"""Background worker for assisted skill learning."""

from __future__ import annotations

import asyncio
import os
from dataclasses import dataclass, field
from typing import Callable

from beaver.engine.providers import ProviderBundle
from beaver.memory.skills import SkillLearningCandidate
from beaver.skills.learning.pipeline import DraftHasNoChanges, SkillLearningPipelineService
from beaver.skills.learning.replay import ReplayRunner


@dataclass(slots=True)
class SkillLearningWorkerConfig:
    enabled: bool = True
    max_drafts_per_run: int = 5
    max_retries: int = 3
    interval_seconds: float = 300.0

    @classmethod
    def from_env(cls) -> "SkillLearningWorkerConfig":
        return cls(
            enabled=_env_bool("BEAVER_SKILL_LEARNING_WORKER_ENABLED", True),
            max_drafts_per_run=_env_int("BEAVER_SKILL_LEARNING_MAX_DRAFTS_PER_RUN", 5),
            max_retries=_env_int("BEAVER_SKILL_LEARNING_MAX_RETRIES", 3),
            interval_seconds=float(os.getenv("BEAVER_SKILL_LEARNING_INTERVAL_SECONDS", "300") or "300"),
        )


@dataclass(slots=True)
class SkillLearningWorkerResult:
    processed: int = 0
    succeeded: int = 0
    failed: int = 0
    skipped: int = 0
    failures: list[dict[str, str]] = field(default_factory=list)

    def to_dict(self) -> dict:
        return {
            "processed": self.processed,
            "succeeded": self.succeeded,
            "failed": self.failed,
            "skipped": self.skipped,
            "failures": [dict(item) for item in self.failures],
        }


class SkillLearningWorker:
    """Synthesizes drafts for open candidates; never approves or publishes."""

    _ACTIVE_DRAFT_STATUSES = {"queued", "synthesizing", "draft_ready", "review_pending", "approved"}

    def __init__(
        self,
        *,
        pipeline: SkillLearningPipelineService,
        provider_bundle_factory: Callable[[], ProviderBundle],
        replay_runner_factory: Callable[[], ReplayRunner] | None = None,
        config: SkillLearningWorkerConfig | None = None,
    ) -> None:
        self.pipeline = pipeline
        self.provider_bundle_factory = provider_bundle_factory
        self.replay_runner_factory = replay_runner_factory
        self.config = config or SkillLearningWorkerConfig.from_env()
        self._running = False
        self._lock = asyncio.Lock()

    async def run_forever(self) -> None:
        if not self.config.enabled:
            return
        self._running = True
        try:
            while self._running:
                await self.run_once()
                await asyncio.sleep(self.config.interval_seconds)
        finally:
            self._running = False

    def stop(self) -> None:
        self._running = False

    async def run_once(self) -> SkillLearningWorkerResult:
        if not self.config.enabled:
            return SkillLearningWorkerResult()
        async with self._lock:
            result = SkillLearningWorkerResult()
            candidates = self._select_candidates()
            for candidate in candidates[: self.config.max_drafts_per_run]:
                result.processed += 1
                try:
                    handled = await self._process_candidate(candidate)
                    if handled:
                        result.succeeded += 1
                    else:
                        result.skipped += 1
                except Exception as exc:
                    result.failed += 1
                    result.failures.append({"candidate_id": candidate.candidate_id, "error": str(exc)})
                    self._mark_failure(candidate, str(exc))
            return result

    def _select_candidates(self) -> list[SkillLearningCandidate]:
        candidates = [
            item
            for item in self.pipeline.list_candidates()
            if item.status == "open" and item.retry_count < self.config.max_retries
        ]
        return sorted(candidates, key=lambda item: (item.priority, item.confidence, item.created_at), reverse=True)

    async def _process_candidate(self, candidate: SkillLearningCandidate) -> bool:
        if self._has_active_draft(candidate):
            self.pipeline.mark_candidate_superseded(candidate.candidate_id, "active draft already exists for this skill")
            return False
        try:
            draft = await self.pipeline.synthesize_draft(
                candidate.candidate_id,
                provider_bundle=self.provider_bundle_factory(),
            )
        except DraftHasNoChanges:
            return False
        safety = self.pipeline.check_safety(draft.skill_name, draft.draft_id)
        if not safety.passed or safety.risk_level == "critical":
            return True
        await self.pipeline.evaluate_draft(
            candidate.candidate_id,
            draft.skill_name,
            draft.draft_id,
            provider_bundle=self.provider_bundle_factory(),
            replay_runner=self.replay_runner_factory() if self.replay_runner_factory is not None else None,
        )
        return True

    def _has_active_draft(self, candidate: SkillLearningCandidate) -> bool:
        target_names = set(candidate.related_skill_names)
        if candidate.draft_skill_name:
            target_names.add(candidate.draft_skill_name)
        if not target_names:
            return False
        for item in self.pipeline.list_candidates():
            if item.candidate_id == candidate.candidate_id:
                continue
            if item.status not in self._ACTIVE_DRAFT_STATUSES:
                continue
            item_names = set(item.related_skill_names)
            if item.draft_skill_name:
                item_names.add(item.draft_skill_name)
            if target_names.intersection(item_names):
                return True
        return False

    def _mark_failure(self, candidate: SkillLearningCandidate, error: str) -> None:
        retry_count = candidate.retry_count + 1
        status = "failed" if retry_count >= self.config.max_retries else "open"
        self.pipeline.mark_candidate_failed(
            candidate.candidate_id,
            error,
            retry_count=retry_count,
            terminal=(status == "failed"),
        )


def _env_bool(name: str, default: bool) -> bool:
    raw = os.getenv(name)
    if raw is None:
        return default
    return raw.strip().lower() not in {"0", "false", "no", "off"}


def _env_int(name: str, default: int) -> int:
    raw = os.getenv(name)
    if raw in (None, ""):
        return default
    try:
        return int(raw)
    except ValueError:
        return default