#include <stdio.h>
#include <stdlib.h>
#include <assimp/cimport.h>
#include <assimp/scene.h>
#include <assimp/postprocess.h>

void export_as_obj(const struct aiScene* scene, const char* output_filename) {
    FILE* file = fopen(output_filename, "w");
    if (!file) {
        fprintf(stderr, "Error opening output file: %s\n", output_filename);
        return;
    }

    fprintf(file, "# OBJ file exported from MD3 using Assimp\n");

    // Write vertices
    for (unsigned int m = 0; m < scene->mNumMeshes; m++) {
        const struct aiMesh* mesh = scene->mMeshes[m];
        for (unsigned int v = 0; v < mesh->mNumVertices; v++) {
            fprintf(file, "v %f %f %f\n",
                    mesh->mVertices[v].x,
                    mesh->mVertices[v].y,
                    mesh->mVertices[v].z);
        }
    }

    // Write faces (indices)
    unsigned int vertex_offset = 1; // OBJ indices start at 1
    for (unsigned int m = 0; m < scene->mNumMeshes; m++) {
        const struct aiMesh* mesh = scene->mMeshes[m];
        fprintf(file, "o Mesh_%d\n", m);

        for (unsigned int f = 0; f < mesh->mNumFaces; f++) {
            const struct aiFace face = mesh->mFaces[f];
            fprintf(file, "f");

            for (unsigned int i = 0; i < face.mNumIndices; i++) {
                fprintf(file, " %u", face.mIndices[i] + vertex_offset);
            }

            fprintf(file, "\n");
        }

        vertex_offset += mesh->mNumVertices;
    }

    fclose(file);
    printf("Successfully exported to: %s\n", output_filename);
}

int main(int argc, char** argv) {
    if (argc != 3) {
        printf("Usage: %s <input.md3> <output.obj>\n", argv[0]);
        return 1;
    }

    const char* input_file = argv[1];
    const char* output_file = argv[2];

    // Import the MD3 file
    const struct aiScene* scene = aiImportFile(
        input_file,
        aiProcess_Triangulate |          // Ensure triangles
        aiProcess_JoinIdenticalVertices  // Combine duplicate vertices
    );

    if (!scene) {
        fprintf(stderr, "Error loading MD3 file: %s\n", aiGetErrorString());
        return 1;
    }

    printf("Successfully loaded MD3 file: %s\n", input_file);
    printf("Meshes: %u\n", scene->mNumMeshes);

    // Export as OBJ
    export_as_obj(scene, output_file);

    // Clean up
    aiReleaseImport(scene);

    return 0;
}