import SwiftUI
import CoreModel
import CoreUI
import DesignSystem

public struct HomeScreen: View {
    private let viewModel: HomeViewModel

    public init(viewModel: HomeViewModel) {
        self.viewModel = viewModel
    }

    public var body: some View {
        content
            .navigationTitle("首页")
            .task { viewModel.load() }
    }

    @ViewBuilder
    private var content: some View {
        switch viewModel.uiState {
        case .loading:
            LoadingView()
        case .empty:
            EmptyStateView(title: "今天还没有待打卡的习惯", systemImage: "checkmark.circle")
        case .success(let data):
            successContent(data)
        case .error(let message):
            ErrorView(message: message) { viewModel.load() }
        }
    }

    private func successContent(_ data: HomeData) -> some View {
        List {
            Section {
                VStack(alignment: .leading, spacing: DS.Spacing.sm) {
                    Text(data.greeting)
                        .font(.largeTitle.bold())
                    Text(data.summary)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                }
                .padding(.vertical, DS.Spacing.sm)
            }

            Section("今日打卡") {
                ForEach(data.habits) { habit in
                    HabitRow(habit: habit)
                }
            }
        }
    }
}

private struct HabitRow: View {
    let habit: Habit

    var body: some View {
        HStack {
            Image(systemName: habit.isCheckedInToday ? "checkmark.circle.fill" : "circle")
                .foregroundStyle(habit.isCheckedInToday ? DS.Color.success : DS.Color.warning)
                .font(.title3)
            VStack(alignment: .leading, spacing: 2) {
                Text(habit.title)
                    .font(.headline)
                Text(habit.detail)
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }
            Spacer()
            Text("🔥 \(habit.streakDays) 天")
                .font(.caption)
                .foregroundStyle(.secondary)
        }
        .padding(.vertical, DS.Spacing.xs)
    }
}