"""Simulation business logic: PATCH rules and state machine transitions."""
from __future__ import annotations

from datetime import UTC, datetime
from typing import Any

from flask import jsonify

from backend.app.extensions import db
from backend.app.models import User
from backend.app.models.simulation import Simulation, SimulationStatus

# Fields only admin/redteam may write (excluding technique_ids/tactic_ids handled separately).
REDTEAM_FIELDS = frozenset(
    {
        "name",
        "description",
        "commands",
        "prerequisites",
        "executed_at",
        "execution_result",
    }
)

SOC_FIELDS = frozenset({"log_source", "logs", "soc_comment", "incident_number"})

_ALLOWED_TRANSITIONS: dict[str, dict[str, set[str]]] = {
    "review_required": {
        "from": {"pending", "in_progress"},
        "roles": {"admin", "redteam"},
    },
    "done": {
        "from": {"review_required"},
        "roles": {"admin", "redteam", "soc"},
    },
}


def _is_non_empty(value: Any) -> bool:
    """Return True if value counts as "filled" for auto-transition purposes."""
    if value is None:
        return False
    if isinstance(value, str) and value == "":
        return False
    return not (isinstance(value, list) and len(value) == 0)


def _resolve_technique_ids(
    technique_ids: list[str],
) -> tuple[list[dict[str, str]] | None, tuple[Any, int] | None]:
    """Validate and resolve technique IDs to [{id, name}] snapshots.

    Returns (resolved_list, None) on success or (None, error_tuple) on failure.
    Deduplicates while preserving order.
    """
    from backend.app.services import mitre as mitre_svc

    if not mitre_svc.mitre_loaded:
        return None, (jsonify({"error": "mitre bundle not loaded"}), 503)

    seen: dict[str, None] = dict.fromkeys(technique_ids)
    resolved: list[dict[str, str]] = []
    for tid in seen:
        name = mitre_svc.lookup_name(tid)
        if name is None:
            return None, (jsonify({"error": f"unknown technique id: {tid}"}), 400)
        resolved.append({"id": tid, "name": name})
    return resolved, None


def _resolve_tactic_ids(
    tactic_ids: list[str],
) -> tuple[list[str] | None, tuple[Any, int] | None]:
    """Validate and deduplicate tactic TA-ids.

    Returns (deduped_list, None) on success or (None, error_tuple) on failure.
    Bundle does not need to be loaded — validation is against the hardcoded _TACTIC_IDS map.
    """
    from backend.app.services import mitre as mitre_svc

    seen: dict[str, None] = dict.fromkeys(tactic_ids)
    for tid in seen:
        if mitre_svc.lookup_tactic(tid) is None:
            return None, (jsonify({"error": f"unknown tactic id: {tid}"}), 400)
    return list(seen), None


def _maybe_activate_engagement(simulation: Simulation) -> None:
    """If simulation's engagement is planned, advance it to active.

    Caller must commit — do not commit here to avoid double-commit.
    """
    from backend.app.models.engagement import Engagement, EngagementStatus

    engagement: Engagement | None = getattr(simulation, "engagement", None)
    if engagement is not None and engagement.status == EngagementStatus.PLANNED:
        engagement.status = EngagementStatus.ACTIVE
        db.session.add(engagement)


def apply_patch(
    simulation: Simulation, payload: dict[str, Any], user: User
) -> tuple[Any, int] | None:
    """Apply a validated PATCH payload to a simulation.

    Returns a (response, status_code) tuple on error, or None on success
    (caller is responsible for committing).
    """
    # Done guard — applies to ALL roles before any RBAC check.
    if simulation.status == SimulationStatus.DONE:
        return jsonify({"error": "simulation is done — reopen first"}), 409

    role = user.role.value

    if role == "soc":
        if simulation.status not in (
            SimulationStatus.REVIEW_REQUIRED,
            SimulationStatus.DONE,
        ):
            return jsonify({"error": "simulation not ready for SOC review"}), 403

        # SOC must not send redteam fields, technique_ids, or tactic_ids.
        redteam_keys_in_payload = (
            REDTEAM_FIELDS | {"technique_ids", "tactic_ids"}
        ) & payload.keys()
        if redteam_keys_in_payload:
            return jsonify({"error": "soc cannot edit redteam fields"}), 403

        for field in SOC_FIELDS:
            if field in payload:
                setattr(simulation, field, payload[field])

    else:
        # admin / redteam path.
        redteam_keys_present = REDTEAM_FIELDS & payload.keys()

        # Validate executed_at upfront before any writes.
        executed_at_value: datetime | None = None
        if "executed_at" in redteam_keys_present:
            val = payload["executed_at"]
            if val is not None:
                if not isinstance(val, str):
                    return jsonify({"error": "invalid executed_at"}), 400
                try:
                    executed_at_value = datetime.fromisoformat(val)
                except ValueError:
                    return jsonify({"error": "invalid executed_at"}), 400

        # Validate and resolve technique_ids upfront.
        resolved_techniques: list[dict[str, str]] | None = None
        if "technique_ids" in payload:
            raw_ids = payload["technique_ids"]
            if not isinstance(raw_ids, list):
                return jsonify({"error": "technique_ids must be a list"}), 400
            resolved_techniques, err = _resolve_technique_ids(raw_ids)
            if err is not None:
                return err

        # Validate and deduplicate tactic_ids upfront.
        resolved_tactic_ids: list[str] | None = None
        if "tactic_ids" in payload:
            raw_tids = payload["tactic_ids"]
            if not isinstance(raw_tids, list):
                return jsonify({"error": "tactic_ids must be a list"}), 400
            resolved_tactic_ids, err = _resolve_tactic_ids(raw_tids)
            if err is not None:
                return err

        # Apply scalar redteam fields.
        for field in redteam_keys_present:
            if field == "executed_at":
                simulation.executed_at = executed_at_value
            else:
                setattr(simulation, field, payload[field])

        # Apply resolved techniques.
        if resolved_techniques is not None:
            simulation.techniques = resolved_techniques

        # Apply resolved tactic_ids.
        if resolved_tactic_ids is not None:
            simulation.tactic_ids = resolved_tactic_ids

        # Apply SOC fields (admin/redteam may also write them).
        for field in SOC_FIELDS:
            if field in payload:
                setattr(simulation, field, payload[field])

        # Auto-transition pending → in_progress.
        # Triggers when any redteam scalar has a non-empty value, technique_ids or tactic_ids non-empty.
        auto_trigger = any(_is_non_empty(payload[k]) for k in redteam_keys_present)
        if not auto_trigger and "technique_ids" in payload:
            auto_trigger = len(payload["technique_ids"]) > 0
        if not auto_trigger and "tactic_ids" in payload:
            auto_trigger = len(payload["tactic_ids"]) > 0

        if simulation.status == SimulationStatus.PENDING and auto_trigger:
            simulation.status = SimulationStatus.IN_PROGRESS
            _maybe_activate_engagement(simulation)

    simulation.updated_at = datetime.now(UTC)
    return None


def transition(
    simulation: Simulation, to_status: str, user: User
) -> tuple[Any, int] | None:
    """Attempt a manual transition. Returns error tuple or None on success."""
    # Special case: done → review_required (Reopen), allowed for all 3 roles.
    if to_status == "review_required" and simulation.status == SimulationStatus.DONE:
        simulation.status = SimulationStatus.REVIEW_REQUIRED
        simulation.updated_at = datetime.now(UTC)
        db.session.commit()
        return None

    rule = _ALLOWED_TRANSITIONS.get(to_status)
    if rule is None:
        return jsonify({"error": "invalid transition"}), 409

    if simulation.status.value not in rule["from"]:
        return jsonify({"error": "invalid transition"}), 409

    if user.role.value not in rule["roles"]:
        return jsonify({"error": "Forbidden"}), 403

    simulation.status = SimulationStatus(to_status)
    simulation.updated_at = datetime.now(UTC)
    db.session.commit()
    return None