use cosmic_text::{Family, Metrics};

use crate::prelude::*;

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

impl Text {
    pub fn font_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(),
            buf: TextBuffer::new_empty(Metrics::new(attrs.font_size, attrs.line_height)),
            attrs,
            align: Align::Center,
            cursor: Cursor::None,
            size: Vec2::ZERO,
        }
    }

    pub fn select(&mut self, pos: Vec2, size: Vec2) {
        let pos = pos - self.region().top_left.to_size(size);
        let Some(cursor) = self.buf.hit(pos.x, pos.y) else {
            return;
        };
        self.cursor = Cursor::Select {
            line: cursor.line as isize,
            col: cursor.index as isize,
        };
    }

    pub fn deselect(&mut self) {
        self.cursor = Cursor::None;
    }

    pub fn insert(&mut self, text: &str) {
        let i = self.update_cursor();
        self.content.insert_str(i, text);

        match &mut self.cursor {
            Cursor::None => (),
            Cursor::Select { line, col } => {
                *col += 1;
            }
        }
    }

    pub fn backspace(&mut self) {
        if let Some(i) = self.update_cursor().checked_sub(1) {
            self.content.remove(i);
            match &mut self.cursor {
                Cursor::None => (),
                Cursor::Select { line, col } => {
                    *col -= 1;
                }
            }
        }
    }

    pub fn delete(&mut self) {
        let i = self.update_cursor();
        if i != self.content.len() {
            self.content.remove(i);
        }
    }

    pub fn move_cursor(&mut self, dir: Dir) {
        if let Cursor::Select { line, col } = &mut self.cursor {
            match dir {
                Dir::LEFT => *col -= 1,
                Dir::RIGHT => *col += 1,
                Dir::UP => *line -= 1,
                Dir::DOWN => *line += 1,
            }
        }
    }

    pub fn update_cursor(&mut self) -> usize {
        match &mut self.cursor {
            Cursor::None => 0,
            Cursor::Select { line, col } => {
                if *col < 0 {
                    *line -= 1;
                }
                if *line < 0 {
                    *line = 0;
                    *col = 0;
                }
                let mut idx = self.content.len();
                let mut l = 0;
                let mut c = 0;
                let mut cur_len = 0;
                for (i, ch) in self.content.chars().enumerate() {
                    if ch == '\n' {
                        l += 1;
                        c = 0;
                    } else {
                        if l == *line {
                            cur_len = i as isize + 1;
                            if c == *col {
                                idx = i;
                            }
                        }
                        c += 1;
                    }
                }
                if *col < 0 {
                    *col = cur_len;
                }
                if *col > cur_len {
                    *col = 0;
                    *line += 1;
                }
                if *line > l {
                    *line = l;
                    *col = cur_len;
                }
                idx
            }
        }
    }

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

impl Widget for Text {
    fn draw(&mut self, painter: &mut Painter) {
        self.update_cursor();
        let (handle, offset) =
            painter.render_text(&mut self.buf, &self.content, &self.attrs, &self.cursor);
        let dims = handle.size();
        self.size = offset.size(&handle);
        let mut region = self.region();
        region.top_left.offset += offset.top_left;
        region.bot_right.offset = region.top_left.offset + dims;
        painter.draw_texture_within(&handle, region);
    }

    fn get_size(&mut self, ctx: &mut SizeCtx) -> Vec2 {
        let (handle, offset) =
            ctx.draw_text(&mut self.buf, &self.content, &self.attrs, &self.cursor);
        offset.size(&handle)
    }
}

pub fn text(content: impl Into<String>) -> Text {
    Text::new(content)
}