//
//  MessageCenterViews.swift
//  suixinkan
//
//  Created by Codex on 2026/6/25.
//

import SwiftUI

/// 消息中心页面，展示消息列表、筛选、已读和删除入口。
struct MessageCenterView: View {
    @Environment(\.messageCenterAPI) private var messageAPI
    @EnvironmentObject private var toastCenter: ToastCenter
    @StateObject private var viewModel = MessageCenterViewModel()
    @State private var selectedMessage: MessageItem?
    @State private var processingMessageId: String?

    var body: some View {
        VStack(spacing: 0) {
            header
            content
        }
        .background(Color(hex: 0xF5F7FA).ignoresSafeArea())
        .navigationTitle("消息中心")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarTrailing) {
                Button("全部已读") {
                    Task { await markAllAsRead() }
                }
                .font(.system(size: AppMetrics.FontSize.subheadline, weight: .semibold))
                .disabled(viewModel.unreadCount == 0 || viewModel.messages.isEmpty)
            }
        }
        .sheet(item: $selectedMessage) { item in
            MessageDetailView(item: item) { deleteItem in
                await deleteMessage(deleteItem)
            }
        }
        .task {
            if viewModel.messages.isEmpty {
                await viewModel.reloadFirstPage(api: messageAPI)
            }
        }
        .refreshable {
            await viewModel.reloadFirstPage(api: messageAPI)
        }
    }

    private var header: some View {
        VStack(alignment: .leading, spacing: AppMetrics.Spacing.medium) {
            HStack(spacing: AppMetrics.Spacing.medium) {
                messageMetric(title: "消息总数", value: "\(viewModel.messages.count)", color: AppDesign.primary)
                messageMetric(title: "未读消息", value: "\(viewModel.unreadCount)", color: AppDesign.warning)
            }

            Picker("消息筛选", selection: Binding(
                get: { viewModel.selectedFilter },
                set: { filter in
                    Task { await viewModel.selectFilter(filter, api: messageAPI) }
                }
            )) {
                ForEach(MessageFilter.allCases) { filter in
                    Text(filter.title).tag(filter)
                }
            }
            .pickerStyle(.segmented)

            Text(viewModel.filterDescription)
                .font(.system(size: AppMetrics.FontSize.caption))
                .foregroundStyle(AppDesign.textSecondary)
        }
        .padding(AppMetrics.Spacing.pageHorizontal)
        .background(.white)
    }

    @ViewBuilder
    private var content: some View {
        if viewModel.isLoading && viewModel.messages.isEmpty {
            ProgressView("加载中...")
                .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else if viewModel.loadFailed {
            AppContentUnavailableView {
                Label("消息加载失败", systemImage: "exclamationmark.triangle")
            } description: {
                Text(viewModel.loadFailureReason ?? "请稍后重试")
            } actions: {
                Button("重新加载") {
                    Task { await viewModel.reloadFirstPage(api: messageAPI) }
                }
                .buttonStyle(.borderedProminent)
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else if viewModel.messages.isEmpty {
            AppContentUnavailableView("暂无消息", systemImage: "bell", description: Text("暂无可查看的系统消息"))
                .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else {
            ScrollView {
                LazyVStack(spacing: AppMetrics.Spacing.medium) {
                    ForEach(viewModel.messages) { item in
                        Button {
                            Task { await openMessage(item) }
                        } label: {
                            MessageRow(item: item, processing: processingMessageId == item.id)
                        }
                        .buttonStyle(.plain)
                        .onAppear {
                            if item.id == viewModel.messages.last?.id {
                                Task { await viewModel.loadMore(api: messageAPI) }
                            }
                        }
                    }

                    if viewModel.isLoadingMore {
                        ProgressView()
                            .frame(maxWidth: .infinity)
                            .padding(.vertical, AppMetrics.Spacing.medium)
                    }
                }
                .padding(AppMetrics.Spacing.pageHorizontal)
            }
        }
    }

    private func messageMetric(title: String, value: String, color: Color) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(title)
                .font(.system(size: AppMetrics.FontSize.caption))
                .foregroundStyle(AppDesign.textSecondary)
            Text(value)
                .font(.system(size: 24, weight: .bold))
                .foregroundStyle(color)
                .lineLimit(1)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(AppMetrics.Spacing.medium)
        .background(color.opacity(0.08), in: RoundedRectangle(cornerRadius: AppMetrics.CornerRadius.card))
    }

    private func openMessage(_ item: MessageItem) async {
        processingMessageId = item.id
        defer { processingMessageId = nil }
        do {
            try await viewModel.markAsRead(api: messageAPI, item: item)
        } catch {
            toastCenter.show(error.localizedDescription)
        }
        selectedMessage = viewModel.messages.first(where: { $0.id == item.id }) ?? item
    }

    private func markAllAsRead() async {
        do {
            try await viewModel.markAllAsRead(api: messageAPI)
            toastCenter.show("已全部标记为已读")
        } catch {
            toastCenter.show(error.localizedDescription)
        }
    }

    @discardableResult
    private func deleteMessage(_ item: MessageItem) async -> Bool {
        processingMessageId = item.id
        defer { processingMessageId = nil }
        do {
            try await viewModel.deleteMessage(api: messageAPI, item: item)
            toastCenter.show("消息已删除")
            return true
        } catch {
            toastCenter.show(error.localizedDescription)
            return false
        }
    }
}

private struct MessageRow: View {
    let item: MessageItem
    let processing: Bool

    var body: some View {
        HStack(alignment: .top, spacing: AppMetrics.Spacing.medium) {
            ZStack {
                RoundedRectangle(cornerRadius: 8)
                    .fill(item.type.color.opacity(0.12))
                Image(systemName: item.type.iconName)
                    .font(.system(size: 20, weight: .semibold))
                    .foregroundStyle(item.type.color)
            }
            .frame(width: 48, height: 48)

            VStack(alignment: .leading, spacing: 8) {
                HStack(alignment: .firstTextBaseline, spacing: 8) {
                    Text(item.title)
                        .font(.system(size: AppMetrics.FontSize.body, weight: .semibold))
                        .foregroundStyle(AppDesign.textPrimary)
                        .lineLimit(1)
                    if !item.isRead {
                        Circle()
                            .fill(Color(hex: 0xEF4444))
                            .frame(width: 7, height: 7)
                    }
                    Spacer()
                    Text(item.type.title)
                        .font(.system(size: AppMetrics.FontSize.caption, weight: .medium))
                        .foregroundStyle(item.type.color)
                }

                Text(item.detail.isEmpty ? "暂无消息内容" : item.detail)
                    .font(.system(size: AppMetrics.FontSize.subheadline))
                    .foregroundStyle(AppDesign.textSecondary)
                    .lineLimit(2)

                Text(item.time)
                    .font(.system(size: AppMetrics.FontSize.caption))
                    .foregroundStyle(Color(hex: 0x9CA3AF))
            }
        }
        .padding(AppMetrics.Spacing.medium)
        .background(.white, in: RoundedRectangle(cornerRadius: AppMetrics.CornerRadius.card))
        .overlay {
            RoundedRectangle(cornerRadius: AppMetrics.CornerRadius.card)
                .stroke(Color(hex: item.isRead ? 0xECEFF3 : 0xBFD7FF), lineWidth: 1)
        }
        .opacity(processing ? 0.6 : 1)
    }
}

private struct MessageDetailView: View {
    let item: MessageItem
    let onDelete: (MessageItem) async -> Bool
    @Environment(\.dismiss) private var dismiss
    @State private var showDeleteConfirm = false
    @State private var deleting = false

    var body: some View {
        NavigationStack {
            ScrollView {
                VStack(spacing: AppMetrics.Spacing.large) {
                    ZStack {
                        RoundedRectangle(cornerRadius: 12)
                            .fill(item.type.color.opacity(0.12))
                        Image(systemName: item.type.iconName)
                            .font(.system(size: 38, weight: .bold))
                            .foregroundStyle(item.type.color)
                    }
                    .frame(width: 82, height: 82)

                    VStack(spacing: AppMetrics.Spacing.small) {
                        Text(item.title)
                            .font(.system(size: AppMetrics.FontSize.title2, weight: .bold))
                            .foregroundStyle(AppDesign.textPrimary)
                            .multilineTextAlignment(.center)
                        Text(item.time)
                            .font(.system(size: AppMetrics.FontSize.subheadline))
                            .foregroundStyle(AppDesign.textSecondary)
                    }

                    Text(item.detail.isEmpty ? "暂无消息内容" : item.detail)
                        .font(.system(size: AppMetrics.FontSize.body))
                        .foregroundStyle(AppDesign.textPrimary)
                        .lineSpacing(6)
                        .frame(maxWidth: .infinity, alignment: .leading)
                        .padding(AppMetrics.Spacing.large)
                        .background(.white, in: RoundedRectangle(cornerRadius: AppMetrics.CornerRadius.card))
                }
                .padding(AppMetrics.Spacing.pageHorizontal)
            }
            .background(Color(hex: 0xF5F7FA).ignoresSafeArea())
            .navigationTitle("消息详情")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("关闭") { dismiss() }
                }
                ToolbarItem(placement: .topBarTrailing) {
                    Button(role: .destructive) {
                        showDeleteConfirm = true
                    } label: {
                        if deleting {
                            ProgressView()
                        } else {
                            Image(systemName: "trash")
                        }
                    }
                    .disabled(deleting || item.msgId == nil)
                }
            }
            .alert("确认删除", isPresented: $showDeleteConfirm) {
                Button("取消", role: .cancel) {}
                Button("删除", role: .destructive) {
                    Task {
                        deleting = true
                        let success = await onDelete(item)
                        deleting = false
                        if success { dismiss() }
                    }
                }
            } message: {
                Text("删除后不可恢复，是否继续？")
            }
        }
    }
}