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_SMALL_CELL_THRESHOLD = 5
MIN_SMALL_CELL_THRESHOLD = 2
MAX_SMALL_CELL_THRESHOLD = 100
SMALL_CELL_THRESHOLD_ENV = "GOVOPLAN_CAMPAIGN_REPORT_SMALL_CELL_THRESHOLD"
CAMPAIGN_REPORT_POLICY_SETTINGS_KEY = "campaign_report_privacy_policy"
SMALL_CELL_THRESHOLD_SETTINGS_KEY = "small_cell_threshold"


class CampaignReportPrivacyPolicyError(RuntimeError):
    pass


@dataclass(frozen=True, slots=True)
class CampaignReportPrivacyPolicy:
    small_cell_threshold: int
    source: str
    deployment_small_cell_threshold: int
    tenant_small_cell_threshold: int | None = None

    def as_dict(self) -> dict[str, Any]:
        return {
            "small_cell_threshold": self.small_cell_threshold,
            "source": self.source,
            "deployment_small_cell_threshold": self.deployment_small_cell_threshold,
            "tenant_small_cell_threshold": self.tenant_small_cell_threshold,
            "deployment_setting": SMALL_CELL_THRESHOLD_ENV,
            "tenant_setting": (
                f"tenant.settings.{CAMPAIGN_REPORT_POLICY_SETTINGS_KEY}."
                f"{SMALL_CELL_THRESHOLD_SETTINGS_KEY}"
            ),
        }


def effective_campaign_report_privacy_policy(
    session: Session,
    *,
    tenant_id: str,
    environ: Mapping[str, str] | None = None,
) -> CampaignReportPrivacyPolicy:
    env = os.environ if environ is None else environ
    deployment_raw = env.get(SMALL_CELL_THRESHOLD_ENV)
    deployment_value = _configured_threshold(
        deployment_raw,
        source=SMALL_CELL_THRESHOLD_ENV,
        default=DEFAULT_SMALL_CELL_THRESHOLD,
    )
    tenant = session.get(Tenant, tenant_id)
    tenant_raw = _tenant_threshold_value(tenant.settings if tenant is not None else None)
    if tenant_raw is None:
        return CampaignReportPrivacyPolicy(
            small_cell_threshold=deployment_value,
            source="deployment" if deployment_raw not in (None, "") else "deployment_default",
            deployment_small_cell_threshold=deployment_value,
        )

    tenant_value = _configured_threshold(
        tenant_raw,
        source=(
            f"tenant.settings.{CAMPAIGN_REPORT_POLICY_SETTINGS_KEY}."
            f"{SMALL_CELL_THRESHOLD_SETTINGS_KEY}"
        ),
    )
    effective_value = max(deployment_value, tenant_value)
    return CampaignReportPrivacyPolicy(
        small_cell_threshold=effective_value,
        source="tenant" if tenant_value >= deployment_value else "deployment_floor",
        deployment_small_cell_threshold=deployment_value,
        tenant_small_cell_threshold=tenant_value,
    )


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


def _configured_threshold(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 CampaignReportPrivacyPolicyError(f"{source} must be configured as an integer")
    if isinstance(value, bool):
        raise CampaignReportPrivacyPolicyError(f"{source} must be an integer, not a boolean")
    try:
        parsed = int(value)
    except (TypeError, ValueError) as exc:
        raise CampaignReportPrivacyPolicyError(f"{source} must be an integer") from exc
    if str(parsed) != str(value).strip() and not isinstance(value, int):
        raise CampaignReportPrivacyPolicyError(f"{source} must be an integer")
    if parsed < MIN_SMALL_CELL_THRESHOLD or parsed > MAX_SMALL_CELL_THRESHOLD:
        raise CampaignReportPrivacyPolicyError(
            f"{source} must be between {MIN_SMALL_CELL_THRESHOLD} and {MAX_SMALL_CELL_THRESHOLD}"
        )
    return parsed