//! `kiln-tui` — a terminal "player" for kiln boards.
//!
//! Pass a `.toml` map file as the single command-line argument; kiln-tui loads
//! that board and lets you walk the player around it with the arrow keys
//! (or HJKL). There is no editor — this is a play-only front-end.
//!
//! Rendering is text-based: kiln's bitmap-font tile indices are reinterpreted
//! as characters (see [`kiln_core::cp437`]) and drawn with each cell's RGB colors.

mod animation;
mod editor;
mod input;
mod log;
mod menu;
mod mode;
mod overlay;
mod render;
mod scroll_overlay;
mod speech;
mod term;
mod transition;
mod ui;
mod utils;
mod editor_menu;

use crate::animation::{AnimWidget, AnimationLayer};
use crate::editor::{
    EditorState, draw_editor, handle_code_editor_input, handle_dialog_input,
    handle_glyph_dialog_input,
};
use crate::input::{
    InputMode, current_input_mode, handle_board_input, handle_editor_input, handle_menu_input,
    handle_scroll_input,
};
use crate::log::{LogWidget, log_preview_line};
use crate::menu::MenuWidget;
use crate::mode::{Mode, PendingMode};
use crate::scroll_overlay::ScrollOverlayWidget;
use crate::speech::SpeechBubblesWidget;
use crate::ui::Ui;
use kiln_core::game::GameState;
use kiln_core::log::LogLine;
use kiln_core::world;
use kiln_ui::render_overlay;
use ratatui::Frame;
use ratatui::crossterm::event::{
    self, DisableBracketedPaste, DisableMouseCapture, EnableBracketedPaste, EnableMouseCapture,
    Event, KeyEventKind,
};
use ratatui::crossterm::execute;
use ratatui::layout::{Constraint, Layout, Rect, Spacing};
use ratatui::symbols::merge::MergeStrategy;
use ratatui::widgets::Block;
use render::BoardWidget;
use std::io;
use std::process::ExitCode;
use std::time::{Duration, Instant};
use term::TerminalCaps;

/// Entry point: parse the map path, load the board, then run the play loop with
/// the terminal in raw/alternate-screen mode (restored on every exit path).
fn main() -> ExitCode {
    // The single positional argument is the map file to play.
    let Some(path) = std::env::args().nth(1) else {
        eprintln!("usage: kiln-tui <map.toml>");
        return ExitCode::from(2);
    };

    // Load before touching the terminal so load errors print to a normal screen.
    let mut game = match world::load(&path) {
        Ok(world) => GameState::from_world(world),
        Err(e) => {
            eprintln!("error loading {path}: {e}");
            return ExitCode::FAILURE;
        }
    };

    // `init` enters the alternate screen and raw mode; `restore` always undoes it.
    let mut terminal = ratatui::init();

    // Capture mouse events so the log panel can be scrolled with the wheel and
    // resized by dragging its divider. Disabled again before restoring.
    let _ = execute!(io::stdout(), EnableMouseCapture);

    // Enable bracketed paste so the code editor receives terminal pastes as one event.
    let _ = execute!(io::stdout(), EnableBracketedPaste);

    // Detect terminal capabilities (now that we're in raw mode) and enable the
    // Kitty keyboard protocol when it's available, so scripts can rely on the
    // richer bindings it provides. Disabled again before restoring the terminal.
    let caps = TerminalCaps::detect();
    if caps.keyboard_enhancement {
        let _ = term::push_kitty_flags();
    }

    game.log(LogLine::raw("[esc] for menu"));
    game.log(LogLine::raw("Welcome to kiln - ").append(caps.status_logline()));

    // Now that the board is fully loaded and the terminal is ready, run each
    // scripted object's `init()` hook.
    game.run_init();

    // Wrap the live game in the top-level Mode; editing later swaps this whole value.
    let mut mode = Mode::Play(game);

    // Remember the world path so the editor (and play-reload) can reload from it.
    let mut ui = Ui {
        world_path: path.clone(),
        ..Ui::default()
    };
    let result = run(&mut terminal, &mut mode, &mut ui);

    if caps.keyboard_enhancement {
        let _ = term::pop_kitty_flags();
    }
    let _ = execute!(io::stdout(), DisableBracketedPaste);
    let _ = execute!(io::stdout(), DisableMouseCapture);
    ratatui::restore();

    if let Err(e) = result {
        eprintln!("error: {e}");
        return ExitCode::FAILURE;
    }
    ExitCode::SUCCESS
}

/// The target frame interval: 30 frames per second.
const FRAME: Duration = Duration::from_nanos(1_000_000_000 / 30);

/// Real-time draw / input / update loop at ~30 FPS. Returns once the user quits.
///
/// Unlike a turn-based loop, this never blocks indefinitely: it waits for input
/// only until the next frame deadline (`event::poll`), then advances the game by
/// the real time elapsed since the last tick. `poll` returns the instant a key
/// arrives, so input stays responsive while the game keeps ticking on its own.
fn run(terminal: &mut ratatui::DefaultTerminal, mode: &mut Mode, ui: &mut Ui) -> io::Result<()> {
    let mut last_tick = Instant::now();
    loop {
        // Redraw every iteration; ratatui diffs against the previous frame so
        // only changed cells are actually written to the terminal.
        terminal.draw(|frame| draw(frame, mode, ui))?;

        // Wait for input only up to the next frame deadline so the loop wakes to
        // tick even with no keypresses.
        let timeout = FRAME.saturating_sub(last_tick.elapsed());
        if event::poll(timeout)? {
            let event = event::read()?;
            // Ignore key-release events (the Kitty protocol emits these; acting on
            // them would fire a second move per keypress).
            if matches!(&event, Event::Key(k) if k.kind == KeyEventKind::Release) {
                continue;
            }
            let size = terminal.size()?;
            // Each Mode only produces a subset of input modes (Editor only in Edit;
            // Board/Scroll/Frozen only in Play; Menu/Ignore in either). Match on Mode
            // first so each handler gets the right `game`/`ed` without re-checking,
            // and assert the impossible combinations away with `unreachable!`.
            let input_mode = current_input_mode(mode, ui);
            if matches!(input_mode, InputMode::Menu) {
                handle_menu_input(event, ui)
            } else if !matches!(input_mode, InputMode::Ignore) {
                // If input_mode is ignore, an animation is running and claiming no input mode — discard all events.
                match mode {
                    Mode::Play(game) => match input_mode {
                        InputMode::Board | InputMode::Frozen => {
                            handle_board_input(event, ui.log.open, size.height, game, ui);
                        }
                        InputMode::Scroll => handle_scroll_input(event, game, ui),
                        _ => unreachable!(
                            "Menu and Ignore handled above; Editor input mode only occurs in Edit mode"
                        ),
                    },
                    Mode::Edit(ed) => match input_mode {
                        InputMode::Editor => handle_editor_input(event, size.width, ed, ui),
                        InputMode::Dialog => handle_dialog_input(event, ed),
                        InputMode::GlyphDialog => handle_glyph_dialog_input(event, ed),
                        InputMode::CodeEditor => handle_code_editor_input(event, ed),
                        _ => unreachable!(
                            "Menu and Ignore handled above; Board/Scroll/Frozen input modes only occur in Play mode"
                        ),
                    },
                }
            }
        }

        // Advance the active mode by the real time elapsed since the last tick.
        // Only resetting `last_tick` when we actually tick means time spent waiting
        // on input (or skipped Release events) is preserved in the next `dt`.
        if last_tick.elapsed() >= FRAME {
            let dt = last_tick.elapsed();
            last_tick = Instant::now();
            ui.tick(dt, mode);
        }

        // Apply any Play↔Edit switch a menu action requested this frame.
        apply_pending_mode(mode, ui);

        // Enter/leave a playtest if the editor or a playtest Esc requested it.
        apply_playtest_transition(mode, ui);

        // A menu action may have set should_quit; exit once any close animation finishes.
        if ui.should_quit && ui.active_animation.is_none() {
            return Ok(());
        }
    }
}

/// Applies a pending [`Mode`] switch, reloading the world from `ui.world_path`.
///
/// Entering the editor drops the running game; returning to play rebuilds a fresh
/// [`GameState`] (so it reflects any edits) and re-runs object `init()` hooks. A
/// load failure is logged to the play game (if any) and leaves the mode unchanged.
fn apply_pending_mode(mode: &mut Mode, ui: &mut Ui) {
    let Some(pending) = ui.pending_mode.take() else {
        return;
    };
    match world::load(&ui.world_path) {
        Ok(world) => match pending {
            PendingMode::EnterEditor => *mode = Mode::Edit(EditorState::new(world)),
            PendingMode::PlayWorld => {
                let mut game = GameState::from_world(world);
                game.run_init();
                *mode = Mode::Play(game);
            }
        },
        Err(e) => {
            // Best-effort: surface the failure in the play log if we're still playing.
            if let Mode::Play(game) = mode {
                game.log(LogLine::error(format!("reload failed: {e}")));
            }
        }
    }
}

/// Applies a pending **playtest** enter or exit, swapping the top-level [`Mode`].
///
/// Entering: the editor parked a built [`GameState`] in
/// [`EditorState::pending_playtest`]; swap to [`Mode::Play`] and stash the editor in
/// [`Ui::suspended_editor`] so `Esc` can restore it. Taking the option first drops the
/// `&mut EditorState` borrow before [`std::mem::replace`], whose return value hands us
/// the old `Mode::Edit` (so the editor is preserved with no placeholder variant).
///
/// Exiting (`Esc` during a playtest set [`Ui::exit_playtest`]): drop the playtest game
/// and restore the suspended editor verbatim. The deep-copied playtest world is simply
/// dropped, so the editor's own boards were never touched.
fn apply_playtest_transition(mode: &mut Mode, ui: &mut Ui) {
    // Enter: take the parked game (this ends the editor borrow before the swap).
    let new_game = if let Mode::Edit(ed) = mode {
        ed.pending_playtest.take()
    } else {
        None
    };
    if let Some(game) = new_game {
        let old = std::mem::replace(mode, Mode::Play(game));
        if let Mode::Edit(editor) = old {
            ui.suspended_editor = Some(editor);
        }
    }

    // Exit: restore the parked editor, dropping the playtest game.
    if ui.exit_playtest {
        ui.exit_playtest = false;
        if let Some(editor) = ui.suspended_editor.take() {
            *mode = Mode::Edit(editor);
        }
    }
}

/// Render a single frame for the active [`Mode`], then the overlay layer on top.
///
/// The body of the frame is either the play view ([`draw_play`]) or the editor
/// view ([`draw_editor`]); overlays (animation, menu, and — play-only — the scroll
/// window) are drawn above whichever was rendered.
fn draw(frame: &mut Frame, mode: &mut Mode, ui: &mut Ui) {
    match mode {
        Mode::Play(game) => draw_play(frame, game, ui),
        Mode::Edit(ed) => draw_editor(frame, ed, ui),
    }

    // Overlay layer: animation > menu > scroll (mutually exclusive at runtime).
    let is_overlay_anim = ui
        .active_animation
        .as_ref()
        .map(|a| matches!(a.layer(), AnimationLayer::Overlay))
        .unwrap_or(false);

    let area = frame.area();
    if is_overlay_anim {
        frame.render_widget(
            AnimWidget(ui.active_animation.as_ref().unwrap().as_ref()),
            area,
        );
    } else if let Some(menu) = ui.menu.as_mut() {
        frame.render_stateful_widget(MenuWidget, area, menu);
    } else {
        match mode {
            // The scroll window only exists while playing.
            Mode::Play(game) => {
                if let Some(scroll) = &game.active_scroll {
                    frame.render_stateful_widget(
                        ScrollOverlayWidget::new(&scroll.lines),
                        area,
                        &mut ui.overlay,
                    );
                }
            }
            // The dialog / glyph-picker overlays only exist while editing.
            Mode::Edit(ed) => {
                if let Some(g) = &ed.glyph_dialog {
                    render_overlay(frame, g);
                } else if let Some(d) = &ed.dialog {
                    render_overlay(frame, d);
                }
            }
        }
    }
}

/// Renders the play view: the board in a bordered block, and — when open — a log
/// panel across the bottom. When the panel is closed the latest log message is
/// previewed in the board's bottom-left border after a `[l]og:` label.
fn draw_play(frame: &mut Frame, game: &GameState, ui: &mut Ui) {
    // Borrow the board for the duration of the frame (no script runs during draw).
    let board = &game.board();

    // A playtest (launched from the editor) marks its title so it's distinct from play.
    let title = if ui.suspended_editor.is_some() {
        format!(" {} (playtest) ", board.name)
    } else {
        format!(" {} ", board.name)
    };

    if ui.log.open {
        // Split the screen: board on top, log panel of `height` at the bottom.
        let [board_area, log_area] =
            Layout::vertical([Constraint::Min(3), Constraint::Length(ui.log.height)])
                .spacing(Spacing::Overlap(1))
                .areas(frame.area());

        let block = Block::bordered()
            .title(title)
            .merge_borders(MergeStrategy::Exact);
        let inner = block.inner(board_area);
        frame.render_widget(block, board_area);
        draw_board_area(frame, inner, game, ui);
        frame.render_stateful_widget(LogWidget::new(&game.log), log_area, &mut ui.log);
    } else {
        // Panel closed: board fills the screen, latest message in the border.
        let mut block = Block::bordered().title(title);
        block = block.title_bottom(log_preview_line(&game.log).left_aligned());
        let inner = block.inner(frame.area());
        frame.render_widget(block, frame.area());
        draw_board_area(frame, inner, game, ui);
    }
}

/// Renders the inner board area: either the active board-layer animation or the live board.
///
/// If `ui.pending_transition` is set, pre-renders both boards into a new
/// [`TransitionAnimation`](transition::TransitionAnimation) (now that we know the
/// exact `inner` area) and activates it via [`Ui::start_transition`].
fn draw_board_area(frame: &mut Frame, inner: Rect, game: &GameState, ui: &mut Ui) {
    // Initialize any pending transition now that we know the exact area.
    if let Some((old_rc, new_rc)) = ui.pending_transition.take() {
        ui.start_transition(&old_rc.borrow(), &new_rc.borrow(), inner);
    }

    let is_board_anim = ui
        .active_animation
        .as_ref()
        .map(|a| matches!(a.layer(), AnimationLayer::Board))
        .unwrap_or(false);

    if is_board_anim {
        // Board-layer animation (wipe): replaces the board entirely.
        frame.render_widget(
            AnimWidget(ui.active_animation.as_ref().unwrap().as_ref()),
            inner,
        );
    } else {
        let board = &game.board();
        frame.render_widget(BoardWidget::new(board), inner);
        frame.render_widget(SpeechBubblesWidget::new(board, &game.speech_bubbles), inner);
    }
}