//! `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 [`cp437`]) and drawn with each cell's RGB colors.

mod cp437;
mod log;
mod render;
mod scroll_overlay;
mod term;
mod utils;
mod speech;
mod ui;

use kiln_core::game::{GameState, ScrollLine};
use kiln_core::log::LogLine;
use kiln_core::map_file;
use kiln_core::Direction;
use ratatui::Frame;
use ratatui::crossterm::event::{
    self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode, KeyEventKind, MouseEventKind,
};
use ratatui::crossterm::execute;
use ratatui::layout::{Constraint, Layout, 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;
use crate::log::{log_preview_line, LogWidget};
use crate::scroll_overlay::{ScrollAnimState, ScrollOverlayWidget};
use crate::speech::SpeechBubblesWidget;
use crate::ui::Ui;

/// Returns the choice string for the given key character, or `None` if it doesn't
/// match any choice in the scroll. Choices are assigned letters a, b, c… in order.
fn resolve_choice(lines: &[ScrollLine], c: char) -> Option<String> {
    let mut letter = b'a';
    for line in lines {
        if let ScrollLine::Choice { choice, .. } = line {
            if c == letter as char {
                return Some(choice.clone());
            }
            letter += 1;
        }
    }
    None
}

/// 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 board = match map_file::load(&path) {
        Ok(board) => board,
        Err(e) => {
            eprintln!("error loading {path}: {e}");
            return ExitCode::FAILURE;
        }
    };

    let mut game = GameState::new(board);

    // `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);

    // 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();
    }

    // Seed the log: the terminal-capabilities badge plus a couple of test
    // messages (temporary, just to exercise the panel).
    // Note these will appear in reverse order, latest on top
    game.log(LogLine::raw("Press 'q' to exit."));
    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();

    let mut ui = Ui::default();
    let result = run(&mut terminal, &mut game, &mut ui);

    if caps.keyboard_enhancement {
        let _ = term::pop_kitty_flags();
    }
    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,
    game: &mut GameState,
    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, game, 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)? {
            match event::read()? {
                // Act on Press and Repeat so holding a key moves the player
                // continuously (the Kitty protocol emits Repeat events while a key
                // is held). Ignore Release, which that protocol also emits and
                // which would otherwise fire a second, spurious move per keypress.
                Event::Key(key) if key.kind != KeyEventKind::Release => {
                    // When a scroll overlay is active (and not already animating
                    // closed), intercept all keys for scroll navigation/choices.
                    let scroll_active = game.active_scroll.is_some()
                        && !matches!(ui.overlay.anim, Some(ScrollAnimState::Closing(_) | ScrollAnimState::Done));
                    if scroll_active {
                        let scroll = game.active_scroll.as_ref().unwrap();
                        let has_choices = scroll.lines.iter()
                            .any(|l| matches!(l, ScrollLine::Choice { .. }));
                        match key.code {
                            // Esc dismisses the scroll only when there are no choices;
                            // with choices present the player must select one.
                            KeyCode::Esc if !has_choices => ui.begin_close(None),
                            KeyCode::Up   => ui.scroll_lines(-1),
                            KeyCode::Down => ui.scroll_lines(1),
                            KeyCode::Char(c) => {
                                if let Some(ch) = resolve_choice(&scroll.lines, c) {
                                    ui.begin_close(Some(ch));
                                }
                            }
                            _ => {}
                        }
                    } else {
                        match key.code {
                            KeyCode::Char('q') | KeyCode::Esc => return Ok(()),
                            KeyCode::Up => game.try_move(Direction::North),
                            KeyCode::Down => game.try_move(Direction::South),
                            KeyCode::Left => game.try_move(Direction::West),
                            // Right arrow moves right; 'l' is the log panel.
                            KeyCode::Right => game.try_move(Direction::East),
                            // 'l' toggles the log panel; reset scroll to newest.
                            KeyCode::Char('l') => ui.log.toggle(),
                            // PageUp/PageDown scroll the log when it's open.
                            KeyCode::PageUp if ui.log.open => ui.log.scroll_by(-5, game.log.len()),
                            KeyCode::PageDown if ui.log.open => ui.log.scroll_by(5, game.log.len()),
                            _ => {}
                        }
                    }
                }
                // Mouse: scroll overlay captures wheel events when active; otherwise
                // wheel scrolls the log and drag resizes it.
                Event::Mouse(m) => {
                    let scroll_active = game.active_scroll.is_some()
                        && !matches!(ui.overlay.anim, Some(ScrollAnimState::Closing(_) | ScrollAnimState::Done));
                    if scroll_active {
                        match m.kind {
                            MouseEventKind::ScrollUp   => ui.scroll_lines(-1),
                            MouseEventKind::ScrollDown => ui.scroll_lines(1),
                            _ => {}
                        }
                    } else if ui.log.open {
                        match m.kind {
                            MouseEventKind::ScrollUp   => ui.log.scroll_by(-1, game.log.len()),
                            MouseEventKind::ScrollDown => ui.log.scroll_by(1, game.log.len()),
                            MouseEventKind::Drag(_) => {
                                // The divider sits at row `total - height`; dragging
                                // it up (smaller row) grows the panel. Keep both usable.
                                let total = terminal.size()?.height;
                                let target = total.saturating_sub(m.row);
                                ui.log.resize(target, total);
                            }
                            _ => {}
                        }
                    }
                }
                _ => {}
            }
        }

        // Advance the game 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, game);
        }
    }
}

/// Render a single frame: 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.
/// A scroll overlay is drawn on top of everything when active.
fn draw(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();
    let board = &*board;

    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(format!(" {} ", board.name))
            .merge_borders(MergeStrategy::Exact);
        let inner = block.inner(board_area);
        frame.render_widget(block, board_area);
        frame.render_widget(BoardWidget::new(board), inner);
        frame.render_widget(SpeechBubblesWidget::new(board, &game.speech_bubbles), inner);
        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(format!(" {} ", board.name));
        block = block.title_bottom(log_preview_line(&game.log).left_aligned());
        let inner = block.inner(frame.area());
        frame.render_widget(block, frame.area());
        frame.render_widget(BoardWidget::new(board), inner);
        frame.render_widget(SpeechBubblesWidget::new(board, &game.speech_bubbles), inner);
    }

    // Scroll overlay: drawn last so it sits above all other content.
    if let Some(scroll) = &game.active_scroll {
        // Capture area before the mutable buffer borrow to satisfy the borrow checker.
        let area = frame.area();
        frame.render_stateful_widget(ScrollOverlayWidget::new(scroll), area, &mut ui.overlay);
    }
}