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//! The [loca (Index to Location)][loca] table
//!
//! [loca]: https://docs.microsoft.com/en-us/typography/opentype/spec/loca

use crate::{
    read::{FontRead, FontReadWithArgs, ReadArgs, ReadError},
    table_provider::TopLevelTable,
    FontData,
};
use types::{BigEndian, GlyphId, Tag};

#[cfg(feature = "experimental_traverse")]
use crate::traversal;

/// The [loca] table.
///
/// [loca]: https://docs.microsoft.com/en-us/typography/opentype/spec/loca
#[derive(Clone)]
pub enum Loca<'a> {
    Short(&'a [BigEndian<u16>]),
    Long(&'a [BigEndian<u32>]),
}

impl TopLevelTable for Loca<'_> {
    const TAG: Tag = Tag::new(b"loca");
}

impl<'a> Loca<'a> {
    pub fn read(data: FontData<'a>, is_long: bool) -> Result<Self, crate::ReadError> {
        Self::read_with_args(data, &is_long)
    }

    pub fn len(&self) -> usize {
        match self {
            Loca::Short(data) => data.len().saturating_sub(1),
            Loca::Long(data) => data.len().saturating_sub(1),
        }
    }

    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Attempt to return the offset for a given glyph id.
    pub fn get_raw(&self, idx: usize) -> Option<u32> {
        match self {
            Loca::Short(data) => data.get(idx).map(|x| x.get() as u32 * 2),
            Loca::Long(data) => data.get(idx).map(|x| x.get()),
        }
    }

    pub fn get_glyf(
        &self,
        gid: GlyphId,
        glyf: &super::glyf::Glyf<'a>,
    ) -> Result<Option<super::glyf::Glyph<'a>>, ReadError> {
        let idx = gid.to_u32() as usize;
        let start = self.get_raw(idx).ok_or(ReadError::OutOfBounds)?;
        let end = self.get_raw(idx + 1).ok_or(ReadError::OutOfBounds)?;
        if start == end {
            return Ok(None);
        }
        let data = glyf
            .offset_data()
            .slice(start as usize..end as usize)
            .ok_or(ReadError::OutOfBounds)?;
        match super::glyf::Glyph::read(data) {
            Ok(glyph) => Ok(Some(glyph)),
            Err(e) => Err(e),
        }
    }
}

impl ReadArgs for Loca<'_> {
    type Args = bool;
}

impl<'a> FontReadWithArgs<'a> for Loca<'a> {
    fn read_with_args(data: FontData<'a>, args: &Self::Args) -> Result<Self, crate::ReadError> {
        let is_long = *args;
        if is_long {
            data.read_array(0..data.len()).map(Loca::Long)
        } else {
            data.read_array(0..data.len()).map(Loca::Short)
        }
    }
}

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

    fn get_field(&self, idx: usize) -> Option<traversal::Field<'a>> {
        match idx {
            0usize => Some(traversal::Field::new("offsets", self.clone())),
            _ => None,
        }
    }
}

#[cfg(feature = "experimental_traverse")]
impl<'a> traversal::SomeArray<'a> for Loca<'a> {
    fn len(&self) -> usize {
        self.len()
    }

    fn get(&self, idx: usize) -> Option<traversal::FieldType<'a>> {
        self.get_raw(idx).map(|off| off.into())
    }

    fn type_name(&self) -> &str {
        "Offset32"
    }
}

#[cfg(feature = "experimental_traverse")]
impl<'a> std::fmt::Debug for Loca<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        (self as &dyn traversal::SomeTable<'a>).fmt(f)
    }
}