use std::time::Duration;

use anyhow::Context;
use clap::Parser;

mod app;
mod color;
mod ui;

#[derive(Parser)]
#[command(name = "log-viewer", about = "A log viewer TUI")]
struct Cli {
    /// Log files to open
    files: Vec<String>,
}

// ── RAII terminal guard ────────────────────────────────────────────
//
// Holds the ratatui Terminal and guarantees terminal state restoration
// (disable raw mode, leave alternate screen, show cursor) on **every**
// exit path: normal return, `?` error propagation, and panic unwind.
//
// IMPORTANT: `Drop` does **not** run on `std::process::exit` or
// `panic = "abort"`.  Therefore we must never call `process::exit`
// inside the guarded scope — use `?` to return `Err` instead.

type Backend = ratatui::backend::CrosstermBackend<std::io::Stdout>;

struct TerminalGuard {
    terminal: ratatui::Terminal<Backend>,
}

impl TerminalGuard {
    /// Enable raw mode, enter alternate screen, and create the terminal.
    /// On partial failure, rolls back any steps that already succeeded.
    fn enter() -> anyhow::Result<Self> {
        crossterm::terminal::enable_raw_mode()
            .map_err(|e| anyhow::anyhow!("enable_raw_mode: {e}"))?;

        let mut stdout = std::io::stdout();
        if let Err(e) = crossterm::execute!(stdout, crossterm::terminal::EnterAlternateScreen) {
            let _ = crossterm::terminal::disable_raw_mode();
            return Err(anyhow::anyhow!("EnterAlternateScreen: {e}"));
        }

        let backend = ratatui::backend::CrosstermBackend::new(stdout);
        match ratatui::Terminal::new(backend) {
            Ok(terminal) => Ok(Self { terminal }),
            Err(e) => {
                // Roll back: leave alternate screen + disable raw mode
                let _ = crossterm::execute!(
                    std::io::stdout(),
                    crossterm::terminal::LeaveAlternateScreen
                );
                let _ = crossterm::terminal::disable_raw_mode();
                Err(anyhow::anyhow!("Terminal::new: {e}"))
            }
        }
    }

    fn terminal(&mut self) -> &mut ratatui::Terminal<Backend> {
        &mut self.terminal
    }
}

impl Drop for TerminalGuard {
    fn drop(&mut self) {
        // Best-effort cleanup; suppress errors (Drop must not panic).
        let _ = crossterm::terminal::disable_raw_mode();
        let _ = crossterm::execute!(
            self.terminal.backend_mut(),
            crossterm::terminal::LeaveAlternateScreen
        );
        let _ = self.terminal.show_cursor();
    }
}

// ── main ───────────────────────────────────────────────────────────

fn main() -> anyhow::Result<()> {
    let cli = Cli::parse();

    let mut guard = TerminalGuard::enter()?;
    let mut app = app::App::new();
    app.color_config = log_viewer_core::config::ColorConfig::load();

    if let Some(file) = cli.files.first() {
        app.load_file(file)
            .with_context(|| format!("loading file {file}"))?;
    }

    while !app.should_quit {
        app.poll_background_indexer();
        app.poll_file_watcher();
        guard.terminal().draw(|frame| ui::render(frame, &mut app))?;
        if crossterm::event::poll(Duration::from_millis(100))? {
            match crossterm::event::read()? {
                crossterm::event::Event::Key(key) => app.handle_key(key),
                crossterm::event::Event::Resize(_, _) => {}
                _ => {}
            }
        }
    }

    Ok(())
}