use {
    super::double_line::DoubleLine,
    crate::{
        app::*,
        display::{Screen, W},
        errors::ProgramError,
        kitty::{self, KittyImageId},
        skin::PanelSkin,
    },
    crokey::crossterm::{
        cursor,
        style::{
            Color,
            SetBackgroundColor,
        },
        QueueableCommand,
    },
    image::{
        DynamicImage,
        GenericImageView,
        imageops::FilterType,
    },
    std::path::{Path, PathBuf},
    termimad::{fill_bg, Area},
};

#[derive(Debug)]
struct DrawingInfo {
    drawing_count: usize,
    area: Area,
}

impl DrawingInfo {
    pub fn follows_in_place(&self, previous: &DrawingInfo) -> bool {
        self.drawing_count == previous.drawing_count + 1
            && self.area == previous.area
    }
}

/// an already resized image, with the dimensions it
/// was computed for (which may be different from the
/// dimensions we got)
struct CachedImage {
    img: DynamicImage,
    target_width: u32,
    target_height: u32,
}

/// an imageview can display an image in the terminal with
/// a ratio of one pixel per char in width.
pub struct ImageView {
    path: PathBuf,
    source_img: DynamicImage,
    display_img: Option<CachedImage>,
    last_drawing: Option<DrawingInfo>,
    kitty_image_id: Option<KittyImageId>,
}

impl ImageView {
    pub fn new(path: &Path) -> Result<Self, ProgramError> {
        let source_img = time!(
            "decode image",
            path,
            super::load(path)?
        );
        Ok(Self {
            path: path.to_path_buf(),
            source_img,
            display_img: None,
            last_drawing: None,
            kitty_image_id: None,
        })
    }
    pub fn is_png(&self) -> bool {
        match self.path.extension() {
            Some(ext) => ext == "png" || ext == "PNG",
            None => false,
        }
    }
    pub fn display(
        &mut self,
        w: &mut W,
        disc: &DisplayContext,
        area: &Area,
    ) -> Result<(), ProgramError> {

        let styles = &disc.panel_skin.styles;
        let bg = styles.preview.get_bg()
            .or_else(|| styles.default.get_bg())
            .unwrap_or(Color::AnsiValue(238));

        // we avoid drawing when we were just displayed
        // on the last drawing_count and the area is the same.
        let drawing_info = DrawingInfo {
            drawing_count: disc.count,
            area: area.clone(),
        };
        let must_draw = self.last_drawing
            .as_ref()
            .map_or(true, |previous| !drawing_info.follows_in_place(previous));
        if must_draw {
            debug!("image_view must be cleared");
        } else {
            debug!("no need to clear image_view");
        }
        self.last_drawing = Some(drawing_info);

        let mut kitty_manager = kitty::manager().lock().unwrap();

        if !must_draw {
            if let Some(kitty_image_id) = self.kitty_image_id {
                // we tell the manager the images must be kept, otherwise
                // they would be erased at end of drawing, as obsolete
                kitty_manager.keep(kitty_image_id, disc.count);
            }
            return Ok(());
        }

        self.kitty_image_id = kitty_manager
            .try_print_image(w, &self.source_img, area, bg, disc.count)?;

        if self.kitty_image_id.is_some() {
            return Ok(());
        }

        let target_width = area.width as u32;
        let target_height = (area.height * 2) as u32;
        let cached = self
            .display_img
            .as_ref()
            .filter(|ci| ci.target_width == target_width && ci.target_height == target_height);
        let img = match cached {
            Some(ci) => &ci.img,
            None => {
                let img = time!(
                    "resize image",
                    self.source_img.resize(target_width, target_height, FilterType::Triangle),
                );
                self.display_img = Some(CachedImage {
                    img,
                    target_width,
                    target_height,
                });
                &self.display_img.as_ref().unwrap().img
            }
        };
        let (width, height) = img.dimensions();
        debug!("resized image dimensions: {},{}", width, height);
        debug_assert!(width <= area.width as u32);
        let mut double_line = DoubleLine::new(width as usize, disc.con.true_colors);
        let mut y = area.top;
        let img_top_offset = (area.height - (height / 2) as u16) / 2;
        for _ in 0..img_top_offset {
            w.queue(cursor::MoveTo(area.left, y))?;
            fill_bg(w, area.width as usize, bg)?;
            y += 1;
        }
        let margin = area.width as usize - width as usize;
        let left_margin = margin / 2;
        let right_margin = margin - left_margin;
        w.queue(cursor::MoveTo(area.left, y))?;
        for pixel in img.pixels() {
            double_line.push(pixel.2);
            if double_line.is_full() {
                double_line.write(w, left_margin, right_margin, bg)?;
                y += 1;
                w.queue(cursor::MoveTo(area.left, y))?;
            }
        }
        if !double_line.is_empty() {
            double_line.write(w, left_margin, right_margin, bg)?;
            y += 1;
        }
        w.queue(SetBackgroundColor(bg))?;
        for y in y..area.top + area.height {
            w.queue(cursor::MoveTo(area.left, y))?;
            fill_bg(w, area.width as usize, bg)?;
        }
        Ok(())
    }
    pub fn display_info(
        &mut self,
        w: &mut W,
        _screen: Screen,
        panel_skin: &PanelSkin,
        area: &Area,
    ) -> Result<(), ProgramError> {
        let dim = self.source_img.dimensions();
        let s = format!("{} x {}", dim.0, dim.1);
        if s.len() > area.width as usize {
            return Ok(());
        }
        w.queue(cursor::MoveTo(
            area.left + area.width - s.len() as u16,
            area.top,
        ))?;
        panel_skin.styles.default.queue(w, s)?;
        Ok(())
    }
}