heraclitus-compiler 0.2.0

use crate::compiler::{ Compiler, Token, SeparatorMode, ScopingMode };
use super::compound_handler::{CompoundHandler, CompoundReaction};
use super::region_handler::{ RegionHandler, RegionReaction };
use super::reader::Reader;
use crate::compiler::logger::ErrorDetails;

// This is just an estimation of token amount
// inside of a typical 200-lined file.
const AVG_TOKEN_AMOUNT: usize = 1024;

/// Lexer's error type
pub enum LexerErrorType {
    /// Unspillable region has been spilled
    Singleline,
    /// Given region left unclosed
    Unclosed
}

/// Type containing full error of lexer
pub type LexerError = (LexerErrorType, ErrorDetails);

/// The Lexer
/// 
/// Lexer takes source code in a form of a string and translates it to a list of tokens.
/// This particular implementation requires additional metadata such as like regions or symbols.
/// These can be supplied by the `Compiler` in a one cohesive package. Hence the API requires to
/// pass a reference to the `Compiler`.
pub struct Lexer<'a> {
    symbols: Vec<char>,
    compound: CompoundHandler,
    region: RegionHandler,
    reader: Reader<'a>,
    /// This attribute stores parsed tokens by the lexer
    pub lexem: Vec<Token>,
    separator_mode: SeparatorMode,
    scoping_mode: ScopingMode
}

impl<'a> Lexer<'a> {
    /// Create a new Lexer based on the compiler metadata
    pub fn new(cc: &'a Compiler) -> Self {
        Lexer {
            symbols: cc.rules.symbols.clone(),
            compound: CompoundHandler::new(&cc.rules),
            region: RegionHandler::new(&cc.rules),
            reader: Reader::new(&cc.code),
            lexem: Vec::with_capacity(AVG_TOKEN_AMOUNT),
            separator_mode: cc.separator_mode.clone(),
            scoping_mode: cc.scoping_mode.clone()
        }
    }

    /// Add indentation to the lexem
    fn add_indent(&mut self, word: String) -> String {
        if word.len() > 0 {
            // Getting position by word here would attempt to
            // substract with overflow since the new line character
            // technically belongs to the previous line
            let (row, _col) = self.reader.get_position();
            self.lexem.push(Token {
                word,
                pos: (row, 1)
            });
            String::new()
        } else { word }
    }

    /// Add word that has been completed in previous iteration to the lexem
    fn add_word(&mut self, word: String) -> String {
        if word.len() > 0 {
            let (row, col) = self.reader.get_word_position(&word);
            self.lexem.push(Token {
                word,
                pos: (row, col)
            });
            String::new()
        }
        else { word }
    }

    /// Add word that has been completed in current iteration to the lexem
    fn add_word_inclusively(&mut self, word: String) -> String {
        if word.len() > 0 {
            let (row, col) = self.reader.get_word_position(&word);
            self.lexem.push(Token {
                word,
                pos: (row, col + 1)
            });
            String::new()
        }
        else { word }
    }

    /// Checks whether this is a nontokenizable region
    fn is_non_token_region(&self, reaction: RegionReaction) -> bool {
        if let Some(region) = self.region.get_region() {
            !region.tokenize && reaction == RegionReaction::Pass
        }
        else { false }
    }

    /// Pattern code for adding a symbol
    /// **[*]**
    fn pattern_add_symbol(&mut self, mut word: String, letter: char) -> String {
        word = self.add_word(word);
        word.push(letter);
        self.add_word_inclusively(word)
    }

    /// Pattern code for beginning a new region
    /// **[**
    fn pattern_begin(&mut self, mut word: String, letter: char) -> String {
        word = self.add_word(word);
        word.push(letter);
        word
    }

    /// Pattern code for ending current region
    /// **]**
    fn pattern_end(&mut self, mut word: String, letter: char) -> String {
        word.push(letter);
        self.add_word_inclusively(word)
    }

    /// Tokenize source code
    /// 
    /// Run lexer and tokenize code. The result is stored in the lexem attribute
    pub fn run(&mut self) -> Result<(), LexerError> {
        let mut word = String::new();
        let mut is_indenting = false;
        while let Some(letter) = self.reader.next() {
            // Reaction stores the reaction of the region handler
            // Have we just opened or closed some region?
            let reaction = self.region.handle_region(&self.reader);
            match reaction {
                // If the region has been opened
                // Finish the part that we have been parsing
                RegionReaction::Begin => {
                    // This is supposed to prevent overshadowing new line
                    // character if region rule opens with newline
                    if letter == '\n' {
                        word = self.pattern_add_symbol(word, letter);
                    }
                    word = self.pattern_begin(word, letter);
                },
                // If the region has been closed
                // Add the closing region and finish the word
                RegionReaction::End => {
                    word = self.pattern_end(word, letter);
                    // This is supposed to prevent overshadowing new line
                    // character if region rule closes with newline
                    if letter == '\n' {
                        word = self.pattern_add_symbol(word, letter);
                    }
                }
                RegionReaction::Pass => {
                    match self.compound.handle_compound(letter, &self.reader) {
                        CompoundReaction::Begin => word = self.pattern_begin(word, letter),
                        CompoundReaction::Keep => word.push(letter),
                        CompoundReaction::End => word = self.pattern_end(word, letter),
                        CompoundReaction::Pass => {
                            // Handle region scope
                            if self.is_non_token_region(reaction) {
                                let region = self.region.get_region().unwrap();
                                // Handle singleline attribute
                                if letter == '\n' && region.singleline {
                                    let pos = self.reader.get_position();
                                    return Err((
                                        LexerErrorType::Singleline,
                                        ErrorDetails::with_pos(pos).data(region.name.clone())
                                    ))
                                }
                                word.push(letter);
                            }
                            else {

                                /******************/
                                /* Mode modifiers */
                                /******************/

                                // Create indent regions: '\n   '
                                if let ScopingMode::Indent = self.scoping_mode {
                                    // If we are still in the indent region - proceed
                                    if is_indenting && vec![' ', '\t'].contains(&letter) {
                                        word.push(letter);
                                    }
                                    // If it's the new line - start indent region
                                    if letter == '\n' {
                                        is_indenting = true;
                                        word = self.pattern_begin(word, letter);
                                    }
                                    // Check if the current letter
                                    // concludes current indent region
                                    if is_indenting {
                                        if let Some(next_char) = self.reader.peek() {
                                            if !vec![' ', '\t'].contains(&next_char) {
                                                word = self.add_indent(word);
                                                is_indenting = false;
                                            }
                                        }
                                        continue
                                    }
                                }
                                // Skip newline character if we want to manually insert semicolons
                                if let SeparatorMode::Manual = self.separator_mode {
                                    if letter == '\n' {
                                        word = self.add_word(word);
                                        continue
                                    }
                                }

                                /*****************/
                                /* Regular Lexer */
                                /*****************/

                                // Skip whitespace
                                if vec![' ', '\t'].contains(&letter) {
                                    word = self.add_word(word);
                                }
                                // Handle special symbols
                                else if self.symbols.contains(&letter) || letter == '\n' {
                                    word = self.pattern_add_symbol(word, letter);
                                }
                                // Handle word
                                else {
                                    word.push(letter);
                                }
                            }
                        }
                    }
                }
            }
        }
        self.add_word(word);
        // If some region exists that was not closed
        if let Err((pos, region)) = self.region.is_region_closed(&self.reader) {
            return Err((
                LexerErrorType::Unclosed,
                ErrorDetails::with_pos(pos).data(region.name)
            ));
        }
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use crate::rules::{ Region, Rules };
    use crate::reg;
    use crate::compiler::{ Compiler, ScopingMode };

    #[test]
    fn test_lexer_base() {
        let symbols = vec!['(', ')'];
        let regions = reg![
            reg!(string as "String literal" => {
                begin: "'",
                end: "'"
            } => [
                reg!(array as "Array Literal" => {
                    begin: "[",
                    end: "]"
                })
            ])
        ];
        let expected = vec![
            ("let".to_string(), 1, 1),
            ("a".to_string(), 1, 5),
            ("=".to_string(), 1, 7),
            ("(".to_string(), 1, 9),
            ("12".to_string(), 1, 10),
            ("+".to_string(), 1, 13),
            ("32".to_string(), 1, 15),
            (")".to_string(), 1, 17)
        ];
        let rules = Rules::new(symbols, vec![], regions);
        let mut cc: Compiler = Compiler::new("TestScript", rules);
        cc.load("let a = (12 + 32)");
        let mut lexer = super::Lexer::new(&cc);
        let mut result = vec![];
        // Simulate lexing
        let res = lexer.run();
        assert!(res.is_ok());
        for lex in lexer.lexem {
            result.push((lex.word, lex.pos.0, lex.pos.1));
        }
        assert_eq!(expected, result);
    }

    #[test]
    fn test_lexer_string_interp() {
        let symbols = vec!['(', ')'];
        let regions = reg![
            reg!(string_literal as "String literal" => {
                begin: "'",
                end: "'"
            } => [
                reg!(string_interp as "String interpolation" => {
                    begin: "{",
                    end: "}",
                    tokenize: true
                } ref global)
            ])
        ];
        let expected = vec![
            ("let".to_string(), 1, 1),
            ("a".to_string(), 1, 5),
            ("=".to_string(), 1, 7),
            ("'this ".to_string(), 1, 9),
            ("{".to_string(), 1, 15),
            ("'is ".to_string(), 1, 16),
            ("{".to_string(), 1, 20),
            ("'reeeeaaaally'".to_string(), 1, 21),
            ("}".to_string(), 1, 35),
            (" long'".to_string(), 1, 36),
            ("}".to_string(), 1, 42),
            (" text'".to_string(), 1, 43)
        ];
        let rules = Rules::new(symbols, vec![], regions);
        let mut cc: Compiler = Compiler::new("TestScript", rules);
        cc.load("let a = 'this {'is {'reeeeaaaally'} long'} text'");
        let mut lexer = super::Lexer::new(&cc);
        let mut result = vec![];
        // Simulate lexing
        let res = lexer.run();
        assert!(res.is_ok());
        for lex in lexer.lexem {
            result.push((lex.word, lex.pos.0, lex.pos.1));
        }
        assert_eq!(expected, result);
    }

    #[test]
    fn test_lexer_indent_scoping_mode() {
        let symbols = vec![':'];
        let regions = reg![];
        let expected = vec![
            ("if".to_string(), 1, 1),
            ("condition".to_string(), 1, 4),
            (":".to_string(), 1, 13),
            ("\n    ".to_string(), 2, 1),
            ("if".to_string(), 2, 5),
            ("subcondition".to_string(), 2, 8),
            (":".to_string(), 2, 20),
            ("\n        ".to_string(), 3, 1),
            ("pass".to_string(), 3, 9)
        ];
        let rules = Rules::new(symbols, vec![], regions);
        let mut cc: Compiler = Compiler::new("Testhon", rules);
        cc.scoping_mode = ScopingMode::Indent;
        cc.load(vec![
            "if condition:",
            "    if subcondition:",
            "        pass"
        ].join("\n"));
        let mut lexer = super::Lexer::new(&cc);
        let mut result = vec![];
        // Simulate lexing
        let res = lexer.run();
        assert!(res.is_ok());
        for lex in lexer.lexem {
            result.push((lex.word, lex.pos.0, lex.pos.1));
        }
        assert_eq!(expected, result);
    }

    #[test]
    fn test_lexer_manual_separator_mode() {
        let symbols = vec![';', '+', '='];
        let regions = reg![];
        let expected = vec![
            ("let".to_string(), 1, 1),
            ("age".to_string(), 1, 5),
            ("=".to_string(), 1, 9),
            ("12".to_string(), 1, 11),
            ("+".to_string(), 2, 1),
            ("12".to_string(), 3, 1),
            (";".to_string(), 3, 3)
        ];
        let rules = Rules::new(symbols, vec![], regions);
        let mut cc: Compiler = Compiler::new("Testhon", rules);
        cc.load(vec![
            "let age = 12",
            "+",
            "12;"
        ].join("\n"));
        let mut lexer = super::Lexer::new(&cc);
        let mut result = vec![];
        // Simulate lexing
        let res = lexer.run();
        assert!(res.is_ok());
        for lex in lexer.lexem {
            result.push((lex.word, lex.pos.0, lex.pos.1));
        }
        assert_eq!(expected, result);
    }
}