/*
 * Tuxánci 2 - A first person shooter
 * 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 <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include "ta_sdl.h"
#include "window.h"
#include "files.h"
#include "text.h"
#include "logging.h"
#include "screen.h"

#define SPIRV_ENTRY_POINT "main"

typedef enum ta_gpu_shape_type {
    TA_GPU_SHAPE_FILLED_RECTANGLE,
    TA_GPU_SHAPE_RECTANGLE,
    TA_GPU_SHAPE_LINE,
    TA_GPU_SHAPE_FILLED_CIRCLE,
    TA_GPU_SHAPE_CIRCLE,
    TA_GPU_SHAPE_FILLED_TRIANGLE,
    TA_GPU_SHAPE_TRIANGLE,
} ta_gpu_shape_type;

typedef struct ta_gpu_shape {
    ta_gpu_shape_type type;
    float             bounds[4];
    float             points[3][2];
    float             color[4];
    float             thickness;
} ta_gpu_shape;

typedef struct ta_gpu_shape_uniforms {
    float bounds[4];
    float points[3][4];
    float viewport[4];
    float color[4];
    float params[4];
} ta_gpu_shape_uniforms;

// NOTE: Does this formatting look good?
       SDL_GPUDevice           *ta_gpu_device;
       SDL_GPUGraphicsPipeline *ta_gpu_text_pipeline;
       SDL_GPUTexture          *ta_gpu_text_texture;
       SDL_GPUSampler          *ta_gpu_text_sampler;
       Uint32                   ta_gpu_text_texture_width;
       Uint32                   ta_gpu_text_texture_height;
static SDL_GPUGraphicsPipeline *ta_gpu_shape_pipeline;
static SDL_GPUTexture          *ta_gpu_msaa_texture;
static SDL_GPUTexture          *ta_gpu_depth_texture;
       SDL_GPUSampleCount       ta_gpu_sample_count         = SDL_GPU_SAMPLECOUNT_8;
       SDL_GPUTextureFormat     ta_gpu_swapchain_format;
static Uint32                   ta_gpu_msaa_texture_width;
static Uint32                   ta_gpu_msaa_texture_height;
static SDL_GPUCommandBuffer    *ta_gpu_command_buffer;
static SDL_GPUTexture          *ta_gpu_swapchain_texture;
static ta_gpu_shape            *ta_gpu_shapes;
static size_t                   ta_gpu_shape_count;
static size_t                   ta_gpu_shape_capacity;

static void ta_gpu_resize_msaa_texture(SDL_GPUTextureFormat format) {
    if (ta_gpu_msaa_texture_width  == (Uint32)ta_window_width  &&
        ta_gpu_msaa_texture_height == (Uint32)ta_window_height &&
        ta_gpu_msaa_texture) {
        return;
    }

    SDL_ReleaseGPUTexture(ta_gpu_device, ta_gpu_msaa_texture);
    SDL_ReleaseGPUTexture(ta_gpu_device, ta_gpu_depth_texture);
    ta_gpu_msaa_texture  = NULL;
    ta_gpu_depth_texture = NULL;

    SDL_GPUTextureCreateInfo texture_info = {
        .type                 = SDL_GPU_TEXTURETYPE_2D,
        .format               = format,
        .usage                = SDL_GPU_TEXTUREUSAGE_COLOR_TARGET,
        .width                = (Uint32)ta_window_width,
        .height               = (Uint32)ta_window_height,
        .layer_count_or_depth = 1,
        .num_levels           = 1,
        .sample_count         = ta_gpu_sample_count,
    };
    ta_gpu_msaa_texture        = ta_sdl_create_gpu_texture(ta_gpu_device, &texture_info);
    texture_info.format        = SDL_GPU_TEXTUREFORMAT_D32_FLOAT;
    texture_info.usage         = SDL_GPU_TEXTUREUSAGE_DEPTH_STENCIL_TARGET;
    ta_gpu_depth_texture       = ta_sdl_create_gpu_texture(ta_gpu_device, &texture_info);
    ta_gpu_msaa_texture_width  = (Uint32)ta_window_width;
    ta_gpu_msaa_texture_height = (Uint32)ta_window_height;
}

static SDL_GPUShader *ta_gpu_load_shader(SDL_GPUDevice *device, const void *code, size_t code_size, SDL_GPUShaderStage stage, Uint32 num_samplers, Uint32 num_uniform_buffers) {
    SDL_GPUShaderCreateInfo info = {
        .code                = code,
        .code_size           = code_size,
        .entrypoint          = SPIRV_ENTRY_POINT,
        .format              = SDL_GPU_SHADERFORMAT_SPIRV,
        .stage               = stage,
        .num_samplers        = num_samplers,
        .num_uniform_buffers = num_uniform_buffers,
    };

    SDL_GPUShader *shader = ta_sdl_create_gpu_shader(device, &info);
    return shader;
}

void ta_gpu_init(void) {
    ta_gpu_device = ta_sdl_create_gpu_device();

    ta_sdl_claim_window_for_gpu_device(ta_gpu_device, ta_window);

    ta_gpu_swapchain_format = SDL_GetGPUSwapchainTextureFormat(ta_gpu_device, ta_window);
    ta_gpu_resize_msaa_texture(ta_gpu_swapchain_format);

    SDL_GPUShader *vertex_shader = ta_gpu_load_shader(
        ta_gpu_device,
        file_text_vert_slang_spv_start,
        file_text_vert_slang_spv_size,
        SDL_GPU_SHADERSTAGE_VERTEX,
        0,
        1
    );
    SDL_GPUShader *fragment_shader = ta_gpu_load_shader(
        ta_gpu_device,
        file_text_frag_slang_spv_start,
        file_text_frag_slang_spv_size,
        SDL_GPU_SHADERSTAGE_FRAGMENT,
        1,
        0
    );

    SDL_GPUColorTargetDescription color_target = {
        .format = ta_gpu_swapchain_format,
        .blend_state = {
            .src_color_blendfactor = SDL_GPU_BLENDFACTOR_SRC_ALPHA,
            .dst_color_blendfactor = SDL_GPU_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
            .color_blend_op        = SDL_GPU_BLENDOP_ADD,
            .src_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ONE,
            .dst_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
            .alpha_blend_op        = SDL_GPU_BLENDOP_ADD,
            .enable_blend          = true,
        },
    };
    SDL_GPUGraphicsPipelineCreateInfo pipeline_info = {
        .vertex_shader     = vertex_shader,
        .fragment_shader   = fragment_shader,
        .primitive_type    = SDL_GPU_PRIMITIVETYPE_TRIANGLELIST,
        .target_info       = {
            .num_color_targets = 1,
            .color_target_descriptions = &color_target,
        },
        .multisample_state = {
            .sample_count = ta_gpu_sample_count,
        },
    };
    ta_gpu_text_pipeline = ta_sdl_create_gpu_graphics_pipeline(ta_gpu_device, &pipeline_info);
    SDL_ReleaseGPUShader(ta_gpu_device, vertex_shader);
    SDL_ReleaseGPUShader(ta_gpu_device, fragment_shader);

    vertex_shader = ta_gpu_load_shader(
        ta_gpu_device,
        file_shape_vert_slang_spv_start,
        file_shape_vert_slang_spv_size,
        SDL_GPU_SHADERSTAGE_VERTEX,
        0,
        1
    );
    fragment_shader = ta_gpu_load_shader(
        ta_gpu_device,
        file_shape_frag_slang_spv_start,
        file_shape_frag_slang_spv_size,
        SDL_GPU_SHADERSTAGE_FRAGMENT,
        0,
        1
    );
    pipeline_info.vertex_shader              = vertex_shader;
    pipeline_info.fragment_shader            = fragment_shader;
    pipeline_info.rasterizer_state.cull_mode = SDL_GPU_CULLMODE_NONE;
    pipeline_info.depth_stencil_state        = (SDL_GPUDepthStencilState){ 0 };
    ta_gpu_shape_pipeline                    = ta_sdl_create_gpu_graphics_pipeline(ta_gpu_device, &pipeline_info);
    SDL_ReleaseGPUShader(ta_gpu_device, vertex_shader);
    SDL_ReleaseGPUShader(ta_gpu_device, fragment_shader);

    SDL_GPUSamplerCreateInfo sampler_info = {
        .min_filter     = SDL_GPU_FILTER_LINEAR,
        .mag_filter     = SDL_GPU_FILTER_LINEAR,
        .mipmap_mode    = SDL_GPU_SAMPLERMIPMAPMODE_NEAREST,
        .address_mode_u = SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE,
        .address_mode_v = SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE,
        .address_mode_w = SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE,
    };
    ta_gpu_text_sampler = ta_sdl_create_gpu_sampler(ta_gpu_device, &sampler_info);
}

void ta_gpu_start_frame(void) {
    ta_gpu_shape_count       = 0;
    ta_gpu_command_buffer    = ta_sdl_acquire_gpu_command_buffer(ta_gpu_device);
    ta_gpu_swapchain_texture = NULL;
    ta_gpu_swapchain_format  = SDL_GetGPUSwapchainTextureFormat(ta_gpu_device, ta_window);

    ta_sdl_wait_and_acquire_gpu_swapchain_texture(ta_gpu_command_buffer, ta_window, &ta_gpu_swapchain_texture);
    if (ta_gpu_swapchain_texture) {
        ta_gpu_resize_msaa_texture(ta_gpu_swapchain_format);
    }
}

static void ta_gpu_queue_shape(const ta_gpu_shape *shape) {
    if (ta_gpu_shape_count == ta_gpu_shape_capacity) {
        size_t next_capacity = ta_gpu_shape_capacity == 0 ? 64 : ta_gpu_shape_capacity * 2;
        ta_gpu_shape *shapes = realloc(ta_gpu_shapes, next_capacity * sizeof(*shapes));
        if (!shapes) {
            return;
        }
        ta_gpu_shapes         = shapes;
        ta_gpu_shape_capacity = next_capacity;
    }

    ta_gpu_shapes[ta_gpu_shape_count++] = *shape;
}

static void ta_gpu_set_shape_color(float output[4], ta_color color) {
    output[0] = (float)color.red   / 255.0f;
    output[1] = (float)color.green / 255.0f;
    output[2] = (float)color.blue  / 255.0f;
    output[3] = (float)color.alpha / 255.0f;
}

void ta_gpu_draw_filled_rectangle(ta_color color, int x, int y, int width, int height) {
    if (width <= 0 || height <= 0) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_FILLED_RECTANGLE
    };
    shape.bounds[0] = (float)x;
    shape.bounds[1] = (float)y;
    shape.bounds[2] = (float)width;
    shape.bounds[3] = (float)height;
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_draw_rectangle(ta_color color, int x, int y, int width, int height, int thickness) {
    if (width <= 0 || height <= 0 || thickness <= 0) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_RECTANGLE
    };
    shape.bounds[0] = (float)x;
    shape.bounds[1] = (float)y;
    shape.bounds[2] = (float)width;
    shape.bounds[3] = (float)height;
    shape.thickness = (float)thickness;
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_draw_line(ta_color color, int x1, int y1, int x2, int y2, int thickness) {
    if (thickness <= 0 || (x1 == x2 && y1 == y2)) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_LINE
    };
    shape.points[0][0] = (float)x1;
    shape.points[0][1] = (float)y1;
    shape.points[1][0] = (float)x2;
    shape.points[1][1] = (float)y2;
    shape.thickness    = (float)thickness;
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_draw_filled_circle(ta_color color, int x, int y, int radius) {
    if (radius <= 0) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_FILLED_CIRCLE
    };
    shape.bounds[0] = (float)(x - radius);
    shape.bounds[1] = (float)(y - radius);
    shape.bounds[2] = (float)(radius * 2);
    shape.bounds[3] = (float)(radius * 2);
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_draw_circle(ta_color color, int x, int y, int radius, int thickness) {
    if (radius <= 0 || thickness <= 0) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_CIRCLE
    };
    shape.bounds[0] = (float)(x - radius);
    shape.bounds[1] = (float)(y - radius);
    shape.bounds[2] = (float)(radius * 2);
    shape.bounds[3] = (float)(radius * 2);
    shape.thickness = (float)thickness;
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

static void ta_gpu_set_triangle_points(ta_gpu_shape *shape, int x1, int y1, int x2, int y2, int x3, int y3) {
    shape->points[0][0] = (float)x1;
    shape->points[0][1] = (float)y1;
    shape->points[1][0] = (float)x2;
    shape->points[1][1] = (float)y2;
    shape->points[2][0] = (float)x3;
    shape->points[2][1] = (float)y3;
}

void ta_gpu_draw_filled_triangle(ta_color color, int x1, int y1, int x2, int y2, int x3, int y3) {
    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_FILLED_TRIANGLE
    };
    ta_gpu_set_triangle_points(&shape, x1, y1, x2, y2, x3, y3);
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_draw_triangle(ta_color color, int x1, int y1, int x2, int y2, int x3, int y3, int thickness) {
    if (thickness <= 0) {
        return;
    }

    ta_gpu_shape shape = {
        .type = TA_GPU_SHAPE_TRIANGLE
    };
    ta_gpu_set_triangle_points(&shape, x1, y1, x2, y2, x3, y3);
    shape.thickness = (float)thickness;
    ta_gpu_set_shape_color(shape.color, color);
    ta_gpu_queue_shape(&shape);
}

void ta_gpu_end_frame(void) {
    if (ta_gpu_swapchain_texture) {
        ta_gpu_upload_text(ta_gpu_command_buffer);
        ta_screen_upload(ta_gpu_command_buffer);

        SDL_GPUColorTargetInfo color_target = {
            .texture         = ta_gpu_msaa_texture,
            .load_op         = SDL_GPU_LOADOP_CLEAR,
            .store_op        = SDL_GPU_STOREOP_RESOLVE,
            .resolve_texture = ta_gpu_swapchain_texture,
            .clear_color     = {
                ta_color_black.red,
                ta_color_black.green,
                ta_color_black.blue,
                ta_color_black.alpha
            },
        };

        SDL_GPUDepthStencilTargetInfo depth_target = {
            .texture          = ta_gpu_depth_texture,
            .clear_depth      = 1.0f,
            .load_op          = SDL_GPU_LOADOP_CLEAR,
            .store_op         = SDL_GPU_STOREOP_DONT_CARE,
            .stencil_load_op  = SDL_GPU_LOADOP_DONT_CARE,
            .stencil_store_op = SDL_GPU_STOREOP_DONT_CARE,
        };
        SDL_GPURenderPass *render_pass = ta_sdl_begin_gpu_render_pass(
            ta_gpu_command_buffer,
            &color_target,
            1,
            &depth_target
        );

        ta_text_render(ta_gpu_command_buffer, render_pass);
        ta_screen_render(ta_gpu_command_buffer, render_pass);
        SDL_BindGPUGraphicsPipeline(render_pass, ta_gpu_shape_pipeline);
        for (size_t index = 0; index < ta_gpu_shape_count; index++) {
            ta_gpu_shape *shape = &ta_gpu_shapes[index];
            ta_gpu_shape_uniforms uniforms = {
                0
            };
            memcpy(uniforms.bounds, shape->bounds, sizeof(uniforms.bounds));
            for (int point = 0; point < 3; point++) {
                uniforms.points[point][0] = shape->points[point][0];
                uniforms.points[point][1] = shape->points[point][1];
            }
            uniforms.viewport[0] = (float)ta_window_width;
            uniforms.viewport[1] = (float)ta_window_height;
            memcpy(uniforms.color, shape->color, sizeof(uniforms.color));
            uniforms.params[0] = (float)shape->type;
            uniforms.params[1] = shape->thickness;
            SDL_PushGPUVertexUniformData(ta_gpu_command_buffer, 0, &uniforms, sizeof(uniforms));
            SDL_PushGPUFragmentUniformData(ta_gpu_command_buffer, 0, &uniforms, sizeof(uniforms));
            Uint32 vertex_count = shape->type == TA_GPU_SHAPE_FILLED_TRIANGLE ? 3 : shape->type == TA_GPU_SHAPE_TRIANGLE ? 18 : 6;
            SDL_DrawGPUPrimitives(render_pass, vertex_count, 1, 0, 0);
        }
        SDL_EndGPURenderPass(render_pass);
    }

    ta_sdl_submit_gpu_command_buffer(ta_gpu_command_buffer);
}