subsetter 0.2.3

pub(crate) mod font_dict;
pub(crate) mod private_dict;
pub(crate) mod top_dict;

// The `DictionaryParser` was taken from ttf-parser.

use crate::cff::number::{Number, StringId};
use crate::cff::operator::{Operator, TWO_BYTE_OPERATOR_MARK};
use crate::read::Reader;
use std::ops::Range;

pub struct DictionaryParser<'a> {
    data: &'a [u8],
    offset: usize,
    operands_offset: usize,
    operands: &'a mut [Number],
    operands_len: u16,
}

impl<'a> DictionaryParser<'a> {
    pub fn new(data: &'a [u8], operands_buffer: &'a mut [Number]) -> Self {
        DictionaryParser {
            data,
            offset: 0,
            operands_offset: 0,
            operands: operands_buffer,
            operands_len: 0,
        }
    }

    pub fn parse_next(&mut self) -> Option<Operator> {
        let mut r = Reader::new_at(self.data, self.offset);
        self.operands_offset = self.offset;
        while !r.at_end() {
            // 0..=21 bytes are operators.
            if is_dict_one_byte_op(r.peak::<u8>()?) {
                let b = r.read::<u8>()?;
                let mut operator = Operator::from_one_byte(b);

                if b == TWO_BYTE_OPERATOR_MARK {
                    operator = Operator::from_two_byte(r.read::<u8>()?);
                }

                self.offset = r.offset();
                return Some(operator);
            } else {
                let _ = Number::parse_cff_number(&mut r)?;
            }
        }

        None
    }

    pub fn parse_operands(&mut self) -> Option<()> {
        let mut r = Reader::new_at(self.data, self.operands_offset);
        self.operands_len = 0;
        while !r.at_end() {
            let b = r.peak::<u8>()?;
            // 0..=21 bytes are operators.
            if is_dict_one_byte_op(b) {
                r.read::<u8>()?;
                break;
            } else {
                let op = Number::parse_cff_number(&mut r)?;
                self.operands[usize::from(self.operands_len)] = op;
                self.operands_len += 1;

                if usize::from(self.operands_len) >= self.operands.len() {
                    break;
                }
            }
        }

        Some(())
    }

    pub fn operands(&self) -> &[Number] {
        &self.operands[..usize::from(self.operands_len)]
    }

    pub fn parse_sid(&mut self) -> Option<StringId> {
        self.parse_operands()?;
        let operands = self.operands();
        if operands.len() == 1 {
            Some(StringId(u16::try_from(operands[0].as_i32()?).ok()?))
        } else {
            None
        }
    }

    pub fn parse_offset(&mut self) -> Option<usize> {
        self.parse_operands()?;
        let operands = self.operands();
        if operands.len() == 1 {
            usize::try_from(operands[0].as_u32()?).ok()
        } else {
            None
        }
    }

    pub fn parse_font_bbox(&mut self) -> Option<[Number; 4]> {
        self.parse_operands()?;
        let operands = self.operands();
        if operands.len() == 4 {
            Some([operands[0], operands[1], operands[2], operands[3]])
        } else {
            None
        }
    }

    pub fn parse_font_matrix(&mut self) -> Option<[Number; 6]> {
        self.parse_operands()?;
        let operands = self.operands();
        if operands.len() == 6 {
            Some([
                operands[0],
                operands[1],
                operands[2],
                operands[3],
                operands[4],
                operands[5],
            ])
        } else {
            None
        }
    }

    pub fn parse_range(&mut self) -> Option<Range<usize>> {
        self.parse_operands()?;
        let operands = self.operands();
        if operands.len() == 2 {
            let len = usize::try_from(operands[0].as_u32()?).ok()?;
            let start = usize::try_from(operands[1].as_u32()?).ok()?;
            let end = start.checked_add(len)?;
            Some(start..end)
        } else {
            None
        }
    }
}

fn is_dict_one_byte_op(b: u8) -> bool {
    match b {
        0..=27 => true,
        28..=30 => false,  // numbers
        31 => true,        // Reserved
        32..=254 => false, // numbers
        255 => true,       // Reserved
    }
}

/// A subset of the operators for DICT's we care about.
pub(crate) mod operators {
    use crate::cff::operator::{Operator, OperatorType, TWO_BYTE_OPERATOR_MARK};

    // TOP DICT OPERATORS
    pub const NOTICE: Operator = Operator(OperatorType::OneByteOperator([1]));
    pub const FONT_BBOX: Operator = Operator(OperatorType::OneByteOperator([5]));
    pub const COPYRIGHT: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 0]));
    pub const FONT_MATRIX: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 7]));
    pub const CHARSET: Operator = Operator(OperatorType::OneByteOperator([15]));
    pub const ENCODING: Operator = Operator(OperatorType::OneByteOperator([16]));
    pub const CHAR_STRINGS: Operator = Operator(OperatorType::OneByteOperator([17]));
    pub const PRIVATE: Operator = Operator(OperatorType::OneByteOperator([18]));

    // TOP DICT OPERATORS (CID FONTS)
    pub const ROS: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 30]));
    pub const CID_COUNT: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 34]));
    pub const FD_ARRAY: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 36]));
    pub const FD_SELECT: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 37]));
    pub const FONT_NAME: Operator =
        Operator(OperatorType::TwoByteOperator([TWO_BYTE_OPERATOR_MARK, 38]));

    // PRIVATE DICT OPERATORS
    pub const SUBRS: Operator = Operator(OperatorType::OneByteOperator([19]));
}