from datetime import UTC, datetime
from enum import StrEnum
from uuid import UUID, uuid4

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


def now_utc() -> datetime:
    return datetime.now(UTC)


class State(StrEnum):
    NEVER_CHECKED = "never_checked"
    UP = "up"
    DOWN = "down"
    ERROR = "error"
    BLOCKED = "blocked"


class MonitorCreate(BaseModel):
    name: str = Field(min_length=1, max_length=100)
    url: HttpUrl
    expected_status: int = Field(default=200, ge=100, le=599)


class MonitorUpdate(BaseModel):
    name: str | None = Field(default=None, min_length=1, max_length=100)
    url: HttpUrl | None = None
    expected_status: int | None = Field(default=None, ge=100, le=599)

    @model_validator(mode="after")
    def not_empty(self) -> "MonitorUpdate":
        if not self.model_fields_set:
            raise ValueError("at least one field is required")
        return self


class CurrentStatus(BaseModel):
    model_config = ConfigDict(frozen=True)

    state: State = State.NEVER_CHECKED
    checked_at: datetime | None = None
    observed_status: int | None = None
    latency_ms: float | None = None
    error: str | None = None


class Monitor(BaseModel):
    model_config = ConfigDict(frozen=True)

    id: UUID = Field(default_factory=uuid4)
    name: str
    url: HttpUrl
    expected_status: int
    created_at: datetime = Field(default_factory=now_utc)
    updated_at: datetime = Field(default_factory=now_utc)
    current_status: CurrentStatus = Field(default_factory=CurrentStatus)


class CheckResult(CurrentStatus):
    monitor_id: UUID


class ErrorBody(BaseModel):
    code: str
    message: str


class ErrorResponse(BaseModel):
    error: ErrorBody