import SwiftUI

/// The conversation screen for a revealed connection.
///
/// This is where two people who met in the real world actually talk. The UI
/// is deliberately calm and human — no engagement-baiting, no streaks, no
/// algorithms. Just a conversation between two people who chose to meet.
struct ChatView: View {
    @EnvironmentObject private var vm: ChatViewModel
    @EnvironmentObject private var revealFlow: RevealFlow
    @State private var input = ""

    let connection: Connection

    var body: some View {
        VStack(spacing: 0) {
            // Header
            HStack(spacing: 12) {
                Circle()
                    .fill(Color.green.opacity(0.2))
                    .frame(width: 40, height: 40)
                    .overlay(Text(String(connection.displayName.prefix(1))))

                VStack(alignment: .leading, spacing: 2) {
                    Text(connection.displayName)
                        .font(.headline)
                    Text("Met in person · \(connection.createdAt, format: .dateTime.month().day())")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
                Spacer()
                Image(systemName: "lock.fill")
                    .font(.caption)
                    .foregroundColor(.green)
                    .accessibilityLabel("End-to-end encrypted")
            }
            .padding()
            .background(Color(.secondarySystemBackground))

            Divider()

            // Messages
            ScrollViewReader { proxy in
                ScrollView {
                    LazyVStack(spacing: 12) {
                        ForEach(vm.messages) { message in
                            MessageBubble(message: message, isMine: message.senderID == "me")
                        }
                    }
                    .padding()
                }
                .onChange(of: vm.messages.count) { _, _ in
                    if let last = vm.messages.last {
                        withAnimation {
                            proxy.scrollTo(last.id, anchor: .bottom)
                        }
                    }
                }
            }

            // Input
            HStack(spacing: 12) {
                TextField("Say hello…", text: $input, axis: .vertical)
                    .lineLimit(1...4)
                    .padding(10)
                    .background(Color(.secondarySystemBackground))
                    .clipShape(RoundedRectangle(cornerRadius: 18))

                Button {
                    vm.draft = input
                    input = ""
                    Task { await vm.send() }
                } label: {
                    Image(systemName: "arrow.up.circle.fill")
                        .font(.system(size: 28))
                }
                .disabled(input.trimmingCharacters(in: .whitespaces).isEmpty)
            }
            .padding()
        }
        .navigationTitle("")
        .navigationBarTitleDisplayMode(.inline)
        .onAppear {
            // Use the E2E session key established at reveal time.
            vm.start(with: connection, sessionKey: revealFlow.currentSessionKey())
        }
    }
}

/// A single message bubble.
struct MessageBubble: View {
    @EnvironmentObject private var vm: ChatViewModel
    let message: ChatMessage
    let isMine: Bool

    var body: some View {
        HStack {
            if isMine { Spacer() }
            Text(vm.text(for: message))
                .padding(.horizontal, 14)
                .padding(.vertical, 10)
                .background(
                    RoundedRectangle(cornerRadius: 18)
                        .fill(isMine ? Color.green : Color(.secondarySystemBackground))
                )
                .foregroundColor(isMine ? .white : .primary)
            if !isMine { Spacer() }
        }
    }
}