feat: support for stdin and stdout

README.md

@@ -28,6 +28,19 @@ Options:
   --stylesheet   Set CSS file path used for rendering.
 ```
 
+### `stdin` / `stdout` Support
+
+md2pdf supports reading from `stdin` and writing to `stdout`.\
+You can pipe markdown content directly to md2pdf, making it easy to integrate with other CLI tools:
+
+```sh
+# Convert piped input to PDF
+cat input.md | md2pdf > path/to/output.pdf
+
+# Use with curl to convert remote markdown
+curl -s https://raw.githubusercontent.com/ryuapp/md2pdf/main/README.md | md2pdf > README.pdf
+```
+
 ## Front matter (Experimental)
 
 We can specify CSS file used in the front matter of markdown.

src/animation.ts

@@ -36,7 +36,7 @@ export function createWaveAnimation(
     }
 
     const encoder = new TextEncoder();
-    Deno.stdout.writeSync(encoder.encode(`\r${coloredText}`));
+    Deno.stderr.writeSync(encoder.encode(`\r${coloredText}`));
     frame++;
   };
 
@@ -51,7 +51,7 @@ export function createWaveAnimation(
         clearInterval(intervalId);
         intervalId = null;
         const encoder = new TextEncoder();
-        Deno.stdout.writeSync(
+        Deno.stderr.writeSync(
           encoder.encode(`\r${" ".repeat(fullText.length + 2)}\r`),
         );
       }

src/cli.ts

@@ -20,10 +20,12 @@ import {
   underline,
   yellow,
 } from "@std/fmt/colors";
-import { mdToPdf } from "./md-to-pdf.ts";
-import { getFilename } from "./utils/filename.ts";
 import { createWaveAnimation } from "./animation.ts";
-import type { MdToPdfOptions } from "./types.ts";
+import {
+  generatePdfFromMarkdown,
+  generatePdfFromStdin,
+} from "./generate-pdf.ts";
+import { getFilename } from "./utils/filename.ts";
 import denoJson from "../deno.json" with { type: "json" };
 
 function printHelp(): void {
@@ -41,23 +43,6 @@ ${yellow("Options:")}
   console.log(help);
 }
 
-async function generatePdfFromMarkdown(path: string, options?: MdToPdfOptions) {
-  const pdfName = getFilename(path) + ".pdf";
-
-  const waveAnimation = createWaveAnimation("generating PDF from", path);
-  waveAnimation.start();
-  await mdToPdf(path, options).then(
-    (pdf) => {
-      Deno.writeFileSync(
-        pdfName,
-        pdf,
-      );
-      waveAnimation.stop();
-      console.log(green("✓") + " generated " + underline(pdfName));
-    },
-  );
-}
-
 // Inline
 
 const args = parseArgs(Deno.args, {
@@ -75,6 +60,16 @@ if (args.h || args.help) {
   Deno.exit(0);
 }
 
+// Check if input is piped
+if (!Deno.stdin.isTerminal()) {
+  // Handle piped input - output to stdout
+  const waveAnimation = createWaveAnimation("generating PDF from", "stdin");
+  waveAnimation.start();
+  await generatePdfFromStdin(args);
+  waveAnimation.stop();
+  Deno.exit(0);
+}
+
 const paths: Array<string> = [];
 if (args._) {
   for await (const path of args._) {
@@ -98,6 +93,7 @@ if (paths.length < 1) {
         brightRed("error")
       }: Set a valid markdown file path you wanna convert to PDF\n`,
       "      e.g.) md2pdf README.md\n",
+      "      e.g.) cat README.md | md2pdf\n",
     );
     console.error("For more information, try '--help'.");
   } else {
@@ -108,7 +104,12 @@ if (paths.length < 1) {
 
 await (async () => {
   for (let i = 0; i < paths.length; i++) {
-    await generatePdfFromMarkdown(paths[i], args);
+    const pdfPath = getFilename(paths[i]) + ".pdf";
+    const waveAnimation = createWaveAnimation("generating PDF from", paths[i]);
+    waveAnimation.start();
+    await generatePdfFromMarkdown(paths[i], pdfPath, args);
+    waveAnimation.stop();
+    console.log(green("✓") + " generated " + underline(pdfPath));
   }
 })();
 
@@ -129,7 +130,15 @@ if (args.w || args.watch) {
       ) {
         pastRealPath = realPath;
         pastMTime = stat.mtime?.toString();
-        await generatePdfFromMarkdown(paths[0], args);
+        const pdfPath = getFilename(paths[0]) + ".pdf";
+        const waveAnimation = createWaveAnimation(
+          "generating PDF from",
+          paths[0],
+        );
+        waveAnimation.start();
+        await generatePdfFromMarkdown(paths[0], pdfPath, args);
+        waveAnimation.stop();
+        console.log(green("✓") + " generated " + underline(pdfPath));
       }
     }
   }

src/generate-pdf.ts

@@ -0,0 +1,76 @@
+import { join } from "@std/path";
+import { brightRed } from "@std/fmt/colors";
+import { mdToPdf } from "./md-to-pdf.ts";
+import type { MdToPdfOptions } from "./types.ts";
+
+export async function generatePdfFromMarkdown(
+  markdownPath: string,
+  pdfPath: string,
+  options?: MdToPdfOptions,
+) {
+  await mdToPdf(markdownPath, options).then(
+    (pdf) => {
+      Deno.writeFileSync(
+        pdfPath,
+        pdf,
+      );
+    },
+  );
+}
+
+export async function generatePdfFromStdin(options?: MdToPdfOptions) {
+  const chunks: Uint8Array[] = [];
+  const reader = Deno.stdin.readable.getReader();
+
+  try {
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) break;
+      chunks.push(value);
+    }
+  } finally {
+    reader.releaseLock();
+  }
+
+  const markdownContent = new TextDecoder().decode(
+    new Uint8Array(
+      chunks.reduce((acc, chunk) => [...acc, ...chunk], [] as number[]),
+    ),
+  );
+
+  // Create temporary file using Deno's standard approach
+  const tempDir = await Deno.makeTempDir();
+  const tempPath = join(tempDir, "stdin.md");
+  // Cleanup
+  const cleanupTempDir = () => {
+    try {
+      Deno.removeSync(tempDir, { recursive: true });
+    } catch (error) {
+      console.error(
+        `${brightRed("warning")}: Failed to cleanup temp directory: ${error}`,
+      );
+    }
+  };
+  // Setup cleanup on SIGINT (Ctrl+C) and SIGBREAK (Ctrl + Break)
+  const signalHandler = () => {
+    console.debug("Called Signal Handler");
+    cleanupTempDir();
+    Deno.exit(1);
+  };
+
+  Deno.addSignalListener("SIGINT", signalHandler);
+  Deno.addSignalListener("SIGBREAK", signalHandler);
+  await Deno.writeTextFile(tempPath, markdownContent);
+
+  try {
+    await mdToPdf(tempPath, options).then(
+      (pdf) => {
+        Deno.stdout.writeSync(pdf);
+      },
+    );
+  } finally {
+    Deno.removeSignalListener("SIGINT", signalHandler);
+    Deno.removeSignalListener("SIGBREAK", signalHandler);
+    cleanupTempDir();
+  }
+}