import hashlib
import json
import base64
import os
import requests
from datetime import datetime
from flask import Flask, jsonify, request, render_template, flash, redirect, url_for

class Block:
    def __init__(self, index, timestamp, data, previous_hash, nonce=0):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.nonce = nonce
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        data_string = json.dumps(self.data, sort_keys=True)
        hash_data = str(self.index) + self.timestamp + data_string + self.previous_hash + str(self.nonce)
        return hashlib.sha256(hash_data.encode()).hexdigest()

    def mine_block(self, difficulty):
        target = '0' * difficulty
        while self.hash[:difficulty] != target:
            self.nonce += 1
            self.hash = self.calculate_hash()
            print(f"Mining block {self.index}: Nonce = {self.nonce}, Hash = {self.hash}")
        print(f"Block {self.index} mined successfully!")


class Blockchain:
    def __init__(self):
        self.chain = []
        self.difficulty = 4
        self.load_chain()

    def create_genesis_block(self):
        return Block(0, "0000-00-00 00:00:00", "Genesis Block", "0")

    def get_latest_block(self):
        return self.chain[-1]

    def add_block(self, new_block):
        new_block.previous_hash = self.get_latest_block().hash
        new_block.hash = new_block.calculate_hash()
        self.chain.append(new_block)
        self.save_chain()

    def load_chain(self):
        if os.path.exists('blockchain.json'):
            with open('blockchain.json', 'r') as file:
                chain_data = json.load(file)
                for block_data in chain_data:
                    block = Block(block_data['index'], block_data['timestamp'], block_data['data'], block_data['previous_hash'])
                    block.hash = block_data['hash']
                    self.chain.append(block)
        else:
            self.chain.append(self.create_genesis_block())

    def save_chain(self):
        chain_data = []
        for block in self.chain:
            chain_data.append({
                'index': block.index,
                'timestamp': block.timestamp,
                'data': block.data,
                'previous_hash': block.previous_hash,
                'hash': block.hash
            })
        with open('blockchain.json', 'w') as file:
            json.dump(chain_data, file)
    
    def is_chain_valid(self):
        for i in range(1, len(self.chain)):
            current_block = self.chain[i]
            previous_block = self.chain[i - 1]

            if current_block.hash != current_block.calculate_hash():
                return False

            if current_block.previous_hash != previous_block.hash:
                return False

            if current_block.hash[:self.difficulty] != '0' * self.difficulty:
                return False

        return True

app = Flask(__name__)
app.secret_key = 'lesecretkey'
blockchain = Blockchain()
CONNECTED_NODES = []

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/upload', methods=['POST'])
def upload_image():
    file = request.files['image']
    image_data = base64.b64encode(file.read()).decode('utf-8')
    current_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    block = Block(len(blockchain.chain), current_time, image_data, blockchain.get_latest_block().hash)
    block.mine_block(blockchain.difficulty)
    blockchain.add_block(block)

    if blockchain.is_chain_valid():
        flash('Image uploaded successfully.', 'success')
    else:
        flash('Corrupted blocks detected. Image upload failed.', 'danger')
        blockchain.chain.pop()

    return redirect(url_for('index'))

@app.route('/chain', methods=['GET'])
def get_chain():
    chain_data = []
    for block in blockchain.chain:
        chain_data.append({
            'index': block.index,
            'timestamp': block.timestamp,
            'data': block.data,
            'previous_hash': block.previous_hash,
            'hash': block.hash
        })
    return jsonify(chain_data)

@app.route('/register_node', methods=['POST'])
def register_node():
    node_url = request.form['node_url']
    if not node_url.startswith('http://') and not node_url.startswith('https://'):
        node_url = 'http://' + node_url
    if node_url not in CONNECTED_NODES:
        CONNECTED_NODES.append(node_url)
    return redirect(url_for('index'))

@app.route('/sync_chain', methods=['GET'])
def sync_chain():
    longest_chain = None
    current_len = len(blockchain.chain)

    for node_url in CONNECTED_NODES:
        response = requests.get(f'{node_url}/chain')
        if response.status_code == 200:
            chain_data = response.json()
            chain_len = len(chain_data)
            if chain_len > current_len:
                current_len = chain_len
                longest_chain = chain_data

    if longest_chain:
        blockchain.chain = [Block(block['index'], block['timestamp'], block['data'], block['previous_hash']) for block in longest_chain]
        blockchain.save_chain()
        flash('Blockchain synchronized successfully', 'success')
    else:
        flash('Blockchain is already up to date', 'info')

    return redirect(url_for('index'))

@app.route('/validate', methods=['GET'])
def validate_blockchain():
    is_valid = blockchain.is_chain_valid()
    if is_valid:
        return jsonify({"message": "Blockchain is valid"})
    else:
        return jsonify({"message": "Blockchain is invalid"}), 400
    
@app.route('/nodes', methods=['GET'])
def get_nodes():
    return jsonify(CONNECTED_NODES)

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000, debug=True)