feat: give bin ability to output svg files, closes #2

bin/threatdown.ts

@@ -6,6 +6,7 @@ import { parseArgs } from "node:util";
 import {
   parse,
   compileToMermaid,
+  renderMermaid,
 } from "../lib";
 
 const {
@@ -20,6 +21,7 @@ const {
     },
     outputType: {
       type: "string",
+      alias: "type",
       short: "t",
       default: "mermaid",
     },
@@ -34,11 +36,11 @@ function usage () {
 `);
 }
 
-function main () {
+async function main () {
   const inputFile = positionals.shift();
   // non-null assertion safe because the outputType has a default
   // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-  if (!inputFile || !["json", "mermaid"].includes(values.outputType!)) {
+  if (!inputFile || !["json", "mermaid", "svg"].includes(values.outputType!)) {
     usage();
   } else {
     const fileContent = readFileSync(resolve(process.cwd(), inputFile), { encoding: "utf8" });
@@ -59,8 +61,22 @@ function main () {
       } else {
         console.log(mermaidContent);
       }
+      return;
+    }
+
+    const svgContent = await renderMermaid(mermaidContent);
+    if (values.outputType === "svg") {
+      if (values.output) {
+        writeFileSync(resolve(process.cwd(), values.output), svgContent);
+      } else {
+        console.log(svgContent);
+      }
     }
   }
 }
 
-main();
+main()
+  .catch((err: Error) => {
+    process.exitCode = 1;
+    console.error(err.stack);
+  });

lib/index.ts

@@ -1,2 +1,3 @@
 export { parse } from "./parser";
 export { compileToMermaid } from "./compiler";
+export { renderMermaid } from "./renderer";

lib/renderer.ts

@@ -0,0 +1,31 @@
+import { spawn } from "node:child_process";
+import { readFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+export async function renderMermaid (contents: string): Promise<string> {
+  const tmpOutput = join(tmpdir(), `.threatdown-${Date.now()}.svg`);
+
+  let resolve: (value?: unknown) => void;
+  let reject: (err: Error) => void;
+  const p = new Promise((_resolve, _reject) => {
+    resolve = _resolve;
+    reject = _reject;
+  });
+
+  const mmdc = spawn("mmdc", ["--input", "-", "--output", tmpOutput], { stdio: "pipe" });
+
+  mmdc.on("error", (err: Error) => {
+    reject(err);
+  });
+
+  mmdc.on("close", () => {
+    resolve();
+  });
+
+  mmdc.stdin.end(contents);
+  await p;
+
+  const rendered = await readFile(tmpOutput, { encoding: "utf8" });
+  return rendered;
+}

package.json

@@ -53,5 +53,8 @@
     "lib/**/*.js",
     "lib/**/*.d.ts",
     "!lib/types/**"
-  ]
+  ],
+  "dependencies": {
+    "mermaid-cli": "^0.2.4"
+  }
 }