//! TUI event loop — single-process mode entry point.
//!
//! Provides `run_single_process()` which sets up the terminal,
//! creates a session, and enters the render/input loop.
//!
//! Flow: create session + lock → enable raw mode + alternate screen →
//! run_loop (render → poll events → handle key → tick) →
//! restore terminal → save settings → release lock.

use anyhow::Result;
use crossterm::execute;
use crossterm::event::{DisableBracketedPaste, DisableMouseCapture, Event, KeyEventKind, MouseEventKind};
use crossterm::terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen};
use ratatui::backend::CrosstermBackend;
use ratatui::Terminal;
use std::io::{self, Write};
use std::time::Duration;

use tracing::{debug, info};

use crate::action::{apply_action, Action};
use crate::controller::input::handle_key;
use crate::state::AppStateRest;
use crate::view;

/// Run zesdex as a self-contained TUI + agent loop in one process.
///
/// Flow: build `AppStateRest` → enter raw mode / alternate screen →
/// run the event loop → always restore the terminal (even on error) →
/// save settings.
#[tracing::instrument]
pub fn run_single_process() -> Result<()> {
    let rt = tokio::runtime::Runtime::new()?;
    let _guard = rt.enter();

    // Create session state
    info!("starting single-process TUI");
    let (_store, mut state) = create_local_session()?;

    // Enter raw mode and alternate screen for the TUI
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen)?;
    execute!(stdout, crossterm::event::EnableBracketedPaste)?;
    execute!(stdout, crossterm::event::EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;
    terminal.clear()?;

    let run_result = run_loop(&mut state, &mut terminal);

    let mut restore_stdout = io::stdout();
    let _ = execute!(restore_stdout, DisableBracketedPaste);
    let _ = execute!(restore_stdout, DisableMouseCapture);
    let _ = execute!(restore_stdout, LeaveAlternateScreen);
    let _ = disable_raw_mode();

    if let Err(e) = run_result {
        let _ = writeln!(restore_stdout, "error: {e}");
        let _ = restore_stdout.flush();
    }

    // Save settings
    state.save_settings();

    Ok(())
}

/// Run the event loop, guaranteeing terminal restoration on error.
///
/// Wraps `run_loop_inner` so that if it panics or returns an error the
/// terminal is restored to a usable state before propagating the error.
#[tracing::instrument(skip(state, terminal))]
fn run_loop(
    state: &mut AppStateRest,
    terminal: &mut Terminal<CrosstermBackend<io::Stdout>>,
) -> Result<()> {
    debug!("entering run_loop");
    let result = run_loop_inner(state, terminal);
    if let Err(ref _e) = result {
        let _ = terminal.clear();
        let _ = disable_raw_mode();
        let _ = execute!(io::stdout(), DisableBracketedPaste);
        let _ = execute!(io::stdout(), DisableMouseCapture);
        let _ = execute!(io::stdout(), LeaveAlternateScreen);
    }
    result
}

/// The core single-process render/input loop.
///
/// Performance optimizations applied here:
/// - Skip `terminal.draw()` when `state.dirty == false` (nothing changed)
/// - Adaptive poll timeout: 50ms when a turn is in-flight (spinner needs
///   smooth updates), 200ms when idle (no reason to busy-loop)
/// - Toast expiry is drained once here instead of in two places
/// - Chat display lines are cached and rebuilt only when content changes
#[tracing::instrument(skip(state, terminal))]
fn run_loop_inner(
    state: &mut AppStateRest,
    terminal: &mut Terminal<CrosstermBackend<io::Stdout>>,
) -> Result<()> {
    info!("TUI event loop started");
    loop {
        if state.quit {
            info!("TUI event loop exiting (quit=true)");
            break;
        }

        // Drain expired toasts exactly once per loop iteration (was being
        // done here AND in Action::Tick before this fix).
        let now_ms = chrono::Utc::now().timestamp_millis();
        state.misc.drain_expired_toasts(now_ms);

        // Skip render when nothing has changed — avoids expensive markdown
        // re-parse and layout recalculation every cycle while idle.
        if state.dirty {
            // Pre-warm display caches before entering the terminal.draw closure.
            // This lets view::draw work with &AppStateRest (no mutation inside draw).
            view::pre_render(state);
            terminal.draw(|f| {
                view::draw(f, state);
                state.dirty = false;
            })?;
        }

        // Adaptive poll: fast when animating, slow when idle.
        let poll_timeout = if state.turn_in_flight() {
            Duration::from_millis(50)   // smooth spinner @ ~20fps
        } else {
            Duration::from_millis(200)  // idle: 5fps, saves CPU
        };

        if crossterm::event::poll(poll_timeout)? {
            match crossterm::event::read()? {
                Event::Key(key) => {
                    if key.kind == KeyEventKind::Press || key.kind == KeyEventKind::Repeat {
                        let actions = handle_key(key, state);
                        for action in actions {
                            apply_action(state, action);
                        }
                        if let Some(text) = state.misc.pending_clipboard_copy.take() {
                            let _ = zesdex_infrastructure::utils::write_osc52(&mut io::stdout(), &text);
                            state.push_toast(zesdex_infrastructure::Toast::new(
                                zesdex_infrastructure::ToastKind::Success,
                                "Copied to clipboard".to_string(),
                            ));
                        }
                    }
                }
                Event::Paste(text) => {
                    if state.input.autocomplete_visible {
                        state.input.close_autocomplete();
                    }
                    state.input.buffer.insert_str(state.input.cursor, &text);
                    state.input.cursor += text.len();
                    if state.input.buffer.starts_with('/') {
                        state.input.open_autocomplete();
                    }
                    state.dirty = true;
                }
                Event::Resize(w, h) => {
                    apply_action(state, Action::Resize(w, h));
                }
                Event::Mouse(mouse_event) => {
                    if mouse_event.kind == MouseEventKind::ScrollUp {
                        apply_action(state, Action::ScrollUp);
                    } else if mouse_event.kind == MouseEventKind::ScrollDown {
                        apply_action(state, Action::ScrollDown);
                    }
                }
                _ => {}
            }
        }
        // Tick always fires each iteration
        apply_action(state, Action::Tick);
    }
    terminal.clear()?;
    Ok(())
}

/// Create session state with real infrastructure wired in.
///
/// Flow: initialise `Store` → ensure data directories → generate session ID →
/// load `Settings` and `AppConfig` from disk → construct `AppStateRest`.
#[tracing::instrument]
fn create_local_session() -> Result<(zesdex_domain::core::Store, AppStateRest)> {
    let store = zesdex_domain::core::Store::new();
    debug!("store created at {:?}", store.base_dir);
    store.ensure_dirs()?;

    let session_id = uuid::Uuid::new_v4().to_string();
    let session_dir = store.base_dir.join("sessions").join(&session_id);
    std::fs::create_dir_all(&session_dir)?;

    // Load real settings from disk
    use zesdex_domain::cms::{AppConfigRepository, SettingsRepository};
    let settings = zesdex_infrastructure::persistence::cms::settings_repo::JsonSettingsRepository::new()
        .load(&store.base_dir)
        .unwrap_or_default();

    let app_config = zesdex_infrastructure::persistence::cms::app_config_repo::JsonAppConfigRepository::new()
        .load(&store.base_dir)
        .unwrap_or_default();

    let workspace_roots = vec![std::env::current_dir()?];
    let mut state = AppStateRest::new(workspace_roots, &session_dir, store.memory_dir.clone());
    state.settings = settings;
    state.app_config = app_config;

    Ok((store, state))
}