import os

def process_obj_file(input_file, output_file):
    """
    处理OBJ文件，使用顶点x,y坐标映射纹理UV坐标，忽略z值，同时保持原有文件结构和注释顺序
    
    参数:
        input_file: 输入OBJ文件路径
        output_file: 输出OBJ文件路径
    """
    # 检查输入文件是否存在
    if not os.path.exists(input_file):
        print(f"错误: 输入文件 {input_file} 不存在")
        return False
    
    try:
        with open(input_file, 'r', encoding='utf-8') as f_in:
            lines = f_in.readlines()
        
        # 提取顶点坐标并计算UV坐标
        vertices = []  # 存储顶点坐标 (x, y)
        vertex_lines = []  # 存储原始的顶点行
        
        for line in lines:
            stripped_line = line.strip()
            if stripped_line.startswith('v ') and not stripped_line.startswith('vt ') and not stripped_line.startswith('vn '):
                parts = stripped_line.split()
                if len(parts) >= 3:  # 至少要有v x y
                    try:
                        x = float(parts[1])
                        y = float(parts[2])
                        vertices.append((x, y))
                        vertex_lines.append(line.rstrip())
                    except ValueError:
                        # 如果解析失败，使用默认值
                        vertices.append((0.0, 0.0))
                        vertex_lines.append(line.rstrip())
        
        # 计算UV坐标的边界范围
        if vertices:
            x_coords = [v[0] for v in vertices]
            y_coords = [v[1] for v in vertices]
            min_x, max_x = min(x_coords), max(x_coords)
            min_y, max_y = min(y_coords), max(y_coords)
            
            # 避免除零错误
            x_range = max_x - min_x if max_x != min_x else 1.0
            y_range = max_y - min_y if max_y != min_y else 1.0
            
            # 为每个顶点生成UV坐标（基于x,y坐标映射到0-1范围）
            uv_coords = []
            for x, y in vertices:
                # 将x,y坐标归一化到0-1范围
                u = (x - min_x) / x_range
                v = (y - min_y) / y_range
                uv_coords.append(f"vt {u:.6f} {v:.6f}")
        else:
            uv_coords = []
        
        # 处理每一行，保持原有顺序
        processed_lines = []
        current_vertex_index = 0
        face_count = 0
        
        for line in lines:
            original_line = line.rstrip()  # 去除右侧空白，保持左侧缩进
            
            # 如果是顶点数据，保持原样
            if original_line.startswith('v ') and not original_line.startswith('vt ') and not original_line.startswith('vn '):
                processed_lines.append(original_line)
                current_vertex_index += 1
            
            # 如果是面数据，为每个顶点引用对应的纹理坐标
            elif original_line.startswith('f '):
                face_parts = original_line.split()
                if len(face_parts) >= 4:  # 至少应该有 "f" 和三个顶点
                    # 重建面数据，为每个顶点添加对应的纹理坐标索引
                    new_face_parts = ['f']
                    vertex_indices = []
                    
                    # 首先提取所有顶点索引
                    for part in face_parts[1:]:
                        if '//' in part:  # 格式: v//vn
                            v_index, vn_index = part.split('//')
                            vertex_indices.append(int(v_index))
                        elif '/' in part:  # 格式: v/vt/vn 或 v/vt
                            parts = part.split('/')
                            vertex_indices.append(int(parts[0]))
                        else:  # 只有顶点索引
                            vertex_indices.append(int(part))
                    
                    # 为每个顶点构建新的面数据
                    for j, part in enumerate(face_parts[1:]):
                        vertex_index = vertex_indices[j]
                        
                        if '//' in part:  # 格式: v//vn
                            v_index, vn_index = part.split('//')
                            # 使用顶点索引作为纹理坐标索引（因为是一一对应的）
                            new_part = f"{v_index}/{vertex_index}//{vn_index}"
                        elif '/' in part:  # 格式: v/vt/vn 或 v/vt
                            parts = part.split('/')
                            if len(parts) == 2:  # v/vt
                                new_part = f"{parts[0]}/{vertex_index}"
                            else:  # v/vt/vn
                                new_part = f"{parts[0]}/{vertex_index}/{parts[2]}"
                        else:  # 只有顶点索引
                            new_part = f"{part}/{vertex_index}"
                        
                        new_face_parts.append(new_part)
                    
                    processed_lines.append(' '.join(new_face_parts))
                    face_count += 1
                else:
                    processed_lines.append(original_line)
            else:
                processed_lines.append(original_line)
        
        # 在顶点数据之后插入纹理坐标定义
        output_lines = []
        vertices_ended = False
        uv_inserted = False
        vertex_count = 0
        
        for i, line in enumerate(processed_lines):
            output_lines.append(line)
            
            # 统计顶点数量
            if line.startswith('v ') and not line.startswith('vt ') and not line.startswith('vn '):
                vertex_count += 1
            
            # 检测顶点数据块的结束（当遇到非顶点数据时）
            if not vertices_ended and line.startswith('v ') and not line.startswith('vt ') and not line.startswith('vn '):
                # 当前行是顶点数据，继续
                pass
            elif not vertices_ended and i > 0 and vertex_count > 0:
                # 当前行不是顶点数据，且我们已经处理过顶点数据
                # 这意味着顶点数据块已经结束
                vertices_ended = True
                
                # 在顶点数据块结束后插入纹理坐标
                if not uv_inserted and uv_coords:
                    output_lines.append("")  # 空行分隔
                    output_lines.append("# 添加的纹理坐标 (基于顶点x,y坐标映射，忽略z值)")
                    output_lines.append(f"# UV坐标范围: x[{min_x:.6f}-{max_x:.6f}] -> u[0-1], y[{min_y:.6f}-{max_y:.6f}] -> v[0-1]")
                    for uv in uv_coords:
                        output_lines.append(uv)
                    uv_inserted = True
        
        # 如果文件中顶点数据在最后，在最后插入UV坐标
        if not uv_inserted and uv_coords:
            output_lines.append("")  # 空行分隔
            output_lines.append("# 添加的纹理坐标 (基于顶点x,y坐标映射，忽略z值)")
            output_lines.append(f"# UV坐标范围: x[{min_x:.6f}-{max_x:.6f}] -> u[0-1], y[{min_y:.6f}-{max_y:.6f}] -> v[0-1]")
            for uv in uv_coords:
                output_lines.append(uv)
        
        # 写入输出文件
        with open(output_file, 'w', encoding='utf-8') as f_out:
            for line in output_lines:
                f_out.write(line + '\n')
        
        print(f"成功处理文件: {input_file} -> {output_file}")
        print(f"顶点数量: {len(vertices)}")
        print(f"处理面数量: {face_count}")
        print(f"生成的纹理坐标数量: {len(uv_coords)}")
        print(f"顶点X坐标范围: {min_x:.6f} 到 {max_x:.6f}")
        print(f"顶点Y坐标范围: {min_y:.6f} 到 {max_y:.6f}")
        
        return True
        
    except Exception as e:
        print(f"处理文件时出错: {e}")
        import traceback
        traceback.print_exc()
        return False

if __name__ == "__main__":
    input_file = "face.obj"  # 默认输入文件
    output_file = "face_with_uv.obj"  # 默认输出文件
    process_obj_file(input_file, output_file)