use cosmic_text::{Attrs, Family, FontSystem, Metrics, Shaping};

use crate::{prelude::*, util::MutDetect};

pub struct Text {
    pub content: MutDetect<String>,
    pub attrs: TextAttrs,
    /// inner alignment of text region (within where its drawn)
    pub align: Align,
    pub(super) buf: TextBuffer,
    size: Vec2,
}

impl Text {
    pub fn size(mut self, size: impl UiNum) -> Self {
        self.attrs.font_size = size.to_f32();
        self.attrs.line_height = self.attrs.font_size * 1.1;
        self
    }
    pub fn color(mut self, color: UiColor) -> Self {
        self.attrs.color = color;
        self
    }
    pub fn family(mut self, family: Family<'static>) -> Self {
        self.attrs.family = family;
        self
    }
    pub fn line_height(mut self, height: f32) -> Self {
        self.attrs.line_height = height;
        self
    }
    pub fn new(content: impl Into<String>) -> Self {
        let attrs = TextAttrs::default();
        Self {
            content: content.into().into(),
            buf: TextBuffer::new_empty(Metrics::new(attrs.font_size, attrs.line_height)),
            attrs,
            align: Align::Center,
            size: Vec2::ZERO,
        }
    }

    pub fn region(&self) -> UiRegion {
        UiRegion::from_size_align(self.size, self.align)
    }

    fn update_buf(&mut self, font_system: &mut FontSystem) {
        self.buf.set_metrics(
            font_system,
            Metrics::new(self.attrs.font_size, self.attrs.line_height),
        );
        if self.content.changed {
            self.content.changed = false;
            self.buf.set_text(
                font_system,
                &self.content,
                &Attrs::new().family(self.attrs.family),
                Shaping::Advanced,
            );
        }
    }
}

impl Widget for Text {
    fn draw(&mut self, painter: &mut Painter) {
        let font_system = &mut painter.text_data().font_system;
        self.update_buf(font_system);
        let (handle, offset) = painter.render_text(&mut self.buf, &self.attrs);
        let dims = handle.size();
        self.size = offset.size(&handle);
        let mut region = self.region();
        region.top_left.abs += offset.top_left;
        region.bot_right.abs = region.top_left.abs + dims;
        painter.texture_within(&handle, region);
    }

    fn desired_size(&mut self, ctx: &mut SizeCtx) -> UiVec2 {
        self.update_buf(&mut ctx.text.font_system);
        let (handle, offset) = ctx.draw_text(&mut self.buf, &self.attrs);
        UiVec2::abs(offset.size(&handle))
    }
}

pub fn text(content: impl Into<String>) -> TextBuilder {
    TextBuilder {
        content: content.into(),
        align: Align::Center,
        attrs: TextAttrs::default(),
    }
}

pub struct TextBuilder {
    pub content: String,
    pub attrs: TextAttrs,
    /// inner alignment of text region (within where its drawn)
    pub align: Align,
}

impl TextBuilder {
    pub fn size(mut self, size: impl UiNum) -> Self {
        self.attrs.font_size = size.to_f32();
        self.attrs.line_height = self.attrs.font_size * 1.1;
        self
    }
    pub fn color(mut self, color: UiColor) -> Self {
        self.attrs.color = color;
        self
    }
    pub fn family(mut self, family: Family<'static>) -> Self {
        self.attrs.family = family;
        self
    }
    pub fn line_height(mut self, height: f32) -> Self {
        self.attrs.line_height = height;
        self
    }
}

impl FnOnce<(&mut Ui,)> for TextBuilder {
    type Output = Text;

    extern "rust-call" fn call_once(self, args: (&mut Ui,)) -> Self::Output {
        let mut buf =
            TextBuffer::new_empty(Metrics::new(self.attrs.font_size, self.attrs.line_height));
        buf.set_text(
            &mut args.0.text.font_system,
            &self.content,
            &Attrs::new(),
            Shaping::Advanced,
        );
        let mut text = Text {
            content: self.content.into(),
            buf,
            attrs: self.attrs,
            align: self.align,
            size: Vec2::ZERO,
        };
        text.content.changed = false;
        self.attrs
            .apply(&mut args.0.text.font_system, &mut text.buf);
        text
    }
}