From 54d5c081eb48724bf8afdcb93b932c45723b782b Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Fri, 4 Jul 2025 15:38:42 +0100
Subject: [PATCH] substitute: implement an interface for performing variable
 reference substitution

---
 src/substitute.c | 104 +++++++++++++++++++++++++++++++++++++++++++++++
 src/substitute.h |  25 ++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 src/substitute.c
 create mode 100644 src/substitute.h

diff --git a/src/substitute.c b/src/substitute.c
new file mode 100644
index 0000000..dc92eeb
--- /dev/null
+++ b/src/substitute.c
@@ -0,0 +1,104 @@
+#include "substitute.h"
+
+#define INVALID_INDEX ((size_t) - 1)
+
+enum ec3_status substitution_list_init(struct substitution_list *list)
+{
+	memset(list, 0x0, sizeof *list);
+	list->s_entries = b_dict_create();
+
+	return EC3_SUCCESS;
+}
+
+enum ec3_status substitution_list_finish(struct substitution_list *list)
+{
+	b_dict_release(list->s_entries);
+	list->s_entries = NULL;
+
+	return EC3_SUCCESS;
+}
+
+enum ec3_status substitution_list_add_substitution(
+	struct substitution_list *list,
+	const char *find,
+	const char *replace_with)
+{
+	b_string *sub = b_string_create_from_cstr(replace_with);
+	b_status status = b_dict_put(list->s_entries, find, B_OBJECT(sub));
+	b_string_release(sub);
+
+	if (!B_OK(status)) {
+		return ec3_status_from_b_status(
+			status,
+			EC3_ERR_INTERNAL_FAILURE);
+	}
+
+	return EC3_SUCCESS;
+}
+
+static enum ec3_status perform_substitution(
+	struct substitution_list *list,
+	b_string *base,
+	size_t sub_start,
+	size_t sub_end)
+{
+	char sub[128];
+	const char *s = b_string_ptr(base);
+	size_t sub_name_length = sub_end - sub_start - 2;
+	memcpy(sub, s + sub_start + 2, sub_name_length);
+	sub[sub_name_length] = '\0';
+
+	b_string *value = B_STRING(b_dict_at(list->s_entries, sub));
+	if (value) {
+		b_string_replace(
+			base,
+			sub_start,
+			sub_end - sub_start + 1,
+			b_string_ptr(value));
+	} else {
+		b_string_remove(base, sub_start, sub_end - sub_start + 1);
+	}
+
+	return EC3_SUCCESS;
+}
+
+enum ec3_status substitution_list_substitute(
+	struct substitution_list *list,
+	b_string *str)
+{
+	const char *s = b_string_ptr(str);
+
+	size_t sub_start = INVALID_INDEX;
+	enum ec3_status status = EC3_SUCCESS;
+
+	for (size_t i = 0; s[i]; i++) {
+		if (s[i] == '$' && s[i + 1] == '{') {
+			if (sub_start != INVALID_INDEX) {
+				status = EC3_ERR_BAD_FORMAT;
+				break;
+			}
+
+			sub_start = i;
+		} else if (s[i] == '}') {
+			if (sub_start == INVALID_INDEX) {
+				status = EC3_ERR_BAD_FORMAT;
+				break;
+			}
+
+			size_t sub_end = i;
+			status = perform_substitution(
+				list,
+				str,
+				sub_start,
+				sub_end);
+			if (status != EC3_SUCCESS) {
+				break;
+			}
+
+			sub_start = INVALID_INDEX;
+			s = b_string_ptr(str);
+		}
+	}
+
+	return status;
+}
diff --git a/src/substitute.h b/src/substitute.h
new file mode 100644
index 0000000..2b15e9f
--- /dev/null
+++ b/src/substitute.h
@@ -0,0 +1,25 @@
+#ifndef SUBSTITUTE_H_
+#define SUBSTITUTE_H_
+
+#include "status.h"
+
+#include <blue/object/dict.h>
+#include <blue/object/string.h>
+
+struct substitution_list {
+	b_dict *s_entries;
+};
+
+extern enum ec3_status substitution_list_init(struct substitution_list *list);
+extern enum ec3_status substitution_list_finish(struct substitution_list *list);
+
+extern enum ec3_status substitution_list_add_substitution(
+	struct substitution_list *list,
+	const char *find,
+	const char *replace_with);
+
+extern enum ec3_status substitution_list_substitute(
+	struct substitution_list *list,
+	b_string *str);
+
+#endif