vis: refactor Lua integration

Lua support can now be disabled at compile time using:

 $ make CONFIG_LUA=0

This commit also adds an initial Lua API and provides a few
default hooks.

We now also require Lua >= 5.2 due to the uservalue constructs.
In principle the same functionality could be implemented using
function environments from Lua 5.1.

13 files changed, 746 insertions, 273 deletions

diff --git a/Makefile b/Makefile
index 16d62cb..5e71790 100644
--- a/Makefile
+++ b/Makefile
@@ -21,10 +21,10 @@ LIBTERMKEY_SHA1 = 0a78ba7aaa2f3b53f2273268366fef349c9be4ab
 
 #LIBLUA = lua-5.3.1
 #LIBLUA_SHA1 = 1676c6a041d90b6982db8cef1e5fb26000ab6dee
-#LIBLUA = lua-5.2.4
-#LIBLUA_SHA1 = ef15259421197e3d85b7d6e4871b8c26fd82c1cf
-LIBLUA = lua-5.1.5
-LIBLUA_SHA1 = b3882111ad02ecc6b972f8c1241647905cb2e3fc
+LIBLUA = lua-5.2.4
+LIBLUA_SHA1 = ef15259421197e3d85b7d6e4871b8c26fd82c1cf
+#LIBLUA = lua-5.1.5
+#LIBLUA_SHA1 = b3882111ad02ecc6b972f8c1241647905cb2e3fc
 
 LIBLPEG = lpeg-1.0.0
 LIBLPEG_SHA1 = 64a0920c9243b624a277c987d2219b6c50c43971
diff --git a/README.md b/README.md
index 58a0a6f..a349381 100644
--- a/README.md
+++ b/README.md
@@ -610,7 +610,7 @@ In order to build vis you will need a C99 compiler as well as:
  * [libcurses](http://www.gnu.org/software/ncurses/), preferably in the
    wide-character version
  * [libtermkey](http://www.leonerd.org.uk/code/libtermkey/)
- * [lua](http://www.lua.org/) >= 5.1
+ * [lua](http://www.lua.org/) >= 5.2
  * [LPeg](http://www.inf.puc-rio.br/~roberto/lpeg/) >= 0.12 (runtime
    dependency required for syntax highlighting)
 
diff --git a/config.mk b/config.mk
index f11e8c1..0391284 100644
--- a/config.mk
+++ b/config.mk
@@ -1,6 +1,7 @@
 # optional features
 HAVE_ACL=0
 HAVE_SELINUX=0
+CONFIG_LUA=1
 
 # vis version
 RELEASE = HEAD
@@ -26,17 +27,22 @@ PREFIX ?= /usr/local
 MANPREFIX = ${PREFIX}/share/man
 SHAREPREFIX = ${PREFIX}/share/vis
 
-CFLAGS_LUA = $(shell pkg-config --cflags lua5.1 2> /dev/null || echo "-I/usr/include/lua5.1")
-CFLAGS_TERMKEY = $(shell pkg-config --cflags termkey 2> /dev/null || echo "")
-CFLAGS_CURSES = $(shell pkg-config --cflags ncursesw 2> /dev/null || echo "-I/usr/include/ncursesw")
+ifeq (${CONFIG_LUA},1)
+	CFLAGS_LUA = $(shell pkg-config --cflags lua5.2 2> /dev/null || echo "-I/usr/include/lua5.2")
+	LDFLAGS_LUA = $(shell pkg-config --libs lua5.2 2> /dev/null || echo "-llua")
+endif
 
-LDFLAGS_LUA = $(shell pkg-config --libs lua5.1 2> /dev/null || echo "-llua")
+CFLAGS_TERMKEY = $(shell pkg-config --cflags termkey 2> /dev/null || echo "")
 LDFLAGS_TERMKEY = $(shell pkg-config --libs termkey 2> /dev/null || echo "-ltermkey")
+
+CFLAGS_CURSES = $(shell pkg-config --cflags ncursesw 2> /dev/null || echo "-I/usr/include/ncursesw")
 LDFLAGS_CURSES = $(shell pkg-config --libs ncursesw 2> /dev/null || echo "-lncursesw")
 
 LIBS = -lm -ldl -lc
 OS = $(shell uname)
 
+CFLAGS += -DCONFIG_LUA=${CONFIG_LUA}
+
 ifeq (${OS},Linux)
 	ifeq (${HAVE_SELINUX},1)
 		CFLAGS += -DHAVE_SELINUX
diff --git a/main.c b/main.c
index 5bb04d4..b0f5b8d 100644
--- a/main.c
+++ b/main.c
@@ -6,6 +6,7 @@
 
 #include "ui-curses.h"
 #include "vis.h"
+#include "vis-lua.h"
 #include "text-util.h"
 #include "text-motions.h"
 #include "text-objects.h"
@@ -1620,7 +1621,17 @@ static void signal_handler(int signum, siginfo_t *siginfo, void *context) {
 
 int main(int argc, char *argv[]) {
 
-	vis = vis_new(ui_curses_new());
+	VisEvent event = {
+		.vis_start = vis_lua_start,
+		.vis_quit = vis_lua_quit,
+		.file_open = vis_lua_file_open,
+		.file_save = vis_lua_file_save,
+		.file_close = vis_lua_file_close,
+		.win_open = vis_lua_win_open,
+		.win_close = vis_lua_win_close,
+	};
+
+	vis = vis_new(ui_curses_new(), &event);
 	if (!vis)
 		return EXIT_FAILURE;
 
diff --git a/ui-curses.c b/ui-curses.c
index 5535dbc..a9ae5f9 100644
--- a/ui-curses.c
+++ b/ui-curses.c
@@ -26,8 +26,9 @@
 #include <poll.h>
 #include <sys/ioctl.h>
 
-#include "ui.h"
 #include "ui-curses.h"
+#include "vis.h"
+#include "text.h"
 #include "util.h"
 #include "text-util.h"
 
diff --git a/view.c b/view.c
index 4e3f869..76d7a45 100644
--- a/view.c
+++ b/view.c
@@ -19,7 +19,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <regex.h>
-#include "vis.h"
+#include "vis-lua.h"
 #include "view.h"
 #include "text.h"
 #include "text-motions.h"
@@ -115,6 +115,178 @@ static void view_cursors_free(Cursor *c);
 /* set/move current cursor position to a given (line, column) pair */
 static size_t cursor_set(Cursor *cursor, Line *line, int col);
 
+#if !CONFIG_LUA
+
+static void view_syntax_color(View *view) { }
+bool view_syntax_set(View *view, const char *name) { return false; }
+
+#else
+
+static void view_syntax_color(View *view) {
+	lua_State *L = view->lua;
+	if (!L || !view->lexer_name)
+		return;
+	lua_getglobal(L, "vis");
+	lua_getfield(L, -1, "lexers");
+	if (lua_isnil(L, -1))
+		return;
+
+	/* maximal number of bytes to consider for syntax highlighting before
+	 * the visible area */
+	const size_t lexer_before_max = 16384;
+	/* absolute position to start syntax highlighting */
+	const size_t lexer_start = view->start >= lexer_before_max ? view->start - lexer_before_max : 0;
+	/* number of bytes used for syntax highlighting before visible are */
+	const size_t lexer_before = view->start - lexer_start;
+	/* number of bytes to read in one go */
+	const size_t text_size = lexer_before + (view->end - view->start);
+	/* current buffer to work with */
+	char text[text_size+1];
+	/* bytes to process */
+	const size_t text_len = text_bytes_get(view->text, lexer_start, text_size, text);
+	/* NUL terminate text section */
+	text[text_len] = '\0';
+
+	lua_getfield(L, -1, "load");
+	lua_pushstring(L, view->lexer_name);
+	lua_pcall(L, 1, 1, 0);
+
+	lua_getfield(L, -1, "_TOKENSTYLES");
+	lua_getfield(L, -2, "lex");
+
+	lua_pushvalue(L, -3); /* lexer obj */
+
+	const char *lex_text = text;
+	if (lexer_start > 0) {
+		/* try to start lexing at a line boundry */
+		/* TODO: start at known state, handle nested lexers */
+		const char *newline = memchr(text, '\n', lexer_before);
+		if (newline)
+			lex_text = newline;
+	}
+
+	lua_pushlstring(L, lex_text, text_len - (lex_text - text));
+	lua_pushinteger(L, 1 /* inital style: whitespace */);
+
+	int token_count;
+
+	if (lua_isfunction(L, -4) &&  !lua_pcall(L, 3, 1, 0) && lua_istable(L, -1) &&
+	   (token_count = lua_objlen(L, -1)) > 0) {
+
+		size_t pos = lexer_before - (lex_text - text);
+		Line *line = view->topline;
+		int col = 0;
+
+		for (int i = 1; i < token_count; i += 2) {
+			lua_rawgeti(L, -1, i);
+			//const char *name = lua_tostring(L, -1);
+			lua_gettable(L, -3); /* _TOKENSTYLES[token] */
+			size_t token_style = lua_tointeger(L, -1);
+			lua_pop(L, 1); /* style */
+			lua_rawgeti(L, -1, i + 1);
+			size_t token_end = lua_tointeger(L, -1) - 1;
+			lua_pop(L, 1); /* pos */
+
+			for (bool token_next = false; line; line = line->next, col = 0) {
+				for (; col < line->width; col++) {
+					if (pos < token_end) {
+						line->cells[col].attr = token_style;
+						pos += line->cells[col].len;
+					} else {
+						token_next = true;
+						break;
+					}
+				}
+				if (token_next)
+					break;
+			}
+		}
+		lua_pop(L, 1);
+	}
+
+	lua_pop(L, 3); /* _TOKENSTYLES, language specific lexer, lexers global */
+}
+
+bool view_syntax_set(View *view, const char *name) {
+	if (!name) {
+		free(view->lexer_name);
+		view->lexer_name = NULL;
+		return true;
+	}
+
+	lua_State *L = view->lua;
+	if (!L)
+		return false;
+
+	/* Try to load the specified lexer and parse its token styles.
+	 * Roughly equivalent to the following lua code:
+	 *
+	 * lang = vis.lexers.load(name)
+	 * for token_name, id in pairs(lang._TOKENSTYLES) do
+	 * 	ui->syntax_style(id, vis.lexers:get_style(lang, token_name);
+	 */
+	lua_getglobal(L, "vis");
+	lua_getfield(L, -1, "lexers");
+
+	lua_getfield(L, -1, "STYLE_DEFAULT");
+	view->ui->syntax_style(view->ui, UI_STYLE_DEFAULT, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_CURSOR");
+	view->ui->syntax_style(view->ui, UI_STYLE_CURSOR, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_CURSOR_LINE");
+	view->ui->syntax_style(view->ui, UI_STYLE_CURSOR_LINE, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_SELECTION");
+	view->ui->syntax_style(view->ui, UI_STYLE_SELECTION, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_LINENUMBER");
+	view->ui->syntax_style(view->ui, UI_STYLE_LINENUMBER, lua_tostring(L, -1));
+	lua_pop(L, 1);
+	lua_getfield(L, -1, "STYLE_COLOR_COLUMN");
+	view->ui->syntax_style(view->ui, UI_STYLE_COLOR_COLUMN, lua_tostring(L, -1));
+	lua_pop(L, 1);
+
+	lua_getfield(L, -1, "load");
+	lua_pushstring(L, name);
+
+	if (lua_pcall(L, 1, 1, 0))
+		return false;
+
+	if (!lua_istable(L, -1)) {
+		lua_pop(L, 2);
+		return false;
+	}
+
+	view->lexer_name = strdup(name);
+	/* loop through all _TOKENSTYLES and parse them */
+	lua_getfield(L, -1, "_TOKENSTYLES");
+	lua_pushnil(L); /* first key */
+
+	while (lua_next(L, -2)) {
+		size_t id = lua_tointeger(L, -1);
+		//const char *name = lua_tostring(L, -2);
+		lua_pop(L, 1); /* remove value (=id), keep key (=name) */
+		lua_getfield(L, -4, "get_style");
+		lua_pushvalue(L, -5); /* lexer */
+		lua_pushvalue(L, -5); /* lang */
+		lua_pushvalue(L, -4); /* token_name */
+		if (lua_pcall(L, 3, 1, 0))
+			return false;
+		const char *style = lua_tostring(L, -1);
+		//printf("%s\t%d\t%s\n", name, id, style);
+		view->ui->syntax_style(view->ui, id, style);
+		lua_pop(L, 1); /* style */
+	}
+
+	lua_pop(L, 4); /* _TOKENSTYLES, grammar, lexers, vis */
+
+	return true;
+}
+
+#endif
+
+
 void view_tabwidth_set(View *view, int tabwidth) {
 	view->tabwidth = tabwidth;
 	view_draw(view);
@@ -456,86 +628,8 @@ void view_draw(View *view) {
 void view_update(View *view) {
 	if (!view->need_update)
 		return;
-	/* maximal number of bytes to consider for syntax highlighting before
-	 * the visible area */
-	const size_t lexer_before_max = 16384;
-	/* absolute position to start syntax highlighting */
-	const size_t lexer_start = view->start >= lexer_before_max ? view->start - lexer_before_max : 0;
-	/* number of bytes used for syntax highlighting before visible are */
-	const size_t lexer_before = view->start - lexer_start;
-	/* number of bytes to read in one go */
-	const size_t text_size = lexer_before + (view->end - view->start);
-	/* current buffer to work with */
-	char text[text_size+1];
-	/* bytes to process */
-	const size_t text_len = text_bytes_get(view->text, lexer_start, text_size, text);
-	/* NUL terminate text section */
-	text[text_len] = '\0';
-
-	lua_State *L = view->lua;
-	if (L && view->lexer_name) {
-
-		lua_getglobal(L, "vis");
-		lua_getfield(L, -1, "lexers");
-		lua_getfield(L, -1, "load");
-		lua_pushstring(L, view->lexer_name);
-		lua_pcall(L, 1, 1, 0);
-
-		lua_getfield(L, -1, "_TOKENSTYLES");
-		lua_getfield(L, -2, "lex");
-
-		lua_pushvalue(L, -3); /* lexer obj */
-
-		const char *lex_text = text;
-		if (lexer_start > 0) {
-			/* try to start lexing at a line boundry */
-			/* TODO: start at known state, handle nested lexers */
-			const char *newline = memchr(text, '\n', lexer_before);
-			if (newline)
-				lex_text = newline;
-		}
-
-		lua_pushlstring(L, lex_text, text_len - (lex_text - text));
-		lua_pushinteger(L, 1 /* inital style: whitespace */);
-
-		int token_count;
-
-		if (lua_isfunction(L, -4) &&  !lua_pcall(L, 3, 1, 0) && lua_istable(L, -1) &&
-		   (token_count = lua_objlen(L, -1)) > 0) {
-
-			size_t pos = lexer_before - (lex_text - text);
-			Line *line = view->topline;
-			int col = 0;
-
-			for (int i = 1; i < token_count; i += 2) {
-				lua_rawgeti(L, -1, i);
-				//const char *name = lua_tostring(L, -1);
-				lua_gettable(L, -3); /* _TOKENSTYLES[token] */
-				size_t token_style = lua_tointeger(L, -1);
-				lua_pop(L, 1); /* style */
-				lua_rawgeti(L, -1, i + 1);
-				size_t token_end = lua_tointeger(L, -1) - 1;
-				lua_pop(L, 1); /* pos */
-
-				for (bool token_next = false; line; line = line->next, col = 0) {
-					for (; col < line->width; col++) {
-						if (pos < token_end) {
-							line->cells[col].attr = token_style;
-							pos += line->cells[col].len;
-						} else {
-							token_next = true;
-							break;
-						}
-					}
-					if (token_next)
-						break;
-				}
-			}
-			lua_pop(L, 1);
-		}
 
-		lua_pop(L, 3); /* _TOKENSTYLES, language specific lexer, lexers global */
-	}
+	view_syntax_color(view);
 
 	if (view->colorcolumn > 0 && view->colorcolumn <= view->width) {
 		size_t lineno = 0;
@@ -906,83 +1000,6 @@ void view_scroll_to(View *view, size_t pos) {
 	view_cursors_scroll_to(view->cursor, pos);
 }
 
-bool view_syntax_set(View *view, const char *name) {
-	if (!name) {
-		free(view->lexer_name);
-		view->lexer_name = NULL;
-		return true;
-	}
-
-	lua_State *L = view->lua;
-	if (!L)
-		return false;
-
-	/* Try to load the specified lexer and parse its token styles.
-	 * Roughly equivalent to the following lua code:
-	 *
-	 * lang = vis.lexers.load(name)
-	 * for token_name, id in pairs(lang._TOKENSTYLES) do
-	 * 	ui->syntax_style(id, vis.lexers:get_style(lang, token_name);
-	 */
-	lua_getglobal(L, "vis");
-	lua_getfield(L, -1, "lexers");
-
-	lua_getfield(L, -1, "STYLE_DEFAULT");
-	view->ui->syntax_style(view->ui, UI_STYLE_DEFAULT, lua_tostring(L, -1));
-	lua_pop(L, 1);
-	lua_getfield(L, -1, "STYLE_CURSOR");
-	view->ui->syntax_style(view->ui, UI_STYLE_CURSOR, lua_tostring(L, -1));
-	lua_pop(L, 1);
-	lua_getfield(L, -1, "STYLE_CURSOR_LINE");
-	view->ui->syntax_style(view->ui, UI_STYLE_CURSOR_LINE, lua_tostring(L, -1));
-	lua_pop(L, 1);
-	lua_getfield(L, -1, "STYLE_SELECTION");
-	view->ui->syntax_style(view->ui, UI_STYLE_SELECTION, lua_tostring(L, -1));
-	lua_pop(L, 1);
-	lua_getfield(L, -1, "STYLE_LINENUMBER");
-	view->ui->syntax_style(view->ui, UI_STYLE_LINENUMBER, lua_tostring(L, -1));
-	lua_pop(L, 1);
-	lua_getfield(L, -1, "STYLE_COLOR_COLUMN");
-	view->ui->syntax_style(view->ui, UI_STYLE_COLOR_COLUMN, lua_tostring(L, -1));
-	lua_pop(L, 1);
-
-	lua_getfield(L, -1, "load");
-	lua_pushstring(L, name);
-
-	if (lua_pcall(L, 1, 1, 0))
-		return false;
-
-	if (!lua_istable(L, -1)) {
-		lua_pop(L, 2);
-		return false;
-	}
-
-	view->lexer_name = strdup(name);
-	/* loop through all _TOKENSTYLES and parse them */
-	lua_getfield(L, -1, "_TOKENSTYLES");
-	lua_pushnil(L); /* first key */
-
-	while (lua_next(L, -2)) {
-		size_t id = lua_tointeger(L, -1);
-		//const char *name = lua_tostring(L, -2);
-		lua_pop(L, 1); /* remove value (=id), keep key (=name) */
-		lua_getfield(L, -4, "get_style");
-		lua_pushvalue(L, -5); /* lexer */
-		lua_pushvalue(L, -5); /* lang */
-		lua_pushvalue(L, -4); /* token_name */
-		if (lua_pcall(L, 3, 1, 0))
-			return false;
-		const char *style = lua_tostring(L, -1);
-		//printf("%s\t%d\t%s\n", name, id, style);
-		view->ui->syntax_style(view->ui, id, style);
-		lua_pop(L, 1); /* style */
-	}
-
-	lua_pop(L, 4); /* _TOKENSTYLES, grammar, lexers, vis */
-
-	return true;
-}
-
 const char *view_syntax_get(View *view) {
 	return view->lexer_name;
 }
diff --git a/view.h b/view.h
index 25b186f..ea8bca6 100644
--- a/view.h
+++ b/view.h
@@ -3,7 +3,6 @@
 
 #include <stddef.h>
 #include <stdbool.h>
-#include <lua.h>
 #include "register.h"
 #include "text.h"
 #include "ui.h"
@@ -11,6 +10,7 @@
 typedef struct View View;
 typedef struct Cursor Cursor;
 typedef struct Selection Selection;
+typedef struct lua_State lua_State;
 
 typedef struct {
 	int width;          /* display width i.e. number of columns ocupied by this character */
diff --git a/vis-cmds.c b/vis-cmds.c
index 477e29c..3a89d2a 100644
--- a/vis-cmds.c
+++ b/vis-cmds.c
@@ -595,6 +595,8 @@ static bool cmd_write(Vis *vis, Filerange *range, enum CmdOpt opt, const char *a
 		}
 		if (strcmp(file->name, *name) == 0)
 			file->stat = text_stat(text);
+		if (vis->event && vis->event->file_save)
+			vis->event->file_save(vis, file);
 	}
 	return true;
 }
diff --git a/vis-core.h b/vis-core.h
index 22bec33..6554410 100644
--- a/vis-core.h
+++ b/vis-core.h
@@ -156,6 +156,7 @@ struct Vis {
 	sigjmp_buf sigbus_jmpbuf;            /* used to jump back to a known good state in the mainloop after (SIGBUS) */
 	Map *actions;                        /* registered editor actions / special keys commands */
 	lua_State *lua;                      /* lua context used for syntax highligthing */
+	VisEvent *event;
 };
 
 /** stuff used by multiple of the vis-* files */
diff --git a/vis-lua.c b/vis-lua.c
new file mode 100644
index 0000000..d597772
--- /dev/null
+++ b/vis-lua.c
@@ -0,0 +1,491 @@
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <pwd.h>
+
+#include "vis-lua.h"
+#include "vis-core.h"
+#include "text-motions.h"
+
+#if !CONFIG_LUA
+
+void vis_lua_start(Vis *vis) { }
+void vis_lua_quit(Vis *vis) { }
+void vis_lua_file_open(Vis *vis, File *file) { }
+void vis_lua_file_save(Vis *vis, File *file) { }
+void vis_lua_file_close(Vis *vis, File *file) { }
+void vis_lua_win_open(Vis *vis, Win *win) { }
+void vis_lua_win_close(Vis *vis, Win *win) { }
+bool vis_theme_load(Vis *vis, const char *name) { return true; }
+
+#else
+
+#if 0
+static void stack_dump_entry(lua_State *L, int i) {
+	int t = lua_type(L, i);
+	switch (t) {
+	case LUA_TNIL:
+		printf("nil");
+		break;
+	case LUA_TBOOLEAN:
+		printf(lua_toboolean(L, i) ? "true" : "false");
+		break;
+	case LUA_TLIGHTUSERDATA:
+		printf("lightuserdata(%p)", (void*)lua_touserdata(L, i));
+		break;
+	case LUA_TNUMBER:
+		printf("%g", lua_tonumber(L, i));
+		break;
+	case LUA_TSTRING:
+		printf("`%s'", lua_tostring(L, i));
+		break;
+	case LUA_TTABLE:
+		printf("table[");
+		lua_pushnil(L); /* first key */
+		while (lua_next(L, i > 0 ? i : i - 1)) {
+			stack_dump_entry(L, -2);
+			printf("=");
+			stack_dump_entry(L, -1);
+			printf(",");
+			lua_pop(L, 1); /* remove value, keep key */
+		}
+		printf("]");
+		break;
+	case LUA_TUSERDATA:
+		printf("userdata(%p)", (void*)lua_touserdata(L, i));
+		break;
+	default:  /* other values */
+		printf("%s", lua_typename(L, t));
+		break;
+	}
+}
+
+static void stack_dump(lua_State *L, const char *format, ...) {
+	va_list ap;
+	va_start(ap, format);
+	vprintf(format, ap);
+	va_end(ap);
+	int top = lua_gettop(L);
+	for (int i = 1; i <= top; i++) {
+		printf("%d: ", i);
+		stack_dump_entry(L, i);
+		printf("\n");
+	}
+	printf("\n\n");
+}
+
+#endif
+
+/* returns registry["vis.objects"][addr] if it is of correct type */
+static void *obj_get(lua_State *L, void *addr, const char *type) {
+	lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
+	lua_pushlightuserdata(L, addr);
+	lua_gettable(L, -2);
+	lua_remove(L, -2);
+	if (lua_isnil(L, -1)) {
+		lua_pop(L, 1);
+		return NULL;
+	}
+	return luaL_checkudata(L, -1, type);
+}
+
+/* expects a userdatum at the top of the stack and sets
+ *
+ *   registry["vis.objects"][addr] = userdata
+ */
+static void obj_set(lua_State *L, void *addr) {
+	lua_getfield(L, LUA_REGISTRYINDEX, "vis.objects");
+	lua_pushlightuserdata(L, addr);
+	lua_pushvalue(L, -3);
+	lua_settable(L, -3);
+	lua_pop(L, 1);
+}
+
+static void obj_del(lua_State *L, void *addr) {
+	lua_pushnil(L);
+	obj_set(L, addr);
+}
+
+static void *obj_new(lua_State *L, void *addr, const char *type) {
+	if (!addr)
+		return NULL;
+	void **handle = (void**)obj_get(L, addr, type);
+	if (!handle) {
+		handle = lua_newuserdata(L, sizeof(addr));
+		obj_set(L, addr);
+		*handle = addr;
+		luaL_getmetatable(L, type);
+		lua_setmetatable(L, -2);
+		lua_newtable(L);
+		lua_setuservalue(L, -2);
+	}
+	return *handle;
+}
+
+static void *obj_arg_get(lua_State *L, int idx, const char *type) {
+	void **addr = luaL_checkudata(L, idx, type);
+	return obj_get(L, *addr, type);
+}
+
+static void *obj_check(lua_State *L, int idx, const char *type) {
+	void **addr = luaL_checkudata(L, idx, type);
+	if (!obj_get(L, *addr, type))
+		return NULL;
+	lua_pop(L, 1);
+	return *addr;
+}
+
+static int index_common(lua_State *L) {
+	lua_getmetatable(L, 1);
+	lua_pushvalue(L, 2);
+	lua_gettable(L, -2);
+	if (lua_isnil(L, -1)) {
+		lua_getuservalue(L, 1);
+		lua_pushvalue(L, 2);
+		lua_gettable(L, -2);
+	}
+	return 1;
+}
+
+static int newindex_common(lua_State *L) {
+	lua_getuservalue(L, 1);
+	lua_pushvalue(L, 2);
+	lua_pushvalue(L, 3);
+	lua_settable(L, -3);
+	return 0;
+}
+
+static int windows_iter(lua_State *L);
+
+static int windows(lua_State *L) {
+	Vis *vis = (Vis*)lua_touserdata(L, lua_upvalueindex(1));
+	Win **handle = lua_newuserdata(L, sizeof *handle);
+	*handle = vis->windows;
+	lua_pushcclosure(L, windows_iter, 1);
+	return 1;
+}
+
+static int windows_iter(lua_State *L) {
+	Win **handle = (Win**)lua_touserdata(L, lua_upvalueindex(1));
+	if (!*handle)
+		return 0;
+	Win *win = obj_new(L, *handle, "vis.window");
+	if (!win)
+		return 0;
+	*handle = win->next;
+	return 1;
+}
+
+static int files_iter(lua_State *L);
+
+static int files(lua_State *L) {
+	Vis *vis = (Vis*)lua_touserdata(L, lua_upvalueindex(1));
+	File **handle = lua_newuserdata(L, sizeof *handle);
+	*handle = vis->files;
+	lua_pushcclosure(L, files_iter, 1);
+	return 1;
+}
+
+static int files_iter(lua_State *L) {
+	File **handle = (File**)lua_touserdata(L, lua_upvalueindex(1));
+	if (!*handle)
+		return 0;
+	File *file = obj_new(L, *handle, "vis.file");
+	if (!file)
+		return 0;
+	*handle = file->next;
+	return 1;
+}
+
+static int command(lua_State *L) {
+	Vis *vis = (Vis*)lua_touserdata(L, lua_upvalueindex(1));
+	const char *cmd = luaL_checkstring(L, 1);
+	bool ret = vis_cmd(vis, cmd);
+	lua_pushboolean(L, ret);
+	return 1;
+}
+
+static int info(lua_State *L) {
+	Vis *vis = (Vis*)lua_touserdata(L, lua_upvalueindex(1));
+	const char *msg = luaL_checkstring(L, 1);
+	vis_info_show(vis, "%s", msg);
+	return 0;
+}
+
+static const struct luaL_Reg vis_lua[] = {
+	{ "files", files },
+	{ "windows", windows },
+	{ "command", command },
+	{ "info", info },
+	{ NULL, NULL },
+};
+
+static int window_index(lua_State *L) {
+	Win *win = obj_check(L, 1, "vis.window");
+	if (!win) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	if (lua_isstring(L, 2)) {
+		const char *key = lua_tostring(L, 2);
+		if (strcmp(key, "file") == 0) {
+			obj_new(L, win->file, "vis.file");
+			return 1;
+		}
+	}
+
+	return index_common(L);
+}
+
+static int window_newindex(lua_State *L) {
+	Win *win = obj_check(L, 1, "vis.window");
+	if (!win)
+		return 0;
+	return newindex_common(L);
+}
+
+static const struct luaL_Reg window_funcs[] = {
+	{ "__index", window_index },
+	{ "__newindex", window_newindex },
+	{ NULL, NULL },
+};
+
+static int file_index(lua_State *L) {
+	File *file = obj_check(L, 1, "vis.file");
+	if (!file) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	if (lua_isstring(L, 2)) {
+		const char *key = lua_tostring(L, 2);
+		if (strcmp(key, "name") == 0) {
+			lua_pushstring(L, file->name);
+			return 1;
+		}
+	}
+
+	return index_common(L);
+}
+
+static int file_newindex(lua_State *L) {
+	File *file = obj_check(L, 1, "vis.file");
+	if (!file)
+		return 0;
+	return newindex_common(L);
+}
+
+static int file_insert(lua_State *L) {
+	File *file = obj_check(L, 1, "vis.file");
+	if (file) {
+		size_t pos = luaL_checkunsigned(L, 2);
+		size_t len;
+		luaL_checkstring(L, 3);
+		const char *data = lua_tolstring(L, 3, &len);
+ 		bool ret = text_insert(file->text, pos, data, len);
+		lua_pushboolean(L, ret);
+	} else {
+		lua_pushboolean(L, false);
+	}
+	return 1;
+}
+
+static int file_delete(lua_State *L) {
+	File *file = obj_check(L, 1, "vis.file");
+	if (file) {
+		size_t pos = luaL_checkunsigned(L, 2);
+		size_t len = luaL_checkunsigned(L, 3);
+		bool ret = text_delete(file->text, pos, len);
+		lua_pushboolean(L, ret);
+	} else {
+		lua_pushboolean(L, false);
+	}
+	return 1;
+}
+
+static int file_lines_iter(lua_State *L);
+
+static int file_lines(lua_State *L) {
+	obj_arg_get(L, 1, "vis.file");
+	size_t *pos = lua_newuserdata(L, sizeof *pos);
+	*pos = 0;
+	lua_pushcclosure(L, file_lines_iter, 2);
+	return 1;
+}
+
+static int file_lines_iter(lua_State *L) {
+	File *file = *(File**)lua_touserdata(L, lua_upvalueindex(1));
+	size_t *pos = lua_touserdata(L, lua_upvalueindex(2));
+	size_t new_pos = text_line_next(file->text, *pos);
+	size_t len = new_pos - *pos;
+	if (len == 0)
+		return 0;
+	char *buf = malloc(len);
+	if (!buf)
+		return 0;
+	len = text_bytes_get(file->text, *pos, len, buf);
+	lua_pushlstring(L, buf, len);
+	free(buf);
+	*pos = new_pos;
+	return 1;
+}
+
+static const struct luaL_Reg file_funcs[] = {
+	{ "__index", file_index },
+	{ "__newindex", file_newindex },
+	{ "insert", file_insert },
+	{ "delete", file_delete },
+	{ "lines", file_lines },
+	{ NULL, NULL },
+};
+
+
+static void vis_lua_event(Vis *vis, const char *name) {
+	lua_State *L = vis->lua;
+	lua_getglobal(L, "vis");
+	lua_getfield(L, -1, "events");
+	if (lua_istable(L, -1)) {
+		lua_getfield(L, -1, name);
+	}
+	lua_remove(L, -2);
+}
+
+void vis_lua_start(Vis *vis) {
+	lua_State *L = luaL_newstate();
+	if (!L)
+		return;
+	vis->lua = L;
+	luaL_openlibs(L);
+
+	/* try to get users home directory */
+	const char *home = getenv("HOME");
+	if (!home || !*home) {
+		struct passwd *pw = getpwuid(getuid());
+		if (pw)
+			home = pw->pw_dir;
+	}
+
+	/* extends lua's package.path with:
+	 * - $VIS_PATH/lexers
+	 * - $HOME/.vis/lexers
+	 * - /usr/local/share/vis/lexers
+	 * - /usr/share/vis/lexers
+	 * - package.path (standard lua search path)
+	 */
+	int paths = 3;
+	lua_getglobal(L, "package");
+
+	const char *vis_path = getenv("VIS_PATH");
+	if (vis_path) {
+		lua_pushstring(L, vis_path);
+		lua_pushstring(L, "/lexers/?.lua;");
+		lua_concat(L, 2);
+		paths++;
+	}
+
+	if (home && *home) {
+		lua_pushstring(L, home);
+		lua_pushstring(L, "/.vis/lexers/?.lua;");
+		lua_concat(L, 2);
+		paths++;
+	}
+
+	lua_pushstring(L, "/usr/local/share/vis/lexers/?.lua;");
+	lua_pushstring(L, "/usr/share/vis/lexers/?.lua;");
+	lua_getfield(L, -paths, "path");
+	lua_concat(L, paths);
+	lua_setfield(L, -2, "path");
+	lua_pop(L, 1); /* package */
+
+	/* table in registry to track lifetimes of C objects */
+	lua_newtable(L);
+	lua_setfield(L, LUA_REGISTRYINDEX, "vis.objects");
+	/* metatable used to type check user data */
+	luaL_newmetatable(L, "vis.file");
+	luaL_setfuncs(L, file_funcs, 0);
+	luaL_newmetatable(L, "vis.window");
+	luaL_setfuncs(L, window_funcs, 0);
+	/* vis module table with up value as the C pointer */
+	luaL_newlibtable(L, vis_lua);
+	lua_pushlightuserdata(L, vis);
+	luaL_setfuncs(L, vis_lua, 1);
+	lua_setglobal(L, "vis");
+
+	lua_getglobal(L, "require");
+	lua_pushstring(L, "visrc");
+	lua_pcall(L, 1, 0, 0);
+}
+
+void vis_lua_quit(Vis *vis) {
+	lua_State *L = vis->lua;
+	if (L)
+		lua_close(L);
+}
+
+void vis_lua_file_open(Vis *vis, File *file) {
+
+}
+
+void vis_lua_file_save(Vis *vis, File *file) {
+
+}
+
+void vis_lua_file_close(Vis *vis, File *file) {
+	lua_State *L = vis->lua;
+	vis_lua_event(vis, "file_close");
+	if (lua_isfunction(L, -1)) {
+		obj_new(L, file, "vis.file");
+		lua_pcall(L, 1, 0, 0);
+	}
+	obj_del(L, file);
+	lua_pop(L, 1);
+}
+
+void vis_lua_win_open(Vis *vis, Win *win) {
+	lua_State *L = vis->lua;
+	vis_lua_event(vis, "win_open");
+	if (lua_isfunction(L, -1)) {
+		obj_new(L, win, "vis.window");
+		lua_pcall(L, 1, 0, 0);
+	}
+	lua_pop(L, 1);
+}
+
+void vis_lua_win_close(Vis *vis, Win *win) {
+	lua_State *L = vis->lua;
+	vis_lua_event(vis, "win_close");
+	if (lua_isfunction(L, -1)) {
+		obj_new(L, win, "vis.window");
+		lua_pcall(L, 1, 0, 0);
+	}
+	obj_del(L, win);
+	lua_pop(L, 1);
+}
+
+bool vis_theme_load(Vis *vis, const char *name) {
+	lua_State *L = vis->lua;
+	if (!L)
+		return false;
+	/* package.loaded['themes/'..name] = nil
+	 * require 'themes/'..name */
+	lua_pushstring(L, "themes/");
+	lua_pushstring(L, name);
+	lua_concat(L, 2);
+	lua_getglobal(L, "package");
+	lua_getfield(L, -1, "loaded");
+	lua_pushvalue(L, -3);
+	lua_pushnil(L);
+	lua_settable(L, -3);
+	lua_pop(L, 2);
+	lua_getglobal(L, "require");
+	lua_pushvalue(L, -2);
+	if (lua_pcall(L, 1, 0, 0))
+		return false;
+	for (Win *win = vis->windows; win; win = win->next)
+		view_syntax_set(win->view, view_syntax_get(win->view));
+	return true;
+}
+
+#endif
diff --git a/vis-lua.h b/vis-lua.h
new file mode 100644
index 0000000..b0f1293
--- /dev/null
+++ b/vis-lua.h
@@ -0,0 +1,22 @@
+#ifndef VIS_LUA_H
+#define VIS_LUA_H
+
+#if CONFIG_LUA
+#include <lua.h>
+#include <lualib.h>
+#include <lauxlib.h>
+#else
+typedef struct lua_State lua_State;
+#endif
+
+#include "vis.h"
+
+void vis_lua_start(Vis*);
+void vis_lua_quit(Vis*);
+void vis_lua_file_open(Vis*, File*);
+void vis_lua_file_save(Vis*, File*);
+void vis_lua_file_close(Vis*, File*);
+void vis_lua_win_open(Vis*, Win*);
+void vis_lua_win_close(Vis*, Win*);
+
+#endif
\ No newline at end of file
diff --git a/vis.c b/vis.c
index 3825500..f23c42e 100644
--- a/vis.c
+++ b/vis.c
@@ -34,9 +34,6 @@
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <pwd.h>
-#include <lauxlib.h>
-#include <lualib.h>
-#include <lua.h>
 #include <termkey.h>
 
 #include "vis.h"
@@ -67,7 +64,8 @@ static void file_free(Vis *vis, File *file) {
 		return;
 	if (--file->refcount > 0)
 		return;
-
+	if (vis->event && vis->event->file_close)
+		vis->event->file_close(vis, file);
 	text_free(file->text);
 	free((char*)file->name);
 
@@ -120,30 +118,17 @@ static File *file_new(Vis *vis, const char *filename) {
 
 	if (filename)
 		file->name = strdup(filename);
+	if (vis->event && vis->event->file_open)
+		vis->event->file_open(vis, file);
 	return file;
 }
 
 void vis_window_name(Win *win, const char *filename) {
-	lua_State *L = win->vis->lua;
 	File *file = win->file;
 	if (filename != file->name) {
 		free((char*)file->name);
 		file->name = filename ? strdup(filename) : NULL;
 	}
-
-	if (filename && L) {
-		lua_getglobal(L, "vis");
-		lua_getfield(L, -1, "lexers");
-		lua_getfield(L, -1, "lexer_name");
-		lua_pushstring(L, filename);
-		lua_pcall(L, 1, 1, 0);
-		if (lua_isstring(L, -1)) {
-			const char *lexer_name = lua_tostring(L, -1);
-			if (lexer_name)
-				view_syntax_set(win->view, lexer_name);
-		}
-		lua_pop(L, 2); /* return value: lexer name, lexers variable */
-	}
 }
 
 static void windows_invalidate(Vis *vis, size_t start, size_t end) {
@@ -189,6 +174,8 @@ static Win *window_new_file(Vis *vis, File *file) {
 	vis->windows = win;
 	vis->win = win;
 	vis->ui->window_focus(win->ui);
+	if (vis->event && vis->event->win_open)
+		vis->event->win_open(vis, win);
 	return win;
 }
 
@@ -278,6 +265,8 @@ bool vis_window_new(Vis *vis, const char *filename) {
 
 void vis_window_close(Win *win) {
 	Vis *vis = win->vis;
+	if (vis->event && vis->event->win_close)
+		vis->event->win_close(vis, win);
 	file_free(vis, win->file);
 	if (win->prev)
 		win->prev->next = win->next;
@@ -295,70 +284,14 @@ void vis_window_close(Win *win) {
 	vis_draw(vis);
 }
 
-Vis *vis_new(Ui *ui) {
+Vis *vis_new(Ui *ui, VisEvent *event) {
 	if (!ui)
 		return NULL;
 	Vis *vis = calloc(1, sizeof(Vis));
 	if (!vis)
 		return NULL;
-	lua_State *L = luaL_newstate();
-	if (!(vis->lua = L))
-		goto err;
-	luaL_openlibs(L);
-
-	/* try to get users home directory */
-	const char *home = getenv("HOME");
-	if (!home || !*home) {
-		struct passwd *pw = getpwuid(getuid());
-		if (pw)
-			home = pw->pw_dir;
-	}
-
-	/* extends lua's package.path with:
-	 * - $VIS_PATH/lexers
-	 * - $HOME/.vis/lexers
-	 * - /usr/local/share/vis/lexers
-	 * - /usr/share/vis/lexers
-	 * - package.path (standard lua search path)
-	 */
-	int paths = 3;
-	lua_getglobal(L, "package");
-
-	const char *vis_path = getenv("VIS_PATH");
-	if (vis_path) {
-		lua_pushstring(L, vis_path);
-		lua_pushstring(L, "/lexers/?.lua;");
-		lua_concat(L, 2);
-		paths++;
-	}
-
-	if (home && *home) {
-		lua_pushstring(L, home);
-		lua_pushstring(L, "/.vis/lexers/?.lua;");
-		lua_concat(L, 2);
-		paths++;
-	}
-
-	lua_pushstring(L, "/usr/local/share/vis/lexers/?.lua;");
-	lua_pushstring(L, "/usr/share/vis/lexers/?.lua;");
-	lua_getfield(L, -paths, "path");
-	lua_concat(L, paths);
-	lua_setfield(L, -2, "path");
-	lua_pop(L, 1); /* package */
-
-	/* try to load the lexer module */
-	lua_getglobal(L, "require");
-	lua_pushstring(L, "lexer");
-	if (lua_pcall(L, 1, 1, 0)) {
-		lua_close(L);
-		vis->lua = L = NULL;
-	} else {
-		lua_newtable(L); /* vis */
-		lua_pushvalue(L, -2); /* require return value */
-		lua_setfield(L, -2, "lexers");
-		lua_setglobal(L, "vis");
-	}
-
+	if (event && event->vis_start)
+		event->vis_start(vis);
 	vis->ui = ui;
 	vis->ui->init(vis->ui, vis);
 	vis->tabwidth = 8;
@@ -381,6 +314,7 @@ Vis *vis_new(Ui *ui) {
 	if (!(vis->search_pattern = text_regex_new()))
 		goto err;
 	vis->mode_prev = vis->mode = &vis_modes[VIS_MODE_NORMAL];
+	vis->event = event;
 	return vis;
 err:
 	vis_free(vis);
@@ -390,8 +324,9 @@ err:
 void vis_free(Vis *vis) {
 	if (!vis)
 		return;
-	if (vis->lua)
-		lua_close(vis->lua);
+	if (vis->event && vis->event->vis_quit)
+		vis->event->vis_quit(vis);
+	vis->event = NULL;
 	while (vis->windows)
 		vis_window_close(vis->windows);
 	file_free(vis, vis->prompt->file);
@@ -1352,26 +1287,3 @@ const char *vis_file_name(File *file) {
 	return file->name;
 }
 
-bool vis_theme_load(Vis *vis, const char *name) {
-	lua_State *L = vis->lua;
-	if (!L)
-		return false;
-	/* package.loaded['themes/'..name] = nil
-	 * require 'themes/'..name */
-	lua_pushstring(L, "themes/");
-	lua_pushstring(L, name);
-	lua_concat(L, 2);
-	lua_getglobal(L, "package");
-	lua_getfield(L, -1, "loaded");
-	lua_pushvalue(L, -3);
-	lua_pushnil(L);
-	lua_settable(L, -3);
-	lua_pop(L, 2);
-	lua_getglobal(L, "require");
-	lua_pushvalue(L, -2);
-	if (lua_pcall(L, 1, 0, 0))
-		return false;
-	for (Win *win = vis->windows; win; win = win->next)
-		view_syntax_set(win->view, view_syntax_get(win->view));
-	return true;
-}
diff --git a/vis.h b/vis.h
index b5c48ea..e007710 100644
--- a/vis.h
+++ b/vis.h
@@ -13,6 +13,16 @@ typedef struct Win Win;
 #include "view.h"
 #include "register.h"
 
+typedef struct {
+	void (*vis_start)(Vis*);
+	void (*vis_quit)(Vis*);
+	void (*file_open)(Vis*, File*);
+	void (*file_save)(Vis*, File*);
+	void (*file_close)(Vis*, File*);
+	void (*win_open)(Vis*, Win*);
+	void (*win_close)(Vis*, Win*);
+} VisEvent;
+
 typedef union { /* various types of arguments passed to key action functions */
 	bool b;
 	int i;
@@ -40,7 +50,7 @@ typedef struct {           /* a key binding either refers to an action or an ali
 } KeyBinding;
 
 /* creates a new editor instance using the specified user interface */
-Vis *vis_new(Ui*);
+Vis *vis_new(Ui*, VisEvent*);
 /* frees all resources associated with this editor instance, terminates ui */
 void vis_free(Vis*);
 /* instructs the user interface to draw to an internal buffer */