From d86d70fc7c6751713a6b9f02d9f77814e2f75718 Mon Sep 17 00:00:00 2001
From: Johnny Richard <johnny@johnnyrichard.com>
Date: Fri, 21 Apr 2023 15:11:17 +0200
Subject: parser: Parse integers arithmetic expression

This patch implements the AST creation for arithmetic expressions.

NOTE:

The implementation works only for integer numbers.

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>
Reviewed-by: Carlos Maniero <carlosmaniero@gmail.com>
---
 src/parser.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 74 insertions(+), 4 deletions(-)

(limited to 'src/parser.c')

diff --git a/src/parser.c b/src/parser.c
index 176a4a8..ad38125 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -109,16 +109,20 @@ parser_literal_integer_node(ast_node_t *node, token_t *token)
 }
 
 bool
-parser_parse_next_expression(parser_t *parser, ast_node_t *node)
+parser_parse_factor(parser_t *parser, ast_node_t *node)
 {
   token_t token;
   lexer_next_token(parser->lexer, &token);
 
-  if (token.kind == TOKEN_NUMBER)
-  {
+  if (token.kind == TOKEN_NUMBER) {
     return parser_literal_integer_node(node, &token);
+  } else if (token.kind == TOKEN_OPAREN) {
+    parser_parse_expression(parser, node);
+    if (!drop_expected_token(parser, TOKEN_CPAREN)) return false;
+    return true;
   }
 
+  // FIXME: Extract this erros logic to a function
   parser_error_t error;
   error.token = token;
   sprintf(
@@ -128,9 +132,75 @@ parser_parse_next_expression(parser_t *parser, ast_node_t *node)
       SVARG(&token.value)
   );
   parser->errors[parser->errors_len++] = error;
+
   return false;
 }
 
+bool
+parser_parse_term(parser_t *parser, ast_node_t *node)
+{
+  if (!parser_parse_factor(parser, node)) return false;
+
+  token_t token;
+  lexer_next_token(parser->lexer, &token);
+
+  while (token.kind == TOKEN_OP && (string_view_eq(token.value, string_view_from_str("*")) || string_view_eq(token.value, string_view_from_str("/")))) {
+    ast_node_t *binary_op = ast_node_new();
+    binary_op->kind = AST_BINARY_OPERATION;
+    binary_op->data.binary_operation.op = token.value;
+
+    binary_op->data.binary_operation.left = ast_node_new();
+    *binary_op->data.binary_operation.left = *node;
+
+    binary_op->data.binary_operation.right = ast_node_new();
+    if (!parser_parse_factor(parser, binary_op->data.binary_operation.right)) return false;
+
+    *node = *binary_op;
+
+    lexer_next_token(parser->lexer, &token);
+  }
+
+  lexer_step_back_to(parser->lexer, &token);
+
+  return true;
+}
+
+/**
+ *
+ * <expression> ::= <term> (('+' | '-') term)*
+ * <term>       ::= <factor> (('*' | '/') factor)*
+ * <factor>     ::= <integer> | '(' <expression> ')'
+ *
+ */
+bool
+parser_parse_expression(parser_t *parser, ast_node_t *node)
+{
+  if (!parser_parse_term(parser, node)) return false;
+
+  token_t token;
+  lexer_next_token(parser->lexer, &token);
+
+  while (token.kind == TOKEN_OP && (string_view_eq(token.value, string_view_from_str("+")) || string_view_eq(token.value, string_view_from_str("-")))) {
+
+    ast_node_t *binary_op = ast_node_new();
+    binary_op->kind = AST_BINARY_OPERATION;
+    binary_op->data.binary_operation.op = token.value;
+
+    binary_op->data.binary_operation.left = ast_node_new();
+    *binary_op->data.binary_operation.left = *node;
+
+    binary_op->data.binary_operation.right = ast_node_new();
+    if (!parser_parse_term(parser, binary_op->data.binary_operation.right)) return false;
+
+    *node = *binary_op;
+    lexer_next_token(parser->lexer, &token);
+  }
+
+  lexer_step_back_to(parser->lexer, &token);
+
+  return true;
+}
+
 bool
 parser_parse_return_stmt(parser_t *parser, ast_node_t *node)
 {
@@ -155,7 +225,7 @@ parser_parse_return_stmt(parser_t *parser, ast_node_t *node)
   }
 
   ast_node_t *argument_token = ast_node_new();
-  if (!parser_parse_next_expression(parser, argument_token)) return false;
+  if (!parser_parse_expression(parser, argument_token)) return false;
 
   if (!drop_expected_token(parser, TOKEN_SEMICOLON)) return false;
   if (!drop_expected_token(parser, TOKEN_CCURLY)) return false;
-- 
cgit v1.2.3