8 files changed, 32 insertions, 0 deletions

diff --git a/README.md b/README.md
index 608e1c5..f8d7a99 100644
--- a/README.md
+++ b/README.md
@@ -590,6 +590,7 @@ At this time there exists no API stability guarantees.
      - `start()`
      - `quit()`
      - `file_open(file)`
+     - `file_save_pre(file, path)` triggered *before* an attempted write to `path` boolean return value determines whether write will be proceeded
      - `file_save_post(file, path)` triggered *after* a successfull write to `path`
      - `file_close(file)`
      - `win_open(win)`
diff --git a/main.c b/main.c
index 5b2a9bb..c558ced 100644
--- a/main.c
+++ b/main.c
@@ -2203,6 +2203,7 @@ int main(int argc, char *argv[]) {
 		.vis_start = vis_lua_start,
 		.vis_quit = vis_lua_quit,
 		.file_open = vis_lua_file_open,
+		.file_save_pre = vis_lua_file_save_pre,
 		.file_save_post = vis_lua_file_save_post,
 		.file_close = vis_lua_file_close,
 		.win_open = vis_lua_win_open,
diff --git a/sam.c b/sam.c
index 4bd10d5..1b30258 100644
--- a/sam.c
+++ b/sam.c
@@ -1295,6 +1295,11 @@ static bool cmd_write(Vis *vis, Win *win, Command *cmd, const char *argv[], Curs
 			return false;
 		}
 
+		if (!vis_event_emit(vis, VIS_EVENT_FILE_SAVE_PRE, file, *name) && cmd->flags != '!') {
+			vis_info_show(vis, "Rejected write to `%s' by pre-save hook", *name);
+			return false;
+		}
+
 		TextSave *ctx = text_save_begin(text, *name);
 		if (!ctx) {
 			vis_info_show(vis, "Can't write `%s': %s", *name, strerror(errno));
diff --git a/vis-core.h b/vis-core.h
index 6d79f18..56c51bf 100644
--- a/vis-core.h
+++ b/vis-core.h
@@ -191,6 +191,7 @@ enum VisEvents {
 	VIS_EVENT_START,
 	VIS_EVENT_QUIT,
 	VIS_EVENT_FILE_OPEN,
+	VIS_EVENT_FILE_SAVE_PRE,
 	VIS_EVENT_FILE_SAVE_POST,
 	VIS_EVENT_FILE_CLOSE,
 	VIS_EVENT_WIN_OPEN,
diff --git a/vis-lua.c b/vis-lua.c
index c48eb43..019f8cf 100644
--- a/vis-lua.c
+++ b/vis-lua.c
@@ -128,6 +128,7 @@ void vis_lua_init(Vis *vis) { }
 void vis_lua_start(Vis *vis) { }
 void vis_lua_quit(Vis *vis) { }
 void vis_lua_file_open(Vis *vis, File *file) { }
+bool vis_lua_file_save_pre(Vis *vis, File *file, const char *path) { return true; }
 void vis_lua_file_save_post(Vis *vis, File *file, const char *path) { }
 void vis_lua_file_close(Vis *vis, File *file) { }
 void vis_lua_win_open(Vis *vis, Win *win) { }
@@ -1544,6 +1545,23 @@ void vis_lua_file_open(Vis *vis, File *file) {
 	lua_pop(L, 1);
 }
 
+bool vis_lua_file_save_pre(Vis *vis, File *file, const char *path) {
+	lua_State *L = vis->lua;
+	vis_lua_event_get(L, "file_save_pre");
+	if (lua_isfunction(L, -1)) {
+		obj_ref_new(L, file, "vis.file");
+		if (path)
+			lua_pushstring(L, path);
+		else
+			lua_pushnil(L);
+		if (pcall(vis, L, 2, 1) != 0)
+			return false;
+		return lua_toboolean(L, -1);
+	}
+	lua_pop(L, 1);
+	return true;
+}
+
 void vis_lua_file_save_post(Vis *vis, File *file, const char *path) {
 	lua_State *L = vis->lua;
 	vis_lua_event_get(L, "file_save_post");
diff --git a/vis-lua.h b/vis-lua.h
index 7dab14e..71e30fc 100644
--- a/vis-lua.h
+++ b/vis-lua.h
@@ -23,6 +23,7 @@ void vis_lua_init(Vis*);
 void vis_lua_start(Vis*);
 void vis_lua_quit(Vis*);
 void vis_lua_file_open(Vis*, File*);
+bool vis_lua_file_save_pre(Vis*, File*, const char *path);
 void vis_lua_file_save_post(Vis*, File*, const char *path);
 void vis_lua_file_close(Vis*, File*);
 void vis_lua_win_open(Vis*, Win*);
diff --git a/vis.c b/vis.c
index dcd7457..f8d3dbf 100644
--- a/vis.c
+++ b/vis.c
@@ -58,6 +58,7 @@ bool vis_event_emit(Vis *vis, enum VisEvents id, ...) {
 			vis->event->vis_start(vis);
 		break;
 	case VIS_EVENT_FILE_OPEN:
+	case VIS_EVENT_FILE_SAVE_PRE:
 	case VIS_EVENT_FILE_SAVE_POST:
 	case VIS_EVENT_FILE_CLOSE:
 	{
@@ -66,6 +67,9 @@ bool vis_event_emit(Vis *vis, enum VisEvents id, ...) {
 			break;
 		if (id == VIS_EVENT_FILE_OPEN && vis->event->file_open) {
 			vis->event->file_open(vis, file);
+		} else if (id == VIS_EVENT_FILE_SAVE_PRE && vis->event->file_save_pre) {
+			const char *path = va_arg(ap, const char*);
+			ret = vis->event->file_save_pre(vis, file, path);
 		} else if (id == VIS_EVENT_FILE_SAVE_POST && vis->event->file_save_post) {
 			const char *path = va_arg(ap, const char*);
 			vis->event->file_save_post(vis, file, path);
diff --git a/vis.h b/vis.h
index f3366c7..9d6ba4d 100644
--- a/vis.h
+++ b/vis.h
@@ -32,6 +32,7 @@ typedef struct {
 	void (*vis_start)(Vis*);
 	void (*vis_quit)(Vis*);
 	void (*file_open)(Vis*, File*);
+	bool (*file_save_pre)(Vis*, File*, const char *path);
 	void (*file_save_post)(Vis*, File*, const char *path);
 	void (*file_close)(Vis*, File*);
 	void (*win_open)(Vis*, Win*);