//! `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;
mod input;

use kiln_core::game::GameState;
use kiln_core::log::LogLine;
use kiln_core::world;
use ratatui::Frame;
use ratatui::crossterm::event::{
    self, DisableMouseCapture, EnableMouseCapture, Event, KeyEventKind,
};
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::input::{current_input_mode, handle_board_input, handle_scroll_input, InputMode};
use crate::log::{log_preview_line, LogWidget};
use crate::scroll_overlay::ScrollOverlayWidget;
use crate::speech::SpeechBubblesWidget;
use crate::ui::Ui;

/// 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 world::load(&path) {
        Ok(mut w) => match w.boards.remove(&w.start) {
            Some(b) => b,
            None => {
                eprintln!("error: start board '{}' not found", w.start);
                return ExitCode::FAILURE;
            }
        },
        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)? {
            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 terminal_h = terminal.size()?.height;
            match current_input_mode(game, ui) {
                InputMode::Board(log_open) => {
                    if handle_board_input(event, log_open, terminal_h, game, ui) {
                        return Ok(());
                    }
                }
                InputMode::Scroll => handle_scroll_input(event, game, ui),
            }
        }

        // 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();

    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);
    }
}