lisp-8bit/src/parser.rs

use crate::*;

#[derive(Debug)]
pub struct Parser {
    row: usize,
    column: usize,
    lines: Vec<Vec<char>>,
}

#[derive(Debug)]
pub(crate) struct Instruction {
    name: String,
    arguments: Vec<Value>,
}

#[derive(Debug)]
enum Value {
    Instruction(Instruction),
    StringLiteral(String),
    IntegerLiteral(usize),
    Identifier(String),
}

impl Parser {
    pub fn parse(stream: String) -> Result<Instruction> {
        let mut parser = Parser {
            row: 0,
            column: 0,
            lines: stream
                .split('\n')
                .map(|a| a.chars().collect::<Vec<_>>())
                .collect::<Vec<_>>(),
        };
        parser.instruction()
    }

    fn increment(&mut self) -> Option<()> {
        self.column += 1;
        if self.column == self.lines[self.row].len() {
            self.row += 1;
            if self.row == self.lines.len() {
                self.row -= 1;
                self.column -= 1;
                return None;
            }
            self.column = 0;
        }
        return Some(());
    }

    fn jump_whitespace(&mut self) -> Option<()> {
        self.increment()?;
        while self.lines[self.row][self.column].is_whitespace() {
            self.increment()?;
        }
        Some(())
    }

    fn instruction(&mut self) -> Result<Instruction> {
        if self.lines[self.row][self.column] != '(' {
            return Err(Error::SyntaxError(SyntaxError {
                row: self.row,
                column: self.column,
                message: "SyntaxError: Expected '('".to_string(),
            }));
        }

        self.jump_whitespace();

        let name = self.identifier()?;

        let mut arguments = Vec::new();

        while self.lines[self.row][self.column] != ')' {
            match self.lines[self.row][self.column] {
                '\"' => arguments.push(Value::StringLiteral(self.string_literal()?)),
                '(' => arguments.push(Value::Instruction(self.instruction()?)),
                character => {
                    if character.is_numeric() {
                        arguments.push(Value::IntegerLiteral(self.integer_literal()?));
                    } else {
                        arguments.push(Value::Identifier(self.identifier()?));
                    }
                }
            }
        }

        self.jump_whitespace();

        return Ok(Instruction { name, arguments });
    }

    fn string_literal(&mut self) -> Result<String> {
        self.increment();

        let mut accumulator = String::new();

        while self.lines[self.row][self.column] != '"' {
            accumulator.push(self.lines[self.row][self.column]);
            self.increment();
        }

        self.jump_whitespace();

        Ok(accumulator)
    }

    fn integer_literal(&mut self) -> Result<usize> {
        let mut accumulator = String::new();

        while self.lines[self.row][self.column].is_numeric() {
            accumulator.push(self.lines[self.row][self.column]);
            self.increment();
        }

        self.jump_whitespace();

        match accumulator.parse::<usize>() {
            Ok(v) => Ok(v),
            Err(_e) => Err(Error::SyntaxError(SyntaxError {
                row: self.row,
                column: self.column,
                message: "Couldn't parse integer literal".to_string(),
            })),
        }
    }

    fn identifier(&mut self) -> Result<String> {
        let mut accumulator = String::new();

        let mut current = self.lines[self.row][self.column];

        while !"()\"".contains(current) && !current.is_whitespace() {
            accumulator.push(self.lines[self.row][self.column]);
            self.increment();
            current = self.lines[self.row][self.column];
        }

        self.jump_whitespace();

        Ok(accumulator)
    }
}