/* =============================================================================
 * A00_Common/design/logic/design_pipeline.ts
 * 실시간 계산 묶음 하나(PLAN 344-4) — 조작마다 차례 번호(generation) +1 · 단계 사이마다 번호
 * 확인 · 옛 번호 결과 버림 · 뒤 단계 요청은 AbortController 로 끊음. 계약(키 모양 · 단계 · deps)
 * = `design_pipeline_types.ts` 머리 주석.
 *
 *   const pipe = createDesignPipeline({ stages: { route, stations, ... } });
 *   pipe.subscribe(publishToStore(useDesignStore(projectId, null)));
 *   pipe.start(inputs);                                   // 처음 · 전 구간
 *   pipe.update("grade", edits, { fromM: 40, toM: 60 });  // 조작 · 바뀐 범위
 *
 * 단계 시간 = `window.__aisloPipeline.runs`(마지막 RUN_LOG_SIZE 번 · 단계별 ms · 개발용).
 * 화면 · fetch · 세션은 단계 함수(주입) 몫 — 이 파일은 차례 · 버림 · 범위 · 기록만.
 * ========================================================================== */

import type { DesignStore } from "../design_store";
import type {
  ChangeRange,
  ChangeSource,
  FollowPatch,
  InputKey,
  PipelineInputs,
  PipelineOutputs,
  PipelineRunRecord,
  PipelineStages,
  RangePart,
  StageContext,
  StageName,
} from "./design_pipeline_types";
import { SOURCE_INPUT } from "./design_pipeline_types";

/** 브라우저 즉시 — 차례대로 기다림. */
export const BROWSER_STAGES: StageName[] = [
  "route",
  "follow",
  "stations",
  "ground",
  "planline",
  "profile",
  "cross",
  "footprint",
];
/** 뒤 — 브라우저 단계가 끝나면 함께 띄우고 기다리지 않음. */
export const AFTER_STAGES: StageName[] = ["drainage", "corridor"];

type Dep = StageName | `input.${InputKey}`;

/** 단계가 기대는 값 — 이 판들이 그대로면 다시 안 셈(계약 표와 같음). */
export const STAGE_DEPS: Record<StageName, Dep[]> = {
  route: ["input.route"],
  follow: ["route"],
  stations: ["route", "input.pipes", "input.structures", "input.plusStations"],
  ground: ["stations"],
  planline: ["ground"],
  profile: ["planline", "input.alignment"],
  cross: ["profile", "ground", "input.cross", "input.pipes", "input.structures"],
  footprint: ["cross", "ground"],
  drainage: ["route", "input.pipes"],
  corridor: ["profile", "cross"],
};

/** follow 가 고칠 수 있는 입력 — 노선 · 횡단은 안 됨(고리). */
const FOLLOW_KEYS: ReadonlyArray<keyof FollowPatch> = [
  "pipes",
  "structures",
  "alignment",
  "plusStations",
];
/** 이 단계 뒤 한 번 쉼 — 종단이 먼저 그려지고 횡단이 그다음. */
const YIELD_AFTER = new Set<StageName>(["profile"]);
export const RUN_LOG_SIZE = 20;

export type PipelineEvent =
  | { kind: "generation"; generation: number }
  | { kind: "stage"; stage: StageName; value: unknown; generation: number };

export interface DesignPipeline {
  /** 처음 · 전 구간 — 입력 다섯을 한 번에. */
  start(inputs: PipelineInputs): Promise<PipelineRunRecord>;
  /** 조작 하나 — 값이 같으면 안 셈(null). part 없으면 전 구간. */
  update(
    source: ChangeSource,
    value: unknown,
    part?: RangePart | null,
  ): Promise<PipelineRunRecord> | null;
  /** 입력 그대로 그 출처부터 다시 셈 — 늦게 온 서버 값(계산 자리 follow 「서버」 · 511-B B-5). */
  refresh(source: ChangeSource): Promise<PipelineRunRecord> | null;
  /** `name` = 기록 `work` 칸 이름(알림 받는 쪽 몫 ms · 349-0s). */
  subscribe(fn: (event: PipelineEvent) => void, name?: string): () => void;
  output<K extends StageName>(name: K): PipelineOutputs[K] | null;
  /** 지금 입력(follow 가 고친 뒤 값 포함 · 읽기만). */
  input<K extends InputKey>(key: K): PipelineInputs[K];
  readonly generation: number;
  /** 단계 · 알림 안에서 들어온 입력 쓰기(고리)를 막은 수. */
  readonly blockedWrites: number;
  /** 떠 있는 뒤 단계가 다 끝날 때까지. */
  settled(): Promise<void>;
  /** 페이지를 떠남 — 떠 있는 계산 · 요청을 버림. */
  dispose(): void;
}

type Outs = { [S in StageName]: PipelineOutputs[S] | null };

function emptyOuts(): Outs {
  const out = {} as Record<StageName, null>;
  [...BROWSER_STAGES, ...AFTER_STAGES].forEach((name) => (out[name] = null));
  return out as Outs;
}

/** 두 범위 합침 — null(전 구간)이 이김 · 거리는 앞 ~ 뒤. */
export function mergeRange(
  a: ChangeRange | null | undefined,
  b: ChangeRange | null,
): ChangeRange | null {
  if (a === undefined) return b;
  if (a === null || b === null) return null;
  // ponytail: 떨어진 두 범위도 앞 ~ 뒤 하나로 — 사이까지 셈. 구간 목록은 느릴 때.
  return {
    sources: [...new Set([...a.sources, ...b.sources])],
    fromM: Math.min(a.fromM, b.fromM),
    toM: Math.max(a.toM, b.toM),
    keys: [...new Set([...a.keys, ...b.keys])],
  };
}

const now = (): number => (typeof performance !== "undefined" ? performance.now() : Date.now());

function runLog(): { runs: PipelineRunRecord[] } {
  const root = globalThis as { __aisloPipeline?: { runs: PipelineRunRecord[] } };
  root.__aisloPipeline ??= { runs: [] };
  return root.__aisloPipeline;
}

const addWork = (record: PipelineRunRecord | undefined, name: string, ms: number): void => {
  if (!record) return;
  const work = (record.work ??= {});
  work[name] = Math.round(((work[name] ?? 0) + ms) * 100) / 100;
};

/** 그리기 몫 재기(349-0s) — 마지막 차례 기록 `work[name]` 에 ms 를 더함(차례 뒤 늦은 그리기도 그 차례 몫). */
export function pipelineWork<T>(name: string, fn: () => T): T {
  const t0 = now();
  try {
    return fn();
  } finally {
    const runs = runLog().runs;
    addWork(runs[runs.length - 1], name, now() - t0);
  }
}

export function createDesignPipeline(options: { stages: PipelineStages }): DesignPipeline {
  const stages = options.stages;
  const inputs: PipelineInputs = {
    route: null,
    alignment: null,
    cross: null,
    pipes: null,
    structures: null,
    plusStations: null,
  };
  const inputVer: Record<InputKey, number> = {
    route: 0,
    alignment: 0,
    cross: 0,
    pipes: 0,
    structures: 0,
    plusStations: 0,
  };
  const out = emptyOuts();
  const outVer = {} as Record<StageName, number>;
  const lastSig = {} as Partial<Record<StageName, string>>;
  /** 마지막으로 끝난 뒤 쌓인 범위 — 없음(undefined) · 전 구간(null) · 범위. */
  const pending = {} as Partial<Record<StageName, ChangeRange | null>>;
  [...BROWSER_STAGES, ...AFTER_STAGES].forEach((name) => {
    outVer[name] = 0;
    pending[name] = null;
  });
  /** 알림 받는 쪽 → 기록 이름. */
  const listeners = new Map<(event: PipelineEvent) => void, string>();
  const inFlight = new Set<Promise<unknown>>();
  let generation = 0;
  let controller = new AbortController();
  /** 단계 함수 · 알림을 부르는 동안(동기) — 이때 들어온 입력 쓰기는 고리라 막음. */
  let busy = false;
  let blockedWrites = 0;

  const emit = (event: PipelineEvent, record?: PipelineRunRecord): void => {
    busy = true;
    try {
      listeners.forEach((name, fn) => {
        const t0 = now();
        fn(event);
        addWork(record, name, now() - t0);
      });
    } finally {
      busy = false;
    }
  };

  const sigOf = (name: StageName): string =>
    STAGE_DEPS[name]
      .map((dep) =>
        dep.startsWith("input.") ? inputVer[dep.slice(6) as InputKey] : outVer[dep as StageName],
      )
      .join(",");

  const markAll = (range: ChangeRange | null): void => {
    [...BROWSER_STAGES, ...AFTER_STAGES].forEach((name) => {
      pending[name] = mergeRange(pending[name], range);
    });
  };

  const applyFollow = (patch: FollowPatch | null): void => {
    if (!patch) return;
    for (const key of Object.keys(patch) as Array<keyof FollowPatch>) {
      if (!FOLLOW_KEYS.includes(key)) {
        console.warn(`[pipeline] follow 가 고칠 수 없는 입력 — 버림: ${key}`);
        continue;
      }
      inputs[key] = patch[key] as never;
      inputVer[key] += 1;
    }
  };

  /** 한 단계 — 같은 판이면 건너뜀 · 옛 번호면 버림 · 아니면 출력 내보냄. */
  async function step(
    name: StageName,
    gen: number,
    signal: AbortSignal,
    record: PipelineRunRecord,
    before: Outs,
  ): Promise<"ok" | "dropped" | "error"> {
    const sig = sigOf(name);
    const fn = stages[name] as ((ctx: StageContext<StageName>) => unknown) | undefined;
    if (!fn || sig === lastSig[name]) {
      record.skipped.push(name);
      if (fn) delete pending[name];
      return "ok";
    }
    const ctx: StageContext<StageName> = {
      generation: gen,
      range: pending[name] ?? null,
      signal,
      inputs: { ...inputs },
      out: { ...out },
      before,
      prev: out[name],
    };
    const t0 = now();
    let value: unknown;
    try {
      busy = true;
      let pendingValue: unknown;
      try {
        pendingValue = fn(ctx);
      } finally {
        busy = false;
      }
      value = await pendingValue;
    } catch (error) {
      if (gen !== generation) return "dropped";
      console.error(`[pipeline] ${name} 단계 실패`, error);
      return "error";
    }
    if (gen !== generation) return "dropped";
    record.stages[name] = Math.round((now() - t0) * 100) / 100;
    if (name === "follow") applyFollow(value as FollowPatch | null);
    (out as Record<StageName, unknown>)[name] = value;
    outVer[name] += 1;
    lastSig[name] = sig;
    delete pending[name];
    emit({ kind: "stage", stage: name, value, generation: gen }, record);
    return "ok";
  }

  async function run(): Promise<PipelineRunRecord> {
    const gen = generation;
    const signal = controller.signal;
    const record: PipelineRunRecord = {
      generation: gen,
      sources: [],
      stages: {},
      skipped: [],
      totalMs: 0,
      outcome: "running",
    };
    // 같은 틱의 조작은 마지막 하나만 셈.
    await Promise.resolve();
    if (gen !== generation) {
      record.outcome = "dropped";
      return record;
    }
    record.sources = [...new Set(Object.values(pending).flatMap((range) => range?.sources ?? []))];
    const log = runLog();
    log.runs.push(record);
    if (log.runs.length > RUN_LOG_SIZE) log.runs.splice(0, log.runs.length - RUN_LOG_SIZE);
    const before = { ...out };
    const t0 = now();
    for (const name of BROWSER_STAGES) {
      const result = await step(name, gen, signal, record, before);
      if (result !== "ok") {
        record.outcome = result;
        return record;
      }
      if (YIELD_AFTER.has(name) && record.stages[name] !== undefined) {
        const t1 = now();
        await new Promise((resolve) => setTimeout(resolve, 0));
        addWork(record, "쉼", now() - t1); // 그 사이 늦은 그리기 · 다른 일
        if (gen !== generation) {
          record.outcome = "dropped";
          return record;
        }
      }
    }
    record.totalMs = Math.round((now() - t0) * 100) / 100;
    record.outcome = "done";
    for (const name of AFTER_STAGES) {
      const task = step(name, gen, signal, record, before);
      inFlight.add(task);
      void task.finally(() => inFlight.delete(task));
    }
    return record;
  }

  function begin(range: ChangeRange | null): Promise<PipelineRunRecord> {
    generation += 1;
    controller.abort();
    controller = new AbortController();
    markAll(range);
    emit({ kind: "generation", generation });
    return run();
  }

  return {
    start(next) {
      (Object.keys(inputs) as InputKey[]).forEach((key) => {
        inputs[key] = next[key] as never;
        inputVer[key] += 1;
      });
      return begin(null);
    },
    update(source, value, part = null) {
      if (busy) {
        // 파생(단계 · 알림)이 입력에 쓰는 길 — 고리라 막음. 예외는 follow 반환값뿐.
        blockedWrites += 1;
        console.warn(`[pipeline] 계산 · 알림 안에서 입력 쓰기 막음: ${source}`);
        return null;
      }
      const key = SOURCE_INPUT[source];
      if (JSON.stringify(inputs[key]) === JSON.stringify(value)) return null;
      inputs[key] = value as never;
      inputVer[key] += 1;
      const range = part
        ? { sources: [source], fromM: part.fromM, toM: part.toM, keys: part.keys ?? [] }
        : { sources: [source], fromM: 0, toM: Infinity, keys: [] };
      return begin(range);
    },
    refresh(source) {
      if (busy) return null;
      inputVer[SOURCE_INPUT[source]] += 1;
      return begin({ sources: [source], fromM: 0, toM: Infinity, keys: [] });
    },
    subscribe(fn, name = "알림") {
      listeners.set(fn, name);
      return () => listeners.delete(fn);
    },
    output(name) {
      return out[name] as never;
    },
    input(key) {
      return inputs[key];
    },
    get generation() {
      return generation;
    },
    get blockedWrites() {
      return blockedWrites;
    },
    async settled() {
      while (inFlight.size) await Promise.allSettled([...inFlight]);
    },
    dispose() {
      generation += 1;
      controller.abort();
      listeners.clear();
    },
  };
}

/** 가게 잇기 — 측점(ground 단계 · 지반 채움) · 종단 · 평면 발자국 · 차례 번호를 가게 키로. */
export function publishToStore(store: DesignStore): (event: PipelineEvent) => void {
  return (event) => {
    if (event.kind === "generation") return store.set("generation", event.generation);
    if (event.stage === "ground") {
      store.set("stations", (event.value as PipelineOutputs["ground"] | null)?.stations ?? null);
    } else if (event.stage === "profile") {
      store.set("profile", event.value as PipelineOutputs["profile"] | null);
    } else if (event.stage === "footprint") {
      store.set("footprint", event.value as PipelineOutputs["footprint"] | null);
    }
  };
}