//
//  TodosView.swift
//  iris
//
//  Created by Codex.
//

import SwiftUI

struct TodosView: View {
    @StateObject private var model = TodosViewModel()
    @State private var isDoneExpanded = false
    @State private var lastDoneCount = 0

    private var openTodos: [TodoItem] {
        model.todos.filter { !$0.isCompleted }
    }

    private var doneTodos: [TodoItem] {
        model.todos.filter { $0.isCompleted }
    }

    var body: some View {
        NavigationStack {
            List {
                Section("Add") {
                    HStack(spacing: 12) {
                        TextField("Add a todo", text: $model.newTitle)
                            .textInputAutocapitalization(.sentences)
                            .disableAutocorrection(false)
                            .submitLabel(.done)
                            .onSubmit { model.addTodo() }

                        Button {
                            model.addTodo()
                        } label: {
                            Image(systemName: "plus.circle.fill")
                                .font(.title3)
                        }
                        .buttonStyle(.plain)
                        .disabled(model.newTitle.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
                        .accessibilityLabel("Add todo")
                    }
                }

                Section("Todos") {
                    if openTodos.isEmpty {
                        Text("No open todos")
                            .foregroundStyle(.secondary)
                    } else {
                        ForEach(openTodos) { item in
                            TodoRow(
                                item: item,
                                onToggle: { model.toggleCompleted(id: item.id) },
                                onDelete: { model.deleteTodo(id: item.id) },
                                onUpdateTitle: { model.updateTitle(id: item.id, title: $0) }
                            )
                        }
                    }
                }

                Section {
                    if isDoneExpanded {
                        if doneTodos.isEmpty {
                            Text("No completed todos")
                                .foregroundStyle(.secondary)
                        } else {
                            ForEach(doneTodos) { item in
                                TodoRow(
                                    item: item,
                                    onToggle: { model.toggleCompleted(id: item.id) },
                                    onDelete: { model.deleteTodo(id: item.id) },
                                    onUpdateTitle: { model.updateTitle(id: item.id, title: $0) }
                                )
                            }
                        }
                    }
                } header: {
                    Button {
                        withAnimation(.easeInOut(duration: 0.15)) {
                            isDoneExpanded.toggle()
                        }
                    } label: {
                        HStack(spacing: 8) {
                            Text("Done")
                            Spacer()
                            if doneTodos.count > 0 {
                                Text("\(doneTodos.count)")
                                    .foregroundStyle(.secondary)
                            }
                            Image(systemName: isDoneExpanded ? "chevron.down" : "chevron.right")
                                .foregroundStyle(.secondary)
                                .font(.caption)
                        }
                    }
                    .buttonStyle(.plain)
                }
            }
            .navigationTitle("Todos")
            .onAppear {
                lastDoneCount = doneTodos.count
                if lastDoneCount == 0 {
                    isDoneExpanded = false
                }
            }
            .onChange(of: doneTodos.count) { newCount in
                if lastDoneCount == 0, newCount > 0, !isDoneExpanded {
                    withAnimation(.easeInOut(duration: 0.15)) {
                        isDoneExpanded = true
                    }
                } else if newCount == 0, isDoneExpanded {
                    withAnimation(.easeInOut(duration: 0.15)) {
                        isDoneExpanded = false
                    }
                }
                lastDoneCount = newCount
            }
        }
    }
}

private struct TodoRow: View {
    let item: TodoItem
    let onToggle: () -> Void
    let onDelete: () -> Void
    let onUpdateTitle: (String) -> Void

    @State private var draftTitle: String
    @FocusState private var isFocused: Bool

    init(item: TodoItem,
         onToggle: @escaping () -> Void,
         onDelete: @escaping () -> Void,
         onUpdateTitle: @escaping (String) -> Void) {
        self.item = item
        self.onToggle = onToggle
        self.onDelete = onDelete
        self.onUpdateTitle = onUpdateTitle
        _draftTitle = State(initialValue: item.title)
    }

    var body: some View {
        HStack(spacing: 12) {
            Button(action: onToggle) {
                Image(systemName: item.isCompleted ? "checkmark.circle.fill" : "circle")
                    .foregroundStyle(item.isCompleted ? .secondary : .primary)
            }
            .buttonStyle(.plain)
            .accessibilityLabel(item.isCompleted ? "Mark incomplete" : "Mark complete")

            TextField("Todo", text: $draftTitle)
                .focused($isFocused)
                .submitLabel(.done)
                .onSubmit { commitTitleIfNeeded() }
                .onChange(of: isFocused) { focused in
                    if !focused {
                        commitTitleIfNeeded()
                    }
                }
                .onChange(of: item.title) { newValue in
                    if !isFocused {
                        draftTitle = newValue
                    }
                }
                .foregroundStyle(item.isCompleted ? .secondary : .primary)
                .opacity(item.isCompleted ? 0.7 : 1.0)
        }
        .onDisappear {
            if isFocused {
                commitTitleIfNeeded()
            }
        }
        .swipeActions(edge: .trailing, allowsFullSwipe: true) {
            Button(role: .destructive, action: onDelete) {
                Label("Delete", systemImage: "trash")
            }
        }
    }

    private func commitTitleIfNeeded() {
        let trimmed = draftTitle.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else {
            draftTitle = item.title
            return
        }
        guard trimmed != item.title else { return }
        onUpdateTitle(trimmed)
    }
}

struct TodosView_Previews: PreviewProvider {
    static var previews: some View {
        TodosView()
    }
}