//! impl subset() for hdmx

use crate::serialize::{SerializeErrorFlags, Serializer};

use crate::{Plan, Subset, SubsetError};

use write_fonts::{

    read::{

        tables::hdmx::{DeviceRecord, Hdmx},

        FontRef, TopLevelTable,

    },

    FontBuilder,

};

fn ceil_to_4(v: u32) -> u32 {

    ((v - 1) | 3) + 1

}

// reference: subset() for hmtx/hhea in harfbuzz

// <https://github.com/harfbuzz/harfbuzz/blob/e451e91ec3608a2ebfec34d0c4f0b3d880e00e33/src/hb-ot-hdmx-table.hh#L116>

impl Subset for Hdmx<'_> {

    fn subset(

        &self,

        plan: &Plan,

        _font: &FontRef,

        s: &mut Serializer,

        _builder: &mut FontBuilder,

    ) -> Result<(), SubsetError> {

        s.embed(self.version())

            .map_err(|_| SubsetError::SubsetTableError(Hdmx::TAG))?;

        s.embed(self.num_records())

            .map_err(|_| SubsetError::SubsetTableError(Hdmx::TAG))?;

        let size_device_record = ceil_to_4(2 + plan.num_output_glyphs as u32);

        s.embed(size_device_record)

            .map_err(|_| SubsetError::SubsetTableError(Hdmx::TAG))?;

        for record in self.records().iter() {

            let Ok(r) = record else {

                return Err(SubsetError::SubsetTableError(Hdmx::TAG));

            };

            serialize_device_record(&r, s, plan, size_device_record as usize)

                .map_err(|_| SubsetError::SubsetTableError(Hdmx::TAG))?;

        }

        Ok(())

    }

}

fn serialize_device_record(

    record: &DeviceRecord,

    s: &mut Serializer,

    plan: &Plan,

    size_device_record: usize,

) -> Result<(), SerializeErrorFlags> {

    s.embed(record.pixel_size())?;

    let max_width_pos = s.embed(0_u8)?;

    let widths_array_pos = s.allocate_size(size_device_record - 2, false)?;

    let mut max_width = 0;

    for (new_gid, old_gid) in plan.new_to_old_gid_list.iter() {

        let old_idx = old_gid.to_u32() as usize;

        let Some(wdth) = record.widths().get(old_idx) else {

            return Err(SerializeErrorFlags::SERIALIZE_ERROR_OTHER);

        };

        let new_idx = new_gid.to_u32() as usize;

        s.copy_assign(widths_array_pos + new_idx, *wdth);

        max_width = max_width.max(*wdth);

    }

    s.copy_assign(max_width_pos, max_width);

    Ok(())

}