import os
import json
from datetime import datetime

from module.config import HISTORY_BASE_DIR, SUPPORTED_EXTENSIONS


def validate_username(username):
    """验证用户名合法性（非空、无非法字符、长度限制）"""
    if not username or not username.strip():
        raise ValueError('用户名不能为空')
    username = username.strip()
    invalid_chars = '<>:"/\\|?*'
    for char in invalid_chars:
        if char in username:
            raise ValueError(f"用户名包含非法字符: '{char}'")
    if len(username) > 50:
        raise ValueError('用户名长度不能超过50个字符')
    return username


def get_user_dir(username):
    """获取用户目录路径，若不存在则自动创建"""
    user_dir = os.path.join(HISTORY_BASE_DIR, username)
    os.makedirs(user_dir, exist_ok=True)
    return user_dir


def load_metadata(user_dir):
    """从用户目录加载元数据JSON，文件不存在或损坏时返回空结构"""
    metadata_path = os.path.join(user_dir, 'metadata.json')
    if os.path.exists(metadata_path):
        try:
            with open(metadata_path, 'r', encoding='utf-8') as f:
                return json.load(f)
        except (json.JSONDecodeError, IOError):
            pass
    return {'images': []}


def save_metadata(user_dir, metadata):
    """将元数据JSON写入用户目录"""
    metadata_path = os.path.join(user_dir, 'metadata.json')
    with open(metadata_path, 'w', encoding='utf-8') as f:
        json.dump(metadata, f, ensure_ascii=False, indent=2)


def generate_image_filename(original_name):
    """生成带时间戳的唯一文件名，格式：时间戳_原始文件名"""
    timestamp = datetime.now().strftime('%Y%m%d_%H%M%S_%f')
    name, ext = os.path.splitext(original_name)
    if ext.lower() not in SUPPORTED_EXTENSIONS:
        ext = '.jpg'
    return f'{timestamp}_{name}{ext}'


def save_uploaded_file(file_data, original_name, user_dir):
    """将上传的文件数据保存到用户目录，返回保存路径"""
    filename = generate_image_filename(original_name)
    save_path = os.path.join(user_dir, filename)
    with open(save_path, 'wb') as f:
        f.write(file_data)
    return save_path


def delete_file(path):
    """删除指定路径的文件"""
    if os.path.exists(path):
        os.remove(path)


def get_history_images(user_dir):
    """扫描用户目录下所有支持格式的图片，返回按文件名排序的路径列表"""
    images = []
    if not os.path.exists(user_dir):
        return images
    for fname in sorted(os.listdir(user_dir)):
        ext = os.path.splitext(fname)[1].lower()
        if ext in SUPPORTED_EXTENSIONS:
            images.append(os.path.join(user_dir, fname))
    return images