import SwiftUI

struct SettingsView: View {
    @ObservedObject var settings: SettingsStore
    /// The current voice session, directly observed so the Apply button's
    /// disabled state and help text update reactively when the session
    /// transitions (e.g. `.tearingDown` → `.failed`).
    @ObservedObject var session: VoiceSession
    /// Local draft of the server URL. Only written to `settings` when the user
    /// explicitly applies a value that passes validation — keystrokes never
    /// reach storage or the network layer.
    @State private var urlText: String = ""
    @State private var urlError: String?
    @State private var showVoicePicker = false
    @State private var showModelPicker = false

    init(settings: SettingsStore, session: VoiceSession) {
        self.settings = settings
        self.session = session
    }

    /// Whether the current session is safe to replace. Apply is permitted for
    /// `.idle` (no active call) and `.failed` (fully torn down after failure —
    /// the user needs to correct an unreachable server without relaunching).
    /// Disabled during `.tearingDown`, `.connecting`, `.waitingAgent`, and
    /// `.ready` to avoid disconnecting an active call or racing cleanup.
    private var canApplyServerURL: Bool {
        session.state == .idle || session.state.isFailed
    }

    var body: some View {
        Form {
            Section("Server") {
                TextField(SettingsStore.defaultServerURL, text: $urlText)
                    .keyboardType(.URL)
                    .autocorrectionDisabled()
                    .onAppear { urlText = settings.serverURL }
                if let urlError {
                    Text(urlError)
                        .font(.footnote)
                        .foregroundStyle(.red)
                }
                Button("Apply server URL") { applyServerURL() }
                    .disabled(!canApplyServerURL || urlText.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
                if !canApplyServerURL {
                    Text(session.state == .tearingDown
                         ? "Waiting for failure cleanup to finish…"
                         : "End the conversation before changing servers.")
                        .font(.footnote)
                        .foregroundStyle(.secondary)
                }
            }
            Section("Voice") {
                Button {
                    showVoicePicker = true
                } label: {
                    LabeledContent("Voice", value: Voices.display(for: settings.voiceID) ?? settings.voiceID)
                }
            }
            Section("Model") {
                if session.isReady, !session.models.isEmpty {
                    Button {
                        showModelPicker = true
                    } label: {
                        LabeledContent("Model", value: session.selectedModel ?? settings.modelID ?? "—")
                    }
                } else {
                    Text("Start a conversation to load the model list.")
                        .font(.footnote)
                        .foregroundStyle(.secondary)
                }
            }
            Section("Interaction") {
                Toggle("Text mode", isOn: $settings.textMode)
            }
            Section {
                NavigationLink("Connection test") {
                    ConnectionTestView(settings: settings)
                }
            }
        }
        .navigationTitle("Settings")
        .sheet(isPresented: $showVoicePicker) {
            VoicePickerView(settings: settings, session: session)
        }
        .sheet(isPresented: $showModelPicker) {
            ModelPickerView(settings: settings, session: session)
        }
    }

    /// Validates the draft and persists it only on success. On failure the
    /// draft stays in the field with an inline error; `settings.serverURL` is
    /// left untouched so the active session keeps using its original URL.
    /// Guarded: only applies when the session is idle (no active call).
    private func applyServerURL() {
        guard canApplyServerURL else {
            urlError = "End the conversation before changing servers."
            return
        }
        let trimmed = urlText.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else {
            urlError = "Enter a server URL."
            return
        }
        switch ServerConfig.parse(trimmed) {
        case .success:
            settings.serverURL = trimmed
            urlText = trimmed
            urlError = nil
        case .failure(let error):
            urlError = error.localizedDescription
        }
    }
}

struct VoicePickerView: View {
    @ObservedObject var settings: SettingsStore
    var session: VoiceSession
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            List {
                ForEach(Voices.all, id: \.id) { voice in
                    Button {
                        settings.voiceID = voice.id
                        Task { await session.selectVoice(voice.id) }
                        dismiss()
                    } label: {
                        HStack {
                            Text(voice.displayName)
                            if settings.voiceID == voice.id {
                                Spacer()
                                Image(systemName: "checkmark")
                                    .foregroundStyle(.blue)
                            }
                        }
                    }
                }
            }
            .navigationTitle("Voice")
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") { dismiss() }
                }
            }
        }
    }
}

struct ModelPickerView: View {
    @ObservedObject var settings: SettingsStore
    var session: VoiceSession
    @Environment(\.dismiss) private var dismiss

    private var activeModelID: String? {
        if !session.models.isEmpty,
           let selected = session.selectedModel ?? settings.modelID,
           session.models.contains(where: { $0.id == selected }) {
            return selected
        }
        return session.models.first?.id
    }

    var body: some View {
        NavigationStack {
            List {
                ForEach(session.models, id: \.id) { model in
                    Button {
                        settings.modelID = model.id
                        Task { await session.selectModel(model.id) }
                        dismiss()
                    } label: {
                        HStack {
                            Text(model.name ?? model.id)
                            if activeModelID == model.id {
                                Spacer()
                                Image(systemName: "checkmark")
                                    .foregroundStyle(.blue)
                            }
                        }
                    }
                }
            }
            .navigationTitle("Model")
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") { dismiss() }
                }
            }
        }
    }
}

#Preview {
    let previewSettings = SettingsStore()
    guard case .success(let previewConfig) = ServerConfig.parse(SettingsStore.defaultServerURL) else {
        return AnyView(Text("Invalid default server URL"))
    }
    let previewSession = VoiceSession(config: previewConfig, tokenClient: TokenClient(config: previewConfig), settings: previewSettings)
    return AnyView(NavigationStack {
        SettingsView(settings: previewSettings, session: previewSession)
    })
}