from datetime import datetime
from decimal import Decimal
from typing import Literal

from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator

InventoryMovementType = Literal[
    "initial",
    "purchase",
    "adjustment",
    "reservation",
    "release",
    "consumption",
    "return",
    "correction",
]


def normalize_text(value: object) -> str:
    if value is None:
        return ""
    return str(value).strip()


def normalize_optional_text(value: object) -> str | None:
    text = normalize_text(value)
    return text or None


class InventoryCategoryPayload(BaseModel):
    name: str = Field(min_length=1, max_length=160)
    description: str | None = None

    @field_validator("name", "description", mode="before")
    @classmethod
    def normalize_strings(cls, value: object) -> str | None:
        if value is None:
            return None
        return normalize_text(value)


class InventoryLocationPayload(BaseModel):
    name: str = Field(min_length=1, max_length=160)
    description: str | None = None

    @field_validator("name", "description", mode="before")
    @classmethod
    def normalize_strings(cls, value: object) -> str | None:
        if value is None:
            return None
        return normalize_text(value)


class InventorySupplierPayload(BaseModel):
    name: str = Field(min_length=1, max_length=180)
    contact_name: str | None = None
    email: str | None = None
    phone: str | None = None
    website: str | None = None
    customer_number: str | None = None
    notes: str | None = None

    @field_validator("*", mode="before")
    @classmethod
    def normalize_strings(cls, value: object) -> str | None:
        if value is None:
            return None
        return normalize_optional_text(value)


class InventoryItemPayload(BaseModel):
    sku: str | None = Field(default=None, max_length=40)
    name: str = Field(min_length=1, max_length=255)
    description: str | None = None
    category_id: int | None = None
    manufacturer: str | None = None
    manufacturer_part_number: str | None = None
    supplier_id: int | None = None
    supplier_part_number: str | None = None
    compatible_devices: str | None = None
    location_id: int | None = None
    quantity_on_hand: int = Field(default=0, ge=0)
    quantity_reserved: int = Field(default=0, ge=0)
    reorder_level: int = Field(default=0, ge=0)
    unit: str = Field(default="Stk.", max_length=40)
    purchase_price_cents: int | None = Field(default=None, ge=0)
    selling_price_cents: int | None = Field(default=None, ge=0)
    currency: str = Field(default="EUR", max_length=3)
    tax_rate_percent: Decimal = Field(default=Decimal("19.00"), ge=Decimal("0"))
    notes: str | None = None
    is_active: bool = True

    @field_validator(
        "sku",
        "name",
        "description",
        "manufacturer",
        "manufacturer_part_number",
        "supplier_part_number",
        "compatible_devices",
        "unit",
        "currency",
        "notes",
        mode="before",
    )
    @classmethod
    def normalize_strings(cls, value: object) -> str | None:
        if value is None:
            return None
        return normalize_text(value)

    @field_validator("currency")
    @classmethod
    def normalize_currency(cls, value: str) -> str:
        return value.upper() or "EUR"

    @field_validator("tax_rate_percent", mode="before")
    @classmethod
    def normalize_tax_rate(cls, value: object) -> object:
        if isinstance(value, str):
            return value.strip().replace(",", ".")
        return value

    @model_validator(mode="after")
    def validate_reserved_quantity(self):
        if self.quantity_reserved > self.quantity_on_hand:
            raise ValueError("Reservierter Bestand darf den Lagerbestand nicht überschreiten")
        return self


class InventoryItemCreate(InventoryItemPayload):
    pass


class InventoryItemUpdate(InventoryItemPayload):
    pass


class InventoryStockAction(BaseModel):
    quantity: int = Field(ge=0)
    reason: str = Field(min_length=1, max_length=255)
    note: str | None = None
    reference_type: str | None = Field(default=None, max_length=80)
    reference_id: int | None = None

    @field_validator("reason", "note", "reference_type", mode="before")
    @classmethod
    def normalize_strings(cls, value: object) -> str | None:
        if value is None:
            return None
        return normalize_text(value)


class InventoryCategoryResponse(InventoryCategoryPayload):
    id: int
    slug: str
    created_at: datetime
    updated_at: datetime

    model_config = ConfigDict(from_attributes=True)


class InventoryLocationResponse(InventoryLocationPayload):
    id: int
    created_at: datetime
    updated_at: datetime

    model_config = ConfigDict(from_attributes=True)


class InventorySupplierResponse(InventorySupplierPayload):
    id: int
    created_at: datetime
    updated_at: datetime

    model_config = ConfigDict(from_attributes=True)


class InventoryItemResponse(BaseModel):
    id: int
    sku: str
    name: str
    description: str | None
    category_id: int | None
    manufacturer: str | None
    manufacturer_part_number: str | None
    supplier_id: int | None
    supplier_part_number: str | None
    compatible_devices: str | None
    location_id: int | None
    quantity_on_hand: int
    quantity_reserved: int
    quantity_available: int
    reorder_level: int
    unit: str
    purchase_price_cents: int | None
    selling_price_cents: int | None
    currency: str
    tax_rate_percent: Decimal
    notes: str | None
    is_active: bool
    created_at: datetime
    updated_at: datetime
    category: InventoryCategoryResponse | None
    supplier: InventorySupplierResponse | None
    location: InventoryLocationResponse | None

    model_config = ConfigDict(from_attributes=True)


class InventoryItemListResponse(BaseModel):
    items: list[InventoryItemResponse]
    total: int
    limit: int
    offset: int


class InventoryStockMovementResponse(BaseModel):
    id: int
    item_id: int
    movement_type: str
    quantity: int
    reason: str
    reference_type: str | None
    reference_id: int | None
    note: str | None
    actor_user_id: int | None
    actor_username: str
    created_at: datetime

    model_config = ConfigDict(from_attributes=True)