#!/usr/bin/env python3
"""
Simple file host using Flask.
"""
import os
import sqlite3
import secrets
import string

from passlib.hash import argon2
from flask import Flask, session, request, abort, redirect, url_for, g, \
	render_template
from werkzeug.utils import secure_filename

class ReverseProxied(object):
	"""
	Wrap the application in this middleware and configure the 
	front-end server to add these headers, to let you quietly bind 
	this to a URL other than / and to an HTTP scheme that is 
	different than what is used locally.

	In nginx:
	location /myprefix {
		proxy_pass http://192.168.0.1:5001;
		proxy_set_header Host $host;
		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		proxy_set_header X-Scheme $scheme;
		proxy_set_header X-Script-Name /myprefix;
		}

	:param app: the WSGI application
	"""
	def __init__(self, app):
		self.app = app

	def __call__(self, environ, start_response):
		script_name = environ.get('HTTP_X_SCRIPT_NAME', '')
		if script_name:
			environ['SCRIPT_NAME'] = script_name
			path_info = environ['PATH_INFO']
			if path_info.startswith(script_name):
				environ['PATH_INFO'] = path_info[len(script_name):]

		scheme = environ.get('HTTP_X_SCHEME', '')
		if scheme:
			environ['wsgi.url_scheme'] = scheme
		return self.app(environ, start_response)


app = Flask(__name__)
app.wsgi_app = ReverseProxied(app.wsgi_app)
app.config['MAX_CONTENT_LENGTH'] = 128 * 1024 * 1024
app.config["UPLOAD_DIR"] = "/usr/local/www/html/up"
app.config["DB_NAME"] = "fileHost.db"


def init():
	"""
	Initializes the application.
	"""
	if not os.path.exists("secret_key"):
		print("Error: secret_key file not found.")
		print("If this is the first time the program is being run, run it \
			without your WSGI host first.")
		os.exit()

	with open("secret_key", "rb") as file:
		secret_key = file.read()
	app.secret_key = secret_key

	if not os.path.exists(app.config.get("DB_NAME")):
		print("error: database not found.")
		print("If this is the first time the program is being run, run it \
			without your WSGI host first.")
		os.exit()

	con = sqlite3.connect(app.config.get("DB_NAME"))
	db = con.cursor()

	return con, db


def init_database():
	"""
	Initializes appropriate tables in the database.
	"""
	db.execute("CREATE TABLE users(id INTEGER PRIMARY KEY, \
		username TEXT, pw_hash TEXT, admin BOOL DEFAULT FALSE)")

	db.execute("CREATE TABLE uploads(filename TEXT, uploaded_by TEXT, \
		uploaded_date INT DEFAULT (STRFTIME('%s', 'now')))")


def add_user(username, password, admin="FALSE"):
	"""
	Adds a user to the database.
	"""
	u = db.execute("SELECT username FROM users WHERE username = ?",
		(username,)).fetchone()
	if u:
		return False

	pw_hash = argon2.hash(password)
	db.execute("INSERT INTO users (username, pw_hash, admin) VALUES (?,?,?)",
		(username, pw_hash, admin))
	con.commit()
	return True


def verify_password(username, password):
	"""
	Verifies a user's password.
	"""
	user = verify_username(username)
	if not user:
		return False

	_, _, pw_hash, admin = user

	if argon2.verify(password, pw_hash):
		g.user = username
		g.admin = admin == "TRUE"
		return True
	else:
		return False


def verify_username(username):
	"""
	Checks to see if the given username is in the database.
	"""
	user = db.execute("SELECT * FROM users WHERE username = ?",
		(username,)).fetchone()
	if user:
		return user
	else:
		return False


@app.route("/delete_file", methods=["POST"])
def delete_file():
	"""
	Allows an admin to delete a file from the upload directory and the database.
	"""
	username = request.form.get("user")
	password = request.form.get("pass")
	filename = request.form.get("fname")

	if not verify_password(username, password):
		abort(401)
	if not g.admin:
		abort(401)

	try:
		os.remove(os.path.join(app.config.get("UPLOAD_DIR"), filename))
		db.execute("DELETE FROM uploads WHERE filename = ?", (filename,))
		db.commit()
	except FileNotFoundError:
		return "Error: File not found."
	return "Success"


@app.route("/add_user", methods=["POST"])
def addUser():
	"""
	Allows an admin to add a user via API POST. No frontend allowed.
	"""
	username = request.form.get("user")
	password = request.form.get("pass")
	new_username = request.form.get("new_user")
	new_password = request.form.get("new_pass")
	admin = request.form.get("admin") or "FALSE"

	if not verify_password(username, password):
		abort(401)
	if not g.admin:
		abort(401)

	res = add_user(new_username, new_password, admin)
	if res:
		return "Success"
	else:
		return "Username already exists."


@app.route("/logout", methods=["POST", "GET"])
def logout():
	"""
	Logs the user out and removes his session cookie.
	"""
	session.pop("username")
	return redirect(url_for("login"))


@app.route("/change_password", methods=["POST", "GET"])
def change_password():
	"""
	Allows the user to change their password.
	"""
	username = session.get("username")
	if not verify_username(username):
		abort(401)

	if request.method == "GET":
		return render_template("change_password.html")

	current_password = request.form.get("current_password")
	new_password = request.form.get("new_password")
	new_password_verify = request.form.get("new_password_verify")

	if not verify_password(username, current_password):
		return "The current password does not match!"

	if new_password != new_password_verify:
		return "The new passwords do not match!"

	pw_hash = argon2.hash(new_password)
	db.execute("UPDATE users SET pw_hash = ? WHERE username = ?",
		(pw_hash, username))
	session.pop("username")
	return redirect(url_for("login"))


@app.route("/login", methods=["POST", "GET"])
def login():
	"""
	Logs the user in.
	"""
	if request.method == "GET":
		return render_template("login.html")

	username = request.form.get("user")
	password = request.form.get("pass")

	if verify_password(username, password):
		session["username"] = username
		return redirect(url_for("index"))
	else:
		abort(401)


@app.route("/", methods=["POST", "GET"])
def index():
	"""
	Saves the uploaded file and returns a URL pointing to it.
	"""
	if not session.get("username"):
		if request.method == "GET":
			return redirect(url_for("login"))

		username = request.form.get("user")
		password = request.form.get("pass")
		if not verify_password(username, password):
			abort(401)
	else:
		username = session.get("username")
		if not verify_username(username):
			abort(401)

	if request.method == "GET":
		return render_template("index.html")

	file = request.files.get('file')
	fname = secure_filename(file.filename)
	fdir = app.config.get("UPLOAD_DIR")
	pre = get_rand_chars(8)
	if request.form.get("randname") == "on":
		fname = pre + os.path.splitext(fname)[1]
	else:
		fname = pre + "_" + fname
	file.save(os.path.join(fdir, fname))

	db.execute("INSERT INTO uploads (filename, uploaded_by) VALUES (?,?)",
		(fname, username))
	con.commit()

	#TODO: make this not hardcoded
	# url = request.url_root + "up/" + fname
	url = "https://steelbea.me/up/" + fname
	return url


def get_rand_chars(n):
	"""
	Returns n number of random characters. Character set includes lowercase
	and uppercase ascii letters and digits.
	"""
	chars = []
	for _ in range(n):
		char = secrets.choice(string.ascii_letters + string.digits)
		chars.append(char)
	return "".join(chars)


if __name__ == "__main__":
	os.makedirs(app.config.get("UPLOAD_DIR"), exist_ok=True)
	initDB = not os.path.exists(app.config.get("DB_NAME"))

	con = sqlite3.connect(app.config.get("DB_NAME"))
	db = con.cursor()

	if initDB:
		print("Initializing new database and admin account.")
		init_database()
		import sys
		add_user(sys.argv[1], sys.argv[2], "TRUE")

	if not os.path.exists("secret_key"):
		secret_key = os.urandom(64)
		with open("secret_key", "wb") as file:
			file.write(secret_key)
	else:
		with open("secret_key", "rb") as file:
			secret_key = file.read()
	app.secret_key = secret_key

	app.run(host='0.0.0.0', port=5000)

else:
	con, db = init()