refactor(lexer): now use struct instead of static var

src/lexer/lexer.h

@@ -3,6 +3,15 @@
 
 #include <sys/types.h>
 
+struct lexer_context
+{
+    char *end_last_token;
+    ssize_t remaining_chars;
+
+    struct token *last_token;
+    struct token *current_token;
+};
+
 enum lexing_mode
 {
     LEXER_NORMAL,
@@ -55,7 +64,7 @@ struct token
  * @brief: returns the next (newly allocated) token without consuming it.
  *         if end of input is reached, returns a token of type TOKEN_EOF.
  */
-struct token *peek_token(void);
+struct token *peek_token(struct lexer_context *ctx);
 
 /*
  * @brief: returns the next (newly allocated) token and consumes it.
@@ -66,7 +75,7 @@ struct token *peek_token(void);
  *          and returns NULL. This means that after peeking a token EOF
  *          in the parser, there must be EXACTLY ONE call to pop_token().
  */
-struct token *pop_token(void);
+struct token *pop_token(struct lexer_context *ctx);
 
 /* @note: maybe usefull for subshells.
  *
@@ -96,6 +105,6 @@ void free_token(struct token **tok);
  *
  * @return: char* stream from which we tokenise.
  */
-char *stream_init(void);
+char *stream_init(struct lexer_context *ctx);
 
 #endif /* ! LEXER_H */