use {
    super::*,
    crate::{
        app::{AppContext, LineNumber},
        command::ScrollCommand,
        display::*,
        errors::ProgramError,
        hex::HexView,
        image::ImageView,
        pattern::InputPattern,
        skin::PanelSkin,
        syntactic::SyntacticView,
        task_sync::Dam,
    },
    crossterm::{cursor, QueueableCommand},
    std::{
        io,
        path::Path,
    },
    termimad::Area,
};

pub enum Preview {
    Image(ImageView),
    Syntactic(SyntacticView),
    Hex(HexView),
    ZeroLen(ZeroLenFileView),
    IOError(io::Error),
}

impl Preview {
    /// build a preview, never failing (but the preview can be Preview::IOError).
    /// If the prefered mode can't be applied, an other mode is chosen.
    pub fn new(
        path: &Path,
        prefered_mode: Option<PreviewMode>,
        con: &AppContext,
    ) -> Self {
        match prefered_mode {
            Some(PreviewMode::Hex) => Self::hex(path),
            Some(PreviewMode::Image) => Self::image(path),
            Some(PreviewMode::Text) => Self::unfiltered_text(path, con),
            None => {
                // automatic behavior: image, text, hex
                ImageView::new(path)
                    .map(Self::Image)
                    .unwrap_or_else(|_| Self::unfiltered_text(path, con))
            }
        }
    }
    /// try to build a preview with the designed mode, return an error
    /// if that wasn't possible
    pub fn with_mode(
        path: &Path,
        mode: PreviewMode,
        con: &AppContext,
    ) -> Result<Self, ProgramError> {
        match mode {
            PreviewMode::Hex => {
                Ok(HexView::new(path.to_path_buf()).map(Self::Hex)?)
            }
            PreviewMode::Image => {
                ImageView::new(path).map(Self::Image)
            }
            PreviewMode::Text => {
                Ok(
                    SyntacticView::new(path, InputPattern::none(), &mut Dam::unlimited(), con)
                        .transpose()
                        .expect("syntactic view without pattern shouldn't be none")
                        .map(Self::Syntactic)?,
                )
            }
        }
    }
    /// build an image view, unless the file can't be interpreted
    /// as an image, in which case a hex view is used
    pub fn image(path: &Path) -> Self {
        ImageView::new(path)
            .ok()
            .map(Self::Image)
            .unwrap_or_else(|| Self::hex(path))

    }
    /// build a text preview (maybe with syntaxic coloring) if possible,
    /// a hex (binary) view if content isnt't UTF8, or a IOError when
    /// there's a IO problem
    pub fn unfiltered_text(
        path: &Path,
        con: &AppContext,
    ) -> Self {
        match SyntacticView::new(path, InputPattern::none(), &mut Dam::unlimited(), con) {
            Ok(Some(sv)) => Self::Syntactic(sv),
            Err(ProgramError::ZeroLenFile) => {
                debug!("zero len file - check if system file");
                Self::ZeroLen(ZeroLenFileView::new(path.to_path_buf()))
            }
            // not previewable as UTF8 text
            // we'll try reading it as binary
            _ => Self::hex(path),
        }
    }
    /// try to build a filtered text view. Will return None if
    /// the dam gets an event before it's built
    pub fn filtered(
        &self,
        path: &Path,
        pattern: InputPattern,
        dam: &mut Dam,
        con: &AppContext,
    ) -> Option<Self> {
        match self {
            Self::Syntactic(_) => {
                match SyntacticView::new(path, pattern, dam, con) {

                    // normal finished loading
                    Ok(Some(sv)) => Some(Self::Syntactic(sv)),

                    // interrupted search
                    Ok(None) => None,

                    // not previewable as UTF8 text
                    // we'll try reading it as binary
                    Err(_) => Some(Self::hex(path)),
                }
            }
            _ => None, // not filterable
        }
    }
    /// return a hex_view, suitable for binary, or Self::IOError
    /// if there was an error
    pub fn hex(path: &Path) -> Self {
        match HexView::new(path.to_path_buf()) {
            Ok(reader) => Self::Hex(reader),
            Err(e) => {
                // it's unlikely as the file isn't open at this point
                warn!("error while previewing {:?} : {:?}", path, e);
                Self::IOError(e)
            }
        }
    }
    /// return the preview_mode, or None if we're on IOError
    pub fn get_mode(&self) -> Option<PreviewMode> {
        match self {
            Self::Image(_) => Some(PreviewMode::Image),
            Self::Syntactic(_) => Some(PreviewMode::Text),
            Self::ZeroLen(_) => Some(PreviewMode::Text),
            Self::Hex(_) => Some(PreviewMode::Hex),
            Self::IOError(_) => None,
        }
    }
    pub fn pattern(&self) -> InputPattern {
        match self {
            Self::Syntactic(sv) => sv.pattern.clone(),
            _ => InputPattern::none(),
        }
    }
    pub fn try_scroll(
        &mut self,
        cmd: ScrollCommand,
    ) -> bool {
        match self {
            Self::Syntactic(sv) => sv.try_scroll(cmd),
            Self::Hex(hv) => hv.try_scroll(cmd),
            _ => false,
        }
    }
    pub fn is_filterable(&self) -> bool {
        matches!(self, Self::Syntactic(_))
    }

    pub fn get_selected_line(&self) -> Option<String> {
        match self {
            Self::Syntactic(sv) => sv.get_selected_line(),
            _ => None,
        }
    }
    pub fn get_selected_line_number(&self) -> Option<LineNumber> {
        match self {
            Self::Syntactic(sv) => sv.get_selected_line_number(),
            _ => None,
        }
    }
    pub fn try_select_line_number(&mut self, number: usize) -> bool {
        match self {
            Self::Syntactic(sv) => sv.try_select_line_number(number),
            _ => false,
        }
    }
    pub fn unselect(&mut self) {
        if let Self::Syntactic(sv) = self {
            sv.unselect();
        }
    }
    pub fn try_select_y(&mut self, y: u16) -> bool {
        match self {
            Self::Syntactic(sv) => sv.try_select_y(y),
            _ => false,
        }
    }
    pub fn move_selection(&mut self, dy: i32, cycle: bool) {
        match self {
            Self::Syntactic(sv) => sv.move_selection(dy, cycle),
            Self::Hex(hv) => {
                hv.try_scroll(ScrollCommand::Lines(dy));
            }
            _ => {}
        }
    }
    pub fn select_first(&mut self) {
        match self {
            Self::Syntactic(sv) => sv.select_first(),
            Self::Hex(hv) => hv.select_first(),
            _ => {}
        }
    }
    pub fn select_last(&mut self) {
        match self {
            Self::Syntactic(sv) => sv.select_last(),
            Self::Hex(hv) => hv.select_last(),
            _ => {}
        }
    }
    pub fn display(
        &mut self,
        w: &mut W,
        screen: Screen,
        panel_skin: &PanelSkin,
        area: &Area,
        con: &AppContext,
    ) -> Result<(), ProgramError> {
        match self {
            Self::Image(iv) => iv.display(w, screen, panel_skin, area, con),
            Self::Syntactic(sv) => sv.display(w, screen, panel_skin, area, con),
            Self::ZeroLen(zlv) => zlv.display(w, screen, panel_skin, area),
            Self::Hex(hv) => hv.display(w, screen, panel_skin, area),
            Self::IOError(err) => {
                let mut y = area.top;
                w.queue(cursor::MoveTo(area.left, y))?;
                let mut cw = CropWriter::new(w, area.width as usize);
                cw.queue_str(&panel_skin.styles.default, "An error prevents the preview:")?;
                cw.fill(&panel_skin.styles.default, &SPACE_FILLING)?;
                y += 1;
                w.queue(cursor::MoveTo(area.left, y))?;
                let mut cw = CropWriter::new(w, area.width as usize);
                cw.queue_g_string(&panel_skin.styles.status_error, err.to_string())?;
                cw.fill(&panel_skin.styles.default, &SPACE_FILLING)?;
                y += 1;
                while y < area.top + area.height {
                    w.queue(cursor::MoveTo(area.left, y))?;
                    let mut cw = CropWriter::new(w, area.width as usize);
                    cw.fill(&panel_skin.styles.default, &SPACE_FILLING)?;
                    y += 1;
                }
                Ok(())
            }
        }
    }
    pub fn display_info(
        &mut self,
        w: &mut W,
        screen: Screen,
        panel_skin: &PanelSkin,
        area: &Area,
    ) -> Result<(), ProgramError> {
        match self {
            Self::Image(iv) => iv.display_info(w, screen, panel_skin, area),
            Self::Syntactic(sv) => sv.display_info(w, screen, panel_skin, area),
            Self::Hex(hv) => hv.display_info(w, screen, panel_skin, area),
            _ => Ok(()),
        }
    }
}