import SwiftUI
import CoreModel
import CoreUI
import DesignSystem

public struct HomeScreen: View {
    private let viewModel: HomeViewModel
    private let onNavigateToCheckin: () -> Void
    private let onNavigateToPlan: () -> Void
    private let onNavigateToAuth: () -> Void

    @State private var showLoginDialog = false

    public init(
        viewModel: HomeViewModel,
        onNavigateToCheckin: @escaping () -> Void,
        onNavigateToPlan: @escaping () -> Void,
        onNavigateToAuth: @escaping () -> Void
    ) {
        self.viewModel = viewModel
        self.onNavigateToCheckin = onNavigateToCheckin
        self.onNavigateToPlan = onNavigateToPlan
        self.onNavigateToAuth = onNavigateToAuth
    }

    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 .error(let message):
            ErrorView(message: message) { viewModel.load() }
        case .success(let data, let isGuest):
            successContent(data, isGuest: isGuest)
        }
    }

    private func successContent(_ data: HomeData, isGuest: Bool) -> some View {
        ScrollView {
            VStack(spacing: DS.Spacing.md) {
                HeroCard(data: data)
                ModuleGrid(modules: data.modules) { module in
                    handleModuleTap(module, isGuest: isGuest)
                }
                IntroSection(intros: data.intros)
            }
            .padding(DS.Spacing.md)
        }
        .background(DS.Color.brandPaper)
        .alert("登录提示", isPresented: $showLoginDialog) {
            Button("取消", role: .cancel) {}
            Button("去登录") { onNavigateToAuth() }
        } message: {
            Text("登录后使用此功能，是否前往登录？")
        }
    }

    private func handleModuleTap(_ module: HomeModule, isGuest: Bool) {
        if isGuest {
            showLoginDialog = true
            return
        }
        switch module.destination {
        case .checkin: onNavigateToCheckin()
        case .plan: onNavigateToPlan()
        case .about: break
        }
    }
}

// MARK: - Hero 卡

private struct HeroCard: View {
    let data: HomeData

    var body: some View {
        VStack(alignment: .leading, spacing: DS.Spacing.sm) {
            Text(data.greeting)
                .font(.caption.bold())
                .foregroundStyle(DS.Color.brandLightAmber)
                .padding(.horizontal, DS.Spacing.sm)
                .padding(.vertical, DS.Spacing.xs)
                .background(DS.Color.brandGold.opacity(0.18))
                .clipShape(Capsule())
            Text(data.displayName)
                .font(.title2.bold())
                .foregroundStyle(.white)
            Text(data.encouragement)
                .font(.subheadline)
                .foregroundStyle(DS.Color.brandCream)
        }
        .padding(DS.Spacing.lg)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(DS.Gradient.hero)
        .clipShape(RoundedRectangle(cornerRadius: 24, style: .continuous))
    }
}

// MARK: - 模块宫格

private struct ModuleGrid: View {
    let modules: [HomeModule]
    let onTap: (HomeModule) -> Void

    private let columns = Array(repeating: GridItem(.flexible(), spacing: DS.Spacing.sm), count: 3)

    var body: some View {
        LazyVGrid(columns: columns, spacing: DS.Spacing.sm) {
            ForEach(modules) { module in
                ModuleItem(module: module, onTap: onTap)
            }
        }
    }
}

private struct ModuleItem: View {
    let module: HomeModule
    let onTap: (HomeModule) -> Void

    var body: some View {
        VStack(spacing: DS.Spacing.sm) {
            Text(module.emoji)
                .font(.title2)
                .frame(width: 44, height: 44)
                .background(DS.Color.brandChip)
                .clipShape(Circle())
            Text(module.title)
                .font(.footnote.bold())
                .foregroundStyle(DS.Color.brandDark)
            Text(module.description)
                .font(.caption2)
                .foregroundStyle(DS.Color.brandMuted)
                .multilineTextAlignment(.center)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, DS.Spacing.md)
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: 22, style: .continuous))
        .contentShape(Rectangle())
        .onTapGesture { onTap(module) }
    }
}

// MARK: - 产品介绍

private struct IntroSection: View {
    let intros: [IntroCard]

    var body: some View {
        VStack(alignment: .leading, spacing: DS.Spacing.sm) {
            Text("产品介绍")
                .font(.title3.bold())
                .foregroundStyle(DS.Color.brandDark)
            ForEach(intros, id: \.title) { intro in
                IntroItem(intro: intro)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }
}

private struct IntroItem: View {
    let intro: IntroCard

    var body: some View {
        VStack(alignment: .leading, spacing: DS.Spacing.xs) {
            Text(intro.title)
                .font(.subheadline.bold())
                .foregroundStyle(DS.Color.brandGold)
            Text(intro.body)
                .font(.subheadline)
                .foregroundStyle(DS.Color.brandBrown)
                .lineSpacing(4)
        }
        .padding(DS.Spacing.md)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: 16, style: .continuous))
    }
}