"""
StoryRouteAgent：Celery 批次内判断 new_story vs append_story（JSON）。
"""

from __future__ import annotations

import json
from typing import Any, Literal

from pydantic import BaseModel, field_validator

from app.agents.memoir.prompts import get_story_route_prompt
from app.core.langchain_llm import bind_json_object_mode
from app.core.logging import get_logger
from app.features.story.models import Story

logger = get_logger(__name__)


class StoryRouteDecision(BaseModel):
    decision: Literal["new_story", "append_story"]
    target_story_id: str | None = None
    new_story_title: str | None = None
    reason: str | None = None

    @field_validator("target_story_id", mode="before")
    @classmethod
    def empty_str_to_none(cls, v: Any) -> str | None:
        if v is None or v == "":
            return None
        if isinstance(v, str):
            return v.strip() or None
        return str(v)


def _build_candidate_json(stories: list[Story], *, preview_chars: int = 220) -> str:
    rows: list[dict[str, Any]] = []
    for s in stories:
        md = (s.canonical_markdown or "").strip().replace("\n", " ")
        preview = md[:preview_chars] + ("…" if len(md) > preview_chars else "")
        links: list[str] = []
        for cl in getattr(s, "chapter_links", None) or []:
            ch = getattr(cl, "chapter", None)
            if ch is None:
                continue
            cat = getattr(ch, "category", None) or ""
            tit = getattr(ch, "title", None) or ""
            links.append(f"{tit}({cat})")
        rows.append(
            {
                "id": s.id,
                "title": s.title,
                "preview": preview,
                "linked_chapters": links,
            }
        )
    return json.dumps(rows, ensure_ascii=False, indent=2)


class StoryRouteAgent:
    def decide(
        self,
        *,
        chapter_category: str,
        chapter_title: str,
        batch_transcript: str,
        candidate_stories: list[Story],
        llm: Any,
        valid_story_ids: set[str],
    ) -> StoryRouteDecision:
        if not llm:
            return StoryRouteDecision(
                decision="new_story",
                new_story_title=None,
                reason="no_llm",
            )
        payload = _build_candidate_json(candidate_stories)
        prompt = get_story_route_prompt(
            chapter_category=chapter_category,
            chapter_title=chapter_title,
            batch_transcript=batch_transcript,
            candidate_stories_json=payload,
        )
        try:
            json_llm = bind_json_object_mode(llm, max_tokens=1024)
            response = json_llm.invoke(prompt)
            raw = (response.content or "").strip()
            data = json.loads(raw)
            decision = StoryRouteDecision.model_validate(data)
        except Exception as e:
            logger.warning("StoryRouteAgent 解析失败: %s", e)
            return StoryRouteDecision(
                decision="new_story",
                new_story_title=None,
                reason="parse_error",
            )

        if decision.decision == "append_story":
            tid = decision.target_story_id
            if not tid or tid not in valid_story_ids:
                logger.warning(
                    "StoryRoute append 无效 target_story_id=%s，回退 new_story",
                    tid,
                )
                return StoryRouteDecision(
                    decision="new_story",
                    new_story_title=decision.new_story_title,
                    reason="invalid_target",
                )
        if decision.decision == "new_story" and not (
            decision.new_story_title and decision.new_story_title.strip()
        ):
            decision.new_story_title = None
        return decision