from __future__ import annotations

from collections.abc import Iterable
from typing import Any

from sqlalchemy import or_
from sqlalchemy.orm import Session

from govoplan_policy.backend.db.models import PolicyOverride


POLICY_SCOPE_TYPES = frozenset({"system", "tenant", "group", "user", "campaign"})
POLICY_FAMILIES = frozenset(
    {
        "campaign_archive_encryption",
        "datasource_visibility",
        "definition",
        "distribution_channels",
        "view",
    }
)


class PolicyOverrideError(ValueError):
    pass


def normalize_policy_target(policy_family: str, target_key: str) -> tuple[str, str]:
    family = policy_family.strip().casefold()
    target = target_key.strip().casefold()
    if family not in POLICY_FAMILIES:
        raise PolicyOverrideError(
            "Policy family must be campaign_archive_encryption, datasource_visibility, definition, distribution_channels, or view"
        )
    if not target or len(target) > 120:
        raise PolicyOverrideError("Policy target must contain 1 to 120 characters")
    if family == "view" and target != "*":
        raise PolicyOverrideError("View policy uses the shared '*' target")
    return family, target


def normalize_policy_scope(
    *,
    tenant_id: str,
    scope_type: str,
    scope_id: str | None,
) -> tuple[str | None, str | None, str]:
    clean_scope = scope_type.strip().casefold()
    clean_id = str(scope_id or "").strip() or None
    if clean_scope not in POLICY_SCOPE_TYPES:
        raise PolicyOverrideError(
            "Policy scope must be system, tenant, group, user, or campaign"
        )
    if clean_scope == "system":
        if clean_id is not None:
            raise PolicyOverrideError("System policy cannot declare a scope ID")
        return None, None, "system"
    if clean_scope == "tenant":
        if clean_id not in {None, tenant_id}:
            raise PolicyOverrideError("Tenant policy must target the active tenant")
        return tenant_id, tenant_id, f"tenant:{tenant_id}"
    if clean_id is None:
        raise PolicyOverrideError(
            f"{clean_scope.capitalize()} policy requires a scope ID"
        )
    return tenant_id, clean_id, f"{clean_scope}:{tenant_id}:{clean_id}"


def get_policy_override(
    session: Session,
    *,
    policy_family: str,
    target_key: str,
    tenant_id: str,
    scope_type: str,
    scope_id: str | None = None,
) -> PolicyOverride | None:
    family, target = normalize_policy_target(policy_family, target_key)
    _, _, scope_key = normalize_policy_scope(
        tenant_id=tenant_id,
        scope_type=scope_type,
        scope_id=scope_id,
    )
    return (
        session.query(PolicyOverride)
        .filter(
            PolicyOverride.policy_family == family,
            PolicyOverride.target_key == target,
            PolicyOverride.scope_key == scope_key,
        )
        .first()
    )


def set_policy_override(
    session: Session,
    *,
    policy_family: str,
    target_key: str,
    tenant_id: str,
    scope_type: str,
    scope_id: str | None,
    policy: Any,
    actor_id: str | None,
) -> PolicyOverride:
    family, target = normalize_policy_target(policy_family, target_key)
    row_tenant_id, clean_scope_id, scope_key = normalize_policy_scope(
        tenant_id=tenant_id,
        scope_type=scope_type,
        scope_id=scope_id,
    )
    row = (
        session.query(PolicyOverride)
        .filter(
            PolicyOverride.policy_family == family,
            PolicyOverride.target_key == target,
            PolicyOverride.scope_key == scope_key,
        )
        .first()
    )
    if row is None:
        row = PolicyOverride(
            policy_family=family,
            target_key=target,
            tenant_id=row_tenant_id,
            scope_type=scope_type.strip().casefold(),
            scope_id=clean_scope_id,
            scope_key=scope_key,
            policy=policy,
            created_by=actor_id,
            updated_by=actor_id,
        )
        session.add(row)
    else:
        row.policy = policy
        row.revision += 1
        row.updated_by = actor_id
    session.flush()
    return row


def delete_policy_override(session: Session, row: PolicyOverride) -> None:
    session.delete(row)
    session.flush()


def resolution_policy_overrides(
    session: Session,
    *,
    policy_family: str,
    target_keys: Iterable[str],
    tenant_id: str,
    group_ids: Iterable[str] = (),
    user_ids: Iterable[str] = (),
    campaign_ids: Iterable[str] = (),
) -> tuple[PolicyOverride, ...]:
    family = policy_family.strip().casefold()
    targets = tuple(
        dict.fromkeys(
            normalize_policy_target(family, target)[1] for target in target_keys
        )
    )
    groups = tuple(sorted({str(value) for value in group_ids if str(value)}))
    users = tuple(sorted({str(value) for value in user_ids if str(value)}))
    campaigns = tuple(
        sorted({str(value) for value in campaign_ids if str(value)})
    )
    scope_filters = [
        PolicyOverride.scope_key == "system",
        PolicyOverride.scope_key == f"tenant:{tenant_id}",
    ]
    if groups:
        scope_filters.append(
            PolicyOverride.scope_key.in_(
                [f"group:{tenant_id}:{group_id}" for group_id in groups]
            )
        )
    if users:
        scope_filters.append(
            PolicyOverride.scope_key.in_(
                [f"user:{tenant_id}:{user_id}" for user_id in users]
            )
        )
    if campaigns:
        scope_filters.append(
            PolicyOverride.scope_key.in_(
                [
                    f"campaign:{tenant_id}:{campaign_id}"
                    for campaign_id in campaigns
                ]
            )
        )
    rows = (
        session.query(PolicyOverride)
        .filter(
            PolicyOverride.policy_family == family,
            PolicyOverride.target_key.in_(targets),
            or_(*scope_filters),
        )
        .all()
    )
    target_order = {target: index for index, target in enumerate(targets)}
    scope_order = {
        "system": 0,
        "tenant": 1,
        "group": 2,
        "user": 2,
        "campaign": 3,
    }
    return tuple(
        sorted(
            rows,
            key=lambda row: (
                scope_order.get(row.scope_type, 99),
                row.scope_id or "",
                target_order.get(row.target_key, 99),
                row.id,
            ),
        )
    )


__all__ = [
    "POLICY_FAMILIES",
    "POLICY_SCOPE_TYPES",
    "PolicyOverrideError",
    "delete_policy_override",
    "get_policy_override",
    "normalize_policy_scope",
    "normalize_policy_target",
    "resolution_policy_overrides",
    "set_policy_override",
]