//
//  TranscriptView.swift
//  Zyquo Local
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//

import SwiftUI

/// Lazy transcript: user right in accentSubtle, assistant left on surface,
/// 16 pt rhythm, hover timestamps, streaming tail with caret, jump-to-bottom.
struct TranscriptView: View {
    let conversation: Conversation
    @Environment(AppModel.self) private var app
    @State private var atBottom = true

    private var isStreamingHere: Bool {
        app.chat.isGenerating && app.chat.streamingConversationID == conversation.id
    }

    var body: some View {
        ScrollViewReader { proxy in
            ZStack(alignment: .bottom) {
                ScrollView {
                    LazyVStack(spacing: ZyquoTheme.Spacing.m) {
                        ForEach(conversation.messages.filter { $0.role != .system }) { message in
                            MessageRow(message: message, conversation: conversation)
                        }
                        if isStreamingHere {
                            StreamingRow()
                        }
                        Color.clear
                            .frame(height: 1)
                            .id("bottom")
                            .onAppear { atBottom = true }
                            .onDisappear { atBottom = false }
                    }
                    .padding(.horizontal, ZyquoTheme.Spacing.xl)
                    .padding(.vertical, ZyquoTheme.Spacing.l)
                    .frame(maxWidth: ZyquoTheme.messageColumnMaxWidth)
                    .frame(maxWidth: .infinity)
                }
                .onChange(of: app.chat.streamingText) {
                    if atBottom {
                        proxy.scrollTo("bottom", anchor: .bottom)
                    }
                }
                .onChange(of: conversation.messages.count) {
                    withAnimation(.easeOut(duration: 0.15)) {
                        proxy.scrollTo("bottom", anchor: .bottom)
                    }
                }
                .onChange(of: conversation.id) {
                    proxy.scrollTo("bottom", anchor: .bottom)
                }

                if !atBottom {
                    Button {
                        withAnimation(.snappy(duration: 0.25)) {
                            proxy.scrollTo("bottom", anchor: .bottom)
                        }
                    } label: {
                        Image(systemName: "arrow.down")
                            .font(.system(size: 12, weight: .semibold))
                            .foregroundStyle(ZyquoTheme.textPrimary)
                            .padding(ZyquoTheme.Spacing.xs)
                            .background(ZyquoTheme.surface, in: Circle())
                            .overlay(Circle().stroke(ZyquoTheme.border, lineWidth: ZyquoTheme.hairline))
                            .floatingShadow()
                    }
                    .buttonStyle(PressableButtonStyle())
                    .padding(.bottom, ZyquoTheme.Spacing.m)
                    .transition(.opacity.combined(with: .move(edge: .bottom)))
                }
            }
        }
    }
}

/// The in-flight assistant message: live thinking section, streamed text,
/// blinking caret at the stream tail.
struct StreamingRow: View {
    @Environment(AppModel.self) private var app
    @State private var caretVisible = true

    var body: some View {
        HStack(alignment: .top) {
            VStack(alignment: .leading, spacing: ZyquoTheme.Spacing.xs) {
                if !app.chat.streamingThinking.isEmpty {
                    ThinkingDisclosure(
                        thinking: app.chat.streamingThinking,
                        isLive: app.chat.isThinking
                    )
                }
                if !app.chat.streamingText.isEmpty || !app.chat.isThinking {
                    HStack(alignment: .bottom, spacing: 2) {
                        MarkdownText(app.chat.streamingText)
                        Rectangle()
                            .fill(ZyquoTheme.accent)
                            .frame(width: 2, height: ZyquoTheme.chatFontSize + 2)
                            .opacity(caretVisible ? 1 : 0.15)
                            .onAppear {
                                withAnimation(.easeInOut(duration: 0.55).repeatForever()) {
                                    caretVisible = false
                                }
                            }
                    }
                }
            }
            .padding(ZyquoTheme.Spacing.s)
            .background(ZyquoTheme.surface, in: RoundedRectangle(cornerRadius: ZyquoTheme.Radius.m))
            .overlay(
                RoundedRectangle(cornerRadius: ZyquoTheme.Radius.m)
                    .stroke(ZyquoTheme.border, lineWidth: ZyquoTheme.hairline)
            )
            .frame(maxWidth: ZyquoTheme.messageColumnMaxWidth * 0.86, alignment: .leading)
            Spacer(minLength: ZyquoTheme.Spacing.xxl)
        }
    }
}