// 审稿 SSE 帧归一 + reducer（对齐 C3 / C4 扩 / ARCH §7.3）。
// 帧：`section{name,status}` / `conflict{type,where,refs,suggestion}` / `done{length}` / `error{...}`。
// 纯逻辑，便于 node 环境单测（不依赖 DOM）。

// 五类冲突（C6 ConflictType / ARCH §6.1）。
export type ConflictType =
  | "性格漂移"
  | "能力不符"
  | "设定违例"
  | "地理矛盾"
  | "时间线倒错";

export interface ReviewConflict {
  type: string;
  where: string;
  refs: string[];
  suggestion: string;
}

export type SectionStatus = "started" | "done" | "incomplete";

// 伏笔建议（C4 扩 T3.3）：planted=新埋待确认 / resolved=疑似回收（只读建议）。
export type ForeshadowKind = "planted" | "resolved";

export interface ForeshadowSuggestion {
  kind: ForeshadowKind;
  code?: string | null;
  title: string;
  where?: string | null;
  note?: string | null;
}

// 节奏报告（C4 扩 T3.3）：注水段 + 章末钩子 + 爽点节拍图。
export interface PaceIssue {
  where: string;
  reason: string;
}

export interface PaceReport {
  water: PaceIssue[];
  hook: boolean;
  beat_map: number[];
}

export interface SectionEvent {
  event: "section";
  data: { name: string; status: SectionStatus };
}
export interface ConflictEvent {
  event: "conflict";
  data: ReviewConflict;
}
export interface ForeshadowEvent {
  event: "foreshadow";
  data: {
    kind: ForeshadowKind;
    code?: string | null;
    title: string;
    where?: string | null;
    note?: string | null;
  };
}
export interface PaceEvent {
  event: "pace";
  data: {
    water: PaceIssue[];
    hook: boolean;
    beat_map: number[];
  };
}
export interface DoneEvent {
  event: "done";
  data: { length: number };
}
export interface ErrorEvent {
  event: "error";
  data: { code: string; message: string; request_id?: string | null };
}
export type ReviewSseEvent =
  | SectionEvent
  | ConflictEvent
  | ForeshadowEvent
  | PaceEvent
  | DoneEvent
  | ErrorEvent;

const KNOWN_EVENTS = new Set([
  "section",
  "conflict",
  "foreshadow",
  "pace",
  "done",
  "error",
]);

// 把一个完整 SSE 块（多行）解析成事件；无法解析则返回 null（跳过）。
export function parseReviewBlock(block: string): ReviewSseEvent | null {
  let event = "";
  const dataLines: string[] = [];
  for (const rawLine of block.split("\n")) {
    const line = rawLine.replace(/\r$/, "");
    if (line.startsWith(":")) continue; // 注释/心跳
    const sep = line.indexOf(":");
    if (sep === -1) continue;
    const field = line.slice(0, sep);
    const value = line.slice(sep + 1).replace(/^ /, "");
    if (field === "event") event = value;
    else if (field === "data") dataLines.push(value);
  }
  if (!KNOWN_EVENTS.has(event) || dataLines.length === 0) return null;
  let data: unknown;
  try {
    data = JSON.parse(dataLines.join("\n"));
  } catch {
    return null;
  }
  return { event, data } as ReviewSseEvent;
}

// 增量缓冲：吃进一段文本，吐出已完成的事件块（空行分隔），保留未完成尾部。
export class ReviewFrameBuffer {
  private buf = "";

  push(chunk: string): ReviewSseEvent[] {
    this.buf += chunk;
    const events: ReviewSseEvent[] = [];
    let idx: number;
    while ((idx = this.findBoundary(this.buf)) !== -1) {
      const block = this.buf.slice(0, idx);
      this.buf = this.buf.slice(this.boundaryEnd(this.buf, idx));
      const evt = parseReviewBlock(block);
      if (evt) events.push(evt);
    }
    return events;
  }

  private findBoundary(s: string): number {
    const a = s.indexOf("\n\n");
    const b = s.indexOf("\r\n\r\n");
    if (a === -1) return b;
    if (b === -1) return a;
    return Math.min(a, b);
  }

  private boundaryEnd(s: string, idx: number): number {
    return s.startsWith("\r\n\r\n", idx) ? idx + 4 : idx + 2;
  }
}

export type ReviewPhase = "idle" | "reviewing" | "done" | "error" | "aborted";

export interface ReviewSection {
  name: string;
  status: SectionStatus;
}

export interface ReviewStreamState {
  phase: ReviewPhase;
  sections: ReviewSection[];
  conflicts: ReviewConflict[];
  foreshadow: ForeshadowSuggestion[];
  pace: PaceReport | null;
  error: { code: string; message: string; request_id?: string | null } | null;
}

export const initialReviewState: ReviewStreamState = {
  phase: "idle",
  sections: [],
  conflicts: [],
  foreshadow: [],
  pace: null,
  error: null,
};

// 纯 reducer：把单个事件折叠进状态。section 按 name upsert（最后状态生效）。
export function reduceReview(
  state: ReviewStreamState,
  event: ReviewSseEvent,
): ReviewStreamState {
  switch (event.event) {
    case "section":
      return {
        ...state,
        phase: "reviewing",
        sections: upsertSection(state.sections, event.data),
      };
    case "conflict":
      return {
        ...state,
        phase: "reviewing",
        conflicts: [...state.conflicts, event.data],
      };
    case "foreshadow":
      return {
        ...state,
        phase: "reviewing",
        foreshadow: [...state.foreshadow, { ...event.data }],
      };
    case "pace":
      return {
        ...state,
        phase: "reviewing",
        pace: { ...event.data },
      };
    case "done":
      return { ...state, phase: "done" };
    case "error":
      return { ...state, phase: "error", error: event.data };
    default:
      return state;
  }
}

function upsertSection(
  sections: ReviewSection[],
  next: ReviewSection,
): ReviewSection[] {
  const idx = sections.findIndex((s) => s.name === next.name);
  if (idx === -1) return [...sections, next];
  return sections.map((s, i) => (i === idx ? next : s));
}