"""
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,
    sort_stories_for_route,
)
from app.core.config import settings
from app.core.llm_call import LLMCallError, llm_json_call
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

# 童年 / 求学 / 家庭：模型与后处理均倾向「少拆分、优先续写」
APPEND_FIRST_CHAPTER_CATEGORIES = frozenset({"childhood", "education", "family"})


def default_append_target_story_id(
    candidate_stories: list[Story],
    story_meta: dict[str, dict[str, int]] | None,
    settings: Any,
) -> str | None:
    """排序后的首选续写目标（与路由候选 JSON 顺序一致）。"""
    if not candidate_stories:
        return None
    meta = story_meta or {}
    ordered = sort_stories_for_route(
        candidate_stories,
        meta,
        summary_min_chars=int(settings.story_route_summary_min_chars),
    )
    if not ordered:
        return None
    return str(ordered[0].id)


def merge_consecutive_new_story_units(
    units: list[StoryBatchPlanUnit],
) -> list[StoryBatchPlanUnit]:
    """将相邻的多个 new_story 单元合并为一个，减少同批碎片叙事。"""
    if not units:
        return units
    out: list[StoryBatchPlanUnit] = []
    i = 0
    while i < len(units):
        u = units[i]
        if u.decision != "new_story":
            out.append(u)
            i += 1
            continue
        run_segs: list[str] = list(u.segment_ids)
        j = i + 1
        while j < len(units) and units[j].decision == "new_story":
            run_segs.extend(units[j].segment_ids)
            j += 1
        if j > i + 1:
            out.append(
                StoryBatchPlanUnit(
                    segment_ids=run_segs,
                    decision="new_story",
                    target_story_id=None,
                    reason="coalesced_consecutive_new_story",
                )
            )
        else:
            out.append(u)
        i = j
    return out


def normalize_batch_plan_reduce_new_story_fragmentation(
    plan: StoryBatchPlan,
    ordered_segment_ids: list[str],
    *,
    chapter_category: str,
    candidate_stories: list[Story],
    valid_story_ids: set[str],
    story_meta: dict[str, dict[str, int]] | None,
    settings: Any,
) -> StoryBatchPlan:
    """
    LLM 校验通过后的确定性归一：合并相邻 new_story；在 append-first 类目下若整批只有一个 new 块则改为 append。
    """
    units = merge_consecutive_new_story_units(list(plan.units))
    if (
        chapter_category in APPEND_FIRST_CHAPTER_CATEGORIES
        and candidate_stories
        and len(units) == 1
        and units[0].decision == "new_story"
    ):
        tid = default_append_target_story_id(candidate_stories, story_meta, settings)
        if tid and tid in valid_story_ids:
            units = [
                StoryBatchPlanUnit(
                    segment_ids=list(ordered_segment_ids),
                    decision="append_story",
                    target_story_id=tid,
                    reason="append_first_whole_batch_fallback",
                )
            ]
    candidate = StoryBatchPlan(units=units)
    ok, err = validate_story_batch_plan(
        ordered_segment_ids, candidate, valid_story_ids
    )
    if not ok:
        logger.warning(
            "batch_plan_normalize_revalidate_failed err={} keep_original",
            err,
        )
        return plan
    return candidate


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:
            fb = default_append_target_story_id(
                candidate_stories, story_meta, settings
            )
            if fb and fb in valid_story_ids:
                return StoryRouteDecision(
                    decision="append_story",
                    target_story_id=fb,
                    reason="no_llm_default_append",
                )
            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,
        )

        def _decide_fallback() -> StoryRouteDecision:
            fb = default_append_target_story_id(
                candidate_stories, story_meta, settings
            )
            if fb and fb in valid_story_ids:
                return StoryRouteDecision(
                    decision="append_story",
                    target_story_id=fb,
                    reason="parse_error_default_append",
                )
            return StoryRouteDecision(
                decision="new_story",
                new_story_title=None,
                reason="parse_error",
            )

        decision = llm_json_call(
            llm,
            prompt,
            StoryRouteDecision,
            max_tokens=settings.memoir_story_route_max_tokens,
            agent="StoryRouteAgent.decide",
            fallback_factory=_decide_fallback,
        )

        if decision.decision == "append_story":
            tid = decision.target_story_id
            if not tid or tid not in valid_story_ids:
                fb = default_append_target_story_id(
                    candidate_stories, story_meta, settings
                )
                if fb and fb in valid_story_ids:
                    logger.info(
                        "StoryRoute append 无效 target_story_id={}，回退默认 append {}",
                        tid,
                        fb,
                    )
                    return StoryRouteDecision(
                        decision="append_story",
                        target_story_id=fb,
                        reason="invalid_target_default_append",
                    )
                logger.warning(
                    "StoryRoute append 无效 target_story_id={}，且无可用默认目标，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:
            plan = llm_json_call(
                llm,
                prompt,
                StoryBatchPlan,
                max_tokens=settings.memoir_story_batch_plan_max_tokens,
                agent="StoryRouteAgent.plan_batch",
            )
        except LLMCallError 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 normalize_batch_plan_reduce_new_story_fragmentation(
            plan,
            ordered,
            chapter_category=chapter_category,
            candidate_stories=candidate_stories,
            valid_story_ids=valid_story_ids,
            story_meta=story_meta,
            settings=settings,
        )