//
//  ContentView.swift
//  MultiChrono
//
//  Created by Beatrice Dellacà on 26/01/26.
//

import SwiftUI
import Combine
import UniformTypeIdentifiers

class ContentViewModel: ObservableObject {
    @Published var stopwatches: [Stopwatch] = []
    
    private let saveKey = "SavedStopwatches"
    
    init() {
        load()
    }
    
    func addStopwatch(name: String) {
        let newStopwatch = Stopwatch(name: name)
        stopwatches.append(newStopwatch)
        save()
    }
    
    func deleteStopwatch(at index: Int) {
        stopwatches[index].pause() // Ensure timer is stopped
        stopwatches.remove(at: index)
        save()
    }
    
    func deleteStopwatch(id: UUID) {
        if let index = stopwatches.firstIndex(where: { $0.id == id }) {
            deleteStopwatch(at: index)
        }
    }
    
    func moveStopwatch(fromOffsets source: IndexSet, toOffset destination: Int) {
        stopwatches.move(fromOffsets: source, toOffset: destination)
        save()
    }
    
    func save() {
        if let encoded = try? JSONEncoder().encode(stopwatches) {
            UserDefaults.standard.set(encoded, forKey: saveKey)
        }
    }
    
    func load() {
        if let data = UserDefaults.standard.data(forKey: saveKey) {
            if let decoded = try? JSONDecoder().decode([Stopwatch].self, from: data) {
                stopwatches = decoded
            }
        }
    }
}

struct ContentView: View {
    @StateObject private var viewModel = ContentViewModel()
    @State private var isShowingAddSheet = false
    @State private var isShowingSettings = false
    @State private var selectedStopwatch: Stopwatch?
    @State private var draggingStopwatch: Stopwatch?
    @Environment(\.scenePhase) private var scenePhase
    
    var body: some View {
        NavigationStack {
            ScrollView {
                LazyVStack(spacing: 0) {
                    ForEach(viewModel.stopwatches) { stopwatch in
                        StopwatchListItem(
                            stopwatch: stopwatch,
                            viewModel: viewModel,
                            selectedStopwatch: $selectedStopwatch,
                            draggingStopwatch: $draggingStopwatch
                        )
                    }
                }
            }
            .navigationTitle("MultiChrono")
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button {
                        isShowingSettings = true
                    } label: {
                        Image(systemName: "gearshape")
                    }
                }
                ToolbarItem(placement: .primaryAction) {
                    Button(action: {
                        isShowingAddSheet = true
                    }) {
                        Image(systemName: "plus")
                    }
                }
            }
            .sheet(isPresented: $isShowingAddSheet) {
                AddStopwatchView { name in
                    viewModel.addStopwatch(name: name)
                    isShowingAddSheet = false
                }
            }
            .sheet(isPresented: $isShowingSettings) {
                SettingsView()
            }
            .sheet(item: $selectedStopwatch) { stopwatch in
                StopwatchDetailView(
                    stopwatch: stopwatch,
                    onSave: { newName in
                        stopwatch.name = newName
                        viewModel.save()
                        selectedStopwatch = nil
                    },
                    onCancel: {
                        selectedStopwatch = nil
                    }
                )
            }
            .overlay {
                if viewModel.stopwatches.isEmpty {
                    ContentUnavailableView(
                        "No Stopwatches",
                        systemImage: "timer",
                        description: Text("Tap the + button to create a stopwatch.")
                    )
                }
            }
        }
        .onChange(of: scenePhase) { newPhase in
            if newPhase == .background || newPhase == .inactive {
                viewModel.save()
            }
        }
    }
}

struct StopwatchListItem: View {
    @ObservedObject var stopwatch: Stopwatch
    @ObservedObject var viewModel: ContentViewModel
    @Binding var selectedStopwatch: Stopwatch?
    @Binding var draggingStopwatch: Stopwatch?
    
    var body: some View {
        Button {
            selectedStopwatch = stopwatch
        } label: {
            StopwatchRow(stopwatch: stopwatch, onDelete: {
                withAnimation {
                    viewModel.deleteStopwatch(id: stopwatch.id)
                }
            })
        }
        .buttonStyle(.plain)
        .padding(.horizontal)
        .padding(.vertical, 8)
        .background(Color(UIColor.systemBackground))
        .contentShape(Rectangle())
        .contextMenu {
            Button(role: .destructive) {
                withAnimation {
                    viewModel.deleteStopwatch(id: stopwatch.id)
                }
            } label: {
                Label("Delete", systemImage: "trash")
            }
        }
        .onDrag {
            self.draggingStopwatch = stopwatch
            return NSItemProvider(object: stopwatch.id.uuidString as NSString)
        }
        .onDrop(of: [UTType.text], delegate: StopwatchDropDelegate(item: stopwatch, viewModel: viewModel, draggingItem: $draggingStopwatch))
        
        Divider()
            .padding(.leading)
    }
}

struct StopwatchDropDelegate: DropDelegate {
    let item: Stopwatch
    let viewModel: ContentViewModel
    @Binding var draggingItem: Stopwatch?
    
    func dropEntered(info: DropInfo) {
        guard let draggingItem = draggingItem else { return }
        
        if draggingItem.id != item.id {
            if let from = viewModel.stopwatches.firstIndex(where: { $0.id == draggingItem.id }),
               let to = viewModel.stopwatches.firstIndex(where: { $0.id == item.id }) {
                
                withAnimation {
                    viewModel.stopwatches.move(fromOffsets: IndexSet(integer: from),
                                               toOffset: to > from ? to + 1 : to)
                }
            }
        }
    }
    
    func performDrop(info: DropInfo) -> Bool {
        viewModel.save()
        draggingItem = nil
        return true
    }
    
    func dropUpdated(info: DropInfo) -> DropProposal? {
        return DropProposal(operation: .move)
    }
}

#Preview {
    ContentView()
}