from __future__ import annotations

import os
from dataclasses import dataclass
from typing import Any, Mapping

from sqlalchemy.orm import Session

from govoplan_core.tenancy.scope import Tenant


DEFAULT_SYNCHRONOUS_SEND_MAX_RECIPIENT_JOBS = 25
ABSOLUTE_SYNCHRONOUS_SEND_MAX_RECIPIENT_JOBS = 500
SYNCHRONOUS_SEND_MAX_ENV = "GOVOPLAN_CAMPAIGN_SYNCHRONOUS_SEND_MAX_RECIPIENTS"
CAMPAIGN_DELIVERY_POLICY_SETTINGS_KEY = "campaign_delivery_policy"
SYNCHRONOUS_SEND_MAX_SETTINGS_KEY = "synchronous_send_max_recipients"


class CampaignDeliveryPolicyError(RuntimeError):
    pass


@dataclass(frozen=True, slots=True)
class SynchronousSendPolicy:
    max_recipient_jobs: int
    source: str
    deployment_max_recipient_jobs: int
    tenant_max_recipient_jobs: int | None = None

    def as_dict(self) -> dict[str, Any]:
        return {
            "max_recipient_jobs": self.max_recipient_jobs,
            "source": self.source,
            "deployment_max_recipient_jobs": self.deployment_max_recipient_jobs,
            "tenant_max_recipient_jobs": self.tenant_max_recipient_jobs,
            "deployment_setting": SYNCHRONOUS_SEND_MAX_ENV,
            "tenant_setting": (
                f"tenant.settings.{CAMPAIGN_DELIVERY_POLICY_SETTINGS_KEY}."
                f"{SYNCHRONOUS_SEND_MAX_SETTINGS_KEY}"
            ),
        }


def effective_synchronous_send_policy(
    session: Session,
    *,
    tenant_id: str,
    environ: Mapping[str, str] | None = None,
) -> SynchronousSendPolicy:
    env = os.environ if environ is None else environ
    deployment_value = _configured_limit(
        env.get(SYNCHRONOUS_SEND_MAX_ENV),
        source=SYNCHRONOUS_SEND_MAX_ENV,
        default=DEFAULT_SYNCHRONOUS_SEND_MAX_RECIPIENT_JOBS,
    )
    tenant = session.get(Tenant, tenant_id)
    tenant_raw = _tenant_limit_value(tenant.settings if tenant is not None else None)
    if tenant_raw is None:
        return SynchronousSendPolicy(
            max_recipient_jobs=deployment_value,
            source=("deployment" if env.get(SYNCHRONOUS_SEND_MAX_ENV) not in (None, "") else "deployment_default"),
            deployment_max_recipient_jobs=deployment_value,
        )

    tenant_value = _configured_limit(
        tenant_raw,
        source=(
            f"tenant.settings.{CAMPAIGN_DELIVERY_POLICY_SETTINGS_KEY}."
            f"{SYNCHRONOUS_SEND_MAX_SETTINGS_KEY}"
        ),
    )
    effective_value = min(deployment_value, tenant_value)
    return SynchronousSendPolicy(
        max_recipient_jobs=effective_value,
        source="tenant" if tenant_value <= deployment_value else "deployment_ceiling",
        deployment_max_recipient_jobs=deployment_value,
        tenant_max_recipient_jobs=tenant_value,
    )


def _tenant_limit_value(settings: Mapping[str, Any] | None) -> object | None:
    if not isinstance(settings, Mapping):
        return None
    policy = settings.get(CAMPAIGN_DELIVERY_POLICY_SETTINGS_KEY)
    if not isinstance(policy, Mapping):
        return None
    return policy.get(SYNCHRONOUS_SEND_MAX_SETTINGS_KEY)


def _configured_limit(value: object, *, source: str, default: int | None = None) -> int:
    if value is None or (isinstance(value, str) and not value.strip()):
        if default is not None:
            return default
        raise CampaignDeliveryPolicyError(f"{source} must be configured as an integer")
    if isinstance(value, bool):
        raise CampaignDeliveryPolicyError(f"{source} must be an integer, not a boolean")
    try:
        parsed = int(value)
    except (TypeError, ValueError) as exc:
        raise CampaignDeliveryPolicyError(f"{source} must be an integer") from exc
    if str(parsed) != str(value).strip() and not isinstance(value, int):
        raise CampaignDeliveryPolicyError(f"{source} must be an integer")
    if parsed < 0 or parsed > ABSOLUTE_SYNCHRONOUS_SEND_MAX_RECIPIENT_JOBS:
        raise CampaignDeliveryPolicyError(
            f"{source} must be between 0 and {ABSOLUTE_SYNCHRONOUS_SEND_MAX_RECIPIENT_JOBS}"
        )
    return parsed