From 745649df1c4e5a5d27eafba0c610423476c16b3a Mon Sep 17 00:00:00 2001
From: Matteo Flebus <matteo.flebus@epita.fr>
Date: Mon, 12 Jan 2026 21:31:15 +0100
Subject: [PATCH] feat(lexer): finished

---
 src/lexer/lexer.c | 75 +++++++++++++++++++++++++++++++++++------------
 src/lexer/lexer.h |  1 +
 2 files changed, 57 insertions(+), 19 deletions(-)

diff --git a/src/lexer/lexer.c b/src/lexer/lexer.c
index def814c..5d4ba94 100644
--- a/src/lexer/lexer.c
+++ b/src/lexer/lexer.c
@@ -1,15 +1,53 @@
 #include "lexer.h"
 
+#include <ctype.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "io_backend/io_backend.h"
+#include "utils/string_utils/string_utils.h"
 
 static char *end_last_token;
 static ssize_t remaining_chars;
 
+/* @brief: saves state for the next call the the lexer.
+ *
+ */
+static void save_state(char *stream, ssize_t i)
+{
+    remaining_chars -= i;
+    end_last_token = stream + i;
+    return;
+}
+
+/* @return: true if a special character from the grammar was found,
+ *          false otherwise.
+ *
+ */
+static bool is_special_char(char c)
+{
+    return c == '\'' || c == '\n' || c == ';';
+}
+
+/* @return: true if a keyword from the grammar was found, false otherwise.
+ *
+ */
+static bool is_keyword(char *stream, ssize_t i)
+{
+    if (i == 2)
+    {
+        return strcmp(stream, "if") == 0 || strcmp(stream, "fi") == 0;
+    }
+    if (i == 4)
+    {
+        return strcmp(stream, "then") || strcmp(stream, "else")
+            || strcmp(stream, "elif");
+    }
+    return false;
+}
+
 char *new_token(char *begin, ssize_t size)
 {
     char *res = calloc(size + 1, sizeof(char));
@@ -32,6 +70,10 @@ char *stream_init(void)
         stream = end_last_token;
     }
 
+    char *trimed_stream = trim_blanks_left(stream);
+    remaining_chars -= trimed_stream - stream;
+    stream = trimed_stream;
+
     return stream;
 }
 
@@ -39,34 +81,29 @@ char *get_token(void)
 {
     char *stream = stream_init();
 
-    bool inquotes = false;
     ssize_t i = 0;
 
     while (i < remaining_chars)
     {
-        switch (stream[i])
+        if (is_special_char(stream[i]))
         {
-        case '\'':
-            inquotes = !inquotes;
+            if (i == 0) // where we create spe_char token
+                i++;
             break;
-
-        case ' ' | '\n' | '\t':
-            if (inquotes)
-                break;
-            else
-            {
-                // token creation
-                // skip blank char
-                // exit from loop
-                char *token = new_token(stream, i);
-                return token;
-            }
-        default:
+        }
+        if (isblank(stream[i]))
+        {
+            break;
+        }
+        else if (is_keyword(stream, i))
+        {
+            i++;
             break;
         }
         i++;
     }
 
-    remaining_chars -= i;
-    return NULL;
+    save_state(stream, i);
+
+    return new_token(stream, i);
 }
diff --git a/src/lexer/lexer.h b/src/lexer/lexer.h
index 406ca9c..7e7ca10 100644
--- a/src/lexer/lexer.h
+++ b/src/lexer/lexer.h
@@ -30,6 +30,7 @@ char *new_token(char *begin, ssize_t size);
  *         If it is, it calls stream_read() from IO_backend,
  *         and sets [remaing_chars].
  *         If not, it starts from the end of the last token.
+ *         Also trims left blanks before returning.
  *
  * @return: char* stream from which we tokenise.
  */