"""
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_batch_plan_prompt,
    get_story_route_prompt,
)
from app.agents.memoir.story_route_payload import build_route_candidate_json
from app.core.config import settings
from app.core.langchain_llm import invoke_json_object
from app.core.logging import get_logger
from app.features.story.models import Story

logger = get_logger(__name__)


# 超过此数量跳过批量规划（单次路由），避免 prompt 过大
PLAN_BATCH_MAX_SEGMENTS = 48


class StoryBatchPlanUnit(BaseModel):
    """批量写入中的一个单元（连续 segment 块）。"""

    segment_ids: list[str]
    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_tid(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)


class StoryBatchPlan(BaseModel):
    units: list[StoryBatchPlanUnit]


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_segments_json_for_plan(
    segments: list[tuple[str, str]], *, text_preview_chars: int = 4000
) -> str:
    """segments: (id, user_input_text) 按口述顺序。"""
    rows: list[dict[str, str]] = []
    for sid, text in segments:
        t = (text or "").strip()
        if len(t) > text_preview_chars:
            t = t[:text_preview_chars] + "…"
        rows.append({"id": sid, "text": t})
    return json.dumps(rows, ensure_ascii=False, indent=2)


def validate_story_batch_plan(
    ordered_segment_ids: list[str],
    plan: StoryBatchPlan,
    valid_story_ids: set[str],
) -> tuple[bool, str | None]:
    """
    校验：segment 全覆盖、顺序一致、append 目标合法。
    标题由 NarrativeAgent 延迟生成，路由阶段不再要求 new_story_title。
    返回 (ok, error_code)。
    """
    if not plan.units:
        return False, "empty_units"
    flat: list[str] = []
    for u in plan.units:
        if not u.segment_ids:
            return False, "empty_unit_segment_ids"
        flat.extend(u.segment_ids)
    if len(flat) != len(set(flat)):
        return False, "duplicate_segment"
    if flat != ordered_segment_ids:
        return False, "segment_mismatch"
    for u in plan.units:
        if u.decision == "append_story":
            tid = u.target_story_id
            if not tid or tid not in valid_story_ids:
                return False, "invalid_append_target"
    return True, None


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],
        story_meta: dict[str, dict[str, int]] | None = None,
    ) -> StoryRouteDecision:
        if not llm:
            return StoryRouteDecision(
                decision="new_story",
                new_story_title=None,
                reason="no_llm",
            )
        payload = build_route_candidate_json(candidate_stories, story_meta, settings)
        prompt = get_story_route_prompt(
            chapter_category=chapter_category,
            chapter_title=chapter_title,
            batch_transcript=batch_transcript,
            candidate_stories_json=payload,
        )
        try:
            raw = invoke_json_object(
                llm,
                prompt,
                max_tokens=1024,
                agent="StoryRouteAgent.decide",
            ).strip()
            data = json.loads(raw)
            decision = StoryRouteDecision.model_validate(data)
        except Exception as e:
            logger.warning("StoryRouteAgent 解析失败: {}", 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={}，回退 new_story",
                    tid,
                )
                return StoryRouteDecision(
                    decision="new_story",
                    new_story_title=decision.new_story_title,
                    reason="invalid_target",
                )
        return decision

    def plan_batch(
        self,
        *,
        chapter_category: str,
        chapter_title: str,
        segments: list[tuple[str, str]],
        candidate_stories: list[Story],
        llm: Any,
        valid_story_ids: set[str],
        story_meta: dict[str, dict[str, int]] | None = None,
    ) -> StoryBatchPlan | None:
        """
        将本批 segment 划分为多个写入单元。解析失败返回 None，由调用方回退 decide()。
        """
        if not llm or len(segments) < 2:
            return None
        payload = build_route_candidate_json(candidate_stories, story_meta, settings)
        segments_json = _build_segments_json_for_plan(segments)
        prompt = get_story_batch_plan_prompt(
            chapter_category=chapter_category,
            chapter_title=chapter_title,
            segments_json=segments_json,
            candidate_stories_json=payload,
        )
        try:
            raw = invoke_json_object(
                llm,
                prompt,
                max_tokens=4096,
                agent="StoryRouteAgent.plan_batch",
            ).strip()
            data = json.loads(raw)
            plan = StoryBatchPlan.model_validate(data)
        except Exception as e:
            logger.warning("StoryRouteAgent.plan_batch 解析失败: {}", e)
            return None

        ordered = [s[0] for s in segments]
        ok, err = validate_story_batch_plan(ordered, plan, valid_story_ids)
        if not ok:
            logger.warning("StoryRouteAgent.plan_batch 校验失败: {}", err)
            return None
        return plan