#!/usr/bin/python
# -*- coding: utf-8 -*-

import sqlalchemy
from sqlalchemy.sql import func
from sqlalchemy import desc
import re
import sys
import os
import traceback
import signal
import readline
from helpers import *

exit_commands = ['exit', 'abort', 'quit', 'bye', 'eat flaming death', 'q']
help_commands = ['help', '?']
context_commands = ['what', '??']
local_help_commands = ['help!', '???']
faq_commands = ['faq']
restart_commands = ['restart']

low_credit_warning_limit = -100

class ExitMenu(Exception):
	pass

class Menu():
	def __init__(self, name, items=[], prompt='> ',
		     return_index=True,
		     exit_msg=None, exit_confirm_msg=None, exit_disallowed_msg=None,
		     help_text=None, uses_db=False):
		self.name = name
		self.items = items
		self.prompt = prompt
		self.return_index = return_index
		self.exit_msg = exit_msg
		self.exit_confirm_msg = exit_confirm_msg
		self.exit_disallowed_msg = exit_disallowed_msg
		self.help_text = help_text
		self.context = None
		self.header_format = '[%s]'
		self.uses_db = uses_db

	def exit_menu(self):
		if self.exit_disallowed_msg != None:
			print self.exit_disallowed_msg
			return
		if self.exit_confirm_msg != None:
			if not self.confirm(self.exit_confirm_msg, default=True):
				return
		raise ExitMenu()

	def at_exit(self):
		if self.exit_msg:
			print self.exit_msg

	def set_context(self, string, display=True):
		self.context = string
		if self.context != None and display:
			print self.context

	def add_to_context(self, string):
		self.context += string

	def printc(self, string):
		print string
		if self.context == None:
			self.context = string
		else:
			self.context += '\n' + string

	def show_context(self):
		print self.header_format % self.name
		if self.context != None:
			print self.context

	def item_is_submenu(self, i):
		return isinstance(self.items[i], Menu)

	def item_name(self, i):
		if self.item_is_submenu(i):
			return self.items[i].name
		elif isinstance(self.items[i], tuple):
			return self.items[i][1]
		else:
			return self.items[i]

	def item_value(self, i):
		if isinstance(self.items[i], tuple):
			return self.items[i][0]
		if self.return_index:
			return i
		return self.items[i]

	def input_str(self, prompt=None, regex=None, length_range=(None,None),
		      empty_string_is_none=False):
		if regex != None:
			while True:
				result = self.input_str(prompt, length_range=length_range,
							empty_string_is_none=empty_string_is_none)
				if result == None or re.match(regex+'$', result):
					return result
				else:
					print 'Value must match regular expression "%s"' % regex
		if length_range != (None,None):
			while True:
				result = self.input_str(prompt, empty_string_is_none=empty_string_is_none)
				if result == None:
					length = 0
				else:
					length = len(result)
				if ((length_range[0] and length < length_range[0]) or
				    (length_range[1] and length > length_range[1])):
					if length_range[0] and length_range[1]:
						print 'Value must have length in range [%d,%d]' % length_range
					elif length_range[0]:
						print 'Value must have length at least %d' % length_range[0]
					else:
						print 'Value must have length at most %d' % length_range[1]
				else:
					return result
		if prompt == None:
			prompt = self.prompt
		while True:
			try:
				result = unicode(raw_input(safe_str(prompt)),
						 conf.input_encoding)
			except EOFError:
				print 'quit'
				self.exit_menu()
				continue
			if result in exit_commands:
				self.exit_menu()
				continue
			if result in help_commands:
				self.general_help()
				continue
			if result in local_help_commands:
				self.local_help()
				continue
			if result in context_commands:
				self.show_context()
				continue
			if result in faq_commands:
				FAQMenu().execute()
				continue
			if result in restart_commands:
				if self.confirm('Restart Dibbler?'):
					restart()
				continue
			if empty_string_is_none and result == '':
				return None
			return result

	def input_int(self, prompt=None, allowed_range=(None,None)):
		if prompt == None:
			prompt = self.prompt
		while True:
			result = self.input_str(prompt)
			try:
				value = int(result)
				if ((allowed_range[0] and value < allowed_range[0]) or
				    (allowed_range[1] and value > allowed_range[1])):
					if allowed_range[0] and allowed_range[1]:
						print 'Value must be in range [%d,%d]' % allowed_range
					elif allowed_range[0]:
						print 'Value must be at least %d' % allowed_range[0]
					else:
						print 'Value must be at most %d' % allowed_range[1]
				else:
					return value
			except ValueError:
				print 'Please enter an integer'

	def input_user(self, prompt=None):
		user = None
		while user == None:
			user = self.retrieve_user(self.input_str(prompt))
		return user

	def retrieve_user(self, search_str):
		return self.search_ui(search_user, search_str, 'user')

	def input_product(self, prompt=None):
		product = None
		while product == None:
			product = self.retrieve_product(self.input_str(prompt))
		return product

	def retrieve_product(self, search_str):
		return self.search_ui(search_product, search_str, 'product')

	def input_thing(self, prompt=None, permitted_things=('user','product'),
			add_nonexisting=(), empty_input_permitted=False):
		result = None
		while result == None:
			search_str = self.input_str(prompt)
			if search_str == '' and empty_input_permitted:
				return None
			result = self.search_for_thing(search_str, permitted_things, add_nonexisting)
		return result

	def search_for_thing(self, search_str, permitted_things=('user','product'),
			     add_nonexisting=()):
		search_fun = {'user': search_user,
			      'product': search_product}
		results = {}
		result_values = {}
		for thing in permitted_things:
			results[thing] = search_fun[thing](search_str, self.session)
			result_values[thing] = self.search_result_value(results[thing])
		selected_thing = argmax(result_values)
		if results[selected_thing] == []:
			thing_for_type = {'card': 'user', 'username': 'user',
					  'bar_code': 'product'}
			type_guess = guess_data_type(search_str)
			if type_guess != None and thing_for_type[type_guess] in add_nonexisting:
				return self.search_add(search_str)
			print 'No match found for "%s".' % search_str
			return None
		return self.search_ui2(search_str, results[selected_thing], selected_thing)

	def search_result_value(self, result):
		if result == None:
			return 0
		if not isinstance(result, list):
			return 3
		if len(result) == 0:
			return 0
		if len(result) == 1:
			return 2
		return 1

	def search_add(self, string):
		type_guess = guess_data_type(string)
		if type_guess == 'username':
			print '"%s" looks like a username, but no such user exists.' % string
			if self.confirm('Create user %s?' % string):
				user = User(string, None)
				self.session.add(user)
				return user
			return None
		if type_guess == 'card':
			selector = Selector('"%s" looks like a card number, but no user with that card number exists.' % string,
					    [('create', 'Create user with card number %s' % string),
					     ('set', 'Set card number of an existing user to %s' % string)])
			selection = selector.execute()
			if selection == 'create':
				username = self.input_str('Username for new user (should be same as PVV username)> ',
							  User.name_re, (1,10))
				user = User(username, string)
				self.session.add(user)
				return user
			if selection == 'set':
				user = self.input_user('User to set card number for> ')
				old_card = user.card
				user.card = string
				print 'Card number of %s set to %s (was %s)' % (user.name, string, old_card)
				return user
			return None
		if type_guess == 'bar_code':
			print '"%s" looks like the bar code for a product, but no such product exists.' % string
			return None


	def search_ui(self, search_fun, search_str, thing):
		result = search_fun(search_str, self.session)
		return self.search_ui2(search_str, result, thing)

	def search_ui2(self, search_str, result, thing):
		if not isinstance(result, list):
			return result
		if len(result) == 0:
			print 'No %ss matching "%s"' % (thing, search_str)
			return None
		if len(result) == 1:
			msg = 'One %s matching "%s": %s.  Use this?' %\
			      (thing, search_str, unicode(result[0]))
			if self.confirm(msg, default=True):
				return result[0]
			return None
		limit = 9
		if len(result) > limit:
			select_header = '%d %ss matching "%s"; showing first %d' % \
			    (len(result), thing, search_str, limit)
			select_items = result[:limit]
		else:
			select_header = '%d %ss matching "%s"' % \
			    (len(result), thing, search_str)
			select_items = result
		selector = Selector(select_header, items=select_items,
				    return_index=False)
		return selector.execute()



	def confirm(self, prompt, default=None):
		return ConfirmMenu(prompt, default).execute()

	def print_header(self):
		print
		print self.header_format % self.name

	def pause(self):
		self.input_str('.')

	def general_help(self):
		print '''
DIBBLER HELP

The following commands are recognized (almost) everywhere:

 help, ?          -- display this help
 what, ??         -- redisplay the current context
 help!, ???       -- display context-specific help (if any)
 faq              -- display frequently asked questions (with answers)
 exit, quit, etc. -- exit from the current menu

When prompted for a user, you can type (parts of) the user name or
card number.  When prompted for a product, you can type (parts of) the
product name or barcode.

About payment and "credit": When paying for something, use either
Dibbler or the good old money box -- never both at the same time.
Dibbler keeps track of a "credit" for each user, which is the amount
of money PVVVV owes the user.  This value decreases with the
appropriate amount when you register a purchase, and you may increase
it by putting money in the box and using the "Adjust credit" menu.
'''

	def local_help(self):
		if self.help_text == None:
			print 'no help here'
		else:
			print
			print 'Help for %s:' % (self.header_format%self.name)
			print self.help_text

	def execute(self):
		self.set_context(None)
		try:
			if self.uses_db:
				self.session = Session()
			else:
				self.session = None
			return self._execute()
		except ExitMenu:
			self.at_exit()
			return None
		finally:
			if self.session != None:
				self.session.close()
				self.session = None

	def _execute(self):
		line_format = '%' + str(len(str(len(self.items)))) + 'd ) %s'
		while True:
			self.print_header()
			self.set_context(None)
			if len(self.items)==0:
				self.printc('(empty menu)')
				self.pause()
				return None
			for i in range(len(self.items)):
				self.printc(line_format % (i+1, self.item_name(i)))
			item_i = self.input_int(self.prompt, (1,len(self.items)))-1
			if self.item_is_submenu(item_i):
				self.items[item_i].execute()
			else:
				return self.item_value(item_i)


class Selector(Menu):
	def __init__(self, name, items=[], prompt='select> ',
		     return_index=True,
		     exit_msg=None, exit_confirm_msg=None,
		     help_text=None):
		Menu.__init__(self, name, items, prompt, return_index, exit_msg)
		self.header_format = '%s'

	def print_header(self):
		print self.header_format % self.name

	def local_help(self):
		if self.help_text == None:
			print 'This is a selection menu.  Enter one of the listed numbers, or'
			print '\'exit\' to go out and do something else.'
		else:
			print
			print 'Help for selector (%s):' % self.name
			print self.help_text


class ConfirmMenu(Menu):
	def __init__(self, prompt='confirm?', default=None):
		Menu.__init__(self, 'question', prompt=prompt,
			      exit_disallowed_msg='Please answer yes or no')
		self.default=default

	def _execute(self):
		options = {True: '[y]/n', False: 'y/[n]', None: 'y/n'}[self.default]
		while True:
			result = self.input_str('%s (%s) ' % (self.prompt, options))
			result = result.lower()
			if result in ['y','yes']:
				return True
			if result in ['n','no']:
				return False
			if self.default != None and result == '':
				return self.default
			print 'Please answer yes or no'


class MessageMenu(Menu):
	def __init__(self, name, message, pause_after_message=True):
		Menu.__init__(self, name)
		self.message = message.strip()
		self.pause_after_message = pause_after_message

	def _execute(self):
		self.print_header()
		print
		print self.message
		if self.pause_after_message:
			self.pause()


class FAQMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Frequently Asked Questions')
		self.items = [MessageMenu('What is the meaning with this program?',
					  '''
We want to avoid keeping lots of cash in PVVVV\'s money box and to
make it easy to pay for stuff without using money.  (Without using
money each time, that is.  You do of course have to pay for the things
you buy eventually).

Dibbler stores a "credit" amount for each user.  When you register a
purchase in Dibbler, this amount is decreased.  To increase your
credit, add money to the money box and use "Adjust credit" to tell
Dibbler about it.
'''),
			      MessageMenu('Can I still pay for stuff using cash?',
					  'Yes.  You can safely ignore this program completely.'),
			      MessageMenu('How do I exit from a submenu/dialog/thing?',
					  'Type "exit" or C-d.'),
			      MessageMenu('What does "." mean?',
					  '''
The "." character, known as "full stop" or "period", is most often
used to indicate the end of a sentence.

It is also used by Dibbler to indicate that the program wants you to
read some text before continuing.  Whenever some output ends with a
line containing only a period, you should read the lines above and
then press enter to continue.
					  '''),
			      MessageMenu('Why is the user interface so terribly unintuitive?',
					  '''
Answer #1:  It is not.

Answer #2:  We are trying to compete with PVV\'s microwave oven in
userfriendliness.

Answer #3:  YOU are unintuitive.
'''),
			      MessageMenu('Why is there no help command?',
					  'There is.  Have you tried typing "help"?'),
			      MessageMenu('Where are the easter eggs?  I tried saying "moo", but nothing happened.',
					  'Don\'t say "moo".'),
			      MessageMenu('Why does the program speak English when all the users are Norwegians?',
					  u'Godt spørsmål.  Det virket sikkert som en god idé der og da.'),
			      MessageMenu('I found a bug; is there a reward?',
					  '''
No.

But if you are certain that it is a bug, not a feature, then you
should fix it (or better: force someone else to do it).

Follow this procedure:

1. Check out the Dibbler code from https://dev.pvv.ntnu.no/svn/dibbler

2. Fix the bug.

3. Check that the program still runs (and, preferably, that the bug is
   in fact fixed).

4. Commit.

5. Update the running copy from svn:

    $ su -
    # su -l -s /bin/bash pvvvv
    $ cd dibbler
    $ svn up

6. Type "restart" in Dibbler to replace the running process by a new
   one using the updated files.
'''),
			      MessageMenu('My question isn\'t listed here; what do I do?',
					  '''
DON\'T PANIC.

Follow this procedure:

1. Ask someone (or read the source code) and get an answer.

2. Check out the Dibbler code from https://dev.pvv.ntnu.no/svn/dibbler

3. Add your question (with answer) to the FAQ and commit.

4. Update the running copy from svn:

    $ su -
    # su -l -s /bin/bash pvvvv
    $ cd dibbler
    $ svn up

5. Type "restart" in Dibbler to replace the running process by a new
   one using the updated files.
''')]



class TransferMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Transfer credit between users',
			      uses_db=True)

	def _execute(self):
		self.print_header()
		amount = self.input_int('Transfer amount> ', (1,100000))
		self.set_context('Transfering %d kr' % amount, display=False)
		user1 = self.input_user('From user> ')
		self.add_to_context(' from ' + user1.name)
		user2 = self.input_user('To user> ')
		self.add_to_context(' to ' + user2.name)

		t1 = Transaction(user1, amount,
				 'transfer to '+user2.name)
		t2 = Transaction(user2, -amount,
				 'transfer from '+user1.name)
		t1.perform_transaction()
		t2.perform_transaction()
		self.session.add(t1)
		self.session.add(t2)
		try:
			self.session.commit()
			print 'Transfered %d kr from %s to %s' % (amount, user1, user2)
			print 'User %s\'s credit is now %d kr' % (user1, user1.credit)
			print 'User %s\'s credit is now %d kr' % (user2, user2.credit)
		except sqlalchemy.exc.SQLAlchemyError, e:
			print 'Could not perform transfer: %s' % e
		self.pause()


class AddUserMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Add user', uses_db=True)

	def _execute(self):
		self.print_header()
		username = self.input_str('Username (should be same as PVV username)> ', User.name_re, (1,10))
		cardnum = self.input_str('Card number (optional)> ', User.card_re, (0,10))
                cardnum = cardnum.lower()
		user = User(username, cardnum)
		self.session.add(user)
		try:
			self.session.commit()
			print 'User %s stored' % username
		except sqlalchemy.exc.IntegrityError, e:
			print 'Could not store user %s: %s' % (username,e)
		self.pause()


class EditUserMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Edit user', uses_db=True)
		self.help_text = '''
The only editable part of a user is its card number.

First select an existing user, then enter a new card number for that
user (write an empty line to remove the card number).
'''

	def _execute(self):
		self.print_header()
		user = self.input_user('User> ')
		self.printc('Editing user %s' % user.name)
		card_str = '"%s"' % user.card
		if user.card == None:
			card_str = 'empty'
		user.card = self.input_str('Card number (currently %s)> ' % card_str,
					   User.card_re, (0,10),
					   empty_string_is_none=True)
		user.card = user.card.lower()
		try:
			self.session.commit()
			print 'User %s stored' % user.name
		except sqlalchemy.exc.SQLAlchemyError, e:
			print 'Could not store user %s: %s' % (user.name,e)
		self.pause()


class AddProductMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Add product', uses_db=True)

	def _execute(self):
		self.print_header()
		bar_code = self.input_str('Bar code> ', Product.bar_code_re, (8,13))
		name = self.input_str('Name> ', Product.name_re, (1,Product.name_length))
		price = self.input_int('Price> ', (1,100000))
		product = Product(bar_code, name, price)
		self.session.add(product)
		try:
			self.session.commit()
			print 'Product %s stored' % name
		except sqlalchemy.exc.SQLAlchemyError, e:
			print 'Could not store product %s: %s' % (name,e)
		self.pause()


class EditProductMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Edit product', uses_db=True)

	def _execute(self):
		self.print_header()
		product = self.input_product('Product> ')
		self.printc('Editing product %s' % product.name)
		while True:
			selector = Selector('Do what with %s?' % product.name,
					    items=[('name', 'Edit name'),
						   ('price', 'Edit price (currently %d)' % product.price),
						   ('store', 'Store')])
			what = selector.execute()
			if what == 'name':
				product.name = self.input_str('Name> ', Product.name_re, (1,product.name_length))
			elif what == 'price':
				product.price = self.input_int('Price> ', (1,100000))
			elif what == 'store':
				try:
					self.session.commit()
					print 'Product %s stored' % product.name
				except sqlalchemy.exc.SQLAlchemyError, e:
					print 'Could not store product %s: %s' % (product.name, e)					
				self.pause()
				return
			elif what == None:
				print 'Edit aborted'
				return
			else:
				print 'What what?'


class ShowUserMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Show user', uses_db=True)

	def _execute(self):
		self.print_header()
		user = self.input_user('User name or card number> ')
		print 'User name: %s' % user.name
		print 'Card number: %s' % user.card
		print 'Credit: %s kr' % user.credit
		selector = Selector('What do you want to know about %s?' % user.name,
				    items=[('transactions', 'Everything (list of all transactions)'),
					   ('products', 'Which products %s has bought, and how many' % user.name)])
		what = selector.execute()
		if what == 'transactions':
			self.print_all_transactions(user)
		elif what == 'products':
			self.print_purchased_products(user)
		else:
			print 'What what?'

	def print_all_transactions(self, user):
		num_trans = len(user.transactions)
		string = '%s\'s transactions (%d):\n' % (user.name, num_trans)
		for t in user.transactions:
			string += ' * %s: %s %d kr, ' % \
			    (t.time.strftime('%Y-%m-%d %H:%M'),
			     {True:'in', False:'out'}[t.amount<0],
			     abs(t.amount))
			if t.purchase:
				string += 'purchase ('
				string += ', '.join(map(lambda e: e.product.name,
							t.purchase.entries))
				string += ')'
			else:
				string += t.description
			string += '\n'
		less(string)

	def print_transactions(self, user, limit=10):
		num_trans = len(user.transactions)
		if num_trans == 0:
			print 'No transactions'
			return
		if num_trans <= limit:
			print 'Transactions (%d):' % num_trans
		else:
			print 'Transactions (%d, showing only last %d):' % (num_trans,limit)
		for t in user.transactions[-limit:]:
			string = ' * %s: %s %d kr, ' % \
			    (t.time.strftime('%Y-%m-%d %H:%M'),
			     {True:'in', False:'out'}[t.amount<0],
			     abs(t.amount))
			if t.purchase:
				string += 'purchase ('
				string += ', '.join(map(lambda e: e.product.name,
							t.purchase.entries))
				string += ')'
			else:
				string += t.description
			print string

	def print_purchased_products(self, user):
		products = {}
		for transaction in user.transactions:
			if transaction.purchase:
				for entry in transaction.purchase.entries:
					n = entry.product.name
					if n in products:
						products[n]+=1
					else:
						products[n]=1
		num_products = len(products)
		if num_products == 0:
			print 'No products purchased yet'
		else:
			text = ''
			text += 'Products purchased:\n'
			for product in products:
				text += ('%-'+str(Product.name_length)+'s %3i\n') \
				    % (product, products[product])
			less(text)
		

class UserListMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'User list', uses_db=True)

	def _execute(self):
		self.print_header()
		user_list = self.session.query(User).all()
		total_credit = self.session.query(sqlalchemy.func.sum(User.credit)).first()[0]

		line_format = '%-12s | %6s\n'
		hline = '---------------------\n'
		text = ''
		text += line_format % ('username', 'credit')
		text += hline
		for user in user_list:
			text += line_format % (user.name, user.credit)
		text += hline
		text += line_format % ('total credit', total_credit)
		less(text)


class BuyMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Buy', uses_db=True)
		self.help_text = '''
Each purchase may contain one or more products and one or more buyers.

Enter products (by name or bar code) and buyers (by name or bar code)
in any order.  The information gathered so far is displayed after each
addition, and you can type 'what' at any time to redisplay it.

When finished, write an empty line to confirm the purchase.
'''

	def _execute(self):
		self.print_header()
		self.purchase = Purchase()
		self.exit_confirm_msg=None
		while True:
			self.print_purchase()
			self.printc({(False,False): 'Enter user or product identification',
				     (False,True): 'Enter user identification or more products',
				     (True,False): 'Enter product identification or more users',
				     (True,True): 'Enter more products or users, or an empty line to confirm'
				     }[(len(self.purchase.transactions) > 0,
					len(self.purchase.entries) > 0)])
			thing = self.input_thing(add_nonexisting=('user',),
						 empty_input_permitted=True)
			if thing == None:
				if not self.complete_input():
					if self.confirm('Not enough information entered.  Abort purchase?',
							default=True):
						return False
					continue
				break
			else:
				# once we get something in the
				# purchase, we want to protect the
				# user from accidentally killing it
				self.exit_confirm_msg='Abort purchase?'
			if isinstance(thing, User):
				Transaction(thing, purchase=self.purchase)
			elif isinstance(thing, Product):
				PurchaseEntry(self.purchase, thing, 1)

		self.purchase.perform_purchase()
		self.session.add(self.purchase)
		try:
			self.session.commit()
		except sqlalchemy.exc.SQLAlchemyError, e:
			print 'Could not store purchase: %s' % e
		else:
			print 'Purchase stored.'
			self.print_purchase()
			for t in self.purchase.transactions:
				print 'User %s\'s credit is now %d kr' % (t.user.name, t.user.credit)
				if t.user.credit < low_credit_warning_limit:
					print ('USER %s HAS LOWER CREDIT THAN %d, AND SHOULD CONSIDER PUTTING SOME MONEY IN THE BOX.'
					       % (t.user.name, low_credit_warning_limit))
		self.pause()
		return True
		
	def complete_input(self):
		return self.purchase.is_complete()
			
	def format_purchase(self):
		self.purchase.set_price()
		transactions = self.purchase.transactions
		entries = self.purchase.entries
		if len(transactions) == 0 and len(entries) == 0:
			return None
		string = 'Purchase:'
		string += '\n buyers: '
		if len(transactions) == 0:
			string += '(empty)'
		else:
			string += ', '.join(map(lambda t: t.user.name,
						transactions))
		string += '\n products: '
		if len(entries) == 0:
			string += '(empty)'
		else:
			string += ', '.join(map(lambda e: '%s (%d kr)'%(e.product.name, e.product.price),
						entries))
		if len(transactions) > 1:
			string += '\n price per person: %d kr' % self.purchase.price_per_transaction()
		string += '\n total price: %d kr' % self.purchase.price
		return string

	def print_purchase(self):
		info = self.format_purchase()
		if info != None:
			self.set_context(info)


class AdjustCreditMenu(Menu): # reimplements ChargeMenu; these should be combined to one
	def __init__(self):
		Menu.__init__(self, 'Adjust credit', uses_db=True)

	def _execute(self):
		self.print_header()
		user = self.input_user('User> ')
		print 'User %s\'s credit is %d kr' % (user.name, user.credit)
		self.set_context('Adjusting credit for user %s' % user.name, display=False)
		print '(Note on sign convention: Enter a positive amount here if you have'
		print 'added money to the PVVVV money box, a negative amount if you have'
		print 'taken money from it)'
		amount = self.input_int('Add amount> ', (-100000,100000))
		print '(The "log message" will show up in the transaction history in the'
		print '"Show user" menu.  It is not necessary to enter a message, but it'
		print 'might be useful to help you remember why you adjusted the credit)'
		description = self.input_str('Log message> ', length_range=(0,50))
		if description == '':
			description = 'manually adjusted credit'
		transaction = Transaction(user, -amount, description)
		transaction.perform_transaction()
		self.session.add(transaction)
		try:
			self.session.commit()
			print 'User %s\'s credit is now %d kr' % (user.name, user.credit)
		except sqlalchemy.exc.SQLAlchemyError, e:
			print 'Could not store transaction: %s' % e
		self.pause()


class ProductListMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Product list', uses_db=True)

	def _execute(self):
		self.print_header()
		text = ''
		product_list = self.session.query(Product).all()
		line_format = '%-15s | %5s | %-'+str(Product.name_length)+'s\n'
		text += line_format % ('bar code', 'price', 'name')
		text += '-----------------------------------------------------------------------\n'
		for p in product_list:
			text += line_format % (p.bar_code, p.price, p.name)
		less(text)


class ProductSearchMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Product search', uses_db=True)

	def _execute(self):
		self.print_header()
		self.set_context('Enter (part of) product name or bar code')
		product = self.input_product()
		print 'Result: %s, price: %d kr, bar code: %s' % (product.name, product.price, product.bar_code)
		self.pause()


class ProductPopularityMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Products by popularity', uses_db=True)

	def _execute(self):
		self.print_header()
		text = ''
		sub = \
		    self.session.query(PurchaseEntry.product_bar_code,
				       func.count('*').label('purchase_count'))\
		    .group_by(PurchaseEntry.product_bar_code)\
		    .subquery()
		product_list = \
		    self.session.query(Product, sub.c.purchase_count)\
		    .outerjoin((sub, Product.bar_code==sub.c.product_bar_code))\
		    .order_by(desc(sub.c.purchase_count))\
		    .filter(sub.c.purchase_count != None)\
		    .all()
		line_format = '%10s | %-'+str(Product.name_length)+'s\n'
		text += line_format % ('items sold', 'product')
		text += '-'*58 + '\n'
		for product, number in product_list:
			text += line_format % (number, product.name)
		less(text)

class ProductRevenueMenu(Menu):
	def __init__(self):
		Menu.__init__(self, 'Products by revenue', uses_db=True)

	def _execute(self):
		self.print_header()
		text = ''
		sub = \
		    self.session.query(PurchaseEntry.product_bar_code,
				       func.count('*').label('purchase_count'))\
		    .group_by(PurchaseEntry.product_bar_code)\
		    .subquery()
		product_list = \
		    self.session.query(Product, sub.c.purchase_count)\
		    .outerjoin((sub, Product.bar_code==sub.c.product_bar_code))\
		    .order_by(desc(sub.c.purchase_count*Product.price))\
		    .filter(sub.c.purchase_count != None)\
		    .all()
		line_format = '%7s | %10s | %5s | %-'+str(Product.name_length)+'s\n'
		text += line_format % ('revenue', 'items sold', 'price', 'product')
		text += '-'*76 + '\n'
		for product, number in product_list:
			text += line_format % (number*product.price, number, product.price, product.name)
		less(text)


def restart():
	# Does not work if the script is not executable, or if it was
	# started by searching $PATH.
	os.execv(sys.argv[0], sys.argv)


if not conf.stop_allowed:
	signal.signal(signal.SIGTSTP, signal.SIG_IGN)
main = Menu('Dibbler main menu',
	    items=[BuyMenu(),
		   ProductListMenu(),
		   ShowUserMenu(),
		   UserListMenu(),
		   AdjustCreditMenu(),
		   TransferMenu(),
		   Menu('Add/edit',
			items=[AddUserMenu(),
			       EditUserMenu(),
			       AddProductMenu(),
			       EditProductMenu()]),
		   ProductSearchMenu(),
		   Menu('Statistics',
			items=[ProductPopularityMenu(),
			       ProductRevenueMenu()]),
		   FAQMenu()
		   ],
	    exit_msg='happy happy joy joy',
	    exit_confirm_msg='Really quit Dibbler?')
if not conf.quit_allowed:
	main.exit_disallowed_msg = 'You can check out any time you like, but you can never leave.'
while True:
	try:
		main.execute()
	except KeyboardInterrupt:
		print
		print 'Interrupted.'
	except:
		print 'Something went wrong.'
		print '%s: %s' % sys.exc_info()[0:2]
		if conf.show_tracebacks:
			traceback.print_tb(sys.exc_info()[2])
	else:
		break
	print 'Restarting main menu.'