import { createHash } from "node:crypto";

export const LONGFORM_APPENDIX_TABLE = "personal_report_longform_appendices";
export const LONGFORM_APPENDIX_MAX_ATTEMPTS = 2;

export type LongformAppendixStatus = "pending" | "ready" | "unavailable";

export type LongformAppendixRow = Readonly<{
  reportId: string;
  userId: string;
  requestId: string;
  status: LongformAppendixStatus;
  markdown: string | null;
  contentSha256: string | null;
  attemptCount: number;
  lastErrorCode: string | null;
}>;

export type LongformAppendixWrite = Readonly<{
  status: LongformAppendixStatus;
  attemptCount: number;
  markdown: string | null;
  contentSha256: string | null;
  lastErrorCode: string | null;
}>;

export function hashLongformMarkdown(markdown: string): string {
  return createHash("sha256").update(markdown, "utf8").digest("hex");
}

export function parseLongformAppendixRow(value: unknown): LongformAppendixRow | null {
  if (value === null || typeof value !== "object" || Array.isArray(value)) return null;
  const row = value as Record<string, unknown>;
  const reportId = text(row.report_id ?? row.reportId);
  const userId = text(row.user_id ?? row.userId);
  const requestId = text(row.request_id ?? row.requestId);
  const status = row.status;
  if (!reportId || !userId || !requestId) return null;
  if (status !== "pending" && status !== "ready" && status !== "unavailable") return null;
  const markdown = typeof row.markdown === "string" && row.markdown.trim() ? row.markdown : null;
  const contentSha256 = text(row.content_sha256 ?? row.contentSha256);
  const attemptCount = typeof row.attempt_count === "number" && Number.isFinite(row.attempt_count)
    ? row.attempt_count
    : typeof row.attemptCount === "number" && Number.isFinite(row.attemptCount)
      ? row.attemptCount
      : 0;
  return {
    reportId,
    userId,
    requestId,
    status,
    markdown,
    contentSha256,
    attemptCount,
    lastErrorCode: text(row.last_error_code ?? row.lastErrorCode),
  };
}

export function nextLongformAppendixState(input: Readonly<{
  current: LongformAppendixRow | null;
  successMarkdown?: string | null;
  errorCode?: string | null;
}>): LongformAppendixWrite {
  const successMarkdown = input.successMarkdown?.trim() ? input.successMarkdown : null;
  if (successMarkdown) {
    return {
      status: "ready",
      attemptCount: input.current?.attemptCount ?? 0,
      markdown: successMarkdown,
      contentSha256: hashLongformMarkdown(successMarkdown),
      lastErrorCode: null,
    };
  }
  const attemptCount = Math.min(
    (input.current?.attemptCount ?? 0) + 1,
    LONGFORM_APPENDIX_MAX_ATTEMPTS,
  );
  return {
    status: attemptCount >= LONGFORM_APPENDIX_MAX_ATTEMPTS ? "unavailable" : "pending",
    attemptCount,
    markdown: null,
    contentSha256: null,
    lastErrorCode: input.errorCode ?? "generation_failed",
  };
}

function text(value: unknown): string | null {
  if (typeof value !== "string") return null;
  const trimmed = value.trim();
  return trimmed.length > 0 ? trimmed : null;
}