import SwiftUI
import CoreModel
import CoreUI
import DesignSystem

public struct CheckinScreen: View {
    private let viewModel: CheckinViewModel
    private let onNavigateToAuth: () -> Void

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

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

    @ViewBuilder
    private var content: some View {
        switch viewModel.uiState {
        case .loading:
            LoadingView()
        case .loggedOut:
            LoggedOutView(onNavigateToAuth: onNavigateToAuth)
        case .error(let message):
            ErrorView(message: message) { viewModel.load() }
        case .success(let record):
            successContent(record)
        }
    }

    private func successContent(_ record: CheckinRecord) -> some View {
        ScrollView {
            VStack(spacing: DS.Spacing.md) {
                StatusTitleCard(record: record)
                StatusSelector(
                    selected: viewModel.selectedStatus,
                    submitting: viewModel.submitting,
                    onSelect: { viewModel.submit($0) }
                )
                RecordPanel(record: record)
            }
            .padding(DS.Spacing.md)
        }
        .background(DS.Color.brandPaper)
    }
}

// MARK: - 顶部状态卡

private struct StatusTitleCard: View {
    let record: CheckinRecord

    var body: some View {
        HStack(spacing: DS.Spacing.md) {
            VStack(spacing: 2) {
                Text(record.weekday)
                    .font(.caption)
                    .foregroundStyle(DS.Color.brandCream)
                Text("\(record.dayNum)")
                    .font(.title3.bold())
                    .foregroundStyle(.white)
            }
            .frame(width: 62)
            .padding(.vertical, DS.Spacing.sm)
            .background(DS.Color.brandDark)
            .clipShape(RoundedRectangle(cornerRadius: 14, style: .continuous))

            VStack(alignment: .leading, spacing: DS.Spacing.xs) {
                Text(record.checked ? "已打卡" : "未打卡")
                    .font(.title3.bold())
                    .foregroundStyle(record.checked ? DS.Color.statusNormal : DS.Color.brandGold)
                if record.checked, let status = record.status {
                    StatusBadge(status: status)
                } else {
                    Text("请选择状态完成打卡")
                        .font(.caption)
                        .foregroundStyle(DS.Color.brandMuted)
                }
            }
            Spacer()
        }
        .padding(DS.Spacing.md)
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: 20, style: .continuous))
    }
}

// MARK: - 状态选择器

private struct StatusSelector: View {
    let selected: CheckinStatus
    let submitting: Bool
    let onSelect: (CheckinStatus) -> Void

    var body: some View {
        VStack(spacing: DS.Spacing.sm) {
            LazyVGrid(columns: [GridItem(.flexible()), GridItem(.flexible()), GridItem(.flexible())], spacing: DS.Spacing.sm) {
                ForEach(CheckinStatus.allCases, id: \.self) { status in
                    StatusPill(status: status, isSelected: status == selected) {
                        onSelect(status)
                    }
                }
            }
            if submitting {
                Text("提交中…")
                    .font(.caption)
                    .foregroundStyle(DS.Color.brandMuted)
            }
        }
        .padding(DS.Spacing.md)
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: 16, style: .continuous))
    }
}

private struct StatusPill: View {
    let status: CheckinStatus
    let isSelected: Bool
    let onTap: () -> Void

    var body: some View {
        Button(action: onTap) {
            HStack(spacing: 4) {
                Circle()
                    .fill(isSelected ? Color.white : status.color)
                    .frame(width: 8, height: 8)
                Text(status.rawValue)
                    .font(.footnote)
                    .lineLimit(1)
            }
            .padding(.vertical, DS.Spacing.sm)
            .frame(maxWidth: .infinity)
            .background(isSelected ? status.color : Color.white)
            .foregroundStyle(isSelected ? Color.white : DS.Color.brandBrown)
            .clipShape(Capsule())
            .overlay(Capsule().stroke(isSelected ? Color.clear : DS.Color.disabled, lineWidth: 1))
        }
        .buttonStyle(.plain)
    }
}

// MARK: - 记录面板（小组/个人）

private struct RecordPanel: View {
    let record: CheckinRecord
    @State private var tab: CheckinTab = .group

    var body: some View {
        VStack(alignment: .leading, spacing: DS.Spacing.sm) {
            HStack(spacing: DS.Spacing.lg) {
                tabButton("小组", .group)
                tabButton("个人", .personal)
            }
            if tab == .group {
                groupList
            } else {
                personalList
            }
        }
        .padding(DS.Spacing.md)
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: 16, style: .continuous))
    }

    private func tabButton(_ title: String, _ value: CheckinTab) -> some View {
        Button {
            tab = value
        } label: {
            VStack(spacing: 4) {
                Text(title)
                    .font(.subheadline.bold())
                    .foregroundStyle(tab == value ? DS.Color.brandGold : DS.Color.brandBrown)
                Rectangle()
                    .fill(tab == value ? DS.Color.brandGold : Color.clear)
                    .frame(height: 2)
            }
        }
        .buttonStyle(.plain)
    }

    private var checkedCount: Int {
        record.groupMembers.filter(\.checkedIn).count
    }

    private var groupList: some View {
        VStack(alignment: .leading, spacing: DS.Spacing.sm) {
            HStack {
                Text("\(record.groupName) · \(record.classDate)")
                    .font(.subheadline.bold())
                    .foregroundStyle(DS.Color.brandDark)
                Spacer()
                Text("\(checkedCount)/\(record.groupMembers.count) 已打卡")
                    .font(.caption)
                    .foregroundStyle(DS.Color.brandMuted)
            }
            ForEach(record.groupMembers) { member in
                GroupMemberRow(member: member)
            }
        }
    }

    private var personalList: some View {
        Group {
            if record.personalHistory.isEmpty {
                EmptyStateView(title: "暂无个人打卡记录", systemImage: "book")
            } else {
                VStack(spacing: DS.Spacing.sm) {
                    ForEach(record.personalHistory, id: \.date) { item in
                        HStack {
                            Text(item.date)
                                .font(.subheadline.bold())
                                .foregroundStyle(DS.Color.brandDark)
                            Spacer()
                            StatusBadge(status: item.status)
                            Text(item.time)
                                .font(.caption)
                                .foregroundStyle(DS.Color.brandMuted)
                        }
                    }
                }
            }
        }
    }
}

// MARK: - 成员行 / 状态徽标

private struct GroupMemberRow: View {
    let member: GroupMember

    var body: some View {
        HStack(spacing: DS.Spacing.sm) {
            Text(String(member.name.prefix(1)))
                .font(.subheadline.bold())
                .foregroundStyle(member.checkedIn ? DS.Color.statusNormal : DS.Color.brandGold)
                .frame(width: 30, height: 30)
                .background(member.checkedIn ? DS.Color.fillDone : DS.Color.brandChip)
                .clipShape(Circle())
            Text(member.name)
                .font(.subheadline)
                .foregroundStyle(DS.Color.brandDark)
            Spacer()
            if member.checkedIn, let status = member.status {
                Text("打卡 \(member.checkinTime ?? "")")
                    .font(.caption)
                    .foregroundStyle(DS.Color.brandMuted)
                StatusBadge(status: status)
            } else {
                Text("未打卡")
                    .font(.caption)
                    .foregroundStyle(DS.Color.faintText)
            }
        }
        .padding(.vertical, DS.Spacing.xs)
    }
}

private struct StatusBadge: View {
    let status: CheckinStatus

    var body: some View {
        Text(status.rawValue)
            .font(.caption)
            .foregroundStyle(status.color)
            .padding(.horizontal, DS.Spacing.sm)
            .padding(.vertical, 2)
            .background(status.color.opacity(0.12))
            .clipShape(Capsule())
    }
}

private extension CheckinStatus {
    var color: Color {
        switch self {
        case .normal: return DS.Color.statusNormal
        case .late: return DS.Color.statusLate
        case .leave: return DS.Color.statusLeave
        case .earlyLeave: return DS.Color.statusEarlyLeave
        case .absent: return DS.Color.statusAbsent
        }
    }
}