Start working on a gltf utility program

Signed-off-by: Arthur Brainville (Ybalrid) <ybalrid@ybalrid.info>

examples/gltfutil/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.6)
+project (gltfutil)
+
+set(CMAKE_CXX_STANDARD 11)
+
+include_directories(
+    ../../
+    )
+
+file(GLOB gltfutil_sources *.cc *.h)
+add_executable(gltfutil ${gltfutil_sources})

examples/gltfutil/gltfuilconfig.h

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+#include <string>
+
+namespace gltfutil {
+enum class ui_mode { cli, interactive };
+
+enum class cli_action { not_set, help, dump };
+
+struct configuration {
+  std::string input_path, output_dir;
+  ui_mode mode;
+  cli_action action = cli_action::not_set;
+  bool has_output_dir;
+  bool is_valid() {
+    // TODO impl check
+    return false;
+  }
+};
+}  // namespace gltfutil

examples/gltfutil/main.cc

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+#include <iostream>
+#include <string>
+
+#include "gltfuilconfig.h"
+
+namespace gltfutil {
+int usage() {
+  using std::cout;
+  cout << "gltfutil: tool for manipulating gltf files\n"
+       << " usage information:\n\n"
+       << "\t gltfutil (-i|-d|-h) [path to .gltf/glb] (-o [path to output "
+          "directory])\n\n"
+       << "\t\t -i: start in interactive mode\n"
+       << "\t\t -d: dump enclosed content (image assets)\n"
+       << "\t\t -h: print this help\n";
+  return 0;
+}
+
+int arg_error() {
+  (void)usage();
+  return -1;
+}
+
+int parse_args(int argc, char** argv) {
+  gltfutil::configuration config;
+
+  for (size_t i = 1; i < size_t(argc); ++i) {
+    char* arg = argv[i];
+    if (arg[0] == '-') switch (arg[1]) {
+        case 'h':
+          config.mode = ui_mode::cli;
+          config.action = cli_action::help;
+        case 'd':
+          // TODO impl
+          break;
+        case 'i':
+          config.mode = ui_mode::interactive;
+          break;
+          // TODO impl
+        default:
+          return arg_error();
+      }
+  }
+
+  if (config.is_valid()) {
+    if (config.mode == ui_mode::interactive) {
+      // interactive usage now;
+      // TODO impl
+    } else {
+      switch (config.action) {
+        case cli_action::help:
+          return usage();
+        case cli_action::dump:
+          // TODO impl
+          break;
+        default:
+          return arg_error();
+      }
+    }
+  } else {
+    return arg_error();
+  }
+  return 0;
+}
+}  // namespace gltfutil
+
+int main(int argc, char* argv[]) {
+  if (argc == 1) return gltfutil::usage();
+  if (argc > 1) return gltfutil::parse_args(argc, argv);
+}