Support multi-line commands

Close #5

src/cmd.c

@@ -62,10 +62,10 @@ int cmd_exec(lua_State *l) {
     return 0;
 }
 
-void register_cmds(lua_State *l) {
+void register_cmds(lua_State *lua) {
     for (size_t i = 0; i < NR_CMDS; i++) {
-        lua_pushlightuserdata(l, &CMDS[i]);
-        lua_pushcclosure(l, cmd_exec, 1);
-        lua_setglobal(l, CMDS[i].name);
+        lua_pushlightuserdata(lua, &CMDS[i]);
+        lua_pushcclosure(lua, cmd_exec, 1);
+        lua_setglobal(lua, CMDS[i].name);
     }
 }

src/shell.c

@@ -6,53 +6,109 @@
 #include <stdio.h>
 #include <string.h>
 
-bool report(lua_State *l, int status) {
+static bool report(lua_State *lua, int status) {
     if (status == LUA_OK)
         return false;
+    fprintf(stderr, "\x1B[0;31m%s\x1B[0;0m\n", lua_tostring(lua, -1));
+    lua_pop(lua, 1);
+    return true;
+}
 
-    fprintf(stderr, "\x1B[0;31m%s\x1B[0;0m\n", lua_tostring(l, -1));
-    lua_pop(l, 1);
+static bool push_line(lua_State *lua, bool first) {
+    if (!first) {
+        printf("    ");
+        fflush(stdout);
+    }
+    char buffer[256];
+    if (!fgets(buffer, sizeof(buffer), stdin))
+        return false;
+    for (size_t i = 0; buffer[i]; i++) {
+        if (buffer[i] == '\n') {
+            buffer[i] = '\0';
+            break;
+        }
+    }
+    lua_pushlstring(lua, buffer, strlen(buffer));
+    return true;
+}
+
+#define EOFMARK "<eof>"
+
+static bool incomplete(lua_State *lua, int status) {
+    if (status != LUA_ERRSYNTAX)
+        return false;
+    size_t len;
+    const char *msg = lua_tolstring(lua, -1, &len);
+    if (len < strlen(EOFMARK) ||
+        strcmp(msg + len - strlen(EOFMARK), EOFMARK) != 0)
+        return false;
+    lua_pop(lua, 1);
     return true;
 }
 
+static int load_multiline(lua_State *lua) {
+    while (true) {
+        size_t len;
+        const char *line = lua_tolstring(lua, 1, &len);
+        int status = luaL_loadbuffer(lua, line, len, "=stdin");
+        if (!incomplete(lua, status) || !push_line(lua, false))
+            return status;
+        lua_pushliteral(lua, "\n");
+        lua_insert(lua, -2);
+        lua_concat(lua, 3);
+    }
+}
+
+static int load_retline(lua_State *lua) {
+    const char *line = lua_tostring(lua, -1);
+    const char *retline = lua_pushfstring(lua, "return %s;", line);
+    int status = luaL_loadbuffer(lua, retline, strlen(retline), "=stdin");
+    if (status == LUA_OK) {
+        lua_remove(lua, -2);
+    } else {
+        lua_pop(lua, 2);
+    }
+    return status;
+}
+
+static int load_line(lua_State *lua) {
+    if (!push_line(lua, true))
+        return -1;
+    int status = load_retline(lua);
+    if (status != LUA_OK)
+        status = load_multiline(lua);
+    lua_remove(lua, 1);
+    return status;
+}
+
 void shell(void) {
     print_banner();
 
-    lua_State *l = luaL_newstate();
-    luaL_openlibs(l);
+    lua_State *lua = luaL_newstate();
+    if (!lua) {
+        fprintf(stderr, "failed to intialize Lua state\n");
+        return;
+    }
+    luaL_openlibs(lua);
 
-    register_cmds(l);
+    register_cmds(lua);
 
     while (true) {
         printf("\x1B[0;36m>\x1B[0;0m>\x1B[0;33m>\x1B[0;0m ");
 
-        char line[256];
-        if (fgets(line, sizeof(line), stdin) == NULL)
-            break;
-
-        int status;
-
-        const char *ret_line = lua_pushfstring(l, "return %s", line);
-        if (luaL_loadbuffer(l, ret_line, strlen(ret_line), "=stdin") !=
-            LUA_OK) {
-            lua_pop(l, 2);
-            status = luaL_loadbuffer(l, line, strlen(line), "=stdin");
-            if (report(l, status))
-                continue;
-        } else {
-            lua_remove(l, -2);
-        }
+        int status = load_line(lua);
+        report(lua, status);
 
-        status = lua_pcall(l, 0, LUA_MULTRET, 0);
-        report(l, status);
+        status = lua_pcall(lua, 0, LUA_MULTRET, 0);
+        report(lua, status);
 
-        int n = lua_gettop(l);
+        int n = lua_gettop(lua);
         if (n > 0) {
-            lua_getglobal(l, "print");
-            lua_insert(l, 1);
-            lua_pcall(l, n, 0, 0);
+            lua_getglobal(lua, "print");
+            lua_insert(lua, 1);
+            lua_pcall(lua, n, 0, 0);
         }
     }
 
-    lua_close(l);
+    lua_close(lua);
 }