"""Temporal activity definitions for activity-core.

Activities run inside a Worker bound to 'orchestrator-tq'.
Each function is decorated with @activity.defn and executed by
RunActivityWorkflow via workflow.execute_activity().

DB access pattern: worker.py calls init_session_factory(url) once before
starting workers, which sets the module-level _session_factory used by
activities that need DB access.
"""

from __future__ import annotations

import uuid
from datetime import datetime, timezone

from sqlalchemy import select
from sqlalchemy.dialects.postgresql import insert as pg_insert
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
from temporalio import activity
from temporalio.exceptions import ApplicationError

from activity_core.db import make_engine
from activity_core.issue_sink import get_issue_sink
from activity_core.orm import ActivityDefinition as ActivityDefinitionRow
from activity_core.orm import ActivityRun, TaskInstance, TaskSpawnLog
from activity_core.rules import evaluate_condition


_session_factory: async_sessionmaker[AsyncSession] | None = None


def init_session_factory(url: str) -> None:
    """Initialise the shared DB session factory.

    Must be called once from worker.py before workers are started.
    """
    global _session_factory
    _session_factory = async_sessionmaker(make_engine(url), expire_on_commit=False)


def _get_session_factory() -> async_sessionmaker[AsyncSession]:
    if _session_factory is None:
        raise RuntimeError(
            "DB session factory not initialised — call init_session_factory() first"
        )
    return _session_factory


# ── Activities ─────────────────────────────────────────────────────────────────

@activity.defn
async def load_activity_definition(activity_id: str) -> dict:
    """Load an ActivityDefinition row from Postgres by ID.

    Returns a JSON-serialisable dict suitable for passing between
    Temporal workflow steps.

    Raises:
        ApplicationError (non-retryable): if no row exists for activity_id.
    """
    Session = _get_session_factory()
    async with Session() as session:
        row = await session.scalar(
            select(ActivityDefinitionRow).where(
                ActivityDefinitionRow.id == uuid.UUID(activity_id)
            )
        )

    if row is None:
        raise ApplicationError(
            f"ActivityDefinition {activity_id!r} not found",
            non_retryable=True,
        )

    return {
        "id": str(row.id),
        "name": row.name,
        "enabled": row.enabled,
        "trigger_type": row.trigger_type,
        "trigger_config": row.trigger_config,
        "context_sources": row.context_sources,
        "task_templates": row.task_templates,
        "rules": row.rules_json,
        "instructions": row.instructions_json,
        "dedupe_key_strategy": row.dedupe_key_strategy,
        "version": row.version,
    }


@activity.defn
async def resolve_context(context_sources: list[dict]) -> dict:
    """Resolve each context source and merge into a snapshot dict.

    Returns: {source.name: resolved_value, ...}

    Supported source types:
      static   — returns config["value"] directly
      http_get — not yet implemented
      db_query — not yet implemented
    """
    snapshot: dict = {}
    for source in context_sources:
        name = source["name"]
        source_type = source["type"]
        config = source.get("config", {})

        if source_type == "static":
            snapshot[name] = config.get("value")
        elif source_type in ("http_get", "db_query"):
            raise ApplicationError(
                f"Context source type {source_type!r} is not yet implemented",
                non_retryable=True,
            )
        else:
            raise ApplicationError(
                f"Unknown context source type {source_type!r}",
                non_retryable=True,
            )

    return snapshot


@activity.defn
async def log_run(run_payload: dict) -> str:
    """Persist an ActivityRun record to Postgres and return its run_id.

    Idempotent: uses INSERT … ON CONFLICT (run_id) DO NOTHING so Temporal
    activity retries do not produce duplicate rows.

    Expected keys in run_payload:
        run_id            (str UUID — computed deterministically in workflow)
        activity_id       (str UUID)
        scheduled_for     (ISO-8601 str or None)
        context_snapshot  (dict)
        tasks_spawned     (int)
        version_used      (int)

    Returns:
        run_id as a str UUID.
    """
    Session = _get_session_factory()

    run_id = uuid.UUID(run_payload["run_id"])

    scheduled_for: datetime | None = None
    if run_payload.get("scheduled_for"):
        scheduled_for = datetime.fromisoformat(run_payload["scheduled_for"])

    stmt = (
        pg_insert(ActivityRun)
        .values(
            run_id=run_id,
            activity_id=uuid.UUID(run_payload["activity_id"]),
            scheduled_for=scheduled_for,
            fired_at=datetime.now(tz=timezone.utc),
            context_snapshot=run_payload["context_snapshot"],
            tasks_spawned=run_payload["tasks_spawned"],
            version_used=run_payload["version_used"],
        )
        .on_conflict_do_nothing(index_elements=["run_id"])
    )

    async with Session() as session:
        async with session.begin():
            await session.execute(stmt)

    return str(run_id)


@activity.defn
async def persist_task_instance(task_payload: dict) -> str:
    """Write a TaskInstance row and return its id.

    Idempotent: uses INSERT … ON CONFLICT (id) DO NOTHING.

    Expected keys in task_payload:
        id        (str UUID — deterministic, computed in TaskExecutorWorkflow)
        run_id    (str UUID)
        type      (str)
        params    (dict)
        status    (str, default "done" for stub)

    Returns:
        task instance id as a str UUID.
    """
    Session = _get_session_factory()
    task_id = uuid.UUID(task_payload["id"])

    stmt = (
        pg_insert(TaskInstance)
        .values(
            id=task_id,
            run_id=uuid.UUID(task_payload["run_id"]),
            type=task_payload["type"],
            params=task_payload.get("params", {}),
            status=task_payload.get("status", "done"),
        )
        .on_conflict_do_nothing(index_elements=["id"])
    )

    async with Session() as session:
        async with session.begin():
            await session.execute(stmt)

    return str(task_id)


@activity.defn
async def evaluate_rules(payload: dict) -> list[dict]:
    """Evaluate each rule condition against the event and context.

    Returns the list of matching rule dicts (those whose condition is True).
    Rules that raise UnsafeExpression or any other error are skipped and logged.

    Expected keys in payload:
        rules        list[dict] — RuleDef serialised dicts
        event        dict       — EventEnvelope attributes (or empty for cron)
        context      dict       — context snapshot from resolve_context
    """
    from activity_core.rules.evaluator import UnsafeExpression

    rules = payload.get("rules", [])
    event_attrs = payload.get("event", {})
    context = payload.get("context", {})

    # Build a simple object whose attributes mirror event fields for the evaluator.
    class _Env:
        def __init__(self, attrs: dict) -> None:
            self.attributes = _DictObj(attrs)

    class _DictObj:
        def __init__(self, d: dict) -> None:
            self.__dict__.update(d)

    event_obj = _Env(event_attrs)

    matched: list[dict] = []
    for rule in rules:
        condition = rule.get("condition", "")
        try:
            if evaluate_condition(condition, event_obj, context):
                matched.append(rule)
        except UnsafeExpression as exc:
            activity.logger.warning("rule %r unsafe expression — skipping: %s", rule.get("id"), exc)
        except Exception as exc:
            activity.logger.warning("rule %r eval error — skipping: %s", rule.get("id"), exc)

    return matched


@activity.defn
async def emit_tasks(payload: dict) -> list[str]:
    """Emit TaskSpecs to IssueSink and write task_spawn_log rows.

    Returns list of external task ref IDs.

    Expected keys in payload:
        task_specs       list[dict]  — from evaluate_rules matched actions
        activity_id      str         — UUID of the ActivityDefinition
        triggering_event_id  str     — event ID or workflow ID for cron
        run_id           str         — UUID of the ActivityRun
    """
    from activity_core.rules.models import TaskSpec

    task_specs_raw = payload.get("task_specs", [])
    activity_id = payload.get("activity_id", "")
    triggering_event_id = payload.get("triggering_event_id", "")

    sink = get_issue_sink()
    Session = _get_session_factory()

    refs: list[str] = []
    async with Session() as session:
        async with session.begin():
            for spec_dict in task_specs_raw:
                spec = TaskSpec(
                    title=spec_dict.get("title", ""),
                    description=spec_dict.get("description", ""),
                    target_repo=spec_dict.get("target_repo"),
                    priority=spec_dict.get("priority", "medium"),
                    labels=spec_dict.get("labels", []),
                    due_in_days=spec_dict.get("due_in_days"),
                    source_type=spec_dict.get("source_type", "rule"),
                    source_id=spec_dict.get("source_id", ""),
                    triggering_event_id=triggering_event_id,
                    activity_definition_id=activity_id,
                )
                try:
                    ref = sink.emit(spec)
                    refs.append(ref.external_id)

                    log_row = TaskSpawnLog(
                        activity_def_id=uuid.UUID(activity_id),
                        source_type=spec.source_type,
                        source_id=spec.source_id,
                        source_version="1",
                        triggering_event_id=triggering_event_id,
                        task_ref=ref.external_id,
                        condition_matched=spec_dict.get("condition"),
                    )
                    session.add(log_row)
                except Exception as exc:
                    activity.logger.warning("emit_tasks: sink.emit failed — %s", exc)

    return refs