import type { StoredFile } from "@/lib/intake-files";

/**
 * finance → pantry hand-off for a grocery upload (plan §11 C3).
 *
 * The ORIGINAL files go across, not the extracted items: pantry owns grocery
 * extraction (canonical names, categories, staples) and its capture board is
 * the review surface. What finance adds is the routing decision — which
 * transaction the confirm should enrich, or that it should create one — carried
 * in the `intake` field so pantry's confirm seam (C4) can suppress the ING-10
 * create that would otherwise double-book an order the email already booked.
 */

export type PantryForwardArgs = {
  files: StoredFile[];
  batchId: string;
  platform: string | null;
  sharedBy: string | null;
  financeTargetTransactionId: number | null;
  financeAction: "enrich" | "create";
};

export type PantryForwardResult = { captureId: number; itemCount: number | null };

export class PantryDuplicateError extends Error {
  constructor(
    public readonly captureId: number | null,
    public readonly reason: string
  ) {
    super(reason);
  }
}

export class PantryUnavailableError extends Error {}

export type PantryForward = (args: PantryForwardArgs) => Promise<PantryForwardResult>;

export function pantryForwarder(opts: { baseUrl?: string; token?: string; fetchImpl?: typeof fetch } = {}): PantryForward {
  return async (args) => {
    const baseUrl = (opts.baseUrl ?? process.env.PANTRY_BASE_URL ?? "").replace(/\/$/, "");
    const token = opts.token ?? process.env.RECEIPT_INGEST_TOKEN;
    if (!baseUrl || !token) throw new PantryUnavailableError("PANTRY_BASE_URL / RECEIPT_INGEST_TOKEN are not configured");
    const doFetch = opts.fetchImpl ?? fetch;

    const form = new FormData();
    for (const f of args.files) {
      form.append("image", new Blob([new Uint8Array(f.bytes)], { type: f.type }), f.name);
    }
    form.append("source", "receipt");
    form.append(
      "intake",
      JSON.stringify({
        batch_id: args.batchId,
        platform: args.platform,
        origin: "intake",
        shared_by: args.sharedBy,
        finance_target_transaction_id: args.financeTargetTransactionId,
        finance_action: args.financeAction,
      })
    );

    let response: Response;
    try {
      response = await doFetch(`${baseUrl}/api/capture`, { method: "POST", headers: { "x-ingest-token": token }, body: form });
    } catch (e) {
      throw new PantryUnavailableError(`pantry unreachable: ${e instanceof Error ? e.message : String(e)}`);
    }
    const body = (await response.json().catch(() => ({}))) as { captureId?: number; error?: string; items?: unknown[]; reason?: string };
    if (response.status === 409) {
      throw new PantryDuplicateError(typeof body.captureId === "number" ? body.captureId : null, body.reason ?? body.error ?? "already captured");
    }
    if (!response.ok) throw new PantryUnavailableError(`pantry returned ${response.status}: ${body.error ?? ""}`.trim());
    if (typeof body.captureId !== "number") throw new PantryUnavailableError("pantry returned no captureId");
    return { captureId: body.captureId, itemCount: Array.isArray(body.items) ? body.items.length : null };
  };
}