use crate::app_backtrack::BacktrackState;
use crate::app_event::AppEvent;
use crate::app_event_sender::AppEventSender;
use crate::chatwidget::ChatWidget;
use crate::file_search::FileSearchManager;
use crate::pager_overlay::Overlay;
use crate::resume_picker::ResumeSelection;
use crate::tui;
use crate::tui::TuiEvent;
use codex_ansi_escape::ansi_escape_line;
use codex_core::AuthManager;
use codex_core::ConversationManager;
use codex_core::config::Config;
use codex_core::protocol::TokenUsage;
use color_eyre::eyre::Result;
use color_eyre::eyre::WrapErr;
use crossterm::event::KeyCode;
use crossterm::event::KeyEvent;
use crossterm::event::KeyEventKind;
use crossterm::terminal::supports_keyboard_enhancement;
use ratatui::style::Stylize;
use ratatui::text::Line;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::atomic::AtomicBool;
use std::sync::atomic::Ordering;
use std::thread;
use std::time::Duration;
use tokio::select;
use tokio::sync::mpsc::unbounded_channel;
// use uuid::Uuid;

pub(crate) struct App {
    pub(crate) server: Arc<ConversationManager>,
    pub(crate) app_event_tx: AppEventSender,
    pub(crate) chat_widget: ChatWidget,

    /// Config is stored here so we can recreate ChatWidgets as needed.
    pub(crate) config: Config,

    pub(crate) file_search: FileSearchManager,

    pub(crate) transcript_lines: Vec<Line<'static>>,

    // Pager overlay state (Transcript or Static like Diff)
    pub(crate) overlay: Option<Overlay>,
    pub(crate) deferred_history_lines: Vec<Line<'static>>,
    has_emitted_history_lines: bool,

    pub(crate) enhanced_keys_supported: bool,

    /// Controls the animation thread that sends CommitTick events.
    pub(crate) commit_anim_running: Arc<AtomicBool>,

    // Esc-backtracking state grouped
    pub(crate) backtrack: crate::app_backtrack::BacktrackState,
}

impl App {
    pub async fn run(
        tui: &mut tui::Tui,
        auth_manager: Arc<AuthManager>,
        config: Config,
        initial_prompt: Option<String>,
        initial_images: Vec<PathBuf>,
        resume_selection: ResumeSelection,
    ) -> Result<TokenUsage> {
        use tokio_stream::StreamExt;
        let (app_event_tx, mut app_event_rx) = unbounded_channel();
        let app_event_tx = AppEventSender::new(app_event_tx);

        let conversation_manager = Arc::new(ConversationManager::new(auth_manager.clone()));

        let enhanced_keys_supported = supports_keyboard_enhancement().unwrap_or(false);

        let chat_widget = match resume_selection {
            ResumeSelection::StartFresh | ResumeSelection::Exit => {
                let init = crate::chatwidget::ChatWidgetInit {
                    config: config.clone(),
                    frame_requester: tui.frame_requester(),
                    app_event_tx: app_event_tx.clone(),
                    initial_prompt: initial_prompt.clone(),
                    initial_images: initial_images.clone(),
                    enhanced_keys_supported,
                };
                ChatWidget::new(init, conversation_manager.clone())
            }
            ResumeSelection::Resume(path) => {
                let resumed = conversation_manager
                    .resume_conversation_from_rollout(
                        config.clone(),
                        path.clone(),
                        auth_manager.clone(),
                    )
                    .await
                    .wrap_err_with(|| {
                        format!("Failed to resume session from {}", path.display())
                    })?;
                let init = crate::chatwidget::ChatWidgetInit {
                    config: config.clone(),
                    frame_requester: tui.frame_requester(),
                    app_event_tx: app_event_tx.clone(),
                    initial_prompt: initial_prompt.clone(),
                    initial_images: initial_images.clone(),
                    enhanced_keys_supported,
                };
                ChatWidget::new_from_existing(
                    init,
                    resumed.conversation,
                    resumed.session_configured,
                )
            }
        };

        let file_search = FileSearchManager::new(config.cwd.clone(), app_event_tx.clone());

        let mut app = Self {
            server: conversation_manager,
            app_event_tx,
            chat_widget,
            config,
            file_search,
            enhanced_keys_supported,
            transcript_lines: Vec::new(),
            overlay: None,
            deferred_history_lines: Vec::new(),
            has_emitted_history_lines: false,
            commit_anim_running: Arc::new(AtomicBool::new(false)),
            backtrack: BacktrackState::default(),
        };

        let tui_events = tui.event_stream();
        tokio::pin!(tui_events);

        tui.frame_requester().schedule_frame();

        while select! {
            Some(event) = app_event_rx.recv() => {
                app.handle_event(tui, event).await?
            }
            Some(event) = tui_events.next() => {
                app.handle_tui_event(tui, event).await?
            }
        } {}
        tui.terminal.clear()?;
        Ok(app.token_usage())
    }

    pub(crate) async fn handle_tui_event(
        &mut self,
        tui: &mut tui::Tui,
        event: TuiEvent,
    ) -> Result<bool> {
        if self.overlay.is_some() {
            let _ = self.handle_backtrack_overlay_event(tui, event).await?;
        } else {
            match event {
                TuiEvent::Key(key_event) => {
                    self.handle_key_event(tui, key_event).await;
                }
                TuiEvent::Paste(pasted) => {
                    // Many terminals convert newlines to \r when pasting (e.g., iTerm2),
                    // but tui-textarea expects \n. Normalize CR to LF.
                    // [tui-textarea]: https://github.com/rhysd/tui-textarea/blob/4d18622eeac13b309e0ff6a55a46ac6706da68cf/src/textarea.rs#L782-L783
                    // [iTerm2]: https://github.com/gnachman/iTerm2/blob/5d0c0d9f68523cbd0494dad5422998964a2ecd8d/sources/iTermPasteHelper.m#L206-L216
                    let pasted = pasted.replace("\r", "\n");
                    self.chat_widget.handle_paste(pasted);
                }
                TuiEvent::Draw => {
                    if self
                        .chat_widget
                        .handle_paste_burst_tick(tui.frame_requester())
                    {
                        return Ok(true);
                    }
                    tui.draw(
                        self.chat_widget.desired_height(tui.terminal.size()?.width),
                        |frame| {
                            frame.render_widget_ref(&self.chat_widget, frame.area());
                            if let Some((x, y)) = self.chat_widget.cursor_pos(frame.area()) {
                                frame.set_cursor_position((x, y));
                            }
                        },
                    )?;
                }
                TuiEvent::AttachImage {
                    path,
                    width,
                    height,
                    format_label,
                } => {
                    self.chat_widget
                        .attach_image(path, width, height, format_label);
                }
            }
        }
        Ok(true)
    }

    async fn handle_event(&mut self, tui: &mut tui::Tui, event: AppEvent) -> Result<bool> {
        match event {
            AppEvent::NewSession => {
                let init = crate::chatwidget::ChatWidgetInit {
                    config: self.config.clone(),
                    frame_requester: tui.frame_requester(),
                    app_event_tx: self.app_event_tx.clone(),
                    initial_prompt: None,
                    initial_images: Vec::new(),
                    enhanced_keys_supported: self.enhanced_keys_supported,
                };
                self.chat_widget = ChatWidget::new(init, self.server.clone());
                tui.frame_requester().schedule_frame();
            }
            AppEvent::InsertHistoryCell(cell) => {
                let mut cell_transcript = cell.transcript_lines();
                if !cell.is_stream_continuation() && !self.transcript_lines.is_empty() {
                    cell_transcript.insert(0, Line::from(""));
                }
                if let Some(Overlay::Transcript(t)) = &mut self.overlay {
                    t.insert_lines(cell_transcript.clone());
                    tui.frame_requester().schedule_frame();
                }
                self.transcript_lines.extend(cell_transcript.clone());
                let mut display = cell.display_lines(tui.terminal.last_known_screen_size.width);
                if !display.is_empty() {
                    // Only insert a separating blank line for new cells that are not
                    // part of an ongoing stream. Streaming continuations should not
                    // accrue extra blank lines between chunks.
                    if !cell.is_stream_continuation() {
                        if self.has_emitted_history_lines {
                            display.insert(0, Line::from(""));
                        } else {
                            self.has_emitted_history_lines = true;
                        }
                    }
                    if self.overlay.is_some() {
                        self.deferred_history_lines.extend(display);
                    } else {
                        tui.insert_history_lines(display);
                    }
                }
            }
            AppEvent::StartCommitAnimation => {
                if self
                    .commit_anim_running
                    .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
                    .is_ok()
                {
                    let tx = self.app_event_tx.clone();
                    let running = self.commit_anim_running.clone();
                    thread::spawn(move || {
                        while running.load(Ordering::Relaxed) {
                            thread::sleep(Duration::from_millis(50));
                            tx.send(AppEvent::CommitTick);
                        }
                    });
                }
            }
            AppEvent::StopCommitAnimation => {
                self.commit_anim_running.store(false, Ordering::Release);
            }
            AppEvent::CommitTick => {
                self.chat_widget.on_commit_tick();
            }
            AppEvent::CodexEvent(event) => {
                self.chat_widget.handle_codex_event(event);
            }
            AppEvent::ConversationHistory(ev) => {
                self.on_conversation_history_for_backtrack(tui, ev).await?;
            }
            AppEvent::ExitRequest => {
                return Ok(false);
            }
            AppEvent::CodexOp(op) => self.chat_widget.submit_op(op),
            AppEvent::DiffResult(text) => {
                // Clear the in-progress state in the bottom pane
                self.chat_widget.on_diff_complete();
                // Enter alternate screen using TUI helper and build pager lines
                let _ = tui.enter_alt_screen();
                let pager_lines: Vec<ratatui::text::Line<'static>> = if text.trim().is_empty() {
                    vec!["No changes detected.".italic().into()]
                } else {
                    text.lines().map(ansi_escape_line).collect()
                };
                self.overlay = Some(Overlay::new_static_with_title(
                    pager_lines,
                    "D I F F".to_string(),
                ));
                tui.frame_requester().schedule_frame();
            }
            AppEvent::StartFileSearch(query) => {
                if !query.is_empty() {
                    self.file_search.on_user_query(query);
                }
            }
            AppEvent::FileSearchResult { query, matches } => {
                self.chat_widget.apply_file_search_result(query, matches);
            }
            AppEvent::UpdateReasoningEffort(effort) => {
                self.chat_widget.set_reasoning_effort(effort);
            }
            AppEvent::UpdateModel(model) => {
                self.chat_widget.set_model(model);
            }
            AppEvent::UpdateAskForApprovalPolicy(policy) => {
                self.chat_widget.set_approval_policy(policy);
            }
            AppEvent::UpdateSandboxPolicy(policy) => {
                self.chat_widget.set_sandbox_policy(policy);
            }
        }
        Ok(true)
    }

    pub(crate) fn token_usage(&self) -> codex_core::protocol::TokenUsage {
        self.chat_widget.token_usage().clone()
    }

    async fn handle_key_event(&mut self, tui: &mut tui::Tui, key_event: KeyEvent) {
        match key_event {
            KeyEvent {
                code: KeyCode::Char('t'),
                modifiers: crossterm::event::KeyModifiers::CONTROL,
                kind: KeyEventKind::Press,
                ..
            } => {
                // Enter alternate screen and set viewport to full size.
                let _ = tui.enter_alt_screen();
                self.overlay = Some(Overlay::new_transcript(self.transcript_lines.clone()));
                tui.frame_requester().schedule_frame();
            }
            // Esc primes/advances backtracking only in normal (not working) mode
            // with an empty composer. In any other state, forward Esc so the
            // active UI (e.g. status indicator, modals, popups) handles it.
            KeyEvent {
                code: KeyCode::Esc,
                kind: KeyEventKind::Press | KeyEventKind::Repeat,
                ..
            } => {
                if self.chat_widget.is_normal_backtrack_mode()
                    && self.chat_widget.composer_is_empty()
                {
                    self.handle_backtrack_esc_key(tui);
                } else {
                    self.chat_widget.handle_key_event(key_event);
                }
            }
            // Enter confirms backtrack when primed + count > 0. Otherwise pass to widget.
            KeyEvent {
                code: KeyCode::Enter,
                kind: KeyEventKind::Press,
                ..
            } if self.backtrack.primed
                && self.backtrack.count > 0
                && self.chat_widget.composer_is_empty() =>
            {
                // Delegate to helper for clarity; preserves behavior.
                self.confirm_backtrack_from_main();
            }
            KeyEvent {
                kind: KeyEventKind::Press | KeyEventKind::Repeat,
                ..
            } => {
                // Any non-Esc key press should cancel a primed backtrack.
                // This avoids stale "Esc-primed" state after the user starts typing
                // (even if they later backspace to empty).
                if key_event.code != KeyCode::Esc && self.backtrack.primed {
                    self.reset_backtrack_state();
                }
                self.chat_widget.handle_key_event(key_event);
            }
            _ => {
                // Ignore Release key events.
            }
        };
    }
}