core: parser: Parse and emit define directives

Signed-off-by: Chloe M. <chloe@aptel.org>

2 files changed, 142 insertions, 1 deletions

diff --git a/core/emit.c b/core/emit.c
new file mode 100644
index 0000000..ec00ed2
--- /dev/null
+++ b/core/emit.c
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2026, Apollo Telephone Laboratories.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <stdio.h>
+#include "defconf/emit.h"
+
+int
+emit_data(const char *ident, struct data_value *v)
+{
+    if (ident == NULL || v == NULL) {
+        return -1;
+    }
+
+    switch (v->type) {
+    case DATA_TYPE_INT:
+        printf("-D%s=%zu\n", ident, v->v);
+        return 0;
+    case DATA_TYPE_STR:
+        printf("-D%s=\"%s\"\n", ident, v->s);
+        return 0;
+    }
+
+    printf("fatal: got bad data value during emission\n");
+    return -1;
+}
diff --git a/core/parser.c b/core/parser.c
index 727d5e1..e568504 100644
--- a/core/parser.c
+++ b/core/parser.c
@@ -6,6 +6,8 @@
 #include "defconf/parser.h"
 #include "defconf/lexer.h"
 #include "defconf/token.h"
+#include "defconf/data.h"
+#include "defconf/emit.h"
 
 /* Symbolic token */
 #define SYMTOK(TOKSTR) \
@@ -31,17 +33,129 @@ static const char *toktab[_TT_MAX] = {
     [TT_IDENT]      = SYMTOK("ident")
 };
 
+static int
+token_to_data(struct token *tok, struct data_value *result)
+{
+    if (tok == NULL || result == NULL) {
+        return -1;
+    }
+
+    switch (tok->type) {
+    case TT_TRUE:
+        result->v = 1;
+        result->type = DATA_TYPE_INT;
+        return 0;
+    case TT_FALSE:
+        result->v = 0;
+        result->type = DATA_TYPE_INT;
+        return 0;
+    default:
+        return -1;
+    }
+
+    return -1;
+}
+
+/*
+ * Assert that the next token is of a specific type
+ *
+ * @state:  Defconf state
+ * @tok:    Last token
+ * @exp:    Expected token
+ */
+static int
+parse_expect(struct defconf_state *state, struct token *tok, tt_t exp)
+{
+    int error;
+
+    if (state == NULL || tok == NULL) {
+        return -1;
+    }
+
+    /* Try to grab the next token */
+    if ((error = lexer_scan(state, tok)) < 0) {
+        printf("fatal: expected '%s', got eof\n", TOKSTR(exp));
+        return error;
+    }
+
+    if (tok->type != exp) {
+        printf("fatal: expected '%s', got %s instead\n",
+            TOKSTR(exp), TOKSTR(tok->type));
+        return -1;
+    }
+
+    return 0;
+}
+
+/*
+ * Parse a define directive
+ *
+ * @state:  Defconf state
+ * @tok:    Last token
+ *
+ * Returns zero on success
+ */
+static int
+parse_define(struct defconf_state *state, struct token *tok)
+{
+    struct data_value value;
+    char *ident;
+    int error;
+
+    if (state == NULL || tok == NULL) {
+        return -1;
+    }
+
+    /* Expect an identifier */
+    if ((error = parse_expect(state, tok, TT_IDENT)) < 0) {
+        return error;
+    }
+
+    /* Save the identifier */
+    ident = tok->s;
+
+    /* Scan the value */
+    if ((error = lexer_scan(state, tok)) < 0) {
+        printf("fatal: expected value, got eof\n");
+        return error;
+    }
+
+    /* Convert token to data */
+    if ((error = token_to_data(tok, &value)) < 0) {
+        printf("fatal: got bad data [%s]\n", TOKSTR(tok->type));
+        return error;
+    }
+
+    /* Emit the define */
+    if ((error = emit_data(ident, &value)) < 0) {
+        return error;
+    }
+
+    return 0;
+}
+
 int
 parse_begin(struct defconf_state *state)
 {
     struct token tok;
+    int error;
 
     if (state == NULL) {
         return -1;
     }
 
     while (lexer_scan(state, &tok) == 0) {
-        printf("got %s\n", TOKSTR(tok.type));
+        switch (tok.type) {
+        case TT_DEFINE:
+            if ((error = parse_define(state, &tok)) < 0) {
+                return error;
+            }
+
+            break;
+        default:
+            printf("fatal: got unexpected token: %s\n", TOKSTR(tok.type));
+            return -1;
+        }
     }
 
     return 0;