/*
 * Tuxánci 2 - A first person shooter
 * Copyright (C) 2007-2011  Tuxánci Development Team
 * Copyright (C) 2025-2026  Connor Thomson
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <math.h>
#include <string.h>
#include "obj_model.h"
#include "camera.h"
#include "ta_sdl.h"
#include "files.h"

typedef struct ta_obj_uniforms {
    float mvp[16];
    float model[16];
} ta_obj_uniforms;

static SDL_GPUShader *ta_obj_shader(SDL_GPUDevice *device, const void *code, size_t size, SDL_GPUShaderStage stage) {
    SDL_GPUShaderCreateInfo info = {
        .code = code,
        .code_size = size,
        .entrypoint = "main",
        .format = SDL_GPU_SHADERFORMAT_SPIRV,
        .stage = stage,
        .num_uniform_buffers = stage == SDL_GPU_SHADERSTAGE_VERTEX ? 1 : 0,
    };
    return ta_sdl_create_gpu_shader(device, &info);
}

static void ta_obj_identity(float *matrix) {
    for (int index = 0; index < 16; index++) matrix[index] = index % 5 == 0 ? 1.0f : 0.0f;
}

static void ta_obj_multiply(float *result, const float *left, const float *right) {
    float product[16];
    for (int column = 0; column < 4; column++) for (int row = 0; row < 4; row++) {
        product[column * 4 + row] = 0.0f;
        for (int inner = 0; inner < 4; inner++) product[column * 4 + row] += left[inner * 4 + row] * right[column * 4 + inner];
    }
    memcpy(result, product, sizeof(product));
}

bool ta_obj_model_init(ta_obj_model *model, SDL_GPUDevice *device, const unsigned char *data, size_t size, SDL_GPUTextureFormat color_format, SDL_GPUTextureFormat depth_format, SDL_GPUSampleCount sample_count) {
    memset(model, 0, sizeof(*model));
    if (!ta_obj_parse(data, size, &model->mesh) || model->mesh.vertex_count == 0) return false;
    float minimum[3];
    float maximum[3];
    memcpy(minimum, model->mesh.vertices[0].position, sizeof(minimum));
    memcpy(maximum, minimum, sizeof(maximum));
    for (size_t index = 1; index < model->mesh.vertex_count; index++) for (int axis = 0; axis < 3; axis++) {
        if (model->mesh.vertices[index].position[axis] < minimum[axis]) minimum[axis] = model->mesh.vertices[index].position[axis];
        if (model->mesh.vertices[index].position[axis] > maximum[axis]) maximum[axis] = model->mesh.vertices[index].position[axis];
    }
    float center[3] = {(minimum[0] + maximum[0]) * 0.5f, (minimum[1] + maximum[1]) * 0.5f, (minimum[2] + maximum[2]) * 0.5f};
    float extent = maximum[0] - minimum[0];
    for (int axis = 1; axis < 3; axis++) if (maximum[axis] - minimum[axis] > extent) extent = maximum[axis] - minimum[axis];
    for (size_t index = 0; index < model->mesh.vertex_count; index++) for (int axis = 0; axis < 3; axis++) model->mesh.vertices[index].position[axis] = (model->mesh.vertices[index].position[axis] - center[axis]) * (2.2f / extent);

    SDL_GPUBufferCreateInfo buffer_info = {.usage = SDL_GPU_BUFFERUSAGE_VERTEX, .size = (Uint32)(model->mesh.vertex_count * sizeof(*model->mesh.vertices))};
    model->vertex_buffer = SDL_CreateGPUBuffer(device, &buffer_info);
    if (!model->vertex_buffer) {
        ta_obj_free(&model->mesh);
        return false;
    }
    model->vertex_count = (Uint32)model->mesh.vertex_count;
    SDL_GPUShader *vertex_shader = ta_obj_shader(device, file_obj_vert_slang_spv_start, file_obj_vert_slang_spv_size, SDL_GPU_SHADERSTAGE_VERTEX);
    SDL_GPUShader *fragment_shader = ta_obj_shader(device, file_obj_frag_slang_spv_start, file_obj_frag_slang_spv_size, SDL_GPU_SHADERSTAGE_FRAGMENT);
    SDL_GPUVertexBufferDescription vertex_buffer = {.slot = 0, .pitch = sizeof(ta_obj_vertex), .input_rate = SDL_GPU_VERTEXINPUTRATE_VERTEX};
    SDL_GPUVertexAttribute attributes[2] = {
        {.location = 0, .buffer_slot = 0, .format = SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3, .offset = 0},
        {.location = 1, .buffer_slot = 0, .format = SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3, .offset = sizeof(float) * 3},
    };
    SDL_GPUColorTargetDescription color_target = {.format = color_format};
    SDL_GPUGraphicsPipelineCreateInfo pipeline_info = {
        .vertex_shader = vertex_shader,
        .fragment_shader = fragment_shader,
        .vertex_input_state = {.vertex_buffer_descriptions = &vertex_buffer, .num_vertex_buffers = 1, .vertex_attributes = attributes, .num_vertex_attributes = 2},
        .primitive_type = SDL_GPU_PRIMITIVETYPE_TRIANGLELIST,
        .rasterizer_state = {.cull_mode = SDL_GPU_CULLMODE_NONE},
        .depth_stencil_state = {.compare_op = SDL_GPU_COMPAREOP_LESS, .enable_depth_test = true, .enable_depth_write = true},
        .multisample_state = {.sample_count = sample_count},
        .target_info = {.num_color_targets = 1, .color_target_descriptions = &color_target, .depth_stencil_format = depth_format, .has_depth_stencil_target = true},
    };
    model->pipeline = ta_sdl_create_gpu_graphics_pipeline(device, &pipeline_info);
    SDL_ReleaseGPUShader(device, vertex_shader);
    SDL_ReleaseGPUShader(device, fragment_shader);
    return model->pipeline != NULL;
}

void ta_obj_model_upload(ta_obj_model *model, SDL_GPUCommandBuffer *command_buffer, SDL_GPUDevice *device) {
    if (model->uploaded || !model->vertex_buffer) return;
    Uint32 size = (Uint32)(model->mesh.vertex_count * sizeof(*model->mesh.vertices));
    SDL_GPUTransferBufferCreateInfo transfer_info = {.usage = SDL_GPU_TRANSFERBUFFERUSAGE_UPLOAD, .size = size};
    SDL_GPUTransferBuffer *transfer_buffer = ta_sdl_create_gpu_transfer_buffer(device, &transfer_info);
    void *mapped = ta_sdl_map_gpu_transfer_buffer(device, transfer_buffer, false);
    memcpy(mapped, model->mesh.vertices, size);
    SDL_UnmapGPUTransferBuffer(device, transfer_buffer);
    SDL_GPUCopyPass *copy_pass = ta_sdl_begin_gpu_copy_pass(command_buffer);
    SDL_GPUTransferBufferLocation source = {.transfer_buffer = transfer_buffer};
    SDL_GPUBufferRegion destination = {.buffer = model->vertex_buffer, .size = size};
    SDL_UploadToGPUBuffer(copy_pass, &source, &destination, false);
    SDL_EndGPUCopyPass(copy_pass);
    SDL_ReleaseGPUTransferBuffer(device, transfer_buffer);
    ta_obj_free(&model->mesh);
    model->uploaded = true;
}

void ta_obj_model_render(const ta_obj_model *model, SDL_GPUCommandBuffer *command_buffer, SDL_GPURenderPass *render_pass, int window_width, int window_height) {
    if (!model->pipeline || !model->vertex_buffer || !model->uploaded) return;
    ta_obj_uniforms uniforms;
    float view[16];
    float projection[16] = {0};
    float view_model[16];
    float rotation_x[16];
    float rotation_y[16];
    float rotation_z[16];
    float rotation_xy[16];
    float cosine = cosf(model->rotation[0]);
    float sine = sinf(model->rotation[0]);
    ta_obj_identity(rotation_x);
    rotation_x[5] = cosine;
    rotation_x[6] = sine;
    rotation_x[9] = -sine;
    rotation_x[10] = cosine;
    cosine = cosf(model->rotation[1]);
    sine = sinf(model->rotation[1]);
    ta_obj_identity(rotation_y);
    rotation_y[0] = cosine;
    rotation_y[2] = -sine;
    rotation_y[8] = sine;
    rotation_y[10] = cosine;
    cosine = cosf(model->rotation[2]);
    sine = sinf(model->rotation[2]);
    ta_obj_identity(rotation_z);
    rotation_z[0] = cosine;
    rotation_z[1] = sine;
    rotation_z[4] = -sine;
    rotation_z[5] = cosine;
    ta_obj_multiply(rotation_xy, rotation_y, rotation_x);
    ta_obj_multiply(uniforms.model, rotation_z, rotation_xy);
    uniforms.model[12] = model->position[0];
    uniforms.model[13] = model->position[1];
    uniforms.model[14] = model->position[2];
    float aspect = (float)window_width / (float)window_height;
    float focal_length = 1.0f / tanf(22.5f * 0.01745329252f);
    float near_plane = 0.1f;
    float far_plane = 100.0f;
    ta_camera_get_view_matrix(view);
    projection[0] = focal_length / aspect;
    projection[5] = focal_length;
    projection[10] = far_plane / (near_plane - far_plane);
    projection[11] = -1.0f;
    projection[14] = near_plane * far_plane / (near_plane - far_plane);
    ta_obj_multiply(view_model, view, uniforms.model);
    ta_obj_multiply(uniforms.mvp, projection, view_model);
    SDL_PushGPUVertexUniformData(command_buffer, 0, &uniforms, sizeof(uniforms));
    SDL_BindGPUGraphicsPipeline(render_pass, model->pipeline);
    SDL_GPUBufferBinding binding = {.buffer = model->vertex_buffer};
    SDL_BindGPUVertexBuffers(render_pass, 0, &binding, 1);
    SDL_DrawGPUPrimitives(render_pass, model->vertex_count, 1, 0, 0);
}

void ta_obj_model_destroy(ta_obj_model *model, SDL_GPUDevice *device) {
    SDL_ReleaseGPUGraphicsPipeline(device, model->pipeline);
    SDL_ReleaseGPUBuffer(device, model->vertex_buffer);
    ta_obj_free(&model->mesh);
    memset(model, 0, sizeof(*model));
}