import MusicAssistantCore
import SwiftUI

struct ChatWorkspaceView: View {
    @State private var project: SongProject
    let saveProject: (SongProject) async -> Bool

    @State private var messages: [ChatWorkspaceMessage]
    @State private var draftMessage = ""
    @FocusState private var isComposerFocused: Bool

    init(project: SongProject, saveProject: @escaping (SongProject) async -> Bool = { _ in true }) {
        _project = State(initialValue: project)
        self.saveProject = saveProject
        _messages = State(initialValue: Self.initialMessages(for: project))
    }

    var body: some View {
        HSplitView {
            VStack(spacing: 0) {
                ChatWorkspaceHeader(project: project)

                Divider()

                ScrollViewReader { proxy in
                    ScrollView {
                        LazyVStack(alignment: .leading, spacing: 16) {
                            ForEach(messages) { message in
                                ChatMessageBubble(message: message)
                                    .id(message.id)
                            }
                        }
                        .padding(24)
                        .frame(maxWidth: .infinity, alignment: .leading)
                    }
                    .background(Color(nsColor: .textBackgroundColor))
                    .onChange(of: messages.count) { _, _ in
                        guard let lastMessageID = messages.last?.id else { return }
                        withAnimation(.snappy) {
                            proxy.scrollTo(lastMessageID, anchor: .bottom)
                        }
                    }
                }

                Divider()

                ChatComposer(
                    text: $draftMessage,
                    isFocused: $isComposerFocused,
                    sendAction: sendMessage
                )
                .padding(.horizontal, 20)
                .padding(.vertical, 14)
            }
            .frame(minWidth: 520, maxWidth: .infinity, maxHeight: .infinity)

            ProjectInspectorView(project: $project, saveProject: saveProject)
                .frame(minWidth: 300, idealWidth: 340, maxWidth: 420, maxHeight: .infinity)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .onAppear {
            isComposerFocused = true
        }
    }

    private func sendMessage() {
        let trimmedMessage = draftMessage.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmedMessage.isEmpty else { return }

        messages.append(ChatWorkspaceMessage(role: .user, text: trimmedMessage))
        draftMessage = ""
    }

    private static func initialMessages(for project: SongProject) -> [ChatWorkspaceMessage] {
        let prompt: String

        if project.idea.isEmpty {
            prompt = "What kind of song are we making?"
        } else {
            prompt = project.idea
        }

        return [
            ChatWorkspaceMessage(role: .assistant, text: prompt)
        ]
    }
}

private struct ChatWorkspaceHeader: View {
    let project: SongProject

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            HStack(alignment: .top, spacing: 12) {
                Image(systemName: "music.note")
                    .font(.title3.weight(.semibold))
                    .foregroundStyle(.tint)
                    .frame(width: 42, height: 42)
                    .background(.tint.opacity(0.12), in: RoundedRectangle(cornerRadius: 8))

                VStack(alignment: .leading, spacing: 4) {
                    Text(project.title)
                        .font(.title2.weight(.semibold))
                        .lineLimit(1)

                    Text(project.idea.isEmpty ? "Song Project" : project.idea)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                        .lineLimit(2)
                }

                Spacer(minLength: 12)

                Text(project.updatedAt.formatted(date: .abbreviated, time: .shortened))
                    .font(.caption)
                    .foregroundStyle(.secondary)
                    .lineLimit(1)
            }

            ViewThatFits(in: .horizontal) {
                HStack(spacing: 12) {
                    projectMetrics
                }

                LazyVGrid(
                    columns: [GridItem(.adaptive(minimum: 104), spacing: 10)],
                    alignment: .leading,
                    spacing: 8
                ) {
                    projectMetrics
                }
            }
        }
        .padding(.horizontal, 22)
        .padding(.vertical, 20)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(.bar)
    }

    @ViewBuilder
    private var projectMetrics: some View {
        ProjectMetricLabel(title: "Versions", value: project.versions.count, systemImage: "clock.arrow.circlepath")
        ProjectMetricLabel(title: "Genres", value: project.genres.count, systemImage: "music.quarternote.3")
        ProjectMetricLabel(title: "Instruments", value: project.selectedInstrumentTracks.count, systemImage: "pianokeys")
        ProjectMetricLabel(title: "Sections", value: project.sections.count, systemImage: "text.line.first.and.arrowtriangle.forward")
        ProjectMetricLabel(title: "Vocalists", value: project.vocalists.count, systemImage: "person.wave.2")
    }
}

private struct ProjectMetricLabel: View {
    let title: String
    let value: Int
    let systemImage: String

    var body: some View {
        Label {
            Text("\(value) \(title)")
        } icon: {
            Image(systemName: systemImage)
        }
        .font(.caption)
        .foregroundStyle(.secondary)
        .lineLimit(1)
        .labelStyle(.titleAndIcon)
        .frame(minWidth: 0, maxWidth: .infinity, alignment: .leading)
    }
}

private struct ChatMessageBubble: View {
    let message: ChatWorkspaceMessage

    var body: some View {
        HStack(alignment: .bottom, spacing: 8) {
            if message.role == .user {
                Spacer(minLength: 64)
            }

            if message.role == .assistant {
                ChatRoleMark(role: message.role)
            }

            Text(message.text)
                .font(.body)
                .foregroundStyle(message.role == .user ? .white : .primary)
                .padding(.horizontal, 14)
                .padding(.vertical, 10)
                .background(message.role == .user ? Color.accentColor : Color(nsColor: .controlBackgroundColor), in: RoundedRectangle(cornerRadius: 8))
                .frame(maxWidth: 620, alignment: message.role == .user ? .trailing : .leading)

            if message.role == .user {
                ChatRoleMark(role: message.role)
            }

            if message.role == .assistant {
                Spacer(minLength: 64)
            }
        }
        .frame(maxWidth: .infinity, alignment: message.role == .user ? .trailing : .leading)
    }
}

private struct ChatRoleMark: View {
    let role: ChatWorkspaceMessage.Role

    var body: some View {
        Image(systemName: role == .assistant ? "sparkles" : "person.fill")
            .font(.caption.weight(.semibold))
            .foregroundStyle(role == .assistant ? Color.teal : Color.accentColor)
            .frame(width: 28, height: 28)
            .background(.quaternary, in: RoundedRectangle(cornerRadius: 7))
            .accessibilityHidden(true)
    }
}

private struct ChatComposer: View {
    @Binding var text: String
    var isFocused: FocusState<Bool>.Binding
    let sendAction: () -> Void

    var body: some View {
        HStack(alignment: .bottom, spacing: 10) {
            TextField("Describe the song idea, lyrics, mood, or arrangement", text: $text, axis: .vertical)
                .textFieldStyle(.plain)
                .lineLimit(1...5)
                .focused(isFocused)
                .onSubmit(sendAction)

            Button(action: sendAction) {
                Label("Send", systemImage: "paperplane.fill")
                    .labelStyle(.iconOnly)
            }
            .keyboardShortcut(.return, modifiers: .command)
            .buttonStyle(.borderedProminent)
            .disabled(text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
            .help("Send")
        }
        .padding(10)
        .background(.quaternary, in: RoundedRectangle(cornerRadius: 8))
    }
}

private struct ChatWorkspaceMessage: Identifiable, Equatable {
    enum Role: Equatable {
        case assistant
        case user
    }

    let id: UUID
    let role: Role
    let text: String

    init(id: UUID = UUID(), role: Role, text: String) {
        self.id = id
        self.role = role
        self.text = text
    }
}

#Preview {
    ChatWorkspaceView(
        project: SongProject(
            title: "Untitled Song",
            idea: "A cinematic Arabic pop song with oud, violin, and a hopeful chorus."
        )
    )
}