"""LLM-backed draft synthesis for skill learning."""

from __future__ import annotations

import json
from typing import Any

from beaver.engine.providers.base import LLMProvider
from beaver.skills.learning.evidence import EvidencePacket
from beaver.memory.skills.models import SkillLearningCandidate


class SkillDraftSynthesizer:
    async def synthesize_revision(
        self,
        candidate: SkillLearningCandidate,
        evidence_packet: EvidencePacket,
        provider: LLMProvider,
        model: str,
    ) -> dict[str, Any]:
        return await self._synthesize(candidate, evidence_packet, provider, model, "revise")

    async def synthesize_new_skill(
        self,
        candidate: SkillLearningCandidate,
        evidence_packet: EvidencePacket,
        provider: LLMProvider,
        model: str,
    ) -> dict[str, Any]:
        return await self._synthesize(candidate, evidence_packet, provider, model, "new")

    async def synthesize_merge(
        self,
        candidate: SkillLearningCandidate,
        evidence_packet: EvidencePacket,
        provider: LLMProvider,
        model: str,
    ) -> dict[str, Any]:
        return await self._synthesize(candidate, evidence_packet, provider, model, "merge")

    async def _synthesize(
        self,
        candidate: SkillLearningCandidate,
        evidence_packet: EvidencePacket,
        provider: LLMProvider,
        model: str,
        action: str,
    ) -> dict[str, Any]:
        prompt = self._build_prompt(candidate, evidence_packet, action)
        response = await provider.chat(
            messages=[
                {
                    "role": "system",
                    "content": (
                        "You synthesize Beaver skill drafts from execution evidence. "
                        "Return only JSON with keys: frontmatter, content, change_reason."
                    ),
                },
                {"role": "user", "content": prompt},
            ],
            tools=None,
            model=model,
            max_tokens=1500,
            temperature=0,
        )
        payload = self._parse_payload(response.content or "")
        if payload:
            return payload
        return self._fallback_payload(candidate, evidence_packet, action)

    @staticmethod
    def _build_prompt(candidate: SkillLearningCandidate, evidence_packet: EvidencePacket, action: str) -> str:
        return (
            f"Action: {action}\n"
            f"Candidate kind: {candidate.kind}\n"
            f"Reason: {candidate.reason}\n"
            f"Related skills: {candidate.related_skill_names}\n"
            f"Task summaries:\n- " + "\n- ".join(evidence_packet.task_summaries)
            + "\n\nSession excerpts:\n" + "\n\n".join(evidence_packet.session_excerpts)
            + "\n\nReturn JSON only."
        )

    @staticmethod
    def _parse_payload(content: str) -> dict[str, Any]:
        cleaned = content.strip()
        if cleaned.startswith("```"):
            lines = cleaned.splitlines()
            if len(lines) >= 3 and lines[0].startswith("```") and lines[-1].startswith("```"):
                cleaned = "\n".join(lines[1:-1]).strip()
        try:
            payload = json.loads(cleaned)
        except json.JSONDecodeError:
            return {}
        if not isinstance(payload, dict):
            return {}
        frontmatter = payload.get("frontmatter")
        content_value = payload.get("content")
        if not isinstance(frontmatter, dict) or not isinstance(content_value, str):
            return {}
        return {
            "frontmatter": frontmatter,
            "content": content_value.strip(),
            "change_reason": str(payload.get("change_reason") or ""),
        }

    @staticmethod
    def _fallback_payload(candidate: SkillLearningCandidate, evidence_packet: EvidencePacket, action: str) -> dict[str, Any]:
        related = candidate.related_skill_names[0] if candidate.related_skill_names else "generated-skill"
        title = related.replace("_", "-")
        content = "\n".join(f"- {item}" for item in evidence_packet.task_summaries[:5]) or "- No evidence captured."
        return {
            "frontmatter": {
                "description": candidate.reason or f"Auto-generated {action} draft for {title}.",
                "tools": [],
            },
            "content": f"# {title}\n\n## Evidence\n\n{content}\n",
            "change_reason": candidate.reason or f"Fallback {action} synthesis.",
        }