import SwiftUI
import SwiftData

struct TasksTabView: View {
    @Environment(\.modelContext) private var context
    @Query(sort: \TaskItem.sortOrder) private var tasks: [TaskItem]
    @State private var showAddSheet = false
    @State private var editTarget: TaskItem?

    private var activeTasks: [TaskItem] { tasks.filter { !$0.isArchived } }

    var body: some View {
        NavigationStack {
            Group {
                if activeTasks.isEmpty {
                    EmptyStateView(
                        icon: "checkmark.circle",
                        message: String(localized: "tasks.empty")
                    )
                } else {
                    List {
                        ForEach(activeTasks) { task in
                            TaskRowView(task: task)
                                .swipeActions(edge: .trailing, allowsFullSwipe: false) {
                                    Button(role: .destructive) {
                                        context.delete(task)
                                    } label: {
                                        Label("삭제", systemImage: "trash")
                                    }
                                    Button {
                                        editTarget = task
                                    } label: {
                                        Label("편집", systemImage: "pencil")
                                    }
                                    .tint(.blue)
                                }
                        }
                    }
                    .scrollContentBackground(.hidden)
                }
            }
            .background(Color.tfBackground)
            .navigationTitle(String(localized: "tab.tasks"))
            .toolbar {
                ToolbarItem(placement: .primaryAction) {
                    Button { showAddSheet = true } label: {
                        Image(systemName: "plus")
                    }
                    .tint(Color.tfPrimary)
                }
            }
            .sheet(isPresented: $showAddSheet) {
                TaskFormView()
            }
            .sheet(item: $editTarget) { task in
                TaskFormView(existing: task)
            }
        }
    }
}

// MARK: – Row

private struct TaskRowView: View {
    let task: TaskItem

    private var primaryColor: Color {
        task.tags.first.map { Color(hex: $0.colorHex) } ?? Color.tfPrimary
    }

    var body: some View {
        HStack(spacing: 12) {
            Image(systemName: task.icon)
                .foregroundStyle(primaryColor)
                .frame(width: 28)
            VStack(alignment: .leading, spacing: 2) {
                Text(task.name)
                    .foregroundStyle(Color.tfOnBackground)
                HStack(spacing: 4) {
                    Text(task.taskType == .timer ? "타이머" : "카운터")
                        .font(.caption)
                        .foregroundStyle(Color.tfMuted)
                    if let firstTag = task.tags.first {
                        Text("·")
                            .font(.caption)
                            .foregroundStyle(Color.tfMuted)
                        Text(firstTag.name)
                            .font(.caption)
                            .foregroundStyle(Color(hex: firstTag.colorHex))
                    }
                }
            }
            Spacer()
            Image(systemName: task.taskType == .timer ? "timer" : "number")
                .foregroundStyle(primaryColor)
        }
        .padding(.vertical, 4)
    }
}

// MARK: – Form

struct TaskFormView: View {
    @Environment(\.modelContext) private var context
    @Environment(\.dismiss) private var dismiss
    @Query(sort: \TagEntity.sortOrder) private var allTags: [TagEntity]

    var existing: TaskItem? = nil

    @State private var name = ""
    @State private var icon = "star"
    @State private var taskType: TaskType = .timer
    @State private var selectedTagIDs: Set<UUID> = []

    private let iconPresets = [
        "star", "heart", "bolt", "flame",
        "book.fill", "pencil", "laptopcomputer", "dumbbell.fill",
        "music.note", "camera.fill", "gamecontroller.fill", "fork.knife",
        "figure.walk", "bicycle", "car.fill", "airplane",
        "moon.stars.fill", "sun.max.fill", "drop.fill", "leaf.fill"
    ]

    private var isEditing: Bool { existing != nil }
    private var isSaveDisabled: Bool { name.trimmingCharacters(in: .whitespaces).isEmpty }

    var body: some View {
        NavigationStack {
            Form {
                Section("이름") {
                    TextField("작업 이름", text: $name)
                }

                Section("아이콘") {
                    LazyVGrid(columns: Array(repeating: GridItem(.flexible()), count: 5), spacing: 12) {
                        ForEach(iconPresets, id: \.self) { sym in
                            Image(systemName: sym)
                                .font(.title2)
                                .foregroundStyle(sym == icon ? Color.tfPrimary : Color.tfMuted)
                                .frame(width: 44, height: 44)
                                .background(
                                    RoundedRectangle(cornerRadius: 8)
                                        .fill(sym == icon ? Color.tfPrimary.opacity(0.15) : Color.clear)
                                )
                                .onTapGesture { icon = sym }
                        }
                    }
                    .padding(.vertical, 4)
                }

                Section("유형") {
                    Picker("유형", selection: $taskType) {
                        Text("타이머").tag(TaskType.timer)
                        Text("카운터").tag(TaskType.counter)
                    }
                    .pickerStyle(.segmented)
                }

                if !allTags.isEmpty {
                    Section("태그") {
                        ForEach(allTags) { tag in
                            TagSelectionRow(
                                tag: tag,
                                isSelected: selectedTagIDs.contains(tag.id),
                                onToggle: { toggleTag(tag) }
                            )
                        }
                    }
                }
            }
            .navigationTitle(isEditing ? "작업 편집" : "작업 추가")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("취소") { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button("저장") { save() }
                        .disabled(isSaveDisabled)
                }
            }
            .onAppear { loadExisting() }
        }
    }

    private func loadExisting() {
        guard let task = existing else { return }
        name = task.name
        icon = task.icon
        taskType = task.taskType
        selectedTagIDs = Set(task.tags.map { $0.id })
    }

    private func toggleTag(_ tag: TagEntity) {
        if selectedTagIDs.contains(tag.id) {
            selectedTagIDs.remove(tag.id)
        } else {
            selectedTagIDs.insert(tag.id)
            // Selecting a sub tag implicitly includes its parent super tag
            if let parent = tag.parent {
                selectedTagIDs.insert(parent.id)
            }
        }
    }

    private func save() {
        let trimmed = name.trimmingCharacters(in: .whitespaces)
        guard !trimmed.isEmpty else { return }

        let selectedTags = allTags.filter { selectedTagIDs.contains($0.id) }

        if let task = existing {
            task.name = trimmed
            task.icon = icon
            task.taskType = taskType
            task.tags = selectedTags
        } else {
            let newTask = TaskItem(name: trimmed, icon: icon, taskType: taskType)
            newTask.tags = selectedTags
            context.insert(newTask)
        }
        dismiss()
    }
}

private struct TagSelectionRow: View {
    let tag: TagEntity
    let isSelected: Bool
    let onToggle: () -> Void

    var body: some View {
        HStack(spacing: 8) {
            if tag.isSubTag {
                Spacer().frame(width: 14)
            }
            Circle()
                .fill(Color(hex: tag.colorHex))
                .frame(width: 10, height: 10)
            Text(tag.name)
                .foregroundStyle(Color.tfOnBackground)
            if tag.isSubTag, let parent = tag.parent {
                Text("(\(parent.name))")
                    .font(.caption)
                    .foregroundStyle(Color.tfMuted)
            }
            Spacer()
            if isSelected {
                Image(systemName: "checkmark")
                    .foregroundStyle(Color.tfPrimary)
            }
        }
        .contentShape(Rectangle())
        .onTapGesture { onToggle() }
    }
}

#Preview {
    TasksTabView()
        .modelContainer(for: [TaskItem.self, TagEntity.self, TrackingRecord.self], inMemory: true)
        .environment(AppPreferences())
}