import Foundation
import ManaCore

/// AI-Deck-Generierung + Multipart-Helpers — ausgelagert aus `CardsAPI`,
/// damit der Haupt-Actor unter der Type-Body-Length-Grenze bleibt.
extension CardsAPI {
    /// `POST /api/v1/decks/generate` — KI generiert Deck aus Prompt.
    /// Rate-Limit serverseitig 10/min. Antwort dauert typisch 10–60s
    /// (synchron, kein Streaming).
    func generateDeckFromText(_ body: DeckGenerateBody) async throws -> DeckGenerateResponse {
        let data = try makeJSON(body)
        let (responseData, http) = try await transport.request(
            path: "/api/v1/decks/generate",
            method: "POST",
            body: data
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(DeckGenerateResponse.self, from: responseData)
    }

    /// `POST /api/v1/decks/from-image` — Vision-LLM generiert Deck aus
    /// Bildern und/oder PDFs (max 5 Files, 10 MiB pro Bild, 30 MiB pro PDF)
    /// und optional einer URL für Zusatz-Kontext. Rate-Limit 10/min.
    /// Multipart-Body mit `file`-Parts (wiederholt) + Text-Felder.
    func generateDeckFromMedia(
        files: [GenerationMediaFile],
        language: GenerationLanguage,
        count: Int,
        url: String?
    ) async throws -> DeckGenerateResponse {
        let boundary = "cards-native-\(UUID().uuidString)"
        let body = makeFromImageMultipartBody(
            files: files,
            language: language,
            count: count,
            url: url,
            boundary: boundary
        )
        let (responseData, http) = try await transport.request(
            path: "/api/v1/decks/from-image",
            method: "POST",
            body: body,
            contentType: "multipart/form-data; boundary=\(boundary)"
        )
        try ensureOK(http, data: responseData)
        return try decoder.decode(DeckGenerateResponse.self, from: responseData)
    }

    // MARK: - Multipart

    /// Single-File-Multipart-Body für `/media/upload`.
    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(Data(header.utf8))
        body.append(file)
        body.append(Data(lineBreak.utf8))
        body.append(Data("--\(boundary)--\(lineBreak)".utf8))
        return body
    }

    /// Multi-File-Multipart-Body für `/decks/from-image` — mehrere Files
    /// unter dem Form-Feld `file` (Server liest sie via `getAll('file')`)
    /// plus optional `language`, `count`, `url` als Text-Felder.
    func makeFromImageMultipartBody(
        files: [GenerationMediaFile],
        language: GenerationLanguage,
        count: Int,
        url: String?,
        boundary: String
    ) -> Data {
        var body = Data()
        let lineBreak = "\r\n"

        func appendField(name: String, value: String) {
            let part = """
            --\(boundary)\(lineBreak)\
            Content-Disposition: form-data; name="\(name)"\(lineBreak)\(lineBreak)\
            \(value)\(lineBreak)
            """
            body.append(Data(part.utf8))
        }

        appendField(name: "language", value: language.rawValue)
        appendField(name: "count", value: String(count))
        if let url, !url.trimmingCharacters(in: .whitespaces).isEmpty {
            appendField(name: "url", value: url)
        }

        for file in files {
            let header = """
            --\(boundary)\(lineBreak)\
            Content-Disposition: form-data; name="file"; filename="\(file.filename)"\(lineBreak)\
            Content-Type: \(file.mimeType)\(lineBreak)\(lineBreak)
            """
            body.append(Data(header.utf8))
            body.append(file.data)
            body.append(Data(lineBreak.utf8))
        }

        body.append(Data("--\(boundary)--\(lineBreak)".utf8))
        return body
    }
}