"""AWSBackend Protocol and FixtureAWSBackend for synthetic EC2/ELB/RDS testing.

The Protocol defines the minimal surface the EC2/RDS investigation agent
uses to query AWS topology and instance state. FixtureAWSBackend satisfies
it by serving scenario fixture data in the exact shape the tools under
``tools/EC2InstancesByTagTool/``, ``tools/ELBTargetHealthTool/``,
``tools/RDSDescribeInstanceTool/``, and ``tools/RDSEventsTool/``
return — no boto3 calls, no AWS credentials required.

Usage
-----
    resolved_integrations = {
        "aws": {
            "region": "us-east-1",
            "ec2_backend": FixtureAWSBackend(fixture),
        }
    }

The synthetic source builder reads ``ec2_backend`` and exposes it on
``available_sources["ec2"]["_backend"]`` (and ``available_sources["rds"]``)
without colliding with the EKS slot ``available_sources["eks"]["_backend"]``.

RDS describe semantics
----------------------
``describe_db_instances`` is synthesized from ``scenario.yml`` metadata
(engine, version, instance class, region, db identifier). Every RDS scenario
declares these fields, so this method is always available — it is treated as
foundational metadata, not a separate evidence channel. ``describe_events``,
in contrast, is gated on ``aws_rds_events`` being declared in
``available_evidence``: it is a data feed, and calling it on a scenario that
didn't opt in is a synthetic-suite bug worth surfacing loudly.
"""

from __future__ import annotations

from typing import TYPE_CHECKING, Any, Protocol, runtime_checkable

from integrations.aws.topology_helper import build_ec2_summary, build_elb_summary

if TYPE_CHECKING:
    from tests.synthetic.rds_postgres.scenario_loader import ScenarioFixture


_DEFAULT_ENGINE_PORTS: dict[str, int] = {
    "postgres": 5432,
    "postgresql": 5432,
    "aurora-postgresql": 5432,
    "mysql": 3306,
    "mariadb": 3306,
    "aurora-mysql": 3306,
}


@runtime_checkable
class AWSBackend(Protocol):
    """Minimal AWS interface used by the EC2/RDS investigation agent."""

    def describe_instances_by_tag(
        self,
        tier: str = "",
        instance_ids: list[str] | None = None,
        vpc_id: str = "",
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Return a response matching ``ec2_instances_by_tag``."""

    def describe_target_health(
        self,
        target_group_arns: list[str] | None = None,
        target_group_arn: str = "",
        load_balancer_arn: str = "",
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Return a response matching ``get_elb_target_health``."""

    def describe_db_instances(
        self,
        db_instance_identifier: str,
        region: str = "",
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Return a response matching ``describe_rds_instance``."""

    def describe_db_events(
        self,
        db_instance_identifier: str,
        duration_minutes: int = 60,
        region: str = "",
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Return a response matching ``describe_rds_events``."""

    def lookup_events(
        self,
        lookup_attributes: list[dict[str, str]] | None = None,
        duration_minutes: int = 60,
        max_results: int = 50,
        region: str = "",
        next_token: str = "",
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Return a response matching ``lookup_cloudtrail_events``."""


class FixtureAWSBackend:
    """AWSBackend implementation backed by a ScenarioFixture.

    Each method wraps the corresponding fixture file in the envelope that the
    real tool function returns. Calling a method for an evidence source that
    the scenario did not declare in ``available_evidence`` raises ValueError.
    """

    def __init__(self, fixture: ScenarioFixture) -> None:
        self._fixture = fixture

    # ------------------------------------------------------------------ EC2

    def describe_instances_by_tag(
        self,
        tier: str = "",
        instance_ids: list[str] | None = None,
        vpc_id: str = "",
        **_: Any,
    ) -> dict[str, Any]:
        ec2_fixture = self._fixture.evidence.ec2_instances_by_tag
        if ec2_fixture is None:
            raise ValueError(
                f"{self._fixture.scenario_id}: describe_instances_by_tag called but "
                "'ec2_instances_by_tag' is not declared in available_evidence"
            )

        all_instances = list(ec2_fixture.get("instances", []))
        instances = all_instances
        if instance_ids:
            id_set = set(instance_ids)
            instances = [i for i in all_instances if i.get("instance_id", "") in id_set]
        elif tier:
            instances = [i for i in all_instances if (i.get("tier", "") or "") == tier]
        if vpc_id:
            # Strict equality — real EC2 API never returns instances from other
            # VPCs, and missing/empty vpc_id is a fixture error worth surfacing.
            instances = [i for i in instances if i.get("vpc_id", "") == vpc_id]

        by_tier: dict[str, list[str]] = {}
        for inst in instances:
            bucket = by_tier.setdefault(inst.get("tier") or "untagged", [])
            iid = inst.get("instance_id") or ""
            if iid:
                bucket.append(iid)

        return {
            "source": "ec2",
            "available": True,
            "tier": tier,
            "vpc_id": vpc_id,
            "total_instances": len(instances),
            "instances": instances,
            "by_tier": by_tier,
            "tiers_detected": sorted(by_tier.keys()),
            "summary": build_ec2_summary(instances, by_tier),
            "error": None,
        }

    # ------------------------------------------------------------------ ELB

    def describe_target_health(
        self,
        target_group_arns: list[str] | None = None,
        target_group_arn: str = "",
        load_balancer_arn: str = "",
        **_: Any,
    ) -> dict[str, Any]:
        elb_fixture = self._fixture.evidence.elb_target_health
        if elb_fixture is None:
            raise ValueError(
                f"{self._fixture.scenario_id}: describe_target_health called but "
                "'elb_target_health' is not declared in available_evidence"
            )

        target_groups = list(elb_fixture.get("target_groups", []))
        targets = list(elb_fixture.get("targets", []))

        # Accept the canonical plural list or the singular convenience alias.
        arns = set(target_group_arns or [])
        if target_group_arn:
            arns.add(target_group_arn)

        if arns:
            target_groups = [tg for tg in target_groups if tg.get("TargetGroupArn") in arns]
            targets = [t for t in targets if t.get("target_group_arn") in arns]
        elif load_balancer_arn:
            target_groups = [
                tg
                for tg in target_groups
                if load_balancer_arn in (tg.get("LoadBalancerArns") or [])
            ]
            allowed_arns = {tg.get("TargetGroupArn", "") for tg in target_groups}
            targets = [t for t in targets if t.get("target_group_arn", "") in allowed_arns]

        healthy = [t for t in targets if t.get("state") == "healthy"]
        unhealthy = [t for t in targets if t.get("state") != "healthy"]
        instance_ids = [t.get("instance_id", "") for t in targets if t.get("instance_id")]

        return {
            "source": "ec2",
            "available": True,
            "target_groups": target_groups,
            "healthy_targets": healthy,
            "unhealthy_targets": unhealthy,
            "instance_ids": list(dict.fromkeys(instance_ids)),
            "summary": build_elb_summary(target_groups, healthy, unhealthy),
            "error": None,
        }

    # ------------------------------------------------------------------ RDS

    def describe_db_instances(
        self,
        db_instance_identifier: str,
        region: str = "",
        **_: Any,
    ) -> dict[str, Any]:
        """Synthesize a ``describe_rds_instance`` response from scenario metadata.

        Every RDS scenario fixture supplies its instance identity in
        ``scenario.yml`` (engine, version, class, region, identifier). We
        treat that as the canonical answer to ``describe_db_instances`` so
        all 16+ scenarios are served uniformly without per-scenario fixture
        files. Mismatched identifiers (the agent asks about a DB the scenario
        doesn't define) return the same ``available=False`` envelope the real
        tool uses for ``DBInstanceNotFound``, keeping the failure mode honest.
        """
        meta = self._fixture.metadata
        if db_instance_identifier and db_instance_identifier != meta.db_instance_identifier:
            return {
                "source": "rds",
                "available": False,
                "db_instance_identifier": db_instance_identifier,
                "error": "No RDS instance found with the given identifier.",
            }

        engine = (meta.engine or "").lower()
        port = _DEFAULT_ENGINE_PORTS.get(engine, 5432)
        resolved_region = region or meta.region or "us-east-1"
        endpoint_address = (
            f"{meta.db_instance_identifier}.synthetic.{resolved_region}.rds.amazonaws.com"
        )

        return {
            "source": "rds",
            "available": True,
            "db_instance_identifier": meta.db_instance_identifier,
            "status": "available",
            "engine": meta.engine,
            "engine_version": meta.engine_version,
            "instance_class": meta.instance_class,
            "multi_az": False,
            "publicly_accessible": False,
            "storage_type": "gp3",
            "allocated_storage_gb": 200,
            "endpoint": {"address": endpoint_address, "port": port},
            "availability_zone": f"{resolved_region}a",
            "preferred_backup_window": "03:00-04:00",
            "backup_retention_period": 7,
            "error": None,
        }

    def describe_db_events(
        self,
        db_instance_identifier: str,
        duration_minutes: int = 60,
        **_: Any,
    ) -> dict[str, Any]:
        """Serve ``describe_rds_events`` from the ``aws_rds_events`` fixture.

        Gated on the scenario declaring ``aws_rds_events`` in
        ``available_evidence``. Calling without that opt-in is a synthetic
        suite contract violation and raises so it surfaces during scenario
        development rather than producing empty (and misleading) "no events"
        results that the agent would treat as evidence of absence.

        ``region`` is accepted via ``**kwargs`` to keep the Protocol surface
        symmetric with ``describe_db_instances`` even though fixture events
        are scenario-scoped and don't vary by region.
        """
        events_fixture = self._fixture.evidence.aws_rds_events
        if events_fixture is None:
            raise ValueError(
                f"{self._fixture.scenario_id}: describe_db_events called but "
                "'aws_rds_events' is not declared in available_evidence"
            )

        meta = self._fixture.metadata
        if db_instance_identifier and db_instance_identifier != meta.db_instance_identifier:
            return {
                "source": "rds",
                "available": True,
                "db_instance_identifier": db_instance_identifier,
                "duration_minutes": duration_minutes,
                "total_events": 0,
                "events": [],
                "error": None,
            }

        events = [
            {
                "date": event.get("date"),
                "message": event.get("message"),
                "categories": list(event.get("event_categories", []) or []),
                "source_type": event.get("source_type"),
            }
            for event in events_fixture
        ]

        return {
            "source": "rds",
            "available": True,
            "db_instance_identifier": meta.db_instance_identifier,
            "duration_minutes": duration_minutes,
            "total_events": len(events),
            "events": events,
            "error": None,
        }

    # ------------------------------------------------------------------ CloudTrail

    def lookup_events(
        self,
        lookup_attributes: list[dict[str, str]] | None = None,
        duration_minutes: int = 60,
        region: str = "",
        **_: Any,
    ) -> dict[str, Any]:
        """Serve ``lookup_cloudtrail_events`` from fixture data.

        No scenario currently declares CloudTrail evidence, so this returns an
        empty (but well-shaped) account-wide result. Its purpose is to keep
        synthetic runs off real AWS — never leak a boto3 ``lookup_events`` call —
        while giving the agent a valid "no recent changes" answer. ``filter``
        echoes the single LookupAttribute the tool sent, mirroring the real tool.
        """
        attributes = lookup_attributes or []
        return {
            "source": "cloudtrail",
            "available": True,
            "region": region,
            "duration_minutes": duration_minutes,
            "filter": attributes[0] if attributes else None,
            "total_events": 0,
            "truncated": False,
            "next_token": None,
            "events": [],
            "error": None,
        }