//! The [glyf (Glyph Data)](https://docs.microsoft.com/en-us/typography/opentype/spec/glyf) table

use crate::{FontData, ReadError};

/// 'glyf'
pub const TAG: Tag = Tag::new(b"glyf");

include!("../../generated/generated_glyf.rs");

macro_rules! field_getter {
    ($field:ident, $ty:ty) => {
        pub fn $field(&self) -> $ty {
            match self {
                Self::Simple(table) => table.$field(),
                Self::Composite(table) => table.$field(),
            }
        }
    };
}

impl<'a> Glyph<'a> {
    field_getter!(number_of_contours, i16);
    field_getter!(x_min, i16);
    field_getter!(x_max, i16);
    field_getter!(y_min, i16);
    field_getter!(y_max, i16);
}

//NOTE: This code below was taken from an old implementation, and has a bunch
// of funny warts. It should be replaced at some point, but might be useful in
// the interim?

impl<'a> SimpleGlyph<'a> {
    /// Returns the total number of points.
    pub fn num_points(&self) -> usize {
        self.end_pts_of_contours()
            .last()
            .map(|last| last.get() as usize + 1)
            .unwrap_or(0)
    }

    /// Reads points and flags into the specified buffers. Drops all flag bits
    /// except on-curve. The lengths of the buffers must be equal to the value
    /// returned by [num_points](Self::num_points).
    /// ## Performance
    /// As the name implies, this is faster than using the iterator returned by
    /// [points](Self::points) so should be used when it is possible to
    /// preallocate buffers.
    pub fn read_points_fast(
        &self,
        points: &mut [Point],
        flags: &mut [u8],
    ) -> Result<(), ReadError> {
        let n_points = self.num_points();
        if points.len() != n_points || flags.len() != n_points {
            return Err(ReadError::InvalidArrayLen);
        }
        let mut cursor = FontData::new(self.glyph_data()).cursor();
        let mut i = 0;
        while i < n_points {
            let flag = cursor.read::<SimpleGlyphFlags>()?;
            let flag_bits = flag.bits();
            if flag.contains(SimpleGlyphFlags::REPEAT_FLAG) {
                let count = (cursor.read::<u8>()? as usize + 1).min(n_points - i);
                for f in &mut flags[i..i + count] {
                    *f = flag_bits;
                }
                i += count;
            } else {
                flags[i] = flag_bits;
                i += 1;
            }
        }
        let mut x = 0i32;
        for (&flag_bits, point) in flags.iter().zip(points.as_mut()) {
            let mut delta = 0i32;
            let flag = SimpleGlyphFlags::from_bits_truncate(flag_bits);
            if flag.contains(SimpleGlyphFlags::X_SHORT_VECTOR) {
                delta = cursor.read::<u8>()? as i32;
                if !flag.contains(SimpleGlyphFlags::X_IS_SAME_OR_POSITIVE_X_SHORT_VECTOR) {
                    delta = -delta;
                }
            } else if !flag.contains(SimpleGlyphFlags::X_IS_SAME_OR_POSITIVE_X_SHORT_VECTOR) {
                delta = cursor.read::<i16>()? as i32;
            }
            x = x.wrapping_add(delta);
            point.x = x;
        }
        let mut y = 0i32;
        for (flag_bits, point) in flags.iter_mut().zip(points.as_mut()) {
            let mut delta = 0i32;
            let flag = SimpleGlyphFlags::from_bits_truncate(*flag_bits);
            if flag.contains(SimpleGlyphFlags::Y_SHORT_VECTOR) {
                delta = cursor.read::<u8>()? as i32;
                if !flag.contains(SimpleGlyphFlags::Y_IS_SAME_OR_POSITIVE_Y_SHORT_VECTOR) {
                    delta = -delta;
                }
            } else if !flag.contains(SimpleGlyphFlags::Y_IS_SAME_OR_POSITIVE_Y_SHORT_VECTOR) {
                delta = cursor.read::<i16>()? as i32;
            }
            y = y.wrapping_add(delta);
            point.y = y;
            // Only keep the on-curve bit
            *flag_bits &= 1;
        }
        Ok(())
    }

    /// Returns an iterator over the points in the glyph.
    /// ## Performance
    /// This is slower than [read_points_fast](Self::read_points_fast) but
    /// provides access to the points without requiring a preallocated buffer.
    pub fn points(&self) -> impl Iterator<Item = CurvePoint> + 'a + Clone {
        self.points_impl()
            .unwrap_or_else(|| PointIter::new(&[], &[], &[]))
    }

    fn points_impl(&self) -> Option<PointIter<'a>> {
        let end_points = self.end_pts_of_contours();
        let n_points = end_points.last()?.get().checked_add(1)?;
        let data = self.glyph_data();
        let lens = resolve_coords_len(data, n_points).ok()?;
        let total_len = lens.flags + lens.x_coords + lens.y_coords;
        if data.len() < total_len as usize {
            return None;
        }

        let (flags, data) = data.split_at(lens.flags as usize);
        let (x_coords, y_coords) = data.split_at(lens.x_coords as usize);

        Some(PointIter::new(flags, x_coords, y_coords))
    }
}

/// Point in a simple glyph.
#[derive(Copy, Clone, PartialEq, Eq, Default, Debug)]
pub struct Point {
    /// X cooordinate.
    pub x: i32,
    /// Y coordinate.
    pub y: i32,
}

impl Point {
    /// Creates a new point with the specified x and y coordinates.
    pub const fn new(x: i32, y: i32) -> Self {
        Self { x, y }
    }
}

/// Point with an associated on-curve flag in a simple glyph.
#[derive(Clone, Copy, Debug)]
pub struct CurvePoint {
    /// The point.
    pub point: Point,
    /// True if this is an on-curve point.
    pub on_curve: bool,
}

#[derive(Clone)]
struct PointIter<'a> {
    flags: Cursor<'a>,
    x_coords: Cursor<'a>,
    y_coords: Cursor<'a>,
    flag_repeats: u8,
    cur_flags: SimpleGlyphFlags,
    cur_x: i16,
    cur_y: i16,
}

impl<'a> Iterator for PointIter<'a> {
    type Item = CurvePoint;
    fn next(&mut self) -> Option<Self::Item> {
        self.advance_flags()?;
        self.advance_points();
        Some(CurvePoint {
            point: Point {
                x: self.cur_x as i32,
                y: self.cur_y as i32,
            },
            on_curve: self.cur_flags.contains(SimpleGlyphFlags::ON_CURVE_POINT),
        })
    }
}

impl<'a> PointIter<'a> {
    fn new(flags: &'a [u8], x_coords: &'a [u8], y_coords: &'a [u8]) -> Self {
        Self {
            flags: FontData::new(flags).cursor(),
            x_coords: FontData::new(x_coords).cursor(),
            y_coords: FontData::new(y_coords).cursor(),
            flag_repeats: 0,
            cur_flags: SimpleGlyphFlags::empty(),
            cur_x: 0,
            cur_y: 0,
        }
    }

    fn advance_flags(&mut self) -> Option<()> {
        if self.flag_repeats == 0 {
            self.cur_flags = SimpleGlyphFlags::from_bits_truncate(self.flags.read().ok()?);
            self.flag_repeats = self
                .cur_flags
                .contains(SimpleGlyphFlags::REPEAT_FLAG)
                .then(|| self.flags.read().ok())
                .flatten()
                .unwrap_or(0)
                + 1;
        }
        self.flag_repeats -= 1;
        Some(())
    }

    fn advance_points(&mut self) {
        let x_short = self.cur_flags.contains(SimpleGlyphFlags::X_SHORT_VECTOR);
        let x_same_or_pos = self
            .cur_flags
            .contains(SimpleGlyphFlags::X_IS_SAME_OR_POSITIVE_X_SHORT_VECTOR);
        let y_short = self.cur_flags.contains(SimpleGlyphFlags::Y_SHORT_VECTOR);
        let y_same_or_pos = self
            .cur_flags
            .contains(SimpleGlyphFlags::Y_IS_SAME_OR_POSITIVE_Y_SHORT_VECTOR);

        let delta_x = match (x_short, x_same_or_pos) {
            (true, false) => -(self.x_coords.read::<u8>().unwrap_or(0) as i16),
            (true, true) => self.x_coords.read::<u8>().unwrap_or(0) as i16,
            (false, false) => self.x_coords.read::<i16>().unwrap_or(0),
            _ => 0,
        };

        let delta_y = match (y_short, y_same_or_pos) {
            (true, false) => -(self.y_coords.read::<u8>().unwrap_or(0) as i16),
            (true, true) => self.y_coords.read::<u8>().unwrap_or(0) as i16,
            (false, false) => self.y_coords.read::<i16>().unwrap_or(0),
            _ => 0,
        };

        self.cur_x = self.cur_x.wrapping_add(delta_x);
        self.cur_y = self.cur_y.wrapping_add(delta_y);
    }
}

//taken from ttf_parser https://docs.rs/ttf-parser/latest/src/ttf_parser/tables/glyf.rs.html#1-677
/// Resolves coordinate arrays length.
///
/// The length depends on *Simple Glyph Flags*, so we have to process them all to find it.
fn resolve_coords_len(data: &[u8], points_total: u16) -> Result<FieldLengths, ReadError> {
    let mut cursor = FontData::new(data).cursor();
    let mut flags_left = u32::from(points_total);
    //let mut repeats;
    let mut x_coords_len = 0;
    let mut y_coords_len = 0;
    //let mut flags_seen = 0;
    while flags_left > 0 {
        let flags: SimpleGlyphFlags = cursor.read()?;

        // The number of times a glyph point repeats.
        let repeats = if flags.contains(SimpleGlyphFlags::REPEAT_FLAG) {
            let repeats: u8 = cursor.read()?;
            u32::from(repeats) + 1
        } else {
            1
        };

        if repeats > flags_left {
            return Err(ReadError::MalformedData("repeat count too large in glyf"));
        }

        // Non-obfuscated code below.
        // Branchless version is surprisingly faster.
        //
        // if flags.x_short() {
        //     // Coordinate is 1 byte long.
        //     x_coords_len += repeats;
        // } else if !flags.x_is_same_or_positive_short() {
        //     // Coordinate is 2 bytes long.
        //     x_coords_len += repeats * 2;
        // }
        // if flags.y_short() {
        //     // Coordinate is 1 byte long.
        //     y_coords_len += repeats;
        // } else if !flags.y_is_same_or_positive_short() {
        //     // Coordinate is 2 bytes long.
        //     y_coords_len += repeats * 2;
        // }
        let x_short = SimpleGlyphFlags::X_SHORT_VECTOR;
        let x_long = SimpleGlyphFlags::X_SHORT_VECTOR
            | SimpleGlyphFlags::X_IS_SAME_OR_POSITIVE_X_SHORT_VECTOR;
        let y_short = SimpleGlyphFlags::Y_SHORT_VECTOR;
        let y_long = SimpleGlyphFlags::Y_SHORT_VECTOR
            | SimpleGlyphFlags::Y_IS_SAME_OR_POSITIVE_Y_SHORT_VECTOR;
        x_coords_len += ((flags & x_short).bits() != 0) as u32 * repeats;
        x_coords_len += ((flags & x_long).bits() == 0) as u32 * repeats * 2;

        y_coords_len += ((flags & y_short).bits() != 0) as u32 * repeats;
        y_coords_len += ((flags & y_long).bits() == 0) as u32 * repeats * 2;

        flags_left -= repeats;
    }

    Ok(FieldLengths {
        flags: cursor.position()? as u32,
        x_coords: x_coords_len,
        y_coords: y_coords_len,
    })
    //Some((flags_len, x_coords_len, y_coords_len))
}

struct FieldLengths {
    flags: u32,
    x_coords: u32,
    y_coords: u32,
}

/// Transform for a composite component.
#[derive(Clone, Debug)]
pub struct Transform {
    /// X scale factor.
    pub xx: F2Dot14,
    /// YX skew factor.
    pub yx: F2Dot14,
    /// XY skew factor.
    pub xy: F2Dot14,
    /// Y scale factor.
    pub yy: F2Dot14,
}

impl Default for Transform {
    fn default() -> Self {
        Self {
            xx: F2Dot14::from_f32(1.0),
            yx: F2Dot14::from_f32(0.0),
            xy: F2Dot14::from_f32(0.0),
            yy: F2Dot14::from_f32(1.0),
        }
    }
}

/// A reference to another glyph. Part of [CompositeGlyph].
pub struct Component {
    /// Component flags.
    pub flags: CompositeGlyphFlags,
    /// Glyph identifier.
    pub glyph: GlyphId,
    /// Anchor for component placement.
    pub anchor: Anchor,
    /// Component transformation matrix.
    pub transform: Transform,
}

/// Anchor position for a composite component.
#[derive(Debug, Clone, Copy)]
pub enum Anchor {
    Offset { x: i16, y: i16 },
    Point { base: u16, component: u16 },
}

impl<'a> CompositeGlyph<'a> {
    /// Returns an iterator over the components of the composite glyph.
    pub fn components(&self) -> impl Iterator<Item = Component> + 'a + Clone {
        ComponentIter {
            cur_flags: CompositeGlyphFlags::empty(),
            done: false,
            cursor: FontData::new(self.component_data()).cursor(),
        }
    }

    /// Returns the TrueType interpreter instructions.
    pub fn instructions(&self) -> Option<&'a [u8]> {
        ComponentIter {
            cur_flags: CompositeGlyphFlags::empty(),
            done: false,
            cursor: FontData::new(self.component_data()).cursor(),
        }
        .instructions()
    }
}

#[derive(Clone)]
struct ComponentIter<'a> {
    cur_flags: CompositeGlyphFlags,
    done: bool,
    cursor: Cursor<'a>,
}

impl<'a> ComponentIter<'a> {
    fn instructions(&mut self) -> Option<&'a [u8]> {
        while self.by_ref().next().is_some() {}
        if self
            .cur_flags
            .contains(CompositeGlyphFlags::WE_HAVE_INSTRUCTIONS)
        {
            let len = self.cursor.read::<u16>().ok()? as usize;
            self.cursor.read_array(len).ok()
        } else {
            None
        }
    }
}

impl Iterator for ComponentIter<'_> {
    type Item = Component;

    fn next(&mut self) -> Option<Self::Item> {
        if self.done {
            return None;
        }
        let flags: CompositeGlyphFlags = self.cursor.read().ok()?;
        self.cur_flags = flags;
        let glyph = self.cursor.read::<GlyphId>().ok()?;
        let args_are_words = flags.contains(CompositeGlyphFlags::ARG_1_AND_2_ARE_WORDS);
        let args_are_xy_values = flags.contains(CompositeGlyphFlags::ARGS_ARE_XY_VALUES);
        let anchor = match (args_are_xy_values, args_are_words) {
            (true, true) => Anchor::Offset {
                x: self.cursor.read().ok()?,
                y: self.cursor.read().ok()?,
            },
            (true, false) => Anchor::Offset {
                x: self.cursor.read::<i8>().ok()? as _,
                y: self.cursor.read::<i8>().ok()? as _,
            },
            (false, true) => Anchor::Point {
                base: self.cursor.read().ok()?,
                component: self.cursor.read().ok()?,
            },
            (false, false) => Anchor::Point {
                base: self.cursor.read::<u8>().ok()? as _,
                component: self.cursor.read::<u8>().ok()? as _,
            },
        };
        let mut transform = Transform::default();
        if flags.contains(CompositeGlyphFlags::WE_HAVE_A_SCALE) {
            transform.xx = self.cursor.read().ok()?;
            transform.yy = transform.xx;
        } else if flags.contains(CompositeGlyphFlags::WE_HAVE_AN_X_AND_Y_SCALE) {
            transform.xx = self.cursor.read().ok()?;
            transform.yy = self.cursor.read().ok()?;
        } else if flags.contains(CompositeGlyphFlags::WE_HAVE_A_TWO_BY_TWO) {
            transform.xx = self.cursor.read().ok()?;
            transform.yx = self.cursor.read().ok()?;
            transform.xy = self.cursor.read().ok()?;
            transform.yy = self.cursor.read().ok()?;
        }
        self.done = !flags.contains(CompositeGlyphFlags::MORE_COMPONENTS);

        Some(Component {
            flags,
            glyph,
            anchor,
            transform,
        })
    }
}

#[cfg(feature = "traversal")]
impl<'a> SomeTable<'a> for Component {
    fn type_name(&self) -> &str {
        "Component"
    }

    fn get_field(&self, idx: usize) -> Option<Field<'a>> {
        match idx {
            0 => Some(Field::new("flags", self.flags.bits())),
            1 => Some(Field::new("glyph", self.glyph)),
            2 => match self.anchor {
                Anchor::Point { base, .. } => Some(Field::new("base", base)),
                Anchor::Offset { x, .. } => Some(Field::new("x", x)),
            },
            3 => match self.anchor {
                Anchor::Point { component, .. } => Some(Field::new("component", component)),
                Anchor::Offset { y, .. } => Some(Field::new("y", y)),
            },
            _ => None,
        }
    }
}

//NOTE: we want generated_glyf traversal to include this:
//7usize => {
//let this = self.sneaky_copy();
//Some(Field::new(
//"components",
//FieldType::offset_iter(move || {
//Box::new(
//this.iter_components()
//.map(|item| FieldType::ResolvedOffset(Ok(Box::new(item)))),
//) as Box<dyn Iterator<Item = FieldType<'a>> + 'a>
//}),
//))
//}

#[cfg(test)]
mod tests {
    use super::Glyph;
    use crate::test_data;
    use crate::{FontRef, GlyphId, TableProvider};

    #[test]
    fn simple_glyph() {
        let font = FontRef::new(test_data::test_fonts::COLR_GRADIENT_RECT).unwrap();
        let loca = font.loca(None).unwrap();
        let glyf = font.glyf().unwrap();
        let glyph = loca.get_glyf(GlyphId::new(0), &glyf).unwrap().unwrap();
        assert_eq!(glyph.number_of_contours(), 2);
        let simple_glyph = if let Glyph::Simple(simple) = glyph {
            simple
        } else {
            panic!("expected simple glyph");
        };
        assert_eq!(
            simple_glyph
                .end_pts_of_contours()
                .iter()
                .map(|x| x.get())
                .collect::<Vec<_>>(),
            &[3, 7]
        );
        assert_eq!(
            simple_glyph
                .points()
                .map(|pt| (pt.point.x, pt.point.y, pt.on_curve))
                .collect::<Vec<_>>(),
            &[
                (5, 0, true),
                (5, 100, true),
                (45, 100, true),
                (45, 0, true),
                (10, 5, true),
                (40, 5, true),
                (40, 95, true),
                (10, 95, true),
            ]
        );
    }
}