"""Pydantic request/response schemas — the API contract (spec §8.3 rule 1).

Defined separately from ORM models; services convert via from_attributes.
Validation happens here at the boundary (spec §8.1 rule 11).
"""

from datetime import date, datetime
from typing import Literal

from pydantic import BaseModel, ConfigDict, Field, model_validator

UnitType = Literal["weight", "count"]
FoodSource = Literal["openfoodfacts", "manual", "meal"]
MealSlot = Literal["breakfast", "lunch", "dinner", "snack"]


# ── Foods ────────────────────────────────────────────────────────────────────


class FoodCreate(BaseModel):
    """Schema for POST /api/foods. calories_per_unit required unless is_meal."""

    name: str
    brand: str | None = None
    barcode: str | None = None
    source: FoodSource = "manual"
    is_meal: bool = False
    unit_type: UnitType = "weight"
    calories_per_unit: float | None = Field(default=None, gt=0)
    protein_per_unit: float | None = Field(default=None, ge=0)
    carbs_per_unit: float | None = Field(default=None, ge=0)
    fat_per_unit: float | None = Field(default=None, ge=0)
    fiber_per_unit: float | None = Field(default=None, ge=0)
    saturated_fat_per_unit: float | None = Field(default=None, ge=0)
    sugars_per_unit: float | None = Field(default=None, ge=0)
    sodium_per_unit: float | None = Field(default=None, ge=0)
    serving_size_g: float | None = Field(default=None, gt=0)
    serving_name: str | None = None
    off_data: str | None = None

    @model_validator(mode="after")
    def _check_calories_for_non_meal(self):
        if not self.is_meal and self.calories_per_unit is None:
            raise ValueError("calories_per_unit is required when is_meal=false")
        return self


class FoodUpdate(BaseModel):
    """Schema for PUT /api/foods/{id}. All fields optional — only supplied
    fields are updated."""

    name: str | None = None
    brand: str | None = None
    barcode: str | None = None
    unit_type: UnitType | None = None
    calories_per_unit: float | None = Field(default=None, gt=0)
    protein_per_unit: float | None = Field(default=None, ge=0)
    carbs_per_unit: float | None = Field(default=None, ge=0)
    fat_per_unit: float | None = Field(default=None, ge=0)
    fiber_per_unit: float | None = Field(default=None, ge=0)
    saturated_fat_per_unit: float | None = Field(default=None, ge=0)
    sugars_per_unit: float | None = Field(default=None, ge=0)
    sodium_per_unit: float | None = Field(default=None, ge=0)
    serving_size_g: float | None = Field(default=None, gt=0)
    serving_name: str | None = None
    off_data: str | None = None


class FoodRead(BaseModel):
    """Schema for GET /api/foods responses."""

    model_config = ConfigDict(from_attributes=True)

    id: int
    name: str
    brand: str | None
    barcode: str | None
    source: FoodSource
    is_meal: bool
    unit_type: UnitType
    calories_per_unit: float | None
    protein_per_unit: float | None
    carbs_per_unit: float | None
    fat_per_unit: float | None
    fiber_per_unit: float | None
    saturated_fat_per_unit: float | None
    sugars_per_unit: float | None
    sodium_per_unit: float | None
    serving_size_g: float | None
    serving_name: str | None
    deleted_at: datetime | None
    created_at: datetime
    updated_at: datetime


# ── Log ──────────────────────────────────────────────────────────────────────


class LogEntryCreate(BaseModel):
    food_id: int
    quantity: float = Field(gt=0)
    meal_slot: MealSlot | None = None
    date: date  # client-supplied YYYY-MM-DD (spec §8.1 rule 8)


class LogEntryUpdate(BaseModel):
    """Schema for PUT /api/log/{id}. All fields optional — only supplied
    fields are updated. Send {"meal_slot": null} to clear the slot."""
    quantity: float | None = Field(default=None, gt=0)
    meal_slot: MealSlot | None = None
    sort_order: int | None = None


class LogFoodRead(BaseModel):
    """Embedded food reference in log entry responses (spec §3.3, §8.3 rule 1).
    Includes name, brand, unit_type, and serving info so the frontend can render
    log entries without N+1 lookups. Soft-deleted foods render here (§2.1)."""
    model_config = ConfigDict(from_attributes=True)

    id: int
    name: str
    brand: str | None
    unit_type: UnitType
    serving_size_g: float | None
    serving_name: str | None
    is_meal: bool
    deleted_at: datetime | None


class LogEntryRead(BaseModel):
    model_config = ConfigDict(from_attributes=True)

    id: int
    date: date
    food_id: int
    quantity: float
    meal_slot: MealSlot | None
    sort_order: int
    food: LogFoodRead


# ── Targets ──────────────────────────────────────────────────────────────────


class TargetCreate(BaseModel):
    """Schema for POST /api/targets. end_date is auto-managed by the service."""

    start_date: date  # client-supplied YYYY-MM-DD (spec §8.1 rule 8)
    calories: int = Field(gt=0)
    protein_g: float | None = Field(default=None, ge=0)
    carbs_g: float | None = Field(default=None, ge=0)
    fat_g: float | None = Field(default=None, ge=0)


class TargetUpdate(BaseModel):
    """Schema for PUT /api/targets/{id}. All fields optional — only supplied
    fields are updated. Setting end_date to null will reactivate a historical
    target only if no other active target exists."""

    start_date: date | None = None
    end_date: date | None = None
    calories: int | None = Field(default=None, gt=0)
    protein_g: float | None = Field(default=None, ge=0)
    carbs_g: float | None = Field(default=None, ge=0)
    fat_g: float | None = Field(default=None, ge=0)

    @model_validator(mode="after")
    def _check_date_range(self):
        if self.start_date is not None and self.end_date is not None:
            if self.end_date <= self.start_date:
                raise ValueError("end_date must be after start_date")
        return self


class TargetRead(BaseModel):
    model_config = ConfigDict(from_attributes=True)

    id: int
    start_date: date
    end_date: date | None
    calories: int
    protein_g: float | None
    carbs_g: float | None
    fat_g: float | None


# ── Day Summary (TICKET-004) ────────────────────────────────────────────────


class DaySummaryNutrition(BaseModel):
    """Summed nutrition totals for a single day.

    All fields are floats (summed from scaled per-unit values).
    Foods with null nutrition fields contribute 0.
    """

    calories: float
    protein_g: float
    carbs_g: float
    fat_g: float
    fiber_g: float
    saturated_fat_g: float
    sugars_g: float
    sodium_g: float


class DaySummaryResponse(BaseModel):
    """Response shape for GET /api/log/summary — the contract the frontend
    ProgressBar consumes.

    Remaining-vs-target arithmetic: LEFT TO THE FRONTEND.
    The server returns raw totals and the applicable target (or null).
    The frontend computes remaining = target.calories - totals.calories
    and similar for macros where both target and total exist.
    """

    date: date
    totals: DaySummaryNutrition
    target: TargetRead | None