Deck.self, from: responseData)
    }

    /// `DELETE /api/v1/decks/:id` — Deck löschen (kaskadiert Cards + Reviews).
    func deleteDeck(id: String) async throws {
        let (data, http) = try await transport.request(
            path: "/api/v1/decks/\(id)",
            method: "DELETE"
        )
        try ensureOK(http, data: data)
    }

    // MARK: - Card-Mutations

    /// `POST /api/v1/cards` — Karte anlegen. Server validiert `fields`
    /// gegen den Card-Type und erstellt automatisch Reviews
    /// (1 für basic, 2 für basic-reverse, N für cloze).
    @discardableResult
    func createCard(_ body: CardCreateBody) async throws -> Card {
        let data = try makeJSON(body)
        let (responseData, http) = try await transport.request(
            path: "/api/v1/cards",
            method: "POST",
            body: data
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(Card.self, from: responseData)
    }

    /// `PATCH /api/v1/cards/:id` — nur `fields` und `media_refs`
    /// sind änderbar.
    @discardableResult
    func updateCard(id: String, body: CardUpdateBody) async throws -> Card {
        let data = try makeJSON(body)
        let (responseData, http) = try await transport.request(
            path: "/api/v1/cards/\(id)",
            method: "PATCH",
            body: data
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(Card.self, from: responseData)
    }

    /// `DELETE /api/v1/cards/:id` — Karte + zugehörige Reviews löschen
    /// (Cascade auf DB-Ebene).
    func deleteCard(id: String) async throws {
        let (data, http) = try await transport.request(
            path: "/api/v1/cards/\(id)",
            method: "DELETE"
        )
        try ensureOK(http, data: data)
    }

    // MARK: - Study

    /// `GET /api/v1/reviews/due?deck_id=...&limit=500` — fällige Reviews
    /// inklusive zugehöriger Card-Daten. Hot-Path für die Study-View.
    func dueReviews(deckId: String, limit: Int = 500) async throws -> [DueReview] {
        let (data, http) = try await transport.request(
            path: "/api/v1/reviews/due?deck_id=\(deckId)&limit=\(limit)"
        )
        try ensureOK(http, data: data)
        return try decoder.decode(DueReviewsListResponse.self, from: data).reviews
    }

    /// `POST /api/v1/reviews/:cardId/:subIndex/grade` — gibt eine
    /// Bewertung ab. Server rechnet FSRS, antwortet mit aktualisiertem
    /// Review.
    @discardableResult
    func gradeReview(
        cardId: String,
        subIndex: Int,
        rating: Rating,
        reviewedAt: Date = .now
    ) async throws -> Review {
        let body = try makeJSON(GradeReviewBody(rating: rating, reviewedAt: reviewedAt))
        let (data, http) = try await transport.request(
            path: "/api/v1/reviews/\(cardId)/\(subIndex)/grade",
            method: "POST",
            body: body
        )
        try ensureOK(http, data: data)
        return try decoder.decode(Review.self, from: data)
    }

    // MARK: - JSON-Encoding

    private func makeJSON<T: Encodable>(_ value: T) throws -> Data {
        let encoder = JSONEncoder()
        encoder.dateEncodingStrategy = .iso8601
        return try encoder.encode(value)
    }

    // MARK: - Multipart

    private func makeMultipartBody(
        file: Data,
        filename: String,
        mimeType: String,
        boundary: String
    ) -> Data {
        var body = Data()
        let lineBreak = "\r\n"
        let header = """
        --\(boundary)\(lineBreak)\
        Content-Disposition: form-data; name="file"; filename="\(filename)"\(lineBreak)\
        Content-Type: \(mimeType)\(lineBreak)\(lineBreak)
        """
        body.append(header.data(using: .utf8) ?? Data())
        body.append(file)
        body.append(lineBreak.data(using: .utf8) ?? Data())
        body.append("--\(boundary)--\(lineBreak)".data(using: .utf8) ?? Data())
        return body
    }

    // MARK: - Helpers

    private func ensureOK(_ http: HTTPURLResponse, data: Data) throws {
        guard (200 ..< 300).contains(http.statusCode) else {
            let message = (try? JSONDecoder().decode(CardsServerError.self, from: data))?.error
            throw AuthError.serverError(status: http.statusCode, message: message)
        }
    }
}

private struct CardsServerError: Decodable {
    let error: String?
}

extension JSONDecoder.DateDecodingStrategy {
    /// Cards-API liefert ISO8601 mit Fractional-Seconds aus
    /// `.toISOString()`. Standard-Strategy `.iso8601` akzeptiert die
    /// fractional seconds nicht — wir nutzen einen eigenen Formatter.
    static let iso8601withFractional: JSONDecoder.DateDecodingStrategy = .custom { decoder in
        let container = try decoder.singleValueContainer()
        let raw = try container.decode(String.self)
        let f = ISO8601DateFormatter()
        f.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
        if let date = f.date(from: raw) { return date }
        f.formatOptions = [.withInternetDateTime]
        if let date = f.date(from: raw) { return date }
        throw DecodingError.dataCorruptedError(
            in: container,
            debugDescription: "Cannot decode ISO8601 date: \(raw)"
        )
    }
}