From 94ac826cde6bfdd12136ace6285af71dd5181a1d Mon Sep 17 00:00:00 2001
From: omicron <omicron.me@protonmail.com>
Date: Tue, 1 Apr 2025 20:05:35 +0200
Subject: [PATCH] Add basic parser combinators

---
 src/parser_combinators.c | 75 ++++++++++++++++++++++++++++++++++++++++
 src/parser_combinators.h | 16 +++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 src/parser_combinators.c
 create mode 100644 src/parser_combinators.h

diff --git a/src/parser_combinators.c b/src/parser_combinators.c
new file mode 100644
index 0000000..dfb73c4
--- /dev/null
+++ b/src/parser_combinators.c
@@ -0,0 +1,75 @@
+#include "parser_combinators.h"
+
+parse_result_t parse_any(tokenlist_entry_t *current, parser_t parsers[]) {
+    for (parser_t parser = *parsers; parser; parser = *parsers++) {
+        parse_result_t result = parser(current);
+        if (result.err == nullptr)
+            return result;
+    }
+    return parse_no_match();
+}
+
+// parse as many of the giver parsers objects in a row as possible, potentially
+// allowing none wraps the found objects in a new ast node with the given note
+// id
+parse_result_t parse_many(tokenlist_entry_t *current, node_id_t id,
+                          bool allow_none, parser_t parser) {
+    ast_node_t *many;
+    error_t *err = ast_node_alloc(&many);
+    parse_result_t result;
+    if (err)
+        return parse_error(err);
+    many->id = id;
+
+    while (current) {
+        result = parser(current);
+        if (result.err == err_parse_no_match)
+            break;
+        if (result.err) {
+            ast_node_free(many);
+            return result;
+        }
+        err = ast_node_add_child(many, result.node);
+        if (err) {
+            ast_node_free(many);
+            ast_node_free(result.node);
+            return parse_error(err);
+        }
+        current = result.next;
+    }
+
+    if (!allow_none && many->len == 0) {
+        ast_node_free(many);
+        return parse_no_match();
+    }
+    return parse_success(many, current);
+}
+
+// Parse all tries to parse all parsers consecutively and if it succeeds it
+// wraps the parsed nodes in a new parent node.
+parse_result_t parse_consecutive(tokenlist_entry_t *current, node_id_t id,
+                                 parser_t parsers[]) {
+    ast_node_t *all;
+    error_t *err = ast_node_alloc(&all);
+    parse_result_t result;
+    if (err)
+        return parse_no_match();
+
+    all->id = id;
+
+    for (parser_t parser = *parsers; parser && current; parser = *parsers++) {
+        result = parser(current);
+        if (result.err) {
+            ast_node_free(all);
+            return result;
+        }
+        err = ast_node_add_child(all, result.node);
+        if (err) {
+            ast_node_free(result.node);
+            ast_node_free(all);
+            return parse_error(err);
+        }
+        current = result.next;
+    }
+    return parse_success(all, current);
+}
diff --git a/src/parser_combinators.h b/src/parser_combinators.h
new file mode 100644
index 0000000..2bfcc93
--- /dev/null
+++ b/src/parser_combinators.h
@@ -0,0 +1,16 @@
+#include "parser_util.h"
+
+typedef parse_result_t (*parser_t)(tokenlist_entry_t *);
+
+parse_result_t parse_any(tokenlist_entry_t *current, parser_t parsers[]);
+
+// parse as many of the giver parsers objects in a row as possible, potentially
+// allowing none wraps the found objects in a new ast node with the given note
+// id
+parse_result_t parse_many(tokenlist_entry_t *current, node_id_t id,
+                          bool allow_none, parser_t parser);
+
+// Parse all tries to parse all parsers consecutively and if it succeeds it
+// wraps the parsed nodes in a new parent node.
+parse_result_t parse_consecutive(tokenlist_entry_t *current, node_id_t id,
+                                 parser_t parsers[]);