from django import forms
from django.forms import widgets

from .models import Worker, Leave, RotaSchedule


class WorkerForm(forms.ModelForm):
    class Meta:
        model = Worker
        fields = ["name", "email", "site", "grade", "fte", "active"]


class LeaveForm(forms.ModelForm):
    class Meta:
        model = Leave
        fields = ["start_date", "end_date", "reason"]
        widgets = {
            "start_date": widgets.DateInput(attrs={"class": "datepicker input", "autocomplete": "off"}),
            "end_date": widgets.DateInput(attrs={"class": "datepicker input", "autocomplete": "off"}),
        }


class RotaScheduleForm(forms.ModelForm):
    class Meta:
        model = RotaSchedule
        # Do not expose end_date as editable: computed from start_date + weeks
        fields = ["name", "start_date", "description"]
        widgets = {
            "start_date": widgets.DateInput(attrs={"class": "datepicker input", "autocomplete": "off"}),
        }

    weeks = forms.IntegerField(min_value=1, initial=4, help_text="Number of weeks to generate the rota for")
    end_date = forms.DateField(required=False, disabled=True, widget=widgets.DateInput(attrs={"class": "datepicker input", "autocomplete": "off"}))

    def __init__(self, *args, **kwargs):
        instance = kwargs.get("instance")
        super().__init__(*args, **kwargs)
        if instance and instance.start_date and instance.end_date:
            delta = instance.end_date - instance.start_date
            weeks = max(1, delta.days // 7)
            self.fields["weeks"].initial = weeks
            self.fields["end_date"].initial = instance.end_date

    def clean_start_date(self):
        start = self.cleaned_data.get("start_date")
        if start is None:
            return start
        if start.weekday() != 0:
            raise forms.ValidationError("Start date must be a Monday")
        return start

    def clean(self):
        cleaned = super().clean()
        start = cleaned.get("start_date")
        weeks = cleaned.get("weeks")
        if start and weeks:
            import datetime

            end_date = start + datetime.timedelta(days=weeks * 7)
            cleaned["end_date"] = end_date
            # update the form data/display
            try:
                self.data = self.data.copy()
                self.data["end_date"] = end_date.isoformat()
            except Exception:
                pass
            self.fields["end_date"].initial = end_date
        return cleaned

    def save(self, commit=True):
        instance = super().save(commit=False)
        end_date = self.cleaned_data.get("end_date")
        if end_date:
            instance.end_date = end_date
        if commit:
            instance.save()
            try:
                self.save_m2m()
            except Exception:
                pass
        return instance


class ShiftForm(forms.Form):
    name = forms.CharField(max_length=200)
    sites = forms.CharField(
        help_text="Comma separated list of sites (e.g. exeter,plymouth)",
        required=True,
    )
    length = forms.DecimalField(max_digits=6, decimal_places=2, initial=12.5)
    DAYS = [(d, d) for d in ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]]
    days = forms.MultipleChoiceField(choices=DAYS, widget=forms.CheckboxSelectMultiple)
    workers_required = forms.IntegerField(min_value=1, initial=1)
    assign_as_block = forms.BooleanField(required=False, initial=False)

    def clean_sites(self):
        val = self.cleaned_data["sites"]
        sites = [s.strip() for s in val.split(",") if s.strip()]
        if not sites:
            raise forms.ValidationError("At least one site is required")
        return sites