use crate::ciphertext::Ciphertext;
use crate::decoder::DecoderState;
use crate::storage::AlphabetFile;

use crossterm::{
    event::{self, Event, KeyCode, KeyEventKind},
    execute,
    terminal::{EnterAlternateScreen, LeaveAlternateScreen, disable_raw_mode, enable_raw_mode},
};
use rand_chacha::ChaCha20Rng;
use ratatui::{
    prelude::*,
    widgets::{Block, Borders, List, ListItem, Paragraph},
};
use std::io;
use std::path::PathBuf;
use std::time::Duration;

struct TuiGuard;

impl Drop for TuiGuard {
    fn drop(&mut self) {
        let _ = disable_raw_mode();
        let _ = execute!(io::stdout(), LeaveAlternateScreen);
    }
}

fn get_visible_symbols(
    terminal: &Terminal<CrosstermBackend<std::io::Stdout>>,
) -> io::Result<usize> {
    let size = terminal.size()?;
    let inner_width = size.width.saturating_sub(2) as usize;
    Ok(inner_width.max(1))
}

pub fn run() -> io::Result<()> {
    todo!("call run_decoder_tui(alphabet_path, ciphertext_path) from CLI later")
}

pub fn run_decoder_tui(alphabet_path: PathBuf, ciphertext_path: PathBuf) -> io::Result<()> {
    let alphabet_bytes = std::fs::read(&alphabet_path)?;
    let bytes = std::fs::read(ciphertext_path)?;
    let ciphertext = Ciphertext::from_bytes(&bytes).map_err(io::Error::other)?;

    let rng_seed = [7u8; 32];
    let mut state = DecoderState::new(alphabet_bytes, rng_seed, ciphertext.bits)?;

    enable_raw_mode()?;
    execute!(io::stdout(), EnterAlternateScreen)?;
    let _guard = TuiGuard;

    let mut terminal = Terminal::new(CrosstermBackend::new(io::stdout()))?;

    loop {
        terminal.draw(|f| draw_ui(f, &state))?;

        if event::poll(Duration::from_millis(100))? {
            if let Event::Key(key) = event::read()? {
                if key.kind != KeyEventKind::Press {
                    continue;
                }

                let visible = get_visible_symbols(&terminal)?;

                match key.code {
                    KeyCode::Char('q') => break,
                    KeyCode::Left | KeyCode::Char('h') => state.move_left(visible),
                    KeyCode::Right | KeyCode::Char('l') => state.move_right(visible),
                    KeyCode::Char('u') => {
                        let _ = state.undo_current();
                    }
                    KeyCode::Char('1') => {
                        let _ = state.apply_candidate(0);
                    }
                    KeyCode::Char('2') => {
                        let _ = state.apply_candidate(1);
                    }
                    KeyCode::Char('3') => {
                        let _ = state.apply_candidate(2);
                    }
                    KeyCode::Char('4') => {
                        let _ = state.apply_candidate(3);
                    }
                    KeyCode::Char('5') => {
                        let _ = state.apply_candidate(4);
                    }
                    KeyCode::Char('m') => {
                        state.set_ranking_mode(crate::decoder::RankingMode::LocalFirst);
                    }
                    KeyCode::Char('M') => {
                        state.set_ranking_mode(crate::decoder::RankingMode::FutureFirst);
                    }
                    _ => {}
                }
            }
        }
    }

    Ok(())
}

fn draw_ui(f: &mut Frame, state: &DecoderState) {
    let layout = Layout::vertical([
        Constraint::Length(5),
        Constraint::Min(10),
        Constraint::Length(3),
    ])
    .split(f.area());

    draw_text_panel(f, layout[0], state);
    draw_candidates_panel(f, layout[1], state);
    draw_help_panel(f, layout[2]);
}

fn draw_text_panel(f: &mut Frame, area: Rect, state: &DecoderState) {
    let cursor = state.cursor;
    let rendered: String = state
        .rendered_text
        .chars()
        .enumerate()
        .flat_map(|(i, ch)| {
            if i == cursor {
                vec!['[', ch, ']']
            } else {
                vec![ch]
            }
        })
        .collect();

    let p = Paragraph::new(rendered)
        .block(Block::default().title("Decoded text").borders(Borders::ALL));

    f.render_widget(p, area);
}

fn draw_candidates_panel(f: &mut Frame, area: Rect, state: &DecoderState) {
    let items = match state.current_candidates() {
        Ok(cands) => cands
            .into_iter()
            .enumerate()
            .map(|(i, c)| {
                ListItem::new(format!(
                    "{}. {:?}  local={}  future={}",
                    i + 1,
                    c.symbol,
                    c.distance,
                    c.future_distance
                ))
            })
            .collect::<Vec<_>>(),
        Err(err) => vec![ListItem::new(format!("error: {}", err))],
    };

    let list = List::new(items).block(
        Block::default()
            .title("Top-5 candidates")
            .borders(Borders::ALL),
    );

    f.render_widget(list, area);
}

fn draw_help_panel(f: &mut Frame, area: Rect) {
    let p = Paragraph::new("h/← left   l/→ right   1..5 choose   u undo   q quit")
        .block(Block::default().title("Keys").borders(Borders::ALL));

    f.render_widget(p, area);
}