// PasteSheet.swift
// Confirm-before-paste sheet that previews clipboard content and lets
// the user approve or cancel before sending a bracketed-paste frame.
//
// Privacy note: `UIPasteboard.general.string` is accessed lazily when the
// sheet appears. iOS 16+ shows a system banner ("App pasted from …") but
// does not require an explicit entitlement for this access pattern.

import SwiftUI
import UIKit

// MARK: - PasteSheet

/// A modal sheet that displays the current clipboard text and asks the user
/// to confirm before sending it to the terminal as a `paste` frame.
///
/// Dismiss flow:
/// - **Paste** → encodes content as `{ type:"paste", data:"…" }` and calls
///   `onSend`, then sets `isPresented` to `false`.
/// - **Cancel** → sets `isPresented` to `false` with no send.
@MainActor
struct PasteSheet: View {

    // MARK: Bindings / callbacks

    @Binding var isPresented: Bool
    let onSend: (ClientToServer) -> Void

    // MARK: Private state

    /// The clipboard string captured when the view appears.
    @State private var clipboardContent: String? = nil

    // MARK: Body

    var body: some View {
        NavigationStack {
            Group {
                if let content = clipboardContent {
                    if content.isEmpty {
                        emptyClipboardView
                    } else {
                        previewView(content: content)
                    }
                } else {
                    emptyClipboardView
                }
            }
            .navigationTitle("Paste")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") {
                        isPresented = false
                    }
                }
                if let content = clipboardContent, !content.isEmpty {
                    ToolbarItem(placement: .confirmationAction) {
                        Button("Paste") {
                            onSend(.paste(data: content))
                            isPresented = false
                        }
                        .fontWeight(.semibold)
                    }
                }
            }
        }
        .onAppear {
            // Capture clipboard when the sheet is presented.
            // Accessing on the main actor satisfies UIKit's thread requirement.
            clipboardContent = UIPasteboard.general.string
        }
    }

    // MARK: Sub-views

    /// Shown when the clipboard is nil or empty.
    private var emptyClipboardView: some View {
        VStack(spacing: 12) {
            Image(systemName: "clipboard")
                .font(.largeTitle)
                .foregroundStyle(.secondary)
            Text("Clipboard is empty")
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }

    /// Scrollable preview of the clipboard text with a bottom Paste button.
    private func previewView(content: String) -> some View {
        VStack(spacing: 0) {
            // Scrollable text preview
            ScrollView([.vertical, .horizontal]) {
                Text(content)
                    .font(.system(size: 13, design: .monospaced))
                    .foregroundStyle(.primary)
                    .frame(maxWidth: .infinity, alignment: .leading)
                    .padding()
                    .textSelection(.enabled)
            }
            .background(Color(uiColor: .systemGroupedBackground))

            Divider()

            // Character count footer
            HStack {
                Label(
                    "\(content.count) character\(content.count == 1 ? "" : "s")",
                    systemImage: "text.cursor"
                )
                .font(.caption)
                .foregroundStyle(.secondary)
                Spacer()
            }
            .padding(.horizontal)
            .padding(.vertical, 8)

            // Primary action button
            Button {
                onSend(.paste(data: content))
                isPresented = false
            } label: {
                Label("Paste into Terminal", systemImage: "doc.on.clipboard")
                    .font(.body.weight(.semibold))
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, 14)
            }
            .buttonStyle(.borderedProminent)
            .padding(.horizontal)
            .padding(.bottom, 16)
        }
    }
}