import SwiftUI
import TXCore

/// 连接前的会话选择器（连接流程的一部分）：点主机 → 探测服务器 → 问「接回哪个会话」，选完才进终端。
///
/// 三种连接方式：**接回已有 tmux 会话** · **新建 tmux 会话** · **原生终端**（不经 tmux）。
/// 服务器**没装 tmux 时不显示本 sheet** —— 直接连原生终端，不拿一个只有一个选项的框去打扰用户。
///
/// 措辞注意：右上不是「跳过」（那读起来像"跳过某个步骤"，含义模糊）——它是一种**并列的连接方式**，
/// 所以直接叫「原生终端」。分段控件里 `Herdr` / `最近` 暂时置灰（后续支持），位置先占住避免重排。
struct SessionPickerSheet: View {
    /// 正在连接的主机名（标题里点明"连到哪台"，避免多主机时看不出上下文）。
    let host: String
    let choice: TmuxSessionChoice
    let onAttach: (String) -> Void
    let onCreate: (String) -> Void
    let onNative: () -> Void
    @EnvironmentObject var theme: TXThemeManager
    @State private var newName = ""
    @State private var creating = false
    @FocusState private var nameFocused: Bool
    private var p: TXPalette { theme.palette }

    var body: some View {
        VStack(alignment: .leading, spacing: TX.Space.m) {
            grabber
            title
            header
            if choice.sessions.isEmpty {
                emptyState
            } else {
                sessionList
            }
            newSessionRow
            Spacer(minLength: 0)
        }
        .padding(.horizontal, TX.Space.l)
        .padding(.bottom, TX.Space.l)
        .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)
        .background(p.bg.ignoresSafeArea())
    }

    private var title: some View {
        VStack(alignment: .leading, spacing: 3) {
            Text("连接到 \(host)")
                .font(TX.Font.mono(17, .medium))
                .foregroundStyle(p.text)
            Text("接回一个 tmux 会话，或直接用原生终端")
                .font(TX.Font.mono(12))
                .foregroundStyle(p.textWeak)
        }
    }

    private var grabber: some View {
        RoundedRectangle(cornerRadius: 2.5)
            .fill(p.borderStrong)
            .frame(width: 44, height: 5)
            .frame(maxWidth: .infinity)
            .padding(.top, TX.Space.s)
    }

    // MARK: - 分段控件 + 跳过

    private var header: some View {
        HStack(spacing: TX.Space.s) {
            HStack(spacing: 2) {
                segment(icon: "chevron.left.forwardslash.chevron.right", title: "Tmux", enabled: true)
                segment(icon: "shippingbox", title: "Herdr", enabled: false)
                segment(icon: "clock.arrow.circlepath", title: "最近", enabled: false)
            }
            .padding(4)
            .background(p.surface, in: Capsule())
            Spacer(minLength: TX.Space.s)
            Button(action: onNative) {
                HStack(spacing: TX.Space.xs) {
                    Image(systemName: "terminal")
                        .font(.system(size: 13, weight: .medium))
                    Text("原生终端")
                        .font(TX.Font.mono(15, .medium))
                }
                .foregroundStyle(p.text)
                .padding(.horizontal, TX.Space.m)
                .frame(height: 44)
                .background(p.surface, in: Capsule())
                .overlay(Capsule().strokeBorder(p.border, lineWidth: 1))
            }
            .buttonStyle(.txPress)
            .accessibilityLabel("直接连接原生终端，不经过 tmux")
        }
    }

    private func segment(icon: String, title: String, enabled: Bool) -> some View {
        HStack(spacing: TX.Space.xs) {
            Image(systemName: icon)
                .font(.system(size: 13, weight: .medium))
            Text(title)
                .font(TX.Font.mono(15, .medium))
        }
        .foregroundStyle(enabled ? p.text : p.textWeak.opacity(0.7))
        .padding(.horizontal, TX.Space.m)
        .frame(height: 36)
        .background(enabled ? p.bgDeep : .clear, in: Capsule())
        .overlay {
            if enabled {
                Capsule().strokeBorder(p.border, lineWidth: 1)
            }
        }
    }

    // MARK: - 会话列表

    private var sessionList: some View {
        VStack(spacing: 0) {
            ForEach(Array(choice.sessions.enumerated()), id: \.element.name) { index, s in
                Button { onAttach(s.name) } label: {
                    sessionRow(s)
                }
                .buttonStyle(.txPress)
                if index < choice.sessions.count - 1 {
                    Rectangle().fill(p.divider).frame(height: 1)
                        .padding(.horizontal, TX.Space.m)
                }
            }
        }
        .background(p.surfaceDark, in: RoundedRectangle(cornerRadius: TX.Radius.card))
    }

    private func sessionRow(_ s: TmuxSessionProbe.Session) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            HStack(spacing: TX.Space.s) {
                Text(s.name)
                    .font(TX.Font.mono(22, .medium))
                    .foregroundStyle(p.text)
                // tmux 会话本身就是活着的服务端进程 → 一律「活跃」；被别的客户端占用时另标。
                TXBadge(text: "活跃", emphasized: true)
                if s.isAttached {
                    TXBadge(text: "已被接入")
                }
                Spacer(minLength: 0)
            }
            Text(subtitle(s))
                .font(TX.Font.mono(13))
                .foregroundStyle(p.textWeak)
        }
        .padding(.horizontal, TX.Space.m)
        .padding(.vertical, 18)
        .frame(maxWidth: .infinity, alignment: .leading)
        .contentShape(Rectangle())
    }

    private func subtitle(_ s: TmuxSessionProbe.Session) -> String {
        var parts = ["\(s.windows) 个窗口"]
        if let t = s.lastActivity { parts.append(SessionCard.relative(t)) }
        return parts.joined(separator: " · ")
    }

    private var emptyState: some View {
        VStack(alignment: .leading, spacing: 6) {
            Text("这台主机上还没有 tmux 会话")
                .font(TX.Font.mono(15, .medium))
                .foregroundStyle(p.text)
            Text("新建一个就能让会话留在服务端：关掉 App、换网络都能原样接回。也可以直接用原生终端。")
                .font(TX.Font.mono(12))
                .foregroundStyle(p.textWeak)
                .lineSpacing(3)
        }
        .padding(TX.Space.m)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(p.surfaceDark, in: RoundedRectangle(cornerRadius: TX.Radius.card))
    }

    // MARK: - 新建

    @ViewBuilder private var newSessionRow: some View {
        if creating {
            HStack(spacing: TX.Space.s) {
                TXSearchField(text: $newName, placeholder: choice.defaultNewName)
                    .focused($nameFocused)
                TXButton(title: "创建", emphasized: true) {
                    let name = newName.trimmingCharacters(in: .whitespaces)
                    onCreate(name.isEmpty ? choice.defaultNewName : name)
                }
                TXButton(title: "取消") { creating = false }
            }
        } else {
            Button {
                creating = true
                nameFocused = true
            } label: {
                HStack(spacing: TX.Space.s) {
                    Image(systemName: "plus")
                        .font(.system(size: 13, weight: .medium))
                    Text("新建 tmux 会话…")
                        .font(TX.Font.mono(15, .medium))
                    Spacer(minLength: 0)
                }
                .foregroundStyle(TXAccent.textBright)
                .padding(.horizontal, TX.Space.m)
                .frame(height: 56)
                .background(p.surfaceDark, in: RoundedRectangle(cornerRadius: TX.Radius.card))
                .contentShape(Rectangle())
            }
            .buttonStyle(.txPress)
        }
    }
}