Pass model as a CLI arg

src/main.c

@@ -4,30 +4,82 @@
 #include "obj.h"
 #include "render.h"
 #include "shaders.h"
+#include "str.h"
 #include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 #include <time.h>
 
 #define IMAGE_DIMENSION 1200
-#define RESOURCE(NAME) "resources/" NAME
 
 enum {
   TINY_EXIT_SUCCESS,
+  TINY_EXIT_MISSING_ARGS,
+  TINY_EXIT_OBJ_NOT_EXIST,
   TINY_EXIT_ARENA_INIT_FAILED,
   TINY_EXIT_RENDER_INIT_FAILED,
   TINY_EXIT_MODEL_LOAD_FAILED,
 };
 
-int tinyrenderer(void);
+typedef struct tiny_args TinyArgs;
+struct tiny_args {
+  Str8 obj;
+  Str8 diffuse;
+  Str8 nm_tangent;
+};
 
-int main(void) { return tinyrenderer(); }
+internal TinyArgs parse_args(Arena *arena, int argc, char *argv[]);
+internal i32 tinyrenderer(Arena *arena, TinyArgs args);
+internal bool file_exists(const Str8 *path);
 
-int tinyrenderer(void) {
+i32 main(int argc, char *argv[]) {
   Arena *arena = NULL;
   if (!wapp_mem_arena_init(&arena, GB(10))) {
     return TINY_EXIT_ARENA_INIT_FAILED;
   }
 
+  TinyArgs args = parse_args(arena, argc, argv);
+
+  i32 output = tinyrenderer(arena, args);
+
+  wapp_mem_arena_destroy(&arena);
+
+  return output;
+}
+
+internal TinyArgs parse_args(Arena *arena, int argc, char *argv[]) {
+  if (argc < 2) {
+    exit(TINY_EXIT_MISSING_ARGS);
+  }
+
+  TinyArgs args = {
+      .obj = str8_lit(argv[1]),
+  };
+
+  if (!file_exists(&args.obj)) {
+    exit(TINY_EXIT_OBJ_NOT_EXIST);
+  }
+
+  const Str8 basename = str8_substr(&args.obj, 0, args.obj.length - 4);
+
+  args.diffuse = str8_copy(arena, &basename);
+  str8_concat(arena, &args.diffuse, "_diffuse.pnm");
+  if (!file_exists(&args.diffuse)) {
+    args.diffuse = (Str8){0};
+  }
+
+  args.nm_tangent = str8_copy(arena, &basename);
+  str8_concat(arena, &args.nm_tangent, "_nm_tangent.pnm");
+  if (!file_exists(&args.nm_tangent)) {
+    args.nm_tangent = (Str8){0};
+  }
+
+  return args;
+}
+
+internal i32 tinyrenderer(Arena *arena, TinyArgs args) {
   Colour bg = {.r = 42, .g = 45, .b = 52, .a = 255};
   Colour main_colour = {.r = 14, .g = 156, .b = 208, .a = 255};
   Render render;
@@ -35,8 +87,9 @@ int tinyrenderer(void) {
     return TINY_EXIT_RENDER_INIT_FAILED;
   }
 
-  Model obj = load_obj_file(arena, RESOURCE("head.obj"), RESOURCE("head.pnm"),
-                            RESOURCE("head_nm_tangent.pnm"));
+  Model obj = load_obj_file(
+      arena, args.obj.str, args.diffuse.length > 0 ? args.diffuse.str : NULL,
+      args.nm_tangent.length > 0 ? args.nm_tangent.str : NULL);
   if (IS_INVALID_MODEL(obj)) {
     return TINY_EXIT_MODEL_LOAD_FAILED;
   }
@@ -48,7 +101,10 @@ int tinyrenderer(void) {
                main_colour);
   save_image(&(render.img), "result.pam");
 
-  wapp_mem_arena_destroy(&arena);
-
   return TINY_EXIT_SUCCESS;
 }
+
+internal bool file_exists(const Str8 *path) {
+  struct stat st;
+  return stat(path->str, &st) == 0;
+}