feat: 实现 Chromium PDF 导出与精确预览

apps/web/src/pdf-export.ts

@@ -0,0 +1,134 @@
+import type { ExportConfig } from "@md-to-pdf/core";
+
+export interface PdfExportRequest {
+  markdown: string;
+  fileName: string;
+  language: string;
+  exportConfig: ExportConfig;
+}
+
+export interface PdfExportResult {
+  blob: Blob;
+  fileName: string;
+  pageCount: number | undefined;
+  mermaidErrorCount: number;
+}
+
+export interface CachedPdfExport {
+  key: string;
+  result: PdfExportResult;
+}
+
+export function createPdfExportCacheKey(request: PdfExportRequest) {
+  return JSON.stringify([
+    request.markdown,
+    request.fileName,
+    request.language,
+    request.exportConfig
+  ]);
+}
+
+export function getCachedPdfExport(
+  cache: CachedPdfExport | undefined,
+  key: string
+) {
+  return cache?.key === key ? cache.result : undefined;
+}
+
+export async function getOrRequestPdfExport(
+  request: PdfExportRequest,
+  cache: CachedPdfExport | undefined,
+  requester: (
+    request: PdfExportRequest
+  ) => Promise<PdfExportResult> = requestPdfExport
+): Promise<CachedPdfExport> {
+  const key = createPdfExportCacheKey(request);
+  const cached = getCachedPdfExport(cache, key);
+  return {
+    key,
+    result: cached ?? (await requester(request))
+  };
+}
+
+function parseNumericHeader(value: string | null) {
+  if (value === null) {
+    return undefined;
+  }
+  const parsed = Number.parseInt(value, 10);
+  return Number.isInteger(parsed) && parsed >= 0 ? parsed : undefined;
+}
+
+export function parseContentDispositionFileName(
+  contentDisposition: string | null
+) {
+  const encoded = contentDisposition?.match(
+    /filename\*=UTF-8''([^;]+)/i
+  )?.[1];
+  if (encoded) {
+    try {
+      return decodeURIComponent(encoded);
+    } catch {
+      // 使用兼容文件名回退。
+    }
+  }
+
+  return (
+    contentDisposition
+      ?.match(/filename="([^"]+)"/i)?.[1]
+      ?.trim() || "document.pdf"
+  );
+}
+
+async function readErrorMessage(response: Response) {
+  try {
+    const payload = (await response.json()) as {
+      message?: unknown;
+    };
+    if (typeof payload.message === "string") {
+      return payload.message;
+    }
+  } catch {
+    // 非 JSON 错误响应使用通用提示。
+  }
+  return "PDF 导出失败";
+}
+
+export async function requestPdfExport(
+  request: PdfExportRequest,
+  fetcher: typeof fetch = fetch
+): Promise<PdfExportResult> {
+  const response = await fetcher("/api/pdf", {
+    method: "POST",
+    headers: {
+      "content-type": "application/json"
+    },
+    body: JSON.stringify(request)
+  });
+
+  if (!response.ok) {
+    throw new Error(await readErrorMessage(response));
+  }
+
+  return {
+    blob: await response.blob(),
+    fileName: parseContentDispositionFileName(
+      response.headers.get("content-disposition")
+    ),
+    pageCount: parseNumericHeader(
+      response.headers.get("x-pdf-page-count")
+    ),
+    mermaidErrorCount:
+      parseNumericHeader(
+        response.headers.get("x-mermaid-error-count")
+      ) ?? 0
+  };
+}
+
+export function downloadPdf(blob: Blob, fileName: string) {
+  const url = URL.createObjectURL(blob);
+  const anchor = document.createElement("a");
+  anchor.href = url;
+  anchor.download = fileName;
+  anchor.click();
+  window.setTimeout(() => URL.revokeObjectURL(url), 0);
+}