"""数字推演：在一次运行的基础上改动输入，推演指标会怎样变化，不改原运行。

POST /api/runs/{run_id}/evidence/whatif：证据面板里点开口径卡上的一个数，改某个输入的值、或者排除它背后查询结果里的
几行，看这个指标和报告里引用它的地方会变成多少。推演永远不是出具：不追加任何事件（last_seq 不变）、不落工件、
不改报告，结果只交回给发请求的人。

GET /api/runs/{run_id}/evidence/whatif/rows：推演时勾行用，按页取封存范围内一份查询快照的行（遮罩列写「已遮罩」）。
证据面板的查询步骤只给被引用的行前后各 2 行，整份结果作输入（len(vars.res.rows) 这种）时每一行都可能要勾。

只认这次运行封存范围内的工件，和证据接口同一套白名单（api/evidence.py 的 _sealed / _sealed_loader）：口径卡的指标集
从封存的 node.finished 台账找，排除行只认封存范围内交回过的查询快照，nodes.* 的完整值从封存的节点产出工件取，
vars.* 的完整值（value_artifact）只认封存的指标集里写着的。还在跑、停在审批的运行也能推演，结果里 sealed 为假：
数据可能还会变。遮罩列（查询当时记下的加数据源现在设的，SQL 里改了名字的也算）不给值、也不能拿来推演，用到它的指标
原值也不给，见 engine/recompute.py。

重算本身是纯函数（engine/recompute.py）。这里负责：认请求、找卡、准备工件和遮罩、找报告里引用的地方、标出可能受影响
的下游口径卡。
"""
from __future__ import annotations

import asyncio
from collections.abc import Iterator, Mapping
from dataclasses import replace
from typing import Any

from fastapi import APIRouter, Body

from app.api.coded import CodedHTTPException
from app.api.evidence import (
    MASKED,
    MISSING_QUERY,
    REPORT_NOT_FOUND,
    TAMPERED_QUERY,
    _MEMO,
    _Masks,
    _MaskSets,
    _reports,
    _Sealed,
    _sealed,
    _sealed_cards,
    _sealed_loader,
    _snapshot_secrets,
    copied_inputs,
)
from app.core.artifact_store import load
from app.engine import recompute
from app.engine.merge_query import MERGE_SOURCE

router = APIRouter(prefix="/api/runs", tags=["whatif"])

BAD_REQUEST = "whatif_bad_request"
BAD_INPUT = "whatif_bad_input"
CARD_NOT_FOUND = "whatif_card_not_found"
CARD_TAMPERED = "whatif_card_tampered"
METRIC_NOT_FOUND = "whatif_metric_not_found"

BAD_REQUEST_TEXT = ("请求格式有误：card 应为口径卡节点的 ID；report、metric 可省略，填写时为节点 ID 和指标 ID；"
                    "overrides.inputs 应为「输入路径 → 新值」，overrides.exclude_rows 应为「查询快照的工件 ID → 行号列表」")
#: 一次最多改几个输入、排除几份快照里的行、每份最多几行：再多就是请求写错了
MAX_INPUTS = 200
MAX_SNAPSHOTS = 50
MAX_ROWS = 10000
#: 勾行时一页给几行、最多几行
ROWS_PAGE = 50
MAX_ROWS_PAGE = 200
OUT_OF_SCOPE = "这份查询快照不属于这次运行，或不在封存范围内，不能用于推演"


@router.post("/{run_id}/evidence/whatif")
async def evidence_whatif(run_id: str, payload: Any = Body(None)) -> dict[str, Any]:
    """在一次运行的口径卡上推演：请求体 {report?, card, metric?, overrides: {inputs, exclude_rows}}。

    返回 {sealed, seal, card, metrics, segments, unsupported, affected_cards}：每个指标的旧值、新值、变化量和输入，
    报告里引用这些指标的地方会写成什么，不能用于推演的输入和原因，以及引用了这张卡、可能受影响（未重算）的下游口径卡。
    """
    report, card_node, metric, changes = _request(payload)
    sealed = await _sealed(run_id)
    reports = _reports(sealed)
    if report is not None and not any(r.node_id == report for r in reports):
        raise CodedHTTPException(404, "本次运行中没有所选报告撰写节点的文档", REPORT_NOT_FOUND)
    cards = _sealed_cards(sealed)
    artifact, card, started = _card_of(sealed, cards, card_node, reports, report)
    if metric is not None and not any(isinstance(m, dict) and str(m.get("id")) == metric
                                      for m in card.get("metrics") or []):
        raise CodedHTTPException(404, f"口径卡中没有指标「{metric}」", METRIC_NOT_FOUND)
    # 转抄上游口径卡的输入给不给值：和证据面板同一张指标依赖图（copied_inputs → recompute.masked_closure），在事件循环里
    # 认好交进去，重算的线程里不再查库
    copied = await copied_inputs(sealed, card_node, artifact, card)
    sources = _sources(sealed, cards, started, asyncio.get_running_loop(), copied=copied)
    docs = [(r.node_id, r.doc) for r in reports
            if r.doc is not None and r.hash_ok is True and (report is None or r.node_id == report)]
    try:
        # 重算连同读工件（快照、完整值、节点产出）都在线程里：快照大的时候不挡住同一进程里别的请求。
        # 遮罩用到哪份快照才算哪份（_Hidden），查库那一步交回事件循环
        result, segments = await asyncio.to_thread(_compute, card, changes, sources, metric, docs, card_node, artifact)
    except recompute.WhatIfError as e:
        raise CodedHTTPException(422, str(e), BAD_INPUT) from None
    # 改动可能改变了某个指标——算出来变了，或者碰到了它却推演不了（还原不了、遮罩），新值不知道——下游才可能受影响。
    # 不能只看 changed：整个推演不了的指标 changed 一律为空，什么都没改时也一样（recompute.whatif 的 maybe_changed）
    maybe = result["maybe_changed"]
    edges = [(e.get("source"), e.get("target")) for e in sealed.graph.get("edges") or [] if isinstance(e, dict)]
    return {
        "run_id": run_id,
        "card": {"node_id": card_node, "artifact": artifact, "caliber": card.get("caliber") or "",
                 "version": card.get("caliber_version") or ""},
        "report": report,
        # 封存了、而且封存核对通过：推演依据的数据不会再变。没封存（还在跑、停在审批）或封存核对没过的照样能推演
        "sealed": sealed.trusted,
        "seal": {"sealed": sealed.sealed, "ok": sealed.seal["ok"]},
        "metrics": result["metrics"],
        "segments": segments,
        "unsupported": result["unsupported"],
        # 什么都没变，下游也不会变；顺着画布的边找，经中间节点用到卡上值的下游卡也标
        "affected_cards": recompute.downstream_cards(cards, card_node, edges=edges) if maybe else [],
    }


@router.get("/{run_id}/evidence/whatif/rows")
async def evidence_whatif_rows(run_id: str, artifact: str | None = None, offset: str | None = None,
                               limit: str | None = None) -> dict[str, Any]:
    """一页查询快照的行：{artifact, columns, rows, row_offset, row_index, total_rows, masked, hash_ok, sealed, note?}。

    形状和证据面板的查询步骤一致（界面用同一个函数读）。只认这次运行封存范围内交回过的快照；遮罩列（查询当时记下的
    加数据源现在设的，SQL 里改了名字的也算）写「已遮罩」；读不出来、与哈希不一致的不给行，note 照实说。只读：不追加
    事件、不落工件。
    """
    if not artifact or not artifact.strip():
        raise CodedHTTPException(422, "请求格式有误：artifact 应为查询快照的工件 ID", BAD_REQUEST)
    artifact = artifact.strip()
    start, size = _count(offset, "offset", 0), min(_count(limit, "limit", ROWS_PAGE), MAX_ROWS_PAGE)
    sealed = await _sealed(run_id)
    info = sealed.queries.get(artifact)
    if info is None:
        raise CodedHTTPException(422, OUT_OF_SCOPE, BAD_INPUT)
    try:
        snap = await asyncio.to_thread(load, artifact)
        hash_ok: bool | None = True if snap is not None else None
    except ValueError:
        snap, hash_ok = None, False
    page: dict[str, Any] = {
        "run_id": run_id, "artifact": artifact, "node_id": info.get("node_id"), "tool": info.get("tool"),
        "source": info.get("source") or (snap.get("source") if isinstance(snap, dict) else None),
        "columns": [], "rows": [], "row_offset": start, "row_index": [], "total_rows": None, "truncated": None,
        "masked": [], "hash_ok": hash_ok, "sealed": sealed.trusted,
    }
    if not isinstance(snap, dict) or not isinstance(snap.get("rows"), list):
        return {**page, "note": TAMPERED_QUERY if hash_ok is False else MISSING_QUERY}
    hidden = await _mask_of(snap, info, _Masks())
    columns = [str(c) for c in snap.get("columns") or []]
    masked = {i for i, c in enumerate(columns) if c.lower() in hidden}
    rows = snap["rows"]
    picked = range(start, min(start + size, len(rows)))
    return {**page, "columns": columns, "total_rows": len(rows), "truncated": bool(snap.get("truncated")),
            "masked": [columns[i] for i in sorted(masked)],
            "column_types": snap.get("column_types") if isinstance(snap.get("column_types"), dict) else {},
            "row_index": list(picked),
            "rows": [[MASKED if i in masked else v for i, v in enumerate(rows[r])] if isinstance(rows[r], list)
                     else rows[r] for r in picked]}


def _count(raw: str | None, name: str, default: int) -> int:
    """查询参数里的非负整数；没给用默认值。写错了 422，说清是哪一个。"""
    if raw is None or not raw.strip():
        return default
    try:
        value = int(raw)
    except ValueError:
        value = -1
    if value < 0:
        raise CodedHTTPException(422, f"请求格式有误：{name} 应为不小于 0 的整数", BAD_REQUEST)
    return value


def _compute(card: dict[str, Any], changes: recompute.Changes, sources: recompute.Sources, metric: str | None,
             docs: list[tuple[str, dict[str, Any]]], card_node: str, artifact: str
             ) -> tuple[dict[str, Any], list[dict[str, Any]]]:
    result = recompute.whatif(card, changes, sources, metric=metric)
    segments = recompute.report_segments(docs, card_node=card_node, card_artifact=artifact, results=result["metrics"])
    return result, segments


def _request(payload: Any) -> tuple[str | None, str, str | None, recompute.Changes]:
    """(report, card, metric, 改动)。形状不对一律 422 whatif_bad_request；值对不对（路径在不在、行号越没越界）由重算时核对。"""
    def bad() -> CodedHTTPException:
        return CodedHTTPException(422, BAD_REQUEST_TEXT, BAD_REQUEST)

    if not isinstance(payload, dict):
        raise bad()
    card, report, metric = payload.get("card"), payload.get("report"), payload.get("metric")
    if not isinstance(card, str) or not card.strip():
        raise bad()
    if any(v is not None and (not isinstance(v, str) or not v.strip()) for v in (report, metric)):
        raise bad()
    overrides = payload.get("overrides")
    overrides = {} if overrides is None else overrides
    if not isinstance(overrides, dict):
        raise bad()
    inputs = {} if overrides.get("inputs") is None else overrides["inputs"]
    exclude = {} if overrides.get("exclude_rows") is None else overrides["exclude_rows"]
    if not isinstance(inputs, dict) or not isinstance(exclude, dict) \
            or len(inputs) > MAX_INPUTS or len(exclude) > MAX_SNAPSHOTS:
        raise bad()
    rows: dict[str, frozenset[int]] = {}
    for artifact, picked in exclude.items():
        if not isinstance(picked, list) or len(picked) > MAX_ROWS \
                or not all(isinstance(r, int) and not isinstance(r, bool) for r in picked):
            raise bad()
        if picked:
            rows[str(artifact)] = frozenset(picked)
    return (report.strip() if report else None, card.strip(), metric.strip() if metric else None,
            recompute.Changes(inputs={str(k): v for k, v in inputs.items()}, exclude=rows))


def _card_of(sealed: _Sealed, cards: list[tuple[str, str, dict[str, Any]]], node_id: str, reports: list[Any],
             report: str | None) -> tuple[str, dict[str, Any], int]:
    """要推演的那份指标集：(工件 id, 内容, 那次执行的 node.started 序号)。

    哪些 node.finished 算这张卡的执行，和 _sealed_cards 一样认：台账里的 metric_set 条目；一期以前没有台账的，画布上确实
    是口径卡的节点，产出本身就是指标集。同一张卡在循环里算过几次时，选报告引用的那一份（指定了 report 看那份报告，
    没指定看任意一份），都没引用就取最后一次。内容只认 _sealed_cards 取回、复验过哈希的：执行记录里有、内容却对不上
    哈希的说清是被改过，不说「没有这张卡」。
    """
    calibers = set(sealed.nodes_of("metrics"))
    runs: list[tuple[int, str]] = []
    for seq, etype, nid, data in sealed.events:
        if etype != "node.finished" or nid != node_id or not isinstance(data, dict):
            continue
        arts = [str(e["artifact"]) for e in data.get("evidence") or []
                if isinstance(e, dict) and e.get("kind") == "metric_set" and e.get("artifact")]
        if not arts and nid in calibers and data.get("artifact"):
            arts = [str(data["artifact"])]
        runs.extend((seq, art) for art in arts)
    if not runs:
        raise CodedHTTPException(404, "这次运行中没有这张口径卡的结果：节点不存在、不是口径卡、尚未执行或执行失败",
                                 CARD_NOT_FOUND)
    cited = {e.get("artifact") for r in reports if r.doc is not None and (report is None or r.node_id == report)
             for e in (r.doc.get("catalog") or {}).values()
             if isinstance(e, dict) and e.get("kind") == "metric" and e.get("node_id") == node_id}
    seq, artifact = next(((s, a) for s, a in reversed(runs) if a in cited), runs[-1])
    good = {art: card for nid, art, card in cards if nid == node_id}
    if artifact not in good:
        raise CodedHTTPException(409, "口径卡的指标集与哈希不一致或无法读取，疑似被修改，不能推演", CARD_TAMPERED)
    started = max((s for s, etype, nid, _ in sealed.events if etype == "node.started" and nid == node_id and s < seq),
                  default=seq)
    return artifact, good[artifact], started


def _sources(sealed: _Sealed, cards: list[tuple[str, str, dict[str, Any]]], started: int,
             loop: asyncio.AbstractEventLoop, *, copied: Mapping[int, Mapping[str, Any]] | None = None
             ) -> recompute.Sources:
    """重算要用的东西（recompute.Sources）：封存范围内的工件、口径卡那次执行之前的节点产出和跑完的时刻、快照交回的
    时刻、用到哪份才算哪份的遮罩、转抄上游口径卡的输入给不给值（copied）。拿到的 Sources 要在工作线程里用（_Hidden
    在线程里等事件循环查库）。"""
    loader = _loader(sealed, cards)
    hidden = _Hidden(sealed, loader, loop)
    return recompute.Sources(load=loader, queries=tuple(sealed.queries), outputs=_outputs_before(sealed, started),
                             masked=hidden, returned=_returned(sealed), finished=_finished_before(sealed, started),
                             secrets=hidden.secrets, copied=dict(copied or {}))


def _outputs_before(sealed: _Sealed, started: int) -> dict[str, str]:
    """口径卡那次执行开始之前，每个节点最后一次的产出工件：口径卡当时读到的 nodes.* 就是它们。"""
    out: dict[str, str] = {}
    for seq, etype, node_id, data in sealed.events:
        if seq >= started:
            break
        if etype == "node.finished" and node_id and isinstance(data, dict) and data.get("artifact"):
            out[node_id] = str(data["artifact"])
    return out


def _finished_before(sealed: _Sealed, started: int) -> dict[str, int]:
    """口径卡那次执行开始之前，每个节点最后一次跑完的事件序号：口径卡读到的 vars.*、nodes.* 是那一刻写下的。"""
    out: dict[str, int] = {}
    for seq, etype, node_id, _ in sealed.events:
        if seq >= started:
            break
        if etype == "node.finished" and node_id:
            out[node_id] = seq
    return out


def _returned(sealed: _Sealed) -> dict[str, int]:
    """封存范围内每份查询快照第一次交回的事件序号：tool.end 的 query_artifact，或者 node.finished 台账里的 query
    条目（合并查询只有后者）。排除这份快照里的行，只可能影响在这之后才算出来的值。"""
    out: dict[str, int] = {}
    for seq, etype, _, data in sealed.events:
        if not isinstance(data, dict):
            continue
        if etype == "tool.end" and data.get("query_artifact"):
            out.setdefault(str(data["query_artifact"]), seq)
        elif etype == "node.finished":
            for entry in data.get("evidence") or []:
                if isinstance(entry, dict) and entry.get("kind") == "query" and entry.get("artifact"):
                    out.setdefault(str(entry["artifact"]), seq)
    return out


def _loader(sealed: _Sealed, cards: list[tuple[str, str, dict[str, Any]]]) -> Any:
    """只认这次运行封存范围内的工件：证据接口的白名单（查询、表结构、检索快照和台账记过的），加上封存的节点产出工件，
    以及封存的指标集里写着的完整值（value_artifact——写在内容寻址、又在封存范围内的指标集里，属于封存链的延伸）。

    未封存、封存核对没过的运行也能推演（结果里 sealed 为假）：白名单按同一套规则算，只是不要求封存完好。
    取回时照旧复验哈希，对不上抛 ValueError（artifact_store.load 的约定），由重算照实说。
    """
    base = _sealed_loader(replace(sealed, seal={**sealed.seal, "sealed": True, "ok": True}))
    extra = {str(data["artifact"]) for _, etype, _, data in sealed.events
             if etype == "node.finished" and isinstance(data, dict) and data.get("artifact")}
    extra |= {str(item["value_artifact"]) for _, _, card in cards
              for metric in card.get("metrics") or [] if isinstance(metric, dict)
              for item in metric.get("inputs") or [] if isinstance(item, dict) and item.get("value_artifact")}
    memo: dict[str, Any] = {}

    def loader(artifact: str) -> Any:
        key = str(artifact)
        if key not in memo:
            memo[key] = load(key) if key in extra else base(key)
        return memo[key]
    return loader


class _Hidden(Mapping[str, frozenset[str]]):
    """封存范围内的查询快照 → 要遮的列（小写），推演用到哪份才算哪份。

    遮的列和证据面板查询步骤同一套（api/evidence.py 的 _mask_sets）：查询当时记下的加数据源现在设的，按 SQL 认出
    改了名字的也算，合并查询按它合并的那几个数据源、逐格来历和合并 SQL 算。快照读不出来、被改过时照样按台账记的数据源
    算：遮罩不能因为快照坏了就失效（那一格的值另由重算不给）。

    在重算的工作线程里取用：快照经推演用的同一个 loader 读（重算本来也要读这一份，读过的不再读盘）；查数据源现在
    设的遮罩要访问库，交回事件循环去查（_Masks 是异步的），线程在这里等它。以前每次请求在事件循环里把这次运行的
    全部快照读一遍、复验一遍哈希，不管卡上用没用到。

    secrets 同样在工作线程里收：这次运行查到过的遮罩值（和证据面板的 _Masks.run_secrets 同一个口径、同一份进程内记录
    _MEMO），重算里认不出出处的输入、整份结果当输入的指标要按值认时才收，一次请求只收一次；证据面板、之前的推演收过的
    快照不再读。分析结果同样按快照工件记在进程里。
    """

    def __init__(self, sealed: _Sealed, loader: Any, loop: asyncio.AbstractEventLoop) -> None:
        self._sealed, self._loader, self._loop = sealed, loader, loop
        self._masks = _Masks()
        self._memo: dict[str, _MaskSets] = {}
        self._secrets: Any = None
        self._collected = False

    def __getitem__(self, artifact: str) -> frozenset[str]:
        return frozenset(self._sets(artifact)[1].hidden)

    def _sets(self, artifact: str) -> tuple[Any, _MaskSets]:
        """(读出来的快照，读不出来为 None；它的遮罩)。"""
        key = str(artifact)
        if key not in self._sealed.queries:
            raise KeyError(key)
        try:
            snap = self._loader(key)
        except ValueError:
            snap = None
        snap = snap if isinstance(snap, dict) else None
        if key not in self._memo:
            found = _mask_sets_of(snap, self._sealed.queries[key], self._masks, key)
            self._memo[key] = self._wait(found)
        return snap, self._memo[key]

    def secrets(self) -> Any:
        """这次运行查到过的遮罩值（masking._Secrets，没有为 None）：数据源现在设了遮罩、或者已经不在了的查询快照里确定
        取自遮罩列的值，合并查询不收（api/evidence.py 的 _snapshot_secrets）。每份快照收到的值先查进程内记录（_MEMO），
        记过的不再读。"""
        if not self._collected:
            self._collected = True
            parts = []
            for artifact, _source, key in self._wait(self._masks.value_keys(self._sealed.queries)):
                known, got = _MEMO.values(key)
                if not known:
                    snap, sets = self._sets(artifact)
                    if snap is None or snap.get("source") == MERGE_SOURCE:
                        continue
                    got = _MEMO.keep_values(key, _snapshot_secrets(snap, sets))
                parts.append((key, got))
            self._secrets = _MEMO.pooled(parts)
        return self._secrets

    def _wait(self, coro: Any) -> Any:
        """在工作线程里等事件循环跑完 coro（查库）。在事件循环里同步等会卡死，直接报错。"""
        try:
            running = asyncio.get_running_loop()
        except RuntimeError:
            running = None
        if running is self._loop:
            coro.close()
            raise RuntimeError("遮罩只能在工作线程里取：在事件循环里同步等它查库会卡死")
        return asyncio.run_coroutine_threadsafe(coro, self._loop).result()

    def __iter__(self) -> Iterator[str]:
        return iter(self._sealed.queries)

    def __len__(self) -> int:
        return len(self._sealed.queries)


async def _mask_sets_of(snap: dict[str, Any] | None, info: dict[str, Any], masks: _Masks,
                        artifact: str | None = None) -> _MaskSets:
    """一份查询快照的遮罩，和证据面板的查询步骤同一个函数（api/evidence.py 的 _mask_sets）：查询当时记下的加数据源现在
    设的，SQL 里给遮罩列起了别名、套了函数的结果列也算。snap 为 None（读不出来）时只能按台账记的数据源现在设的遮罩算。
    artifact 是 snap 的工件 id：给了的，分析结果按快照记在进程里，之后的推演、证据面板不再分析。"""
    return await masks.sets(artifact, info.get("source"), snap)


async def _mask_of(snap: dict[str, Any] | None, info: dict[str, Any], masks: _Masks) -> set[str]:
    """一份查询快照要遮的列（小写，_mask_sets_of 的 hidden）。运行对比（api/compare.py）按这个名字调用。"""
    return (await _mask_sets_of(snap, info, masks)).hidden