refactor: inlining lexical analysis utilities (#29)

Author: DeveloperC286

src/lexical_analysis/mod.rs

@@ -3,10 +3,8 @@ use std::str::Chars;
 
 use crate::lexical_analysis::model::lexical_error::LexicalError;
 use crate::lexical_analysis::model::token::Token;
-use crate::lexical_analysis::utilities::*;
 
 pub(crate) mod model;
-mod utilities;
 
 pub(crate) struct LexicalAnalysis<'a> {
     source_code: Peekable<Chars<'a>>,
@@ -153,3 +151,46 @@ impl<'a> LexicalAnalysis<'a> {
         Ok(string)
     }
 }
+
+fn parse_keyword(parsing: &str) -> Option<Token> {
+    match parsing.to_lowercase().as_str() {
+        "fn" => Some(Token::Function),
+        "let" => Some(Token::Let),
+        "true" => Some(Token::True),
+        "false" => Some(Token::False),
+        "if" => Some(Token::If),
+        "else" => Some(Token::Else),
+        "return" => Some(Token::Return),
+        _ => None,
+    }
+}
+
+fn parse_integer(parsing: &str) -> Option<Token> {
+    match parsing.parse() {
+        Ok(integer) => Some(Token::Integer { literal: integer }),
+        Err(_) => None,
+    }
+}
+
+fn parse_identifier(parsing: &str) -> Option<Token> {
+    if is_valid_identifier(parsing) {
+        Some(Token::Identifier {
+            literal: parsing.to_string(),
+        })
+    } else {
+        None
+    }
+}
+
+fn is_valid_identifier(verifying: &str) -> bool {
+    verifying
+        .chars()
+        .map(is_valid_identifier_character)
+        .filter(|results| !(*results))
+        .count()
+        == 0
+}
+
+fn is_valid_identifier_character(character: char) -> bool {
+    character.is_alphabetic() || character == '_'
+}