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use cursive_core::{
    Printer, Vec2, View,
    theme::{BaseColor, Color, ColorStyle}
};
use rand::{
    Rng, thread_rng,
    prelude::{
        SliceRandom as _,
        IteratorRandom as _
    },
    rngs::ThreadRng
};
use audiovis::RawVisualizer;
use mlounge_core::library::Song;

/// An audio visualizer that visualizes the audio as a flickering
/// matrix digital rain
pub struct MatrixVisualizer {
    rand: ThreadRng,
    wave: RawVisualizer,
    latest_data: Vec<f32>,
    art_path: String,
    colors: Vec<Color>,
    width: usize,
    height: usize,
    droplets: Vec<Droplet>
}

impl MatrixVisualizer {
    /// Create a new `MatrixVisualizer`
    pub fn new() -> MatrixVisualizer {
        MatrixVisualizer {
            rand: thread_rng(),
            wave: RawVisualizer::new(),
            latest_data: vec![],
            art_path: String::new(),
            colors: vec![Color::Rgb(90, 174, 222)],
            width: 0,
            height: 0,
            droplets: vec![]
        }
    }

    fn add_droplet(&mut self) {
        if self.width == 0 || self.height == 0 {
            return;
        }

        let x = self.rand.gen_range(0..self.width);
        let length = self.rand.gen_range(20..self.height * 2);
        let color = self.colors.choose(&mut self.rand).unwrap();
        self.droplets.push(Droplet::new(x, length, *color, &mut self.rand));
    }

    /// Update the audio visualizer with the specified song
    pub fn update(&mut self, song: &Song) {
        let mut latest_rev = self.wave.get_wave_data(self.width / 2);
        let mut latest = latest_rev.clone();
        latest.reverse();
        latest.append(&mut latest_rev);
        latest.truncate(self.width);
        self.latest_data = latest;
        self.droplets.retain(|droplet| droplet.tail_y <= self.height as isize);

        for droplet in &mut self.droplets {
            droplet.flicker = false;
            droplet.fall(&mut self.rand);
        }

        if let Some(path) = song.get_art_path() {
            if self.art_path != path {
                self.colors.clear();
                self.art_path = path;
                self.colors = song.cursive_album_colors();
            }
        }

        if self.droplets.len() <= self.width / 3 && !self.art_path.is_empty() {
            self.add_droplet();
        }

        if self.latest_data.len() < 4 { return; }

        for droplet in &mut self.droplets {
            if let Some(freq) = self.latest_data.get(droplet.x) {
                droplet.flicker = *freq >= 0.25;
            }
        }
    }
}

impl View for MatrixVisualizer {
    fn draw(&self, printer: &Printer) {
        for droplet in &self.droplets {
            droplet.print(printer);
        }
    }

    fn required_size(&mut self, constraint: Vec2) -> Vec2 {
        self.width = constraint.x;
        self.height = constraint.y;
        constraint
    }
}

impl Default for MatrixVisualizer  {
    fn default() -> Self { Self::new() }
}

struct Droplet {
    x: usize,
    y: usize,
    tail_y: isize,
    chars: String,
    color: Color,
    flicker: bool
}

impl Droplet {
    fn print(&self, printer: &Printer) {
        for (i, c) in self.chars.chars().enumerate(){
            let style = ColorStyle::new(
                if self.flicker { Color::Light(BaseColor::White) } else { self.color },
                Color::TerminalDefault
            );
            if i > 0 {
                printer.with_color(style, |printer| {
                    if self.y as isize - i as isize >= 0 {
                        printer.print((self.x, self.y - i), &c.to_string());
                    }
                });
            }
            else {
                printer.print((self.x, self.y + i), &c.to_string());
            }
        }
    }

    fn new(x: usize, length: usize, color: Color, rand: &mut ThreadRng) -> Droplet {
        Droplet {
            x,
            y: 0,
            tail_y: -(length as isize),
            chars: gen_rand_str(length, rand),
            color,
            flicker: false
        }
    }

    fn fall(&mut self, rand: &mut ThreadRng) {
        self.chars.insert(0, get_rand_char(rand));
        self.chars.pop();
        self.y += 1;
        self.tail_y += 1;
    }
}

fn gen_rand_str(length: usize, rand: &mut ThreadRng) -> String {
    std::iter::repeat(())
        .map(|_| get_rand_char(rand))
        .take(length)
        .collect()
}

fn get_rand_char(rand: &mut ThreadRng) -> char {
    let valid_chars = (33..127).chain(161..255);
    char::from_u32(valid_chars.choose(rand).unwrap()).unwrap()
}