frontend: Add lexer+parser groundwork

Signed-off-by: Ian M. <ian@aptel.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/core/parser.c b/core/parser.c
new file mode 100644
index 0000000..6cf0a4e
--- /dev/null
+++ b/core/parser.c
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2026, Apollo Telephone Laboratories.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <atas/lexer.h>
+
+/* Symbolic token */
+#define SYMTOK(TOK) \
+    "[" TOK "]"
+
+/* Literal token */
+#define LITTOK(TOK) \
+    "'" TOK "'"
+
+/*
+ * Safe macro to index toktab
+ */
+#define TOK_STR(TT)     \
+    ((TT) >= TT_MAX)    \
+        ? "bad"         \
+        : toktab[(TT)]
+
+/*
+ * Lookup table to convert token constants into
+ * strings.
+ */
+static const char *toktab[] = {
+    [TT_NONE]       = SYMTOK("NONE"),
+    [TT_COMMA]      = LITTOK(",")
+};
+
+int
+atas_parse(struct atas_state *state)
+{
+    int error;
+    struct atas_token tok;
+
+    if (state == NULL) {
+        return -1;
+    }
+
+    for (;;) {
+        error = atas_lexer_scan(state, &tok);
+        if (error < 0) {
+            break;
+        }
+
+        printf("got token %s\n", TOK_STR(tok.type));
+    }
+
+    return 0;
+}