use crate::{
    strutil::TString,
    ui::{
        component::{text::TextStyle, Component, Event, EventCtx, Never},
        geometry::{Alignment, Offset, Rect},
        model_mercury::theme,
        shape::{Renderer, Text},
    },
};

/// Component showing a task instruction (e.g. "Swipe up") and optionally task
/// description (e.g. "Confirm transaction") to a user. A host of this component
/// is responsible of providing the exact area considering also the spacing. The
/// height must be 18px (only instruction) or 37px (both description and
/// instruction). The content and style of both description and instruction is
/// configurable separatedly.
pub struct Footer<'a> {
    area: Rect,
    text_instruction: TString<'a>,
    text_description: Option<TString<'a>>,
    style_instruction: &'static TextStyle,
    style_description: &'static TextStyle,
}

impl<'a> Footer<'a> {
    /// height of the component with only instruction [px]
    pub const HEIGHT_SIMPLE: i16 = 18;
    /// height of the component with both description and instruction [px]
    pub const HEIGHT_DEFAULT: i16 = 37;

    pub fn new<T: Into<TString<'a>>>(instruction: T) -> Self {
        Self {
            area: Rect::zero(),
            text_instruction: instruction.into(),
            text_description: None,
            style_instruction: &theme::TEXT_SUB,
            style_description: &theme::TEXT_SUB,
        }
    }

    pub fn with_description<T: Into<TString<'a>>>(self, description: T) -> Self {
        Self {
            text_description: Some(description.into()),
            ..self
        }
    }

    pub fn update_instruction<T: Into<TString<'a>>>(&mut self, ctx: &mut EventCtx, s: T) {
        self.text_instruction = s.into();
        ctx.request_paint();
    }

    pub fn update_description<T: Into<TString<'a>>>(&mut self, ctx: &mut EventCtx, s: T) {
        self.text_description = Some(s.into());
        ctx.request_paint();
    }

    pub fn update_instruction_style(&mut self, ctx: &mut EventCtx, style: &'static TextStyle) {
        self.style_instruction = style;
        ctx.request_paint();
    }

    pub fn update_description_style(&mut self, ctx: &mut EventCtx, style: &'static TextStyle) {
        self.style_description = style;
        ctx.request_paint();
    }
}

impl<'a> Component for Footer<'a> {
    type Msg = Never;

    fn place(&mut self, bounds: Rect) -> Rect {
        let h = bounds.height();
        assert!(h == Footer::HEIGHT_SIMPLE || h == Footer::HEIGHT_DEFAULT);
        self.area = bounds;
        bounds
    }

    fn event(&mut self, _ctx: &mut EventCtx, _event: Event) -> Option<Self::Msg> {
        None
    }

    fn paint(&mut self) {
        // TODO: remove when ui-t3t1 done
        todo!()
    }

    fn render<'s>(&'s self, target: &mut impl Renderer<'s>) {
        // show description only if there is space for it
        if self.area.height() == Footer::HEIGHT_DEFAULT {
            if let Some(description) = self.text_description {
                let area_description = self.area.split_top(Footer::HEIGHT_SIMPLE).0;
                let text_description_font_descent = self
                    .style_description
                    .text_font
                    .visible_text_height_ex("Ay")
                    .1;
                let text_description_baseline =
                    area_description.bottom_center() - Offset::y(text_description_font_descent);

                description.map(|t| {
                    Text::new(text_description_baseline, t)
                        .with_font(self.style_description.text_font)
                        .with_fg(self.style_description.text_color)
                        .with_align(Alignment::Center)
                        .render(target);
                });
            }
        }

        let area_instruction = self.area.split_bottom(Footer::HEIGHT_SIMPLE).1;
        let text_instruction_font_descent = self
            .style_instruction
            .text_font
            .visible_text_height_ex("Ay")
            .1;
        let text_instruction_baseline =
            area_instruction.bottom_center() - Offset::y(text_instruction_font_descent);
        self.text_instruction.map(|t| {
            Text::new(text_instruction_baseline, t)
                .with_font(self.style_instruction.text_font)
                .with_fg(self.style_instruction.text_color)
                .with_align(Alignment::Center)
                .render(target);
        });
    }
}