# The core application of the Mia project.
#   by imacat <imacat@mail.imacat.idv.tw>, 2020/7/31

#  Copyright (c) 2020 imacat.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

"""The forms of the Mia core application.

"""
import re

from django import forms
from django.core.validators import RegexValidator
from django.utils.translation import gettext as _

from .models import Account, Record
from .validators import validate_record_account_code, validate_record_id, \
    validate_account_code


class RecordForm(forms.Form):
    """An accounting record form.

    Attributes:
        transaction (Transaction|None): The current transaction or None.
        is_credit (bool): Whether this is a credit record.
    """
    id = forms.IntegerField(
        required=False,
        error_messages={
            "invalid": _("This accounting record is not valid."),
        },
        validators=[validate_record_id])
    account = forms.CharField(
        error_messages={
            "required": _("Please select the account."),
        },
        validators=[validate_record_account_code])
    summary = forms.CharField(
        required=False,
        max_length=128,
        error_messages={
            "max_length": _("This summary is too long (max. 128 characters)."),
        })
    amount = forms.IntegerField(
        min_value=1,
        error_messages={
            "required": _("Please fill in the amount."),
            "invalid": _("Please fill in a number."),
            "min_value": _("The amount must be at least 1."),
        })

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.transaction = None
        self.is_credit = None

    def account_title(self):
        """Returns the title of the specified account, if any.

        Returns:
            str: The title of the specified account, or None if the specified
                account is not available.
        """
        try:
            return Account.objects.get(code=self["account"].value()).title
        except KeyError:
            return None
        except Account.DoesNotExist:
            return None

    def clean(self):
        """Validates the form globally.

        Raises:
            ValidationError: When the validation fails.
        """
        errors = []
        if "id" in self.errors:
            errors = errors + self.errors["id"].as_data()
        validators = [self._validate_transaction,
                      self._validate_account_type,
                      self._validate_is_credit]
        for validator in validators:
            try:
                validator()
            except forms.ValidationError as e:
                errors.append(e)
        if errors:
            raise forms.ValidationError(errors)

    def _validate_transaction(self):
        """Validates whether the transaction matches the transaction form.

        Raises:
            ValidationError: When the validation fails.
        """
        if "id" in self.errors:
            return
        if self.transaction is None:
            if "id" in self.data:
                raise forms.ValidationError(
                    _("This record is not for this transaction."),
                    code="not_belong")
        else:
            if "id" in self.data:
                record = Record.objects.get(pk=self.data["id"])
                if record.transaction.pk != self.transaction.pk:
                    raise forms.ValidationError(
                        _("This record is not for this transaction."),
                        code="not_belong")

    def _validate_account_type(self):
        """Validates whether the account is a correct debit or credit account.

        Raises:
            ValidationError: When the validation fails.
        """
        if "account" in self.errors:
            return
        if self.is_credit:
            if not re.match("^([123489]|7[1234])", self.data["account"]):
                error = forms.ValidationError(
                    _("This account is not for credit records."),
                    code="not_credit")
                self.add_error("account", error)
                raise error
        else:
            if not re.match("^([1235689]|7[5678])", self.data["account"]):
                error = forms.ValidationError(
                    _("This account is not for debit records."),
                    code="not_debit")
                self.add_error("account", error)
                raise error

    def _validate_is_credit(self):
        """Validates whether debit and credit records are submitted correctly
        as corresponding debit and credit records.

        Raises:
            ValidationError: When the validation fails.
        """
        if "id" in self.errors:
            return
        if "id" not in self.data:
            return
        record = Record.objects.get(pk=self.data["id"])
        if record.is_credit != self.is_credit:
            if self.is_credit:
                raise forms.ValidationError(
                    _("This accounting record is not a credit record."),
                    code="not_credit")
            else:
                raise forms.ValidationError(
                    _("This accounting record is not a debit record."),
                    code="not_debit")


class TransactionForm(forms.Form):
    """A transaction form.

    Attributes:
        txn_type (str): The transaction type.
        transaction (Transaction|None): The current transaction or None
        debit_records (list[RecordForm]): The debit records.
        credit_records (list[RecordForm]): The credit records.
    """
    date = forms.DateField(
        required=True,
        error_messages={
            "required": _("Please fill in the date."),
            "invalid": _("This date is not valid.")
        })
    notes = forms.CharField(
        required=False,
        max_length=128,
        error_messages={
            "max_length": _("These notes are too long (max. 128 characters).")
        })

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.txn_type = None
        self.transaction = None
        self.debit_records = []
        self.credit_records = []

    def clean(self):
        """Validates the form globally.

        Raises:
            ValidationError: When the validation fails.
        """
        errors = []
        validators = [self._validate_has_debit_records,
                      self._validate_has_credit_records,
                      self._validate_balance]
        for validator in validators:
            try:
                validator()
            except forms.ValidationError as e:
                errors.append(e)
        if errors:
            raise forms.ValidationError(errors)

    def _validate_has_debit_records(self):
        """Validates whether there is any debit record.

        Raises:
            ValidationError: When the validation fails.
        """
        if self.txn_type == "income":
            return
        if len(self.debit_records) > 0:
            return
        if self.txn_type == "transfer":
            raise forms.ValidationError(
                _("Please fill in debit accounting records."),
                code="has_debit_records")
        raise forms.ValidationError(
            _("Please fill in accounting records."),
            code="has_debit_records")

    def _validate_has_credit_records(self):
        """Validates whether there is any credit record.

        Raises:
            ValidationError: When the validation fails.
        """
        if self.txn_type == "expense":
            return
        if len(self.credit_records) > 0:
            return
        if self.txn_type == "transfer":
            raise forms.ValidationError(
                _("Please fill in credit accounting records."),
                code="has_debit_records")
        raise forms.ValidationError(
            _("Please fill in accounting records."),
            code="has_debit_records")

    def _validate_balance(self):
        """Validates whether the total amount of debit and credit records are
        consistent.

        Raises:
            ValidationError: When the validation fails.
        """
        if self.txn_type != "transfer":
            return
        if self.debit_total() == self.credit_total():
            return
        raise forms.ValidationError(
            _("The total of the debit and credit amounts are inconsistent."),
            code="balance")

    def is_valid(self):
        if not super(TransactionForm, self).is_valid():
            return False
        for x in self.debit_records + self.credit_records:
            if not x.is_valid():
                return False
        return True

    def balance_error(self):
        """Returns the error message when the transaction is imbalanced.

        Returns:
            str: The error message when the transaction is imbalanced, or
                None otherwise.
        """
        errors = [x for x in self.non_field_errors().data
                  if x.code == "balance"]
        if errors:
            return errors[0].message
        return None

    def debit_total(self):
        """Returns the total amount of the debit records.

        Returns:
            int: The total amount of the credit records.
        """
        return sum([int(x.data["amount"]) for x in self.debit_records
                    if "amount" not in x.errors])

    def credit_total(self):
        """Returns the total amount of the credit records.

        Returns:
            int: The total amount of the credit records.
        """
        return sum([int(x.data["amount"]) for x in self.credit_records
                    if "amount" not in x.errors])


class AccountForm(forms.Form):
    """An account form."""
    code = forms.CharField(
        error_messages={
            "required": _("Please fill in the code."),
            "invalid": _("Please fill in a number."),
            "max_length": _("This code is too long  (max. 5)."),
            "min_value": _("This code is too long  (max. 5)."),
        }, validators=[
            RegexValidator(
                regex="^[1-9]+$",
                message=_("You can only use numbers 1-9 in the code.")),
            validate_account_code,
        ])
    title = forms.CharField(
        max_length=128,
        error_messages={
            "required": _("Please fill in the title."),
            "max_length": _("This title is too long  (max. 128)."),
        })

    def __init__(self, *args, **kwargs):
        super(AccountForm, self).__init__(*args, **kwargs)

    @property
    def parent(self):
        code = self["code"].value()
        if code is None or len(code) < 2:
            return None
        return Account.objects.get(code=code[:-1])