import Foundation

/// Zero-backend DSClient: loads the 14 bundled fixtures (Bundle.module) with the SAME decoder the
/// live client will use, so "it previews" == "the DTOs decode the real shapes". Powers SwiftUI
/// previews and the contract acceptance test. Write-side methods return a plausible echo.
///
/// Holds no non-Sendable stored state (uses Bundle.module locally) → Sendable.
public struct FixtureDSClient: DSClient {
    public init() {}

    private func load<T: Decodable>(_ name: String, as type: T.Type) throws -> T {
        guard let url = Bundle.module.url(forResource: name, withExtension: "json") else {
            throw DSError.notFound(message: "fixture \(name).json")
        }
        let data = try Data(contentsOf: url)
        do {
            return try DSDecoder.make().decode(T.self, from: data)
        } catch {
            throw DSError.decoding("\(name): \(error)")
        }
    }

    // Auth
    public func login(username: String, password: String, totpCode: String?) async throws -> AccessTokenResponse {
        try load("auth_login", as: AccessTokenResponse.self)
    }
    public func me() async throws -> UserResponse { try load("auth_me", as: UserResponse.self) }
    public func refresh() async throws -> AccessTokenResponse { try load("auth_login", as: AccessTokenResponse.self) }
    public func logout() async throws {}

    // Documents
    public func documents(_ query: DocumentListQuery) async throws -> DocumentListResponse {
        try load("documents_list", as: DocumentListResponse.self)
    }
    public func document(id: Int) async throws -> DocumentDetailResponse {
        // id 5301 = the pending-MD fixture (extracted_text fallback); otherwise the completed MD-first fixture.
        try load(id == 5301 ? "document_detail_pending_md" : "document_detail", as: DocumentDetailResponse.self)
    }
    public func documentContent(id: Int) async throws -> DocumentContentResponse {
        try load("document_content", as: DocumentContentResponse.self)
    }
    public func documentTree() async throws -> [DomainTreeNode] {
        try load("documents_tree", as: [DomainTreeNode].self)
    }
    public func categoryCounts() async throws -> CategoryCounts {
        try load("documents_stats", as: CategoryCounts.self)
    }
    public func duplicates() async throws -> DuplicatesResponse {
        try load("documents_duplicates", as: DuplicatesResponse.self)
    }
    public func patchDocument(id: Int, _ update: DocumentUpdate) async throws -> DocumentResponse {
        try load("document_detail", as: DocumentDetailResponse.self).base
    }
    public func putContent(id: Int, content: String) async throws {}
    public func deleteDocument(id: Int) async throws {}

    // Search / Ask
    public func search(q: String, mode: SearchMode?, page: Int?, debug: Bool?) async throws -> SearchResponse {
        try load("search", as: SearchResponse.self)
    }
    public func ask(q: String, limit: Int?, backend: String?, debug: Bool?) async throws -> AskResponse {
        try load("ask", as: AskResponse.self)
    }

    // Memos
    public func memos(_ query: MemoListQuery) async throws -> MemoListResponse {
        try load("memos_list", as: MemoListResponse.self)
    }
    public func memo(id: Int) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func createMemo(_ create: MemoCreate) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func patchMemo(id: Int, _ update: MemoUpdate) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func pinMemo(id: Int, pinned: Bool) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func archiveMemo(id: Int, archived: Bool) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func toggleMemoTask(id: Int, taskIndex: Int, checked: Bool) async throws -> MemoResponse { try load("memo_detail", as: MemoResponse.self) }
    public func deleteMemo(id: Int) async throws {}

    // Digest
    public func digest(date: String?, country: String?) async throws -> DigestResponse {
        try load("digest", as: DigestResponse.self)
    }
}