#!/usr/bin/env python3
"""
简化版文件哈希演示脚本
"""

import hashlib
import requests
import os

# API基础URL
BASE_URL = "http://localhost:8000/api/v1"
USER_ID = 8

def calculate_sha256_hash(file_content: bytes) -> str:
    """计算文件的SHA-256哈希值"""
    return hashlib.sha256(file_content).hexdigest()

def upload_and_demo_hash():
    """上传文件并演示哈希功能"""

    # 创建测试文件内容
    original_content = "Hello World! 这是演示文件哈希的测试内容。"

    print("=== 文件哈希演示 ===")
    print("原始文件内容:")
    print(f"'{original_content}'")
    print(f"文件大小: {len(original_content.encode('utf-8'))} bytes")
    print()

    # 计算哈希值
    file_hash = calculate_sha256_hash(original_content.encode('utf-8'))
    print("计算的SHA-256哈希值:")
    print(file_hash)
    print()

    # 上传文件
    try:
        files = {
            "file": ("hash_demo.txt", original_content.encode('utf-8'), "text/plain")
        }
        data = {
            "user_id": USER_ID,
            "description": "哈希演示文件",
            "tags": "demo,hash",
            "is_public": "false"
        }

        response = requests.post(
            f"{BASE_URL}/files/upload",
            files=files,
            data=data
        )

        if response.status_code == 201:
            result = response.json()
            if result.get("success"):
                file_info = result["data"]["file"]
                server_hash = file_info["file_hash"]
                file_id = file_info["id"]

                print("文件上传成功!")
                print(f"文件ID: {file_id}")
                print(f"服务器哈希值: {server_hash}")
                print()

                # 验证哈希值一致性
                if file_hash == server_hash:
                    print("哈希值验证通过! 客户端和服务器计算结果一致")
                else:
                    print("哈希值验证失败!")
                    print(f"客户端: {file_hash}")
                    print(f"服务器: {server_hash}")

                return file_id, original_content, file_hash, file_info['filename']
        else:
            print(f"上传失败: {response.text}")
            return None, None, None, None

    except Exception as e:
        print(f"上传出错: {e}")
        return None, None, None, None

def verify_download_integrity(file_id, original_content, original_hash, filename):
    """验证下载文件的完整性"""

    print("\n=== 文件下载和完整性验证 ===")

    try:
        # 下载文件
        data = {
            "user_id": USER_ID,
            "file_id": file_id
        }

        response = requests.post(
            f"{BASE_URL}/files/download",
            json=data
        )

        if response.status_code == 200:
            downloaded_content = response.content.decode('utf-8')

            print("下载的文件内容:")
            print(f"'{downloaded_content}'")
            print()

            # 验证内容完整性
            if downloaded_content == original_content:
                print("内容完整性验证通过!")
            else:
                print("内容完整性验证失败!")

            # 计算下载文件的哈希值
            downloaded_hash = calculate_sha256_hash(downloaded_content.encode('utf-8'))
            print("下载文件的哈希值:")
            print(downloaded_hash)
            print()

            # 验证哈希值
            if downloaded_hash == original_hash:
                print("下载文件哈希验证通过! 文件完整性得到保证")
            else:
                print("下载文件哈希验证失败! 文件可能已损坏")
                print(f"原始哈希: {original_hash}")
                print(f"下载哈希: {downloaded_hash}")

        else:
            print(f"下载失败: {response.text}")

    except Exception as e:
        print(f"下载过程出错: {e}")

def show_server_file_info(filename):
    """显示服务器上文件的信息"""

    print("\n=== 服务器文件信息 ===")

    # 检查uploads目录
    upload_path = os.path.join("uploads", filename)
    if os.path.exists(upload_path):
        file_size = os.path.getsize(upload_path)
        print(f"文件路径: {upload_path}")
        print(f"文件大小: {file_size} bytes")

        # 计算文件哈希
        with open(upload_path, 'rb') as f:
            content = f.read()
            file_hash = calculate_sha256_hash(content)
            print(f"文件SHA-256哈希: {file_hash}")

        # 显示文件内容
        with open(upload_path, 'r', encoding='utf-8') as f:
            content = f.read()
            print(f"文件内容: '{content}'")
    else:
        print(f"文件不存在: {upload_path}")

def demonstrate_hash_properties():
    """演示哈希的重要特性"""

    print("\n=== 哈希特性演示 ===")

    # 特性1: 相同输入产生相同哈希
    text1 = "Hello World"
    text2 = "Hello World"
    hash1 = calculate_sha256_hash(text1.encode())
    hash2 = calculate_sha256_hash(text2.encode())

    print("特性1: 相同输入产生相同哈希")
    print(f"文本1: '{text1}' -> {hash1}")
    print(f"文本2: '{text2}' -> {hash2}")
    print(f"哈希值相同: {hash1 == hash2}")
    print()

    # 特性2: 微小变化导致完全不同的哈希
    text3 = "Hello World"
    text4 = "Hello World!"  # 只多了一个感叹号
    hash3 = calculate_sha256_hash(text3.encode())
    hash4 = calculate_sha256_hash(text4.encode())

    print("特性2: 微小变化导致完全不同的哈希")
    print(f"文本3: '{text3}' -> {hash3}")
    print(f"文本4: '{text4}' -> {hash4}")
    print(f"哈希值不同: {hash3 != hash4}")
    print()

    # 特性3: 不可逆性
    sample_hash = "a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e"
    print("特性3: 哈希是单向的，无法从哈希反推原始内容")
    print(f"示例哈希: {sample_hash}")
    print("无法从这个哈希值推断出原始文本内容")
    print()

def main():
    """主演示函数"""

    # 演示哈希特性
    demonstrate_hash_properties()

    # 上传并演示哈希功能
    file_id, original_content, original_hash, filename = upload_and_demo_hash()

    if file_id:
        # 验证下载完整性
        verify_download_integrity(file_id, original_content, original_hash, filename)

        # 显示服务器文件信息
        show_server_file_info(filename)

        print("\n=== 总结 ===")
        print("file_hash 的作用:")
        print("1. 完整性验证 - 确保文件在传输存储过程中未损坏")
        print("2. 文件去重 - 相同内容只存储一份，节省空间")
        print("3. 安全检查 - 防止恶意文件和内容篡改")
        print("4. 快速比较 - 通过哈希值快速判断文件是否相同")
        print()
        print("如何还原文件:")
        print("1. 通过API下载: POST /api/v1/files/download")
        print("2. 直接从服务器目录读取: backend/uploads/[filename]")
        print("3. 验证文件完整性: 计算SHA-256哈希并与数据库中的file_hash比较")

    else:
        print("演示失败，无法上传测试文件")

if __name__ == "__main__":
    main()