// ===== 1. 生成纹理对象 =====
unsigned int texture;
glGenTextures(1, &texture);

// ===== 2. 绑定纹理 =====
glBindTexture(GL_TEXTURE_2D, texture);

// ===== 3. 设置纹理参数 =====
// 环绕模式（超出 [0,1] 范围时的行为）
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

// 缩小过滤（纹理像素 < 屏幕像素时）
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);

// 放大过滤（纹理像素 > 屏幕像素时）
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

// ===== 4. 加载图片数据 =====
int width, height, nrChannels;
stbi_set_flip_vertically_on_load(true);
unsigned char *data = stbi_load("assets/textures/container.jpg", &width, &height, &nrChannels, 0);

if (data) {
    GLenum format = (nrChannels == 4) ? GL_RGBA : GL_RGB;
    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
} else {
    std::cerr << "Failed to load texture" << std::endl;
}

// ===== 5. 释放图片内存 =====
stbi_image_free(data);

// 设置边框颜色（CLAMP_TO_BORDER 模式）
float borderColor[] = { 1.0f, 0.0f, 0.0f, 1.0f };  // 红色边框
glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, borderColor);

glGenerateMipmap(GL_TEXTURE_2D);  // 自动生成所有 Mipmap 级别

// 手动为每个级别指定不同的纹理数据
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, data_level0);
glTexImage2D(GL_TEXTURE_2D, 1, GL_RGB, 128, 128, 0, GL_RGB, GL_UNSIGNED_BYTE, data_level1);
// ...

// 需要 GL_EXT_texture_filter_anisotropic 扩展
float maxAniso;
glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &maxAniso);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, maxAniso);

// 绑定纹理到不同单元
glActiveTexture(GL_TEXTURE0);   // 激活纹理单元 0
glBindTexture(GL_TEXTURE_2D, diffuseTexture);

glActiveTexture(GL_TEXTURE1);   // 激活纹理单元 1
glBindTexture(GL_TEXTURE_2D, specularTexture);

glActiveTexture(GL_TEXTURE2);   // 激活纹理单元 2
glBindTexture(GL_TEXTURE_2D, normalMapTexture);

// 设置着色器中的 sampler 采样哪个单元
shader.use();
shader.setInt("material.diffuse", 0);    // 采样纹理单元 0
shader.setInt("material.specular", 1);   // 采样纹理单元 1
shader.setInt("material.normal", 2);     // 采样纹理单元 2

int maxUnits;
glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &maxUnits);
printf("Max texture units: %d\n", maxUnits);  // 通常 16 或更多

// 加载 6 个面
const char* faces[6] = {
    "right.jpg", "left.jpg",
    "top.jpg", "bottom.jpg",
    "front.jpg", "back.jpg"
};

unsigned int cubemap;
glGenTextures(1, &cubemap);
glBindTexture(GL_TEXTURE_CUBE_MAP, cubemap);

for (int i = 0; i < 6; i++) {
    int w, h, ch;
    unsigned char* data = stbi_load(faces[i], &w, &h, &ch, 0);
    if (data) {
        glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB,
                     w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
    }
    stbi_image_free(data);
}

glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

// GLSL 中采样立方体贴图
in vec3 vDirection;  // 3D 方向向量
uniform samplerCube skybox;

void main() {
    FragColor = texture(skybox, vDirection);
}

// 使用压缩格式加载
glCompressedTexImage2D(GL_TEXTURE_2D, 0, GL_COMPRESSED_RGBA_S3TC_DXT5,
                       width, height, 0, imageSize, compressedData);

float vertices[] = {
    // 位置              // 颜色           // UV
     0.5f,  0.5f, 0.0f,  1.0f, 0.0f, 0.0f,  1.0f, 1.0f,  // 右上
     0.5f, -0.5f, 0.0f,  0.0f, 1.0f, 0.0f,  1.0f, 0.0f,  // 右下
    -0.5f, -0.5f, 0.0f,  0.0f, 0.0f, 1.0f,  0.0f, 0.0f,  // 左下
    -0.5f,  0.5f, 0.0f,  1.0f, 1.0f, 0.0f,  0.0f, 1.0f,  // 左上
};

unsigned int indices[] = { 0, 1, 3, 1, 2, 3 };

#version 460 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;

out vec3 vColor;
out vec2 vTexCoord;

void main() {
    gl_Position = vec4(aPos, 1.0);
    vColor = aColor;
    vTexCoord = aTexCoord;
}

#version 460 core
in vec3 vColor;
in vec2 vTexCoord;

out vec4 FragColor;

uniform sampler2D ourTexture;
uniform float mixFactor;

void main() {
    vec4 texColor = texture(ourTexture, vTexCoord);
    FragColor = mix(texColor, vec4(vColor, 1.0), mixFactor);
}

// 加载纹理
unsigned int texture = loadTexture("assets/textures/container.jpg");

// 渲染循环中
shader.use();
shader.setFloat("mixFactor", 0.2f);

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
shader.setInt("ourTexture", 0);

glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);