from datetime import date, datetime
from decimal import Decimal, ROUND_HALF_UP
from typing import Literal

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

EstimateStatus = Literal["draft", "sent", "approved", "declined", "expired", "cancelled"]
EstimateItemType = Literal["labor", "part", "flat_rate", "shipping", "other"]
EstimateActorType = Literal["user", "customer", "system"]
EstimateEventType = Literal["created", "updated", "sent", "approved", "declined", "cancelled", "expired", "reminder_sent", "question"]


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


class RepairEstimateItemPayload(BaseModel):
    item_type: EstimateItemType = "other"
    inventory_item_id: int | None = None
    inventory_price_overridden: bool = False
    title: str = Field(default="", max_length=255)
    description: str | None = None
    quantity: Decimal = Field(gt=Decimal("0"))
    unit: str = Field(default="Stk.", max_length=40)
    unit_price_cents: int = Field(ge=0)

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

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

    @model_validator(mode="after")
    def validate_inventory_or_title(self):
        if self.inventory_item_id is None and not self.title.strip():
            raise ValueError("Titel ist erforderlich")
        return self


class RepairEstimatePayload(BaseModel):
    title: str = Field(min_length=1, max_length=255)
    customer_message: str = ""
    internal_note: str | None = None
    tax_rate_percent: Decimal = Field(default=Decimal("19.00"), ge=Decimal("0"))
    currency: str = Field(default="EUR", max_length=3)
    valid_until: date | None = None
    items: list[RepairEstimateItemPayload]

    @field_validator("title", "customer_message", "internal_note", "currency", 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_items(self):
        if not self.items:
            raise ValueError("Mindestens eine Position ist erforderlich")
        return self


class RepairEstimateCreate(RepairEstimatePayload):
    pass


class RepairEstimateUpdate(RepairEstimatePayload):
    pass


class RepairEstimateItemResponse(BaseModel):
    id: int
    estimate_id: int
    inventory_item_id: int | None
    inventory_snapshot_name: str
    inventory_snapshot_sku: str
    inventory_snapshot_manufacturer: str | None
    inventory_snapshot_part_number: str | None
    position: int
    item_type: EstimateItemType
    title: str
    description: str | None
    quantity: Decimal
    unit: str
    unit_price_cents: int
    total_cents: int
    created_at: datetime
    updated_at: datetime

    model_config = ConfigDict(from_attributes=True)


class RepairEstimateEventResponse(BaseModel):
    id: int
    estimate_id: int
    event_type: str
    actor_type: str
    actor_user_id: int | None
    note: str | None
    created_at: datetime

    model_config = ConfigDict(from_attributes=True)


class RepairEstimateResponse(BaseModel):
    id: int
    repair_id: int
    estimate_number: str
    status: EstimateStatus
    title: str
    customer_message: str
    internal_note: str | None
    subtotal_cents: int
    tax_rate_percent: Decimal
    tax_cents: int
    total_cents: int
    currency: str
    valid_until: date | None
    sent_at: datetime | None
    approved_at: datetime | None
    declined_at: datetime | None
    customer_response_message: str | None
    created_by_user_id: int | None
    created_at: datetime
    updated_at: datetime
    items: list[RepairEstimateItemResponse]

    model_config = ConfigDict(from_attributes=True)


class PublicEstimateItemResponse(BaseModel):
    item_type: EstimateItemType
    inventory_snapshot_name: str
    inventory_snapshot_sku: str
    inventory_snapshot_manufacturer: str | None
    inventory_snapshot_part_number: str | None
    title: str
    description: str | None
    quantity: Decimal
    unit: str
    unit_price_cents: int
    total_cents: int


class PublicEstimateResponse(BaseModel):
    estimate_number: str
    status: EstimateStatus
    title: str
    customer_message: str
    subtotal_cents: int
    tax_cents: int
    total_cents: int
    currency: str
    valid_until: date | None
    items: list[PublicEstimateItemResponse]


class PublicEstimateDecisionRequest(BaseModel):
    message: str | None = Field(default=None, max_length=2000)

    @field_validator("message", mode="before")
    @classmethod
    def normalize_message(cls, value: object) -> str | None:
        if value is None:
            return None
        text = normalize_text(value)
        return text or None


def calculate_item_total(quantity: Decimal, unit_price_cents: int) -> int:
    total = (quantity * Decimal(unit_price_cents)).quantize(Decimal("1"), rounding=ROUND_HALF_UP)
    return int(total)


def calculate_tax(subtotal_cents: int, tax_rate_percent: Decimal) -> int:
    tax = (Decimal(subtotal_cents) * tax_rate_percent / Decimal("100")).quantize(Decimal("1"), rounding=ROUND_HALF_UP)
    return int(tax)