from datetime import date
import re
from uuid import UUID

from django import forms

from finance.models import Account, Category, Payee, Transaction
from finance.queries import active_accounts, active_categories, active_payees


_MONTH_RE = re.compile(r"(?P<year>\d{4})-(?P<month>0[1-9]|1[0-2])", re.ASCII)


def _reference_choices(model, *, include=None):
    rows = {Account: active_accounts, Category: active_categories, Payee: active_payees}[model]()
    if include is not None:
        rows = model.objects.filter(pk=include.pk) | rows
        rows = rows.order_by("name", "id")
    return [(str(row.pk), row.name) for row in rows]


def _uuid(value):
    return None if value == "" else UUID(value)


class ManualTransactionForm(forms.Form):
    account = forms.TypedChoiceField(coerce=UUID)
    amount = forms.DecimalField(max_digits=18, decimal_places=2)
    posting_date = forms.DateField(widget=forms.DateInput(attrs={"type": "date"}))
    occurrence_date = forms.DateField(required=False, widget=forms.DateInput(attrs={"type": "date"}))
    kind = forms.ChoiceField(choices=Transaction.Kind.choices)
    description = forms.CharField(required=False, widget=forms.Textarea(attrs={"rows": 3}))
    payee = forms.TypedChoiceField(required=False, empty_value=None, coerce=_uuid)
    category = forms.TypedChoiceField(required=False, empty_value=None, coerce=_uuid)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields["account"].choices = _reference_choices(Account)
        self.fields["payee"].choices = [("", "None"), *_reference_choices(Payee)]
        self.fields["category"].choices = [("", "Uncategorized"), *_reference_choices(Category)]

    def clean(self):
        values = super().clean()
        amount = values.get("amount")
        kind = values.get("kind")
        if amount is not None and kind == Transaction.Kind.EXPENSE and amount >= 0:
            self.add_error("amount", "Expense amounts must be negative.")
        if amount is not None and kind in {Transaction.Kind.INCOME, Transaction.Kind.REFUND} and amount <= 0:
            self.add_error("amount", "Income and refund amounts must be positive.")
        return values


class AnnotationForm(forms.Form):
    description = forms.CharField(required=False, widget=forms.Textarea(attrs={"rows": 3}))
    payee = forms.TypedChoiceField(required=False, empty_value=None, coerce=_uuid)
    category = forms.TypedChoiceField(required=False, empty_value=None, coerce=_uuid)

    def __init__(self, *args, transaction, **kwargs):
        super().__init__(*args, **kwargs)
        self.transaction = transaction
        self.fields["payee"].choices = [("", "None"), *_reference_choices(Payee, include=transaction.payee)]
        self.fields["category"].choices = [("", "Uncategorized"), *_reference_choices(Category, include=transaction.category)]
        if not self.is_bound:
            self.initial = {
                "description": transaction.description,
                "payee": transaction.payee_id,
                "category": transaction.category_id,
            }

    def changes(self):
        values = self.cleaned_data
        changes = {}
        for form_name, model_name in (("description", "description"), ("payee", "payee_id"), ("category", "category_id")):
            if values[form_name] != getattr(self.transaction, model_name):
                changes[model_name] = values[form_name]
        return changes


class AccountForm(forms.Form):
    name = forms.CharField(max_length=255)
    kind = forms.ChoiceField(choices=Account.Kind.choices)
    currency = forms.RegexField(regex=r"^[A-Z]{3}$", max_length=3)


class CategoryForm(forms.Form):
    name = forms.CharField(max_length=255)
    kind = forms.ChoiceField(choices=Category.Kind.choices)


class PayeeForm(forms.Form):
    name = forms.CharField(max_length=255)


class ReconciliationForm(forms.Form):
    account = forms.TypedChoiceField(coerce=UUID)
    as_of_date = forms.DateField(widget=forms.DateInput(attrs={"type": "date"}))
    institution_balance = forms.DecimalField(max_digits=18, decimal_places=2)

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields["account"].choices = _reference_choices(Account)


class ImportMappingForm(forms.Form):
    def __init__(self, *args, sections, **kwargs):
        super().__init__(*args, **kwargs)
        self.sections = sections
        choices = [("", "Choose an account"), *(
            (str(row.pk), row.name) for row in active_accounts().filter(currency="BRL")
        )]
        for index, section in enumerate(sections):
            self.fields[f"section_{index}"] = forms.TypedChoiceField(
                label=f"Section {section}", coerce=UUID, choices=choices,
                error_messages={
                    "required": "Choose an active BRL account for this section.",
                    "invalid_choice": "Choose an active BRL account for this section.",
                },
            )

    def section_mapping(self):
        return {section: str(self.cleaned_data[f"section_{index}"])
                for index, section in enumerate(self.sections)}


class ReportSelectionForm(forms.Form):
    month = forms.CharField(
        error_messages={"required": "invalid_month"},
        widget=forms.TextInput(attrs={"type": "month"}),
    )
    currency = forms.ChoiceField(
        error_messages={"required": "invalid_currency", "invalid_choice": "invalid_currency"}
    )

    def __init__(self, *args, currencies, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields["currency"].choices = [(currency, currency) for currency in currencies]

    def clean_month(self):
        value = self.cleaned_data["month"]
        match = _MONTH_RE.fullmatch(value)
        if match is None:
            raise forms.ValidationError("invalid_month", code="invalid_month")
        try:
            month = date(int(match["year"]), int(match["month"]), 1)
        except ValueError as exc:
            raise forms.ValidationError("invalid_month", code="invalid_month") from exc
        if month.year == date.max.year and month.month == 12:
            raise forms.ValidationError("invalid_month", code="invalid_month")
        return month