import SwiftUI
import UIKit

// 引擎日志独立界面（#3）：展示 EngineController.logs 环形缓冲里最近 N 条诊断（含 pion 内部 ICE/mDNS
// 日志）。按传输会话（session id）聚合分组，每组可一键整体复制——便于真机调试时把某次传输的完整
// 日志一并贴出（无 Web Inspector）。另有「复制全部」「清空」。
struct LogView: View
{
    @Environment(EngineController.self) private var engine

    private struct LogGroup: Identifiable
    {
        let id: String
        let session: String?
        let entries: [LogEntry]
    }

    // 按 sessionId 聚合：保持组内最新在前；组按首次出现（即最新条目）顺序。非会话日志归入「其他」组。
    private var groups: [LogGroup]
    {
        var order: [String] = []
        var map: [String: [LogEntry]] = [:]
        for e in engine.logs
        {
            let key = e.sessionId ?? ""
            if map[key] == nil { order.append(key) }
            map[key, default: []].append(e)
        }
        return order.map
        {
            LogGroup(id: $0.isEmpty ? "—" : $0, session: $0.isEmpty ? nil : $0, entries: map[$0] ?? [])
        }
    }

    var body: some View
    {
        Group
        {
            if engine.logs.isEmpty
            {
                ContentUnavailableView(t("ios.logs.empty"), systemImage: "doc.text")
            }
            else
            {
                List
                {
                    ForEach(groups)
                    { group in
                        Section
                        {
                            ForEach(group.entries) { entry in logRow(entry) }
                        }
                        header:
                        {
                            HStack
                            {
                                Text(sessionLabel(group))
                                Spacer()
                                Button { copy(group.entries) }
                                    label: { Image(systemName: "doc.on.doc") }
                                    .buttonStyle(.borderless)
                            }
                        }
                    }
                }
                .listStyle(.plain)
            }
        }
        .navigationTitle(t("ios.logs.title"))
        .navigationBarTitleDisplayMode(.inline)
        .toolbar
        {
            if !engine.logs.isEmpty
            {
                ToolbarItem(placement: .topBarTrailing)
                {
                    Button { copy(engine.logs) }
                        label: { Label(t("ios.logs.copy"), systemImage: "doc.on.doc") }
                }
                ToolbarItem(placement: .topBarTrailing)
                {
                    Button(role: .destructive) { engine.clearLogs() }
                        label: { Label(t("ios.logs.clear"), systemImage: "trash") }
                }
            }
        }
    }

    // 复制为纯文本进剪贴板：存储为最新在前，复制时反转成时间正序便于阅读。
    private func copy(_ entries: [LogEntry])
    {
        let text = entries.reversed()
            .map { "\(timeString($0.at)) \($0.message)" }
            .joined(separator: "\n")
        UIPasteboard.general.string = text
    }

    private func sessionLabel(_ group: LogGroup) -> String
    {
        guard let s = group.session
        else { return "\(t("ios.logs.ungrouped")) · \(group.entries.count)" }
        return "\(t("ios.logs.session")) \(String(s.prefix(8))) · \(group.entries.count)"
    }

    private func logRow(_ entry: LogEntry) -> some View
    {
        VStack(alignment: .leading, spacing: 4)
        {
            HStack(spacing: 6)
            {
                Image(systemName: levelSymbol(entry.level))
                    .font(.caption)
                    .foregroundStyle(levelTint(entry.level))
                Text(timeString(entry.at))
                    .font(.caption2)
                    .foregroundStyle(.secondary)
                    .monospacedDigit()
            }
            Text(entry.message)
                .font(.caption.monospaced())
                .foregroundStyle(.primary)
                .textSelection(.enabled)
                .fixedSize(horizontal: false, vertical: true)
        }
        .padding(.vertical, 2)
    }

    private func levelSymbol(_ level: String) -> String
    {
        switch level
        {
        case "error": return "xmark.octagon.fill"
        case "warn": return "exclamationmark.triangle.fill"
        default: return "info.circle"
        }
    }

    private func levelTint(_ level: String) -> Color
    {
        switch level
        {
        case "error": return .red
        case "warn": return .orange
        default: return .secondary
        }
    }

    private func timeString(_ date: Date) -> String
    {
        let f = DateFormatter()
        f.dateFormat = "HH:mm:ss"
        return f.string(from: date)
    }
}