from __future__ import annotations

import hashlib
import random
import re
from dataclasses import dataclass
from datetime import UTC, datetime
from enum import StrEnum
from typing import Any

PHONE_RE = re.compile(r"^\+7[0-9]{10}$")
EMAIL_RE = re.compile(r"^[^@\s]+@[^@\s]+\.[^@\s]+$")


class WorkflowState(StrEnum):
    CREATED = "created"
    RUNNING = "running"
    WAITING_CRM = "waiting_crm"
    WAITING_RETRY = "waiting_retry"
    WAITING_MANUAL = "waiting_manual"
    SUCCEEDED = "succeeded"
    FAILED = "failed"
    CANCELLED = "cancelled"


TRANSITIONS: dict[WorkflowState, frozenset[WorkflowState]] = {
    WorkflowState.CREATED: frozenset({WorkflowState.RUNNING, WorkflowState.CANCELLED}),
    WorkflowState.RUNNING: frozenset(
        {
            WorkflowState.WAITING_CRM,
            WorkflowState.WAITING_RETRY,
            WorkflowState.WAITING_MANUAL,
            WorkflowState.SUCCEEDED,
            WorkflowState.FAILED,
            WorkflowState.CANCELLED,
        }
    ),
    WorkflowState.WAITING_CRM: frozenset(
        {
            WorkflowState.RUNNING,
            WorkflowState.WAITING_RETRY,
            WorkflowState.WAITING_MANUAL,
            WorkflowState.FAILED,
        }
    ),
    WorkflowState.WAITING_RETRY: frozenset(
        {WorkflowState.RUNNING, WorkflowState.WAITING_MANUAL, WorkflowState.FAILED}
    ),
    WorkflowState.WAITING_MANUAL: frozenset(
        {WorkflowState.RUNNING, WorkflowState.CANCELLED}
    ),
    WorkflowState.SUCCEEDED: frozenset(),
    WorkflowState.FAILED: frozenset(),
    WorkflowState.CANCELLED: frozenset(),
}


def assert_transition(current: WorkflowState, target: WorkflowState) -> None:
    if target not in TRANSITIONS[current]:
        raise ValueError(f"forbidden workflow transition {current} -> {target}")


@dataclass(frozen=True)
class ContactCandidate:
    b24_id: str
    created_at: datetime
    crm_user_id: str | None


def validate_phone(value: str) -> str:
    if not PHONE_RE.fullmatch(value):
        raise ValueError("phone must be Russian E.164 +7XXXXXXXXXX")
    return value


def choose_newest(candidates: list[ContactCandidate]) -> ContactCandidate | None:
    if not candidates:
        return None
    return max(candidates, key=lambda item: (item.created_at, int(item.b24_id)))


def select_email(items: list[dict[str, Any]]) -> str | None:
    valid = [
        item
        for item in items
        if isinstance(item.get("VALUE"), str) and EMAIL_RE.fullmatch(item["VALUE"])
    ]
    work = next((item for item in valid if item.get("VALUE_TYPE") == "WORK"), None)
    selected = work or (valid[0] if valid else None)
    return selected["VALUE"] if selected else None


def safe_hash(value: str | None) -> str | None:
    return hashlib.sha256(value.encode()).hexdigest() if value is not None else None


def full_jitter_delay(
    attempt: int, base: float, maximum: float, *, rng: random.Random | None = None
) -> float:
    ceiling = min(maximum, base * (2 ** max(0, attempt - 1)))
    return (rng or random.SystemRandom()).uniform(0, ceiling)


def parse_crm_datetime(value: str) -> datetime:
    parsed = datetime.fromisoformat(value.replace("Z", "+00:00"))
    return parsed.astimezone(UTC)