import Foundation
import MusicAssistantCore
import SwiftUI

struct ProjectBrowserView: View {
    @StateObject private var viewModel: ProjectBrowserViewModel
    @State private var selectedProjectID: String?

    init(store: any ProjectStore = LocalSongProjectStore(directoryURL: ProjectBrowserStorage.projectsDirectoryURL)) {
        _viewModel = StateObject(wrappedValue: ProjectBrowserViewModel(store: store))
    }

    var body: some View {
        NavigationSplitView {
            List(selection: $selectedProjectID) {
                Section("Projects") {
                    ForEach(viewModel.projects) { project in
                        ProjectListRow(project: project)
                            .tag(project.id)
                    }
                }
            }
            .navigationTitle("AI Music Studio")
            .overlay {
                if viewModel.isLoading {
                    ProgressView()
                } else if viewModel.projects.isEmpty {
                    ContentUnavailableView(
                        "No Projects",
                        systemImage: "music.note.list",
                        description: Text("Create a song project to begin.")
                    )
                }
            }
            .toolbar {
                ToolbarItem {
                    Button {
                        Task {
                            if let projectID = await viewModel.createProject() {
                                selectedProjectID = projectID
                            }
                        }
                    } label: {
                        Label("New Project", systemImage: "plus")
                    }
                    .keyboardShortcut("n", modifiers: .command)
                    .disabled(viewModel.isCreatingProject)
                }
            }
        } detail: {
            ProjectBrowserDetailView(
                project: viewModel.selectedProject,
                errorMessage: viewModel.errorMessage,
                isLoading: viewModel.isOpeningProject,
                saveProject: viewModel.saveProject
            )
        }
        .task {
            await viewModel.loadProjects()
            selectedProjectID = selectedProjectID ?? viewModel.projects.first?.id
            if let selectedProjectID {
                await viewModel.openProject(id: selectedProjectID)
            }
        }
        .onChange(of: selectedProjectID) { _, projectID in
            guard let projectID else {
                viewModel.clearSelection()
                return
            }

            Task {
                await viewModel.openProject(id: projectID)
            }
        }
    }
}

private struct ProjectListRow: View {
    let project: SongProjectListItem

    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(project.title)
                .font(.headline)
                .lineLimit(1)

            Text(project.idea.isEmpty ? "No idea yet" : project.idea)
                .font(.caption)
                .foregroundStyle(.secondary)
                .lineLimit(2)

            Text(project.updatedAt.formatted(date: .abbreviated, time: .shortened))
                .font(.caption2)
                .foregroundStyle(.tertiary)
        }
        .padding(.vertical, 4)
    }
}

private struct ProjectBrowserDetailView: View {
    let project: SongProject?
    let errorMessage: String?
    let isLoading: Bool
    let saveProject: (SongProject) async -> Bool

    var body: some View {
        Group {
            if isLoading {
                ProgressView()
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            } else if let project {
                ChatWorkspaceView(project: project, saveProject: saveProject)
                    .id(project.id)
            } else {
                ContentUnavailableView(
                    "Select a Project",
                    systemImage: "music.note",
                    description: Text("Choose a saved song project from the browser.")
                )
            }
        }
        .overlay(alignment: .bottom) {
            if let errorMessage {
                Text(errorMessage)
                    .font(.callout)
                    .foregroundStyle(.white)
                    .padding(.horizontal, 12)
                    .padding(.vertical, 8)
                    .background(.red, in: RoundedRectangle(cornerRadius: 8))
                    .padding()
            }
        }
    }
}

@MainActor
final class ProjectBrowserViewModel: ObservableObject {
    @Published private(set) var projects: [SongProjectListItem] = []
    @Published private(set) var selectedProject: SongProject?
    @Published private(set) var isLoading = false
    @Published private(set) var isOpeningProject = false
    @Published private(set) var isCreatingProject = false
    @Published private(set) var errorMessage: String?

    private let store: any ProjectStore

    init(store: any ProjectStore) {
        self.store = store
    }

    func loadProjects() async {
        isLoading = true
        errorMessage = nil

        do {
            projects = try await store.loadProjectList()
        } catch {
            errorMessage = "Unable to load projects."
        }

        isLoading = false
    }

    func openProject(id projectID: String) async {
        isOpeningProject = true
        errorMessage = nil

        do {
            selectedProject = try await store.open(id: projectID)
        } catch {
            selectedProject = nil
            errorMessage = "Unable to open this project."
        }

        isOpeningProject = false
    }

    func createProject() async -> String? {
        isCreatingProject = true
        errorMessage = nil

        let now = Date()
        let project = SongProject(
            title: "Untitled Song",
            idea: "",
            createdAt: now,
            updatedAt: now
        )

        do {
            try await store.create(project)
            projects = try await store.loadProjectList()
            selectedProject = project
            isCreatingProject = false
            return project.id
        } catch {
            errorMessage = "Unable to create a new project."
            isCreatingProject = false
            return nil
        }
    }

    func saveProject(_ project: SongProject) async -> Bool {
        var projectToSave = project
        projectToSave.updatedAt = Date()
        errorMessage = nil

        do {
            try await store.save(projectToSave)
            projects = try await store.loadProjectList()
            selectedProject = projectToSave
            return true
        } catch {
            errorMessage = "Unable to save this project."
            return false
        }
    }

    func clearSelection() {
        selectedProject = nil
    }
}

enum ProjectBrowserStorage {
    static var projectsDirectoryURL: URL {
        let baseURL = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first
            ?? FileManager.default.temporaryDirectory

        return baseURL
            .appendingPathComponent("AI Music Studio", isDirectory: true)
            .appendingPathComponent("Projects", isDirectory: true)
    }
}

#Preview {
    ProjectBrowserView()
}