from pygments.lexers import guess_lexer, guess_lexer_for_filename
from pygments.formatters import HtmlFormatter
from pygments import highlight
from flask import Flask, Response, request, abort, redirect
from random import SystemRandom
from functools import wraps
import string
import os.path

app = Flask(__name__)
app.config.from_pyfile(os.path.join(os.path.dirname(os.path.abspath(__file__)), 'app.cfg'))
rng = SystemRandom()

def check_auth(username, password):
    # Side channel attack on string comparison!
    return username == app.config['USERNAME'] and password == app.config['PASSWORD']

def requires_auth(f):
    @wraps(f)
    def decorated(*args, **kwargs):
        auth = request.authorization
        if not auth or not check_auth(auth.username, auth.password):
            return Response('Wrong username/password', 401, {'WWW-Authenticate': 'Basic realm="Aleph Paste"'})
        return f(*args, **kwargs)
    return decorated

@app.route('/')
def landing():
    return redirect('https://git.zx2c4.com/alephpaste/about/', code=302)

@app.route('/', methods=['POST'])
@requires_auth
def new_paste():
    if 'paste' not in request.files:
        abort(400)
    while True:
        paste = ''.join(rng.choice(string.ascii_letters + string.digits) for _ in range(8))
        file_name = os.path.join(app.config['FILES_PATH'], paste + '.txt')
        if not os.path.exists(file_name):
            break
    f = request.files['paste']
    f.save(file_name)
    f.close()
    return app.config['URI_BASE'] + '/' + paste + '\n'


@app.route('/<paste>', methods=['DELETE'])
@requires_auth
def delete_paste(paste):
    try:
        os.unlink(os.path.join(app.config['FILES_PATH'], paste + '.txt'))
    except:
        abort(404)
    return ''

@app.route('/<paste>')
def send_paste(paste):
    return Response(mimetype='text/plain', headers={'X-Accel-Redirect': os.path.join(app.config['FILES_ACCEL'], paste + '.txt')})

@app.route('/<paste>/')
def send_highlighted_paste_guess(paste):
    return send_highlighted_paste(paste, None)

@app.route('/<paste>/<ftype>')
def send_highlighted_paste(paste, ftype):
    try:
        f = open(os.path.join(app.config['FILES_PATH'], paste + '.txt'), 'r')
        text = f.read()
        f.close()
        if ftype is None or len(ftype) == 0:
            lexer = guess_lexer(text)
        else:
            lexer = guess_lexer_for_filename(paste + '.' + ftype, text)
        formatter = HtmlFormatter(style='pastie', full=True, title='{0} - Aleph Paste'.format(paste), linenos='table', anchorlinenos=True, lineanchors="line")
        return highlight(text, lexer, formatter)
    except:
        return send_paste(paste)