// P4 Files — client-side chunked upload sequence (init -> chunk -> complete)
// extracted from the files upload route so other flows (e.g. the AK-P16d
// signature wizard) can upload a file and get its file id back. Pure fetch
// client, no React; errors carry the server's i18n error key.

import { csrfRequestHeaders } from "~/utils/csrf";

export type UploadFileClientResult = { id: string; displayName: string };
export type ChatAttachmentScanStatus = "pending" | "clean" | "infected" | "skipped";

export class UploadFileClientError extends Error {
  readonly errorKey: string;
  constructor(errorKey: string) {
    super(errorKey);
    this.name = "UploadFileClientError";
    this.errorKey = errorKey;
  }
}

/**
 * MIME types a browser commonly leaves empty on `File.type`, by extension.
 *
 * Markdown is the one that bites: macOS has no system type for `.md`, so Chrome
 * hands over an empty string, the upload declares `application/octet-stream` and
 * the store rejects it as a blocked type — for a file it does allow. Only types
 * the file store accepts are mapped; anything else keeps the octet-stream
 * fallback and gets the store's plain "type not allowed" answer.
 */
const MIME_BY_EXTENSION: Readonly<Record<string, string>> = {
  md: "text/markdown",
  markdown: "text/markdown",
  txt: "text/plain",
  csv: "text/csv",
  pdf: "application/pdf",
  png: "image/png",
  jpg: "image/jpeg",
  jpeg: "image/jpeg",
  webp: "image/webp",
  gif: "image/gif",
  heic: "image/heic",
  heif: "image/heif",
  docx: "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
  xlsx: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
  pptx: "application/vnd.openxmlformats-officedocument.presentationml.presentation",
};

/** The type to declare for a file: what the browser says, else its extension. */
export function resolveUploadMimeType(file: { name: string; type: string }): string {
  if (file.type) return file.type;
  const extension = file.name.split(".").pop()?.toLowerCase() ?? "";
  return MIME_BY_EXTENSION[extension] ?? "application/octet-stream";
}

export async function uploadFileInChunks(input: {
  tenantSlug: string;
  file: File;
  onProgress?: (percent: number) => void;
  onProcessing?: () => void;
  signal?: AbortSignal;
}): Promise<UploadFileClientResult> {
  const { tenantSlug, file } = input;
  const initRes = await fetch(`/${tenantSlug}/files/upload/init`, {
    method: "POST",
    headers: csrfRequestHeaders({ "content-type": "application/json" }),
    body: JSON.stringify({ originalFilename: file.name, mimeType: resolveUploadMimeType(file), totalSizeBytes: file.size }),
    signal: input.signal,
  });
  if (!initRes.ok) {
    const body = (await initRes.json().catch(() => ({}))) as { error?: string };
    throw new UploadFileClientError(body.error ?? "files.error.invalidUploadRequest");
  }
  // The server's chunk size is authoritative for slicing so client and server
  // always agree on chunk boundaries.
  const { uploadId, chunkSize, totalChunks } = (await initRes.json()) as { uploadId: string; chunkSize: number; totalChunks: number };
  for (let index = 0; index < totalChunks; index += 1) {
    const slice = file.slice(index * chunkSize, (index + 1) * chunkSize);
    const chunkRes = await fetch(`/${tenantSlug}/files/upload/${uploadId}/chunk/${index}`, {
      method: "POST",
      headers: csrfRequestHeaders(),
      body: slice,
      signal: input.signal,
    });
    if (!chunkRes.ok) {
      const body = (await chunkRes.json().catch(() => ({}))) as { error?: string };
      throw new UploadFileClientError(body.error ?? "files.error.uploadIncomplete");
    }
    input.onProgress?.(Math.round(((index + 1) / totalChunks) * 100));
  }
  input.onProcessing?.();
  const completeRes = await fetch(`/${tenantSlug}/files/upload/${uploadId}/complete`, {
    method: "POST",
    headers: csrfRequestHeaders({ "content-type": "application/json" }),
    body: JSON.stringify({}),
    signal: input.signal,
  });
  if (!completeRes.ok) {
    const body = (await completeRes.json().catch(() => ({}))) as { error?: string };
    throw new UploadFileClientError(body.error ?? "files.error.uploadIncomplete");
  }
  return (await completeRes.json()) as UploadFileClientResult;
}

export async function waitForChatAttachmentScan(input: {
  tenantSlug: string;
  fileId: string;
  signal?: AbortSignal;
  fetchImpl?: typeof fetch;
  pollIntervalMs?: number;
  maxAttempts?: number;
}): Promise<void> {
  const fetchImpl = input.fetchImpl ?? fetch;
  const maxAttempts = input.maxAttempts ?? 80;
  const pollIntervalMs = input.pollIntervalMs ?? 750;
  for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
    assertNotAborted(input.signal);
    const response = await fetchImpl(`/${input.tenantSlug}/chat/attachments/${encodeURIComponent(input.fileId)}/status`, {
      headers: { accept: "application/json" },
      signal: input.signal,
    });
    if (!response.ok) {
      throw new UploadFileClientError("chat.attachments.scanStatusFailed");
    }
    const body = (await response.json()) as { scanStatus?: ChatAttachmentScanStatus };
    if (body.scanStatus === "clean") return;
    if (body.scanStatus === "infected" || body.scanStatus === "skipped") {
      throw new UploadFileClientError("chat.attachments.blocked");
    }
    if (body.scanStatus !== "pending") {
      throw new UploadFileClientError("chat.attachments.scanStatusFailed");
    }
    if (attempt + 1 < maxAttempts) await abortableDelay(pollIntervalMs, input.signal);
  }
  throw new UploadFileClientError("chat.attachments.scanPendingRetry");
}

function assertNotAborted(signal?: AbortSignal): void {
  if (signal?.aborted) throw new DOMException("The operation was aborted", "AbortError");
}

function abortableDelay(delayMs: number, signal?: AbortSignal): Promise<void> {
  if (delayMs <= 0) return Promise.resolve();
  return new Promise((resolve, reject) => {
    const cleanup = () => signal?.removeEventListener("abort", onAbort);
    const timeout = setTimeout(() => {
      cleanup();
      resolve();
    }, delayMs);
    const onAbort = () => {
      clearTimeout(timeout);
      cleanup();
      reject(new DOMException("The operation was aborted", "AbortError"));
    };
    signal?.addEventListener("abort", onAbort, { once: true });
  });
}