1 files changed, 106 insertions, 0 deletions
diff --git a/mod/lookback.c b/mod/lookback.c
new file mode 100644
index 0000000..115f823
--- /dev/null
+++ b/mod/lookback.c
@@ -0,0 +1,106 @@
+/*
+ * melisma - extensible and scriptable audio engine
+ * Copyright (C) 2026  Ludvig Gunne Lindström
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+
+#include <lauxlib.h>
+
+#include "melisma.h"
+#include "mutil.h"
+
+#define LOOKBACK_TYPENAME "lookback"
+
+struct lookback
+{
+	ml_node *node;
+	size_t   cursor;
+	size_t   len;
+	float    buf[];
+};
+
+static void proc(const ml_proc_args *args)
+{
+	struct lookback *lb = args->userp;
+
+	for (size_t i = 0; i < args->nframes; i++)
+	{
+		args->out[0][i] = lb->buf[lb->cursor];
+		lb->buf[lb->cursor] = args->in[0][i];
+
+		lb->cursor++;
+
+		if (lb->cursor == lb->len)
+		{
+			lb->cursor = 0;
+		}
+	}
+}
+
+static int l_init(lua_State *s)
+{
+	float t = luaL_checknumber(s,1);
+	ml_channel *src = mutil_get_channel(s,2);
+
+	unsigned long sr = ml_sample_rate();
+	unsigned long len = sr*t;
+
+	struct lookback *lb = calloc(1,sizeof(*lb) + len*sizeof(lb->buf[0]));
+	lb->len = len;
+
+	ml_node *node = ml_create_node(proc,lb);
+	ml_label_node(node,"lookback");
+	lb->node = node;
+
+	ml_channel *dst = ml_add_input(node);
+	ml_connect(src,dst);
+	ml_add_output(node);
+
+	*(void**) lua_newuserdata(s,sizeof(void*)) = lb;
+	luaL_setmetatable(s,LOOKBACK_TYPENAME);
+
+	return 1;
+}
+
+static int l_out(lua_State *s)
+{
+	struct lookback *lb = *(void**) luaL_checkudata(s,1,LOOKBACK_TYPENAME);
+	*(void**) lua_newuserdata(s,sizeof(void*)) = ml_get_output(lb->node,0);
+	luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
+	return 1;
+}
+
+int luaopen_melisma_lookback(lua_State *s)
+{
+	lua_newtable(s);
+	int tbl = lua_gettop(s);
+
+	lua_pushcfunction(s,l_init);
+	lua_setfield(s,tbl,"init");
+
+	lua_pushcfunction(s,l_out);
+	lua_setfield(s,tbl,MUTIL_OUTPUT_CHANNEL_FUNCTION);
+
+	luaL_newmetatable(s,LOOKBACK_TYPENAME);
+	int mt = lua_gettop(s);
+
+	lua_pushvalue(s,tbl);
+	lua_setfield(s,mt,"__index");
+
+	lua_settop(s,tbl);
+	return 1;
+}