import SwiftUI
import AIFabric

/// RAG proof page: routes corpusAsk through AIService (-> AIRouter -> MockAIProvider). Explicit backend
/// pick sets explicitProvider; an explicit-unavailable result renders a visible, non-retrying error.
struct AskView: View {
    @Environment(AppModel.self) private var model
    @State private var backend: BackendChoice = .auto

    var body: some View {
        @Bindable var model = model
        ScrollView {
            VStack(alignment: .leading, spacing: 14) {
                Picker("백엔드", selection: $backend) {
                    ForEach(BackendChoice.allCases) { Text($0.label).tag($0) }
                }
                .pickerStyle(.segmented)

                HStack(spacing: 8) {
                    TextField("코퍼스 전체에 질문", text: $model.askQuery)
                        .textFieldStyle(.roundedBorder)
                        .onSubmit { Task { await model.runAsk(backend: backend.provider) } }
                    Button("질문") { Task { await model.runAsk(backend: backend.provider) } }
                        .buttonStyle(.borderedProminent)
                }

                if let result = model.askResult {
                    switch result {
                    case .success(let response):
                        AICompletionView(response: response) { docID in
                            model.section = .documents
                            Task { await model.openDocument(docID) }
                        }
                        if let meta = model.askMeta {
                            HStack(spacing: 6) {
                                Chip("완성도 \(meta.completeness)", Sage.muted)
                                if let aspects = meta.coveredAspects {
                                    ForEach(aspects, id: \.self) { Chip($0, Sage.brand) }
                                }
                            }
                        }
                    case .failure(let err):
                        ErrorBanner(text: message(for: err))
                    }
                } else {
                    EmptyState(text: "질문을 입력하세요").frame(minHeight: 160)
                }
            }
            .padding(16)
        }
        .background(Sage.surface)
    }

    private func message(for error: AIServiceError) -> String {
        switch error {
        case .explicitUnavailable(let id):
            return "\(id.displayName) 백엔드를 쓸 수 없습니다 — 다른 백엔드로 자동 전환하지 않았습니다. 다른 백엔드를 고르세요."
        case .notConfigured(let id): return "\(id.displayName) 백엔드 미구성"
        case .noneAvailable: return "응답 가능한 백엔드가 없습니다."
        case .providerFailed(let s): return "응답 실패: \(s)"
        case .unknown(let s): return "오류: \(s)"
        }
    }
}

enum BackendChoice: String, CaseIterable, Identifiable {
    case auto, onDevice, localMLX, remoteDS
    var id: String { rawValue }
    var label: String {
        switch self {
        case .auto: return "자동"
        case .onDevice: return "온디바이스"
        case .localMLX: return "맥미니"
        case .remoteDS: return "원격 DS"
        }
    }
    var provider: AIProviderID? {
        switch self {
        case .auto: return nil
        case .onDevice: return .onDevice
        case .localMLX: return .localMLX
        case .remoteDS: return .remoteDS
        }
    }
}