//! A window is an abstraction for the UI. Buffers (like [Threads]) draw "to" windows.

use std::io::Write;
use termion::{color, cursor};
use unicode_segmentation::UnicodeSegmentation;

#[derive(Clone, Copy)]
pub struct Area {
    pub x: u16,
    pub y: u16,
    pub w: u16,
    pub h: u16,
}

pub enum Line {
    Normal(String),
    Highlight(String),
}

pub fn truncate_dots(s: &str, to: usize) -> String {
    //TODO We don't have time to do this every tick
    let graphemes = s.graphemes(true).collect::<Vec<_>>();
    if graphemes.len() >= to {
        format!("{}...", graphemes.iter().take(to - 3).fold(String::new(), |acc, s| format!("{}{}", acc, s)))
    } else {
        graphemes.join("")
    }
}

pub struct Window {
    pub lines: Vec<Line>,
    scroll: usize,
}

impl Window {
    pub fn new() -> Self {
        Self {
            lines: Vec::new(),
            scroll: 0,
        }
    }

    pub fn draw<W: Write>(&mut self, out: &mut W, area: Area) -> Result<(), std::io::Error> {
        let mut y = area.y;
        let mut lines = self.lines.iter().skip(self.scroll);
        while y < area.h + 1 {
            match lines.next() {
                Some(line) => {
                    write!(out, "{}", cursor::Goto(area.x, y))?;
                    match line {
                        Line::Normal(s) => write!(out, "{}", truncate_dots(s, area.w as usize))?,
                        Line::Highlight(s) => write!(
                            out,
                            "{}{}{}",
                            color::Fg(color::Red),
                            truncate_dots(s, area.w as usize),
                            color::Fg(color::Reset),
                        )?,
                    }
                    y += 1;
                }
                None => break,
            }
        }
        out.flush()?;

        self.lines.clear();
        Ok(())
    }

    pub fn scroll_down(&mut self, until: usize) {
        if self.scroll < until - 1 {
            self.scroll += 1;
        }
    }

    pub fn scroll_up(&mut self) {
        if self.scroll != 0 {
            self.scroll -= 1;
        }
    }
}