#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#include "libs/cglm/cglm.h"
#include "libs/glad/include/glad/glad.h"
#include <SDL2/SDL.h>
// #include <SDL2/SDL_events.h>
// #include "stb_image.h"
// #include <SDL2/SDL_image.h>
// #include <SDL2/SDL_render.h>
#include "lib.h"

//Screen dimension constants
const int SCREEN_WIDTH = 1024;
const int SCREEN_HEIGHT = 768;

int main(void) {
    SDL_Window *window = NULL;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("error initializing SDL: %s\n", SDL_GetError());
        return 1;
    }

    SDL_GL_LoadLibrary(NULL);

    // Request an OpenGL 4.5 context (should be core)
    SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
    // Also request a depth buffer
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    window = SDL_CreateWindow("Terrain",
                              SDL_WINDOWPOS_UNDEFINED,
                              SDL_WINDOWPOS_UNDEFINED,
                              SCREEN_WIDTH,
                              SCREEN_HEIGHT,
                              SDL_WINDOW_OPENGL );

    if (window == NULL) {
        printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
        return 1;
    }

    SDL_GL_CreateContext(window);
    gladLoadGLLoader(SDL_GL_GetProcAddress);

    printf("Vendor:   %s\n", glGetString(GL_VENDOR));
    printf("Renderer: %s\n", glGetString(GL_RENDERER));
    printf("Version:  %s\n", glGetString(GL_VERSION));

    SDL_GL_SetSwapInterval(1);

    // int w, h, c;
    // unsigned char *terrain_img = stbi_load("terrain.png", &w, &h, &c, 0);
    int w = 3;
    int h = 3;
    int vcount = w * h * 3;
    // float scale_y = 1.0f;
    // float shift_y = 16.0f;
    // for (int row = 0; row < h; row++) {
    //     for (int col = 0; col < w; col++) {
    //         unsigned char *texel = terrain_img + (row * w + col) * c;
    //         unsigned char y = texel[0];

    //         float *v = &verts[(row * w + col) * 3];
    //         *(v+0) = -w/2 + col;
    //         *(v+1) = y * scale_y + shift_y;
    //         *(v+2) = -h/2 + row;
    //     }
    // }

    // float *verts = malloc(vcount * sizeof(float));
    // float terrainVerts[vcount];

    float terrainVerts[] = {
        0.f, 0.f, 0.f,
        1.f, 0.f, 0.f,
        2.f, 0.f, 0.f,
        3.f, 0.f, 0.f,
        0.f, 1.f, 0.f,
        1.f, 1.f, 0.f,
        2.f, 1.f, 0.f,
        3.f, 1.f, 0.f,

        0.f, 2.f, 0.f,
        1.f, 2.f, 0.f,
        2.f, 2.f, 0.f,
        3.f, 2.f, 0.f,
        0.f, 3.f, 0.f,
        1.f, 3.f, 0.f,
        2.f, 3.f, 0.f,
        3.f, 3.f, 0.f,
    };

    // for (int row = 1; row < h / 2; row += 2) {
    //     for (int col = 0; col < w; col++) {
    //         int idx1 = ((row-1) * w + col);
    //         int idx2 = (row * w + col);
    //         terrainVerts[idx1*3+0] = (float)row-1;
    //         terrainVerts[idx1*3+1] = (float)col;
    //         terrainVerts[idx1*3+2] = 0.0f;
    //         terrainVerts[idx1*3+3] = (float)row;
    //         terrainVerts[idx1*3+4] = (float)col;
    //         terrainVerts[idx1*3+5] = 0.0f;
    //     }
    // }

    // unsigned int terrainIndices[w*(h-1)*2];
    // int i = 0;
    // for (int row = 0; row < h-1; row++) {
    //     for (int col = 0; col < w; col++) {
    //         terrainIndices[i++] = row * w + col;
    //         terrainIndices[i++] = (row+1) * w + (w+1);
    //         // printf("1 %d 2 %d\n", idx1, idx2);
    //     }
    // }
    unsigned int terrainIndices[] = {
        0,4,1,5,2,6,3,7,7,
        4,4,8,5,9,6,10,7,11,11
    };


    // = {
    //     0, 1, 3, // first triangle
    //     1, 2, 3  // second triangle
    // };


    printf("Loaded %d vertices\n", w * h);
    // stbi_image_free(terrain_img);

    // const unsigned int NUM_STRIPS = h - 1;
    // const unsigned int NUM_VERTS_PER_STRIP = w * 2;

    unsigned int terrainVAO, terrainVBO, terrainIBO;
    glGenVertexArrays(1, &terrainVAO);
    glBindVertexArray(terrainVAO);

    glGenBuffers(1, &terrainVBO);
    glBindBuffer(GL_ARRAY_BUFFER, terrainVBO);
    // glBufferData(GL_ARRAY_BUFFER, vcount * sizeof(float), verts, GL_STATIC_DRAW);
    glBufferData(GL_ARRAY_BUFFER, sizeof(terrainVerts), terrainVerts, GL_STATIC_DRAW);

    // position attribute
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glGenBuffers(1, &terrainIBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, terrainIBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(terrainIndices), terrainIndices, GL_STATIC_DRAW);
    // Disable depth test and face culling.
    glDisable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);
    int screen_width,screen_height;
    SDL_GetWindowSize(window, &screen_width, &screen_height);
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);

    GLuint shaderProgram =
        compileShaderProgram("shaders/main.vert", "shaders/main.frag", NULL);

    int matrixLocation;

    SDL_Event e;
    bool quit = false;
    Uint64 now = SDL_GetPerformanceCounter();
    Uint64 last = 0;
    double dt = 0;
    bool draw_wireframe = false;
    float x = 0.0f, y = 0.0f;
    Uint64 frame_count = 0;
    while (quit == false) {
        frame_count++;
        last = now;
        now = SDL_GetPerformanceCounter();
        dt = (double)((now - last)*1000 / (double)SDL_GetPerformanceFrequency());
        (void)dt;
        const Uint8* keystates = SDL_GetKeyboardState(NULL);
        float speed = 1.1f;
        if (keystates[SDL_SCANCODE_W]) {
            y += speed;
        }
        if (keystates[SDL_SCANCODE_S]) {
            y -= speed;
        }
        if (keystates[SDL_SCANCODE_A]) {
            x += speed;
        }
        if (keystates[SDL_SCANCODE_D]) {
            x -= speed;
        }

        while (SDL_PollEvent( &e)) {
            if (e.type == SDL_QUIT) {
                quit = true;
            } else if (e.type == SDL_KEYDOWN) {
                char key = e.key.keysym.sym;
                if (key == '1') {
                    draw_wireframe = !draw_wireframe;
                }
            }
        }

        mat4 projection;
        glm_mat4_identity(projection);
        float aspectRatio = (float)SCREEN_WIDTH / (float)SCREEN_HEIGHT;
        glm_perspective(45.0f, aspectRatio, 0.1f, 1000.0f, projection);
        mat4 model;
        glm_mat4_identity(model);
        mat4 view;
        glm_mat4_identity(view);
        glm_translate(model, (vec3){x, 0.0f, y});
        glm_translate(model, (vec3){0.0f, 0.0f, -5.0f});
        // glm_rotate(model, frame_count * 0.01f, (vec3){0.0f, 0.0f, 1.0f});


        matrixLocation = glGetUniformLocation(shaderProgram, "view");
        glUniformMatrix4fv(matrixLocation, 1, GL_FALSE, view[0]);
        matrixLocation = glGetUniformLocation(shaderProgram, "projection");
        glUniformMatrix4fv(matrixLocation, 1, GL_FALSE, projection[0]);
        matrixLocation = glGetUniformLocation(shaderProgram, "model");
        glUniformMatrix4fv(matrixLocation, 1, GL_FALSE, model[0]);

        glUseProgram(shaderProgram);
        glViewport(0, 0, screen_width, screen_height);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        // for (unsigned strip = 0; strip < NUM_STRIPS; strip++) {
        //     glDrawElements(GL_TRIANGLE_STRIP,   // primitive type
        //                    NUM_VERTS_PER_STRIP,   // number of indices to render
        //                    GL_UNSIGNED_INT,     // index data type
        //                    (void*)(sizeof(unsigned) * (NUM_VERTS_PER_STRIP) * strip)); // offset to starting index
        // }

        if (draw_wireframe) {
            glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
        } else {
            glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
        }
        // glEnableClientState(GL_VERTEX_ARRAY);
        // glVertexPointer(3, GL_FLOAT, terrainVerts);
        // glDrawArrays(GL_TRIANGLE_STRIP, 0, w*h);
        // glDisableClientState(GL_VERTEX_ARRAY);
        glBindVertexArray(terrainVAO);
        // glDrawElements(GL_TRIANGLES, 8 * 3, GL_UNSIGNED_INT, 0);
        // glDrawArrays(GL_TRIANGLES, 0, w*h*3);
        size_t s = w*2 * sizeof(unsigned int);
        // glDrawElements(GL_TRIANGLE_STRIP, (w*h)+(w-1)*(h-2), GL_UNSIGNED_INT, (void*)s);
        glDrawElements(GL_TRIANGLE_STRIP, w*3*2, GL_UNSIGNED_INT, 0);

        SDL_GL_SwapWindow(window);
    }

    SDL_DestroyWindow( window );
    return 0;
}