from django.db import models
from django.core.exceptions import ValidationError


class Tag(models.Model):
    """Flexible tagging for ingredients — protein, carb, veg, seasoning, etc.
    An ingredient can have multiple tags."""

    name = models.CharField(max_length=50, unique=True)

    class Meta:
        ordering = ["name"]

    def __str__(self):
        return self.name


class Ingredient(models.Model):
    """Master list of known ingredients."""

    name = models.CharField(max_length=100, unique=True)  # canonical: "egg noodles"
    default_unit = models.CharField(max_length=20)  # "nests", "g", "items"
    tags = models.ManyToManyField(Tag, blank=True)
    shelf_life_days = models.IntegerField(
        null=True, blank=True, help_text="Typical fridge life in days once opened/defrosted"
    )
    aliases = models.JSONField(
        default=list, blank=True, help_text='Alternative names, e.g. ["noodles", "egg noodle nests"]'
    )
    preferences = models.TextField(
        blank=True,
        help_text="How Tom likes this ingredient cooked / qualitative notes. "
        'E.g. "Don\'t traybake — needs to be fried. Not substantial as sole protein."',
    )

    class Meta:
        ordering = ["name"]

    def __str__(self):
        return self.name


class PantryItem(models.Model):
    """What's in the kitchen right now."""

    class Location(models.TextChoices):
        FRIDGE = "fridge", "Fridge"
        FREEZER = "freezer", "Freezer"
        CUPBOARD = "cupboard", "Cupboard"

    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    quantity = models.DecimalField(max_digits=8, decimal_places=2)
    unit = models.CharField(max_length=20)
    location = models.CharField(max_length=20, choices=Location.choices)
    stored_date = models.DateField(auto_now_add=True)
    expiry_date = models.DateField(null=True, blank=True)
    is_staple = models.BooleanField(
        default=False, help_text="Always restock when gone (onions, frozen chips)"
    )
    notes = models.TextField(blank=True)

    class Meta:
        ordering = ["expiry_date", "ingredient__name"]

    def __str__(self):
        return f"{self.ingredient.name} ({self.quantity} {self.unit}) [{self.location}]"

    def clean(self):
        """Business rules for pantry items."""
        if self.location == self.Location.FREEZER and self.expiry_date is not None:
            raise ValidationError("Freezer items should not have an expiry date (frozen = no expiry).")
        if self.location == self.Location.FRIDGE and self.expiry_date is None:
            # Try to auto-set from ingredient shelf life
            if self.ingredient_id and self.ingredient.shelf_life_days:
                from datetime import date, timedelta

                self.expiry_date = date.today() + timedelta(days=self.ingredient.shelf_life_days)
            # Don't raise an error — some fridge items just don't have a known expiry

    def save(self, *args, **kwargs):
        self.full_clean()
        super().save(*args, **kwargs)


# --- Meta-Recipes ---


class MetaRecipe(models.Model):
    """A cooking template with swappable ingredient slots."""

    name = models.CharField(max_length=100)  # "Stir Fry"
    method = models.TextField(help_text="Cooking instructions (markdown)")
    prep_time_mins = models.IntegerField(null=True, blank=True)
    cook_time_mins = models.IntegerField(null=True, blank=True)
    default_servings = models.IntegerField(default=2)
    gear_needed = models.CharField(max_length=200, blank=True)  # "frying pan"
    tags = models.JSONField(default=list, blank=True)  # ["quick", "one-pan"]

    class Meta:
        ordering = ["name"]

    def __str__(self):
        return self.name


class Slot(models.Model):
    """A swappable category in a meta-recipe (e.g. 'protein', 'carb')."""

    meta_recipe = models.ForeignKey(MetaRecipe, on_delete=models.CASCADE, related_name="slots")
    name = models.CharField(max_length=50)  # "protein", "carb", "veg"
    required = models.BooleanField(default=True)
    max_choices = models.IntegerField(
        default=1, help_text="Max ingredients to pick (1 for protein, 3 for veg)"
    )

    class Meta:
        ordering = ["meta_recipe", "name"]

    def __str__(self):
        return f"{self.meta_recipe.name} > {self.name}"


class SlotOption(models.Model):
    """An ingredient that can fill a slot, with quantity per serving.

    Example: Stir Fry > protein slot > pork mince, 250g per serving.
    """

    slot = models.ForeignKey(Slot, on_delete=models.CASCADE, related_name="options")
    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    quantity_per_serving = models.DecimalField(max_digits=8, decimal_places=2)
    unit = models.CharField(max_length=20)
    notes = models.CharField(max_length=200, blank=True)  # "skin off", "defrost first"

    class Meta:
        ordering = ["slot", "ingredient__name"]

    def __str__(self):
        return f"{self.slot} > {self.ingredient.name} ({self.quantity_per_serving} {self.unit})"


class MetaRecipeBase(models.Model):
    """Ingredients always needed regardless of slot choices.

    Example: Stir Fry always needs 1 onion + 2 cloves garlic per serving.
    """

    meta_recipe = models.ForeignKey(
        MetaRecipe, on_delete=models.CASCADE, related_name="base_ingredients"
    )
    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    quantity_per_serving = models.DecimalField(max_digits=8, decimal_places=2)
    unit = models.CharField(max_length=20)

    class Meta:
        ordering = ["meta_recipe", "ingredient__name"]

    def __str__(self):
        return f"{self.meta_recipe.name} base: {self.ingredient.name}"


# --- Fixed Recipes ---


class Recipe(models.Model):
    """Traditional recipe with a fixed ingredient list."""

    name = models.CharField(max_length=200)
    method = models.TextField(help_text="Cooking instructions (markdown)")
    prep_time_mins = models.IntegerField(null=True, blank=True)
    cook_time_mins = models.IntegerField(null=True, blank=True)
    servings = models.IntegerField(default=2)
    source_url = models.URLField(blank=True)
    source_book = models.CharField(max_length=200, blank=True)
    gear_needed = models.CharField(max_length=200, blank=True)
    tags = models.JSONField(default=list, blank=True)

    class Meta:
        ordering = ["name"]

    def __str__(self):
        return self.name


class RecipeIngredient(models.Model):
    """An ingredient in a fixed recipe with quantity."""

    recipe = models.ForeignKey(Recipe, on_delete=models.CASCADE, related_name="ingredients")
    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    quantity = models.DecimalField(max_digits=8, decimal_places=2)
    unit = models.CharField(max_length=20)
    optional = models.BooleanField(default=False)

    class Meta:
        ordering = ["recipe", "ingredient__name"]

    def __str__(self):
        return f"{self.recipe.name}: {self.ingredient.name}"


# --- Cook Log & Shopping ---


class CookLog(models.Model):
    """What was cooked and when. Links to either a meta-recipe or fixed recipe."""

    date = models.DateField(auto_now_add=True)
    meta_recipe = models.ForeignKey(
        MetaRecipe, null=True, blank=True, on_delete=models.SET_NULL
    )
    recipe = models.ForeignKey(Recipe, null=True, blank=True, on_delete=models.SET_NULL)
    slot_choices = models.JSONField(
        default=dict,
        blank=True,
        help_text='Slot choices for meta-recipe, e.g. {"protein": "pork mince", "carb": "noodles"}',
    )
    servings = models.IntegerField(default=2)
    rating = models.IntegerField(
        null=True,
        blank=True,
        help_text="1-5 rating. 1=awful, 3=fine, 5=great",
    )
    notes = models.TextField(blank=True, help_text="What worked, what didn't, what to change next time")

    class Meta:
        ordering = ["-date"]

    def __str__(self):
        recipe_name = self.meta_recipe or self.recipe or "Unknown"
        return f"{self.date}: {recipe_name}"

    def clean(self):
        if not self.meta_recipe and not self.recipe:
            raise ValidationError("Must link to either a meta-recipe or a fixed recipe.")
        if self.meta_recipe and self.recipe:
            raise ValidationError("Cannot link to both a meta-recipe and a fixed recipe.")


class ShoppingListItem(models.Model):
    """Items on the shopping list."""

    ingredient = models.ForeignKey(
        Ingredient, null=True, blank=True, on_delete=models.SET_NULL
    )
    name = models.CharField(max_length=100, help_text="Fallback name if not in ingredients table")
    quantity = models.DecimalField(max_digits=8, decimal_places=2, null=True, blank=True)
    unit = models.CharField(max_length=20, blank=True)
    reason = models.CharField(max_length=200, blank=True)  # "for stir fry" / "restock staple"
    added_date = models.DateField(auto_now_add=True)
    checked = models.BooleanField(default=False)

    class Meta:
        ordering = ["checked", "added_date"]

    def __str__(self):
        display = self.ingredient.name if self.ingredient else self.name
        return f"{'✅' if self.checked else '🛒'} {display}"