use crossterm::{
    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use std::{error::Error, io};
use tui::{
    backend::{Backend, CrosstermBackend},
    layout::{Constraint, Direction, Layout},
    style::{Color, Modifier, Style},
    text::Spans,
    widgets::{self, Block, Borders, Cell, Paragraph, Table, Tabs, Widget},
    Frame, Terminal,
};

// Intended to emulate vim modes.
enum InputMode {
    Normal, // Navigating the ui.
    Insert, // Editing a parameter.
}

// A row in the inputs table has one of each variation.
#[derive(Clone)]
enum InputParam {
    Rpm(String), // Revolutions per minute
    Ve(String),  // Volumetric efficiency
    Map(String), // Manifold absolute pressure
}
impl InputParam {
    /* Acts like the push() method of a Vec.
     * Appends the given char to the end of the string contained by the
     * InputParam.
     */
    fn push(&mut self, c: char) {
        match self {
            Self::Rpm(rpm) => {
                rpm.push(c);
                *self = Self::Rpm(rpm.to_string());
            }
            Self::Ve(ve) => {
                ve.push(c);
                *self = Self::Ve(ve.to_string());
            }
            Self::Map(map) => {
                map.push(c);
                *self = Self::Map(map.to_string());
            }
        }
    }
    /* Acts like the pop() method of a Vec.
     * Removes the last char from the string contained by the InputParam.
     */
    fn pop(&mut self) {
        match self {
            Self::Rpm(rpm) => {
                rpm.pop();
                *self = Self::Rpm(rpm.to_string());
            }
            Self::Ve(ve) => {
                ve.pop();
                *self = Self::Rpm(ve.to_string());
            }
            Self::Map(map) => {
                map.pop();
                *self = Self::Map(map.to_string());
            }
        }
    }
    // Return a copy of the string contained by the InputParam.
    fn string(&self) -> String {
        match self {
            Self::Rpm(rpm) => rpm.to_string(),
            Self::Ve(ve) => ve.to_string(),
            Self::Map(map) => map.to_string(),
        }
    }
    /* next() and previous() allow InputParam to act as a circular iterator of
     * sorts. next() will return the next variation as they are defined. When
     * it reaches the end, the first variation will be returned:
     *     RPM->VE->MAP->RPM->etc...
     * previous() simply goes the opposite direction:
     *     MAP->VE->RPM->MAP->etc...
     */
    fn next(&self) -> Self {
        match self {
            Self::Rpm(_) => Self::Ve(String::new()),
            Self::Ve(_) => Self::Map(String::new()),
            Self::Map(_) => Self::Rpm(String::new()),
        }
    }
    fn previous(&self) -> Self {
        match self {
            Self::Rpm(_) => Self::Map(String::new()),
            Self::Ve(_) => Self::Rpm(String::new()),
            Self::Map(_) => Self::Ve(String::new()),
        }
    }
}

// A row in the inputs table. Contains one of each variation of InputParam.
#[derive(Clone)]
struct Row {
    rpm: InputParam,
    ve: InputParam,
    map: InputParam,
}
impl Default for Row {
    fn default() -> Self {
        Self {
            rpm: InputParam::Rpm(String::from("7000")),
            ve: InputParam::Ve(String::from("95")),
            map: InputParam::Map(String::from("200")),
        }
    }
}

// Holds the state of the application.
struct App {
    tab_index: usize,
    tab_titles: Vec<&'static str>,

    rows: Vec<Row>,
    selected_row: usize,
    selected_column: InputParam,

    input_mode: InputMode,
}
impl App {
    fn next_tab(&mut self) {
        self.tab_index = (self.tab_index + 1) % self.tab_titles.len();
    }

    fn previous_tab(&mut self) {
        if self.tab_index > 0 {
            self.tab_index -= 1;
        } else {
            self.tab_index = self.tab_titles.len() - 1;
        }
    }

    fn next_row(&mut self) {
        if self.selected_row < self.rows.len() - 1 {
            self.selected_row += 1;
        } else {
            self.selected_row = 0;
        }
    }

    fn previous_row(&mut self) {
        if self.selected_row > 0 {
            self.selected_row -= 1;
        } else {
            self.selected_row = self.rows.len() - 1;
        }
    }

    fn next_column(&mut self) {
        self.selected_column = self.selected_column.next();
    }

    fn previous_column(&mut self) {
        self.selected_column = self.selected_column.previous();
    }

    fn insert_row(&mut self) {
        let index = self.selected_row;
        self.rows.insert(index, self.rows[index].clone());
    }

    fn remove_row(&mut self) {
        if self.rows.len() > 1 {
            self.rows.remove(self.selected_row);
            if self.selected_row > 0 {
                self.selected_row -= 1;
            }
        }
    }
}
impl Default for App {
    fn default() -> App {
        App {
            tab_index: 0,
            tab_titles: vec!["Input", "Config"],
            rows: vec![Row::default()],
            selected_row: 0,
            selected_column: InputParam::Rpm(String::new()),
            input_mode: InputMode::Normal,
        }
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    // setup terminal
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    // create app and run it
    let app = App::default();
    let res = run_app(&mut terminal, app);

    // restore terminal
    disable_raw_mode()?;
    execute!(
        terminal.backend_mut(),
        LeaveAlternateScreen,
        DisableMouseCapture
    )?;
    terminal.show_cursor()?;

    if let Err(err) = res {
        println!("{:?}", err)
    }

    Ok(())
}

// Input handling
fn run_app<B: Backend>(terminal: &mut Terminal<B>, mut app: App) -> io::Result<()> {
    loop {
        terminal.draw(|f| ui(f, &app))?;

        if let Event::Key(key) = event::read()? {
            match app.tab_index {
                // Input tab
                0 => match app.input_mode {
                    InputMode::Normal => match key.code {
                        KeyCode::Char('q') => {
                            return Ok(());
                        }
                        KeyCode::Char('L') => app.next_tab(),
                        KeyCode::Char('H') => app.previous_tab(),
                        KeyCode::Char('j') => app.next_row(),
                        KeyCode::Char('k') => app.previous_row(),
                        KeyCode::Char('l') => app.next_column(),
                        KeyCode::Char('h') => app.previous_column(),
                        KeyCode::Char('i') => {
                            app.input_mode = InputMode::Insert;
                        }
                        KeyCode::Char('p') => app.insert_row(),
                        KeyCode::Char('d') => app.remove_row(),
                        _ => {}
                    },
                    InputMode::Insert => match key.code {
                        KeyCode::Esc | KeyCode::Enter => {
                            app.input_mode = InputMode::Normal;
                        }
                        KeyCode::Char(c) => match app.selected_column {
                            InputParam::Rpm(_) => app.rows[app.selected_row].rpm.push(c),
                            InputParam::Ve(_) => app.rows[app.selected_row].ve.push(c),
                            InputParam::Map(_) => app.rows[app.selected_row].map.push(c),
                        },
                        KeyCode::Backspace => match app.selected_column {
                            InputParam::Rpm(_) => app.rows[app.selected_row].rpm.pop(),
                            InputParam::Ve(_) => app.rows[app.selected_row].ve.pop(),
                            InputParam::Map(_) => app.rows[app.selected_row].map.pop(),
                        },
                        _ => {}
                    },
                },
                // Config tab
                1 => match key.code {
                    KeyCode::Char('q') => {
                        return Ok(());
                    }
                    KeyCode::Char('L') => app.next_tab(),
                    KeyCode::Char('H') => app.previous_tab(),
                    _ => {}
                },
                _ => unreachable!(),
            }
        }
    }
}

fn ui<B: Backend>(f: &mut Frame<B>, app: &App) {
    let titles = app.tab_titles.iter().map(|t| Spans::from(*t)).collect();
    let tabs = Tabs::new(titles)
        .block(Block::default().borders(Borders::ALL).title("Tabs"))
        .select(app.tab_index)
        .highlight_style(Style::default().add_modifier(Modifier::BOLD));

    match app.tab_index {
        0 => {
            let layout = Layout::default()
                .direction(Direction::Vertical)
                .constraints(
                    [
                        Constraint::Length(3),
                        Constraint::Min(app.rows.len() as u16 + 2),
                        Constraint::Length(1),
                    ]
                    .as_ref(),
                )
                .split(f.size());
            f.render_widget(tabs, layout[0]);
            f.render_widget(input_table(app), layout[1]);
            f.render_widget(footer(app), layout[2]);
        }
        1 => {
            let layout = Layout::default()
                .direction(Direction::Vertical)
                .constraints([Constraint::Length(3), Constraint::Min(3)].as_ref())
                .split(f.size());
            f.render_widget(tabs, layout[0]);
            f.render_widget(Paragraph::new("Config tab"), layout[1]);
        }
        _ => unreachable!(),
    }
}

fn input_table(app: &App) -> impl Widget {
    // This is used so I can have named fields instead of indexing a vector of
    // Cells when styling the selected input parameter.
    struct VirtualRow<'a> {
        rpm: Cell<'a>,
        ve: Cell<'a>,
        map: Cell<'a>,
    }

    let mut rows: Vec<VirtualRow> = app
        .rows
        .iter()
        .map(|row| VirtualRow {
            rpm: Cell::from(row.rpm.string()),
            ve: Cell::from(row.ve.string()),
            map: Cell::from(row.map.string()),
        })
        .collect();

    // Highlight the selected parameter
    let selected_parameter = match app.selected_column {
        InputParam::Rpm(_) => &mut rows[app.selected_row].rpm,
        InputParam::Ve(_) => &mut rows[app.selected_row].ve,
        InputParam::Map(_) => &mut rows[app.selected_row].map,
    };
    *selected_parameter = selected_parameter.clone().style(match app.input_mode {
        InputMode::Normal => Style::default().fg(Color::Yellow),
        InputMode::Insert => Style::default()
            .fg(Color::Yellow)
            .add_modifier(Modifier::ITALIC),
    });

    Table::new(
        rows.iter()
            .map(|row| widgets::Row::new(vec![row.rpm.clone(), row.ve.clone(), row.map.clone()]))
            .collect::<Vec<widgets::Row>>(),
    )
    .header(widgets::Row::new(vec!["rpm", "ve", "map"]))
    .block(Block::default().borders(Borders::ALL).title("inputs"))
    .widths(&[
        Constraint::Length(5),
        Constraint::Length(3),
        Constraint::Length(3),
    ])
}

fn footer(app: &App) -> impl Widget {
    match app.input_mode {
        InputMode::Normal => {
            Paragraph::new("Normal").style(Style::default().fg(Color::Black).bg(Color::Yellow))
        }
        InputMode::Insert => {
            Paragraph::new("Insert").style(Style::default().fg(Color::Black).bg(Color::Blue))
        }
    }
}