reading

import os
import math
import time
import hashlib
from flask import Flask, request, session, render_template, send_file
from datetime import datetime

app = Flask(__name__)
app.secret_key = hashlib.md5(os.urandom(32)).hexdigest()
key = hashlib.md5(str(time.time_ns()).encode()).hexdigest()

books = os.listdir('./books')
books.sort(reverse=True)


@app.route('/')
def index():
    if session:
        book = session['book']
        page = session['page']
        page_size = session['page_size']
        total_pages = session['total_pages']
        filepath = session['filepath']

        words = read_file_page(filepath, page, page_size)
        return render_template('index.html', books=books, words=words)

    return render_template('index.html', books=books )


@app.route('/books', methods=['GET', 'POST'])
def book_page():
    if request.args.get('book'):
        book = request.args.get('book')
    elif session:
        book = session.get('book')
    else:
        return render_template('index.html', books=books, message='I need book')
    book=book.replace('..','.')
    filepath = './books/' + book

    if request.args.get('page_size'):
        page_size = int(request.args.get('page_size'))
    elif session:
        page_size = int(session.get('page_size'))
    else:
        page_size = 3000

    total_pages = math.ceil(os.path.getsize(filepath) / page_size)

    if request.args.get('page'):
        page = int(request.args.get('page'))
    elif session:
        page = int(session.get('page'))
    else:
        page = 1
    words = read_file_page(filepath, page, page_size)
    prev_page = page - 1 if page > 1 else None
    next_page = page + 1 if page < total_pages else None

    session['book'] = book
    session['page'] = page
    session['page_size'] = page_size
    session['total_pages'] = total_pages
    session['prev_page'] = prev_page
    session['next_page'] = next_page
    session['filepath'] = filepath
    return render_template('index.html', books=books, words=words )


@app.route('/flag', methods=['GET', 'POST'])
def flag():
    if hashlib.md5(session.get('key').encode()).hexdigest() == key:
        return os.popen('/readflag').read()
    else:
        return "no no no"


def read_file_page(filename, page_number, page_size):
    for i in range(3):
        for j in range(3):
            size=page_size + j
            offset = (page_number - 1) * page_size+i
            try:
                with open(filename, 'rb') as file:
                    file.seek(offset)
                    words = file.read(size)
                    return words.decode().split('\n')
            except Exception as e:
                pass
            #if error again
            offset = (page_number - 1) * page_size
            with open(filename, 'rb') as file:
                file.seek(offset)
                words = file.read(page_size)
            return words.split(b'\n')


if __name__ == '__main__':
    app.run(host='0.0.0.0', port='8000')