#    Society Self-Service
#    Copyright © 2018-2019  Yingtong Li (RunasSudo)
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU Affero General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU Affero General Public License for more details.
#
#    You should have received a copy of the GNU Affero General Public License
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.

from django.contrib.auth.models import User

from django.db import models
from django.utils import timezone
from jsonfield import JSONField

from decimal import Decimal
from enum import Enum

class DescriptionEnum(Enum):
	def __new__(cls, value, description):
		obj = object.__new__(cls)
		obj._value_ = value
		obj.description = description
		return obj

class Budget(models.Model):
	pass

class BudgetComment(models.Model):
	budget = models.ForeignKey(Budget, on_delete=models.CASCADE)
	author = models.ForeignKey(User, on_delete=models.PROTECT, related_name='+')
	time = models.DateTimeField()
	content = models.TextField()
	
	class Meta:
		ordering = ['id']

class BudgetState(DescriptionEnum):
	DRAFT = 10, 'Draft'
	RESUBMIT = 20, 'Returned for redrafting'
	AWAIT_REVIEW = 30, 'Awaiting Treasury review'
	ENDORSED = 40, 'Endorsed by Treasury, awaiting committee approval'
	APPROVED = 50, 'Approved'
	#CANCELLED = 60, 'Cancelled'

class BudgetAction(DescriptionEnum):
	CREATE = 5, 'Created'
	EDIT = 10, 'Edited'
	UPDATE_STATE = 20, 'Updated state'

class BudgetRevision(models.Model):
	budget = models.ForeignKey(Budget, on_delete=models.CASCADE)
	name = models.CharField(max_length=100)
	date = models.DateField()
	contributors = models.ManyToManyField(User, related_name='+')
	comments = models.TextField()
	
	author = models.ForeignKey(User, on_delete=models.PROTECT, related_name='+')
	time = models.DateTimeField()
	
	event_dt = models.DateTimeField(null=True)
	event_attendees = models.CharField(max_length=20, null=True)
	
	state = models.IntegerField(choices=[(v.value, v.description) for v in BudgetState])
	
	revenue = JSONField(default=[])
	revenue_comments = models.TextField()
	
	expense = JSONField(default=[])
	expense_no_emergency_fund = models.BooleanField()
	expense_comments = models.TextField()
	
	action = models.IntegerField(choices=[(v.value, v.description) for v in BudgetAction])
	
	class Meta:
		ordering = ['id']
	
	def copy(self):
		contributors = list(self.contributors.all())
		self.pk, self.id = None, None
		self.save()
		self.contributors.add(*contributors)
	
	def update_state(self, user, state):
		self.copy()
		self.author = user
		self.time = timezone.now()
		self.state = state.value
		self.action = BudgetAction.UPDATE_STATE.value
		self.save()
	
	def get_revenue_total(self):
		total = Decimal(0)
		for item in self.revenue:
			total += Decimal(item['Unit price']) * item['Units']
			if item['IWT']:
				total -= (Decimal(item['Unit price']) - (Decimal(item['Unit price']) - Decimal('0.8')) / Decimal('1.019')) * item['Units']
		return total
	
	def get_expense_total(self):
		total = Decimal(0)
		for item in self.expense:
			total += Decimal(item['Unit price']) * item['Units']
		if not self.expense_no_emergency_fund:
			total *= Decimal('1.05')
		return total
	
	# Access control
	
	def can_view(self, user):
		if user == self.author:
			return True
		if user in self.contributors.all():
			return True
		if user.groups.filter(name='Treasury').exists():
			return True
		if (self.state == BudgetState.ENDORSED.value or self.state == BudgetState.APPROVED.value) and user.groups.filter(name='Committee').exists():
			return True
		
		return False
	
	def can_edit(self, user):
		# Cannot edit if cannot view
		if not self.can_view(user):
			return False
		
		# No one can edit if already approved
		if self.state == BudgetState.APPROVED.value:
			return False
		
		# Only Treasurer or Secretary may edit if submitted
		if self.state != BudgetState.DRAFT.value and self.state != BudgetState.RESUBMIT.value:
			if user.groups.filter(name='Treasury').exists() or user.groups.filter(name='Secretary').exists():
				return True
			return False
		
		# Otherwise the submitter may edit
		if user == self.author:
			return True
		if user in self.contributors.all():
			return True
		if user.groups.filter(name='Treasury').exists():
			return True
		
		# Otherwise cannot edit
		return False
	
	def can_submit(self, user):
		if not self.can_edit(user):
			return False
		if self.state == BudgetState.DRAFT.value or self.state == BudgetState.RESUBMIT.value:
			return True
		return False
	
	def can_withdraw(self, user):
		if not self.can_edit(user):
			return False
		if self.state == BudgetState.AWAIT_REVIEW.value or self.state == BudgetState.ENDORSED.value:
			return True
		return False
	
	def can_endorse(self, user):
		if not self.can_edit(user):
			return False
		if not user.groups.filter(name='Treasury').exists():
			return False
		if self.state == BudgetState.AWAIT_REVIEW.value:
			return True
		return False
	
	def can_return(self, user):
		return self.can_endorse(user)
	
	def can_approve(self, user):
		if not self.can_edit(user):
			return False
		if not user.groups.filter(name='Secretary').exists():
			return False
		if self.state == BudgetState.ENDORSED.value:
			return True
		return False
	
	def can_cmtereturn(self, user):
		return self.can_approve(user)

class ClaimState(DescriptionEnum):
	DRAFT = 10, 'Draft'
	RESUBMIT = 20, 'Returned for redrafting'
	AWAIT_REVIEW = 30, 'Awaiting Treasury approval'
	APPROVED = 40, 'Approved by Treasury, awaiting payment'
	PAID = 50, 'Paid'

class ClaimAction(DescriptionEnum):
	CREATE = 5, 'Created'
	EDIT = 10, 'Edited'
	UPDATE_STATE = 20, 'Updated state'

class ReimbursementClaim(models.Model):
	purpose = models.CharField(max_length=100)
	date = models.DateField()
	budget_id = models.CharField(max_length=20)
	comments = models.TextField()
	
	author = models.ForeignKey(User, on_delete=models.PROTECT, related_name='+')
	time = models.DateTimeField()
	
	state = models.IntegerField(choices=[(v.value, v.description) for v in ClaimState])
	
	items = JSONField(default=[])
	
	payee_name = models.TextField()
	payee_bsb = models.CharField(max_length=7)
	payee_account = models.TextField(max_length=20)
	
	def get_total(self):
		total = Decimal(0)
		for item in self.items:
			total += Decimal(item['Unit price']) * item['Units']
		return total
	
	def update_state(self, user, state):
		self.state = state.value
		self.save()
		
		claim_history = ClaimHistory()
		claim_history.claim = self
		claim_history.author = user
		claim_history.state = self.state
		claim_history.time = timezone.now()
		claim_history.action = ClaimAction.UPDATE_STATE.value
		claim_history.save()
	
	# Access control
	
	def can_view(self, user):
		if user == self.author:
			return True
		if user.groups.filter(name='Treasury').exists():
			return True
		return False
	
	def can_edit(self, user):
		# Cannot edit if cannot view
		if not self.can_view(user):
			return False
		
		# No one can edit if already paid
		if self.state == ClaimState.PAID.value:
			return False
		
		# Only Treasurer may edit if submitted
		if self.state != ClaimState.DRAFT.value and self.state != ClaimState.RESUBMIT.value:
			if user.groups.filter(name='Treasury').exists():
				return True
			return False
		
		# Otherwise the submitter or Treasurer may edit
		if user == self.author:
			return True
		if user in self.contributors.all():
			return True
		if user.groups.filter(name='Treasury').exists():
			return True
		
		# Otherwise cannot edit
		return False
	
	def can_submit(self, user):
		if not self.can_edit(user):
			return False
		if self.state == ClaimState.DRAFT.value or self.state == ClaimState.RESUBMIT.value:
			return True
		return False
	
	def can_withdraw(self, user):
		if not self.can_edit(user):
			return False
		if self.state == ClaimState.AWAIT_REVIEW.value or self.state == ClaimState.APPROVED.value:
			return True
		return False
	
	def can_approve(self, user):
		if not self.can_edit(user):
			return False
		if not user.groups.filter(name='Treasury').exists():
			return False
		if self.state == ClaimState.AWAIT_REVIEW.value:
			return True
		return False
	
	def can_return(self, user):
		return self.can_approve(user)

class ClaimReceipt(models.Model):
	claim = models.ForeignKey(ReimbursementClaim, on_delete=models.CASCADE)
	uploaded_file = models.FileField(upload_to='receipt_uploads/%Y/%m/%d/')

class ClaimComment(models.Model):
	claim = models.ForeignKey(ReimbursementClaim, on_delete=models.CASCADE)
	author = models.ForeignKey(User, on_delete=models.PROTECT, related_name='+')
	time = models.DateTimeField()
	content = models.TextField()
	
	class Meta:
		ordering = ['id']

class ClaimHistory(models.Model):
	claim = models.ForeignKey(ReimbursementClaim, on_delete=models.CASCADE)
	author = models.ForeignKey(User, on_delete=models.PROTECT, related_name='+')
	state = models.IntegerField(choices=[(v.value, v.description) for v in ClaimState])
	time = models.DateTimeField()
	action = models.IntegerField(choices=[(v.value, v.description) for v in ClaimAction])