from datetime import UTC, datetime, timedelta
from typing import Literal

from pydantic import BaseModel, field_validator

DEFAULT_LIMIT = 50
MAX_LIMIT = 500

_EPOCH = datetime(1970, 1, 1, tzinfo=UTC)
_MICROSECOND = timedelta(microseconds=1)

ChatKind = Literal["private", "group", "channel"]
HitSource = Literal["text", "stt", "version", "data"]
FoundWhere = Literal[
    "text", "button", "link", "forward", "reply", "file", "preview", "data"
]


def encode_cursor(date: datetime, chat_id: int, message_id: int) -> str:
    return f"{(date - _EPOCH) // _MICROSECOND}_{chat_id}_{message_id}"


def decode_cursor(cursor: str) -> tuple[datetime, int, int]:
    micros, chat_id, message_id = (int(part) for part in cursor.split("_"))
    return _EPOCH + micros * _MICROSECOND, chat_id, message_id


class SearchFilters(BaseModel):
    account_id: int
    query: str | None = None
    chat_id: int | None = None
    sender_id: int | None = None
    kind: ChatKind | None = None
    has_media: bool | None = None
    deleted: bool | None = None
    edited: bool | None = None
    date_from: datetime | None = None
    date_to: datetime | None = None
    regex: str | None = None
    everywhere: bool = False
    cursor: str | None = None
    limit: int = DEFAULT_LIMIT

    @field_validator("cursor")
    @classmethod
    def _valid_cursor(cls, value: str | None) -> str | None:
        if value is not None:
            decode_cursor(value)
        return value


class Found(BaseModel):
    where: FoundWhere
    path: str
    value: str
    button: str | None = None


class SearchHit(BaseModel):
    chat_id: int
    message_id: int
    date: datetime
    sender_id: int | None
    text: str | None
    has_media: bool
    media_kind: str | None
    edited_at: datetime | None
    deleted_at: datetime | None
    source: HitSource
    extracted_text: str | None = None
    version_text: str | None = None
    version_at: datetime | None = None
    found: Found | None = None


class SearchPage(BaseModel):
    hits: list[SearchHit]
    next_cursor: str | None
    terms: list[str]
    scanned_to: datetime | None = None