subsetter 0.2.3

use crate::cff::dict::DictionaryParser;
use crate::cff::index::{create_index, parse_index};
use crate::cff::number::{Number, StringId};
use crate::cff::remapper::SidRemapper;
use crate::cff::{Offsets, DUMMY_VALUE};
use crate::read::Reader;
use crate::write::Writer;
use crate::Error::SubsetError;
use crate::Result;
use std::array;
use std::ops::Range;

// The parsing logic was adapted from ttf-parser.

#[derive(Default, Debug, Clone)]
pub struct TopDictData {
    pub charset: Option<usize>,
    pub char_strings: Option<usize>,
    pub private: Option<Range<usize>>,
    pub fd_array: Option<usize>,
    pub fd_select: Option<usize>,
    pub notice: Option<StringId>,
    pub copyright: Option<StringId>,
    pub font_name: Option<StringId>,
    pub has_ros: bool,
    pub font_matrix: Option<[Number; 6]>,
    pub font_bbox: Option<[Number; 4]>,
}

pub fn parse_top_dict_index(r: &mut Reader) -> Option<TopDictData> {
    use super::operators::*;
    let mut top_dict = TopDictData::default();

    let index = parse_index::<u16>(r)?;

    // The Top DICT INDEX should have only one dictionary in CFF fonts.
    let data = index.get(0)?;

    let mut operands_buffer: [Number; 48] = array::from_fn(|_| Number::zero());
    let mut dict_parser = DictionaryParser::new(data, &mut operands_buffer);

    while let Some(operator) = dict_parser.parse_next() {
        match operator {
            // We only need to preserve the copyrights and font name.
            NOTICE => top_dict.notice = Some(dict_parser.parse_sid()?),
            COPYRIGHT => top_dict.copyright = Some(dict_parser.parse_sid()?),
            FONT_NAME => top_dict.font_name = Some(dict_parser.parse_sid()?),
            CHARSET => top_dict.charset = Some(dict_parser.parse_offset()?),
            // We don't care about encoding since we convert to CID-keyed font anyway.
            ENCODING => {}
            CHAR_STRINGS => top_dict.char_strings = Some(dict_parser.parse_offset()?),
            PRIVATE => top_dict.private = Some(dict_parser.parse_range()?),
            // We will rewrite the ROS, so no need to grab it from here. But we need to
            // register it, so we know we are dealing with a CID-keyed font.
            ROS => top_dict.has_ros = true,
            FD_ARRAY => top_dict.fd_array = Some(dict_parser.parse_offset()?),
            FD_SELECT => top_dict.fd_select = Some(dict_parser.parse_offset()?),
            FONT_MATRIX => top_dict.font_matrix = Some(dict_parser.parse_font_matrix()?),
            FONT_BBOX => top_dict.font_bbox = Some(dict_parser.parse_font_bbox()?),
            _ => {}
        }
    }

    Some(top_dict)
}

/// Rewrite the top dict. Implementation is based on what ghostscript seems to keep when
/// rewriting a font subset.
pub fn rewrite_top_dict_index(
    top_dict_data: &TopDictData,
    offsets: &mut Offsets,
    sid_remapper: &SidRemapper,
    w: &mut Writer,
) -> Result<()> {
    use super::operators::*;

    let mut sub_w = Writer::new();

    // ROS.
    sub_w
        .write(Number::from_i32(sid_remapper.get(b"Adobe").ok_or(SubsetError)?.0 as i32));
    sub_w.write(Number::from_i32(
        sid_remapper.get(b"Identity").ok_or(SubsetError)?.0 as i32,
    ));
    sub_w.write(Number::zero());
    sub_w.write(ROS);

    // Copyright notices.
    if let Some(copyright) =
        top_dict_data.copyright.and_then(|s| sid_remapper.get_new_sid(s))
    {
        sub_w.write(Number::from_i32(copyright.0 as i32));
        sub_w.write(COPYRIGHT);
    }

    if let Some(notice) = top_dict_data.notice.and_then(|s| sid_remapper.get_new_sid(s)) {
        sub_w.write(Number::from_i32(notice.0 as i32));
        sub_w.write(NOTICE);
    }

    // Font name.
    if let Some(font_name) =
        top_dict_data.font_name.and_then(|s| sid_remapper.get_new_sid(s))
    {
        sub_w.write(Number::from_i32(font_name.0 as i32));
        sub_w.write(FONT_NAME);
    }

    // See https://bugs.ghostscript.com/show_bug.cgi?id=690724#c12 and https://leahneukirchen.org/blog/archive/2022/10/50-blank-pages-or-black-box-debugging-of-pdf-rendering-in-printers.html
    // We assume that if at least one font dict has a matrix, all of them do.
    // Case 1: Top DICT MATRIX is some, FONT DICT MATRIX is some -> supplied, supplied
    // Case 2: Top DICT MATRIX is none, FONT DICT MATRIX is some -> (0.001, 0, 0, 0.001, 0, 0), supplied * 1000
    // Case 3: Top DICT MATRIX is some, FONT DICT MATRIX is none -> supplied, (1, 0, 0, 1, 0, 0)
    // Case 4: Top DICT MATRIX is none, FONT DICT MATRIX is none -> (0.001, 0, 0, 0.001, 0 0), (1, 0, 0, 1, 0, 0)
    sub_w.write(top_dict_data.font_matrix.as_ref().unwrap_or(&[
        Number::from_f32(0.001),
        Number::zero(),
        Number::zero(),
        Number::from_f32(0.001),
        Number::zero(),
        Number::zero(),
    ]));
    sub_w.write(FONT_MATRIX);

    // Write a default font bbox, if it does not exist.
    sub_w.write(top_dict_data.font_bbox.as_ref().unwrap_or(&[
        Number::zero(),
        Number::zero(),
        Number::zero(),
        Number::zero(),
    ]));
    sub_w.write(FONT_BBOX);

    // Note: When writing the offsets, we need to add the current length of w AND sub_w.
    // Charset
    offsets.charset_offset.update_location(sub_w.len() + w.len());
    DUMMY_VALUE.write_as_5_bytes(&mut sub_w);
    sub_w.write(CHARSET);

    // Charstrings
    offsets.char_strings_offset.update_location(sub_w.len() + w.len());
    DUMMY_VALUE.write_as_5_bytes(&mut sub_w);
    sub_w.write(CHAR_STRINGS);

    sub_w.write(Number::from_i32(u16::MAX as i32));
    sub_w.write(CID_COUNT);

    // Note: Previously, we wrote those two entries directly after ROS.
    // However, for some reason not known to me, Apple Preview does not like show the CFF font
    // at all if that's the case. This is why we now write the offsets in the very end.

    // FD array.
    offsets.fd_array_offset.update_location(sub_w.len() + w.len());
    DUMMY_VALUE.write_as_5_bytes(&mut sub_w);
    sub_w.write(FD_ARRAY);

    // FD select.
    offsets.fd_select_offset.update_location(sub_w.len() + w.len());
    DUMMY_VALUE.write_as_5_bytes(&mut sub_w);
    sub_w.write(FD_SELECT);

    let finished = sub_w.finish();

    // TOP DICT INDEX always has size 1 in CFF.
    let index = create_index(vec![finished])?;

    // The offsets we calculated before were calculated under the assumption
    // that the contents of sub_w will be appended directly to w. However, when we create an index,
    // the INDEX header data will be appended in the beginning, meaning that we need to adjust the offsets
    // to account for that.
    offsets.charset_offset.adjust_location(index.header_size);
    offsets.char_strings_offset.adjust_location(index.header_size);
    offsets.fd_array_offset.adjust_location(index.header_size);
    offsets.fd_select_offset.adjust_location(index.header_size);

    w.write(index);

    Ok(())
}