feat: LLM context file builder

plugins/vite-plugin-llms-txt.ts

@@ -0,0 +1,105 @@
+/**
+ * Vite plugin for generating llms.txt
+ *
+ * Generates an llms.txt file at build time that describes the Malloy models
+ * and schema to help LLMs understand the data explorer site.
+ *
+ * In dev mode, serves llms.txt dynamically via middleware.
+ */
+
+import type { Plugin, ResolvedConfig, ViteDevServer } from "vite";
+import * as fs from "node:fs/promises";
+import * as path from "node:path";
+import {
+  extractModelsSchema,
+  getDataFiles,
+  getNotebooks,
+  generateLlmsTxtContent,
+} from "../src/llms-txt";
+
+export interface LlmsTxtPluginOptions {
+  siteTitle?: string;
+  modelsDir?: string;
+}
+
+export default function llmsTxtPlugin(
+  options: LlmsTxtPluginOptions = {},
+): Plugin {
+  const { siteTitle = "Malloy Data Explorer", modelsDir = "models" } = options;
+
+  let config: ResolvedConfig;
+
+  async function generateContent(): Promise<string> {
+    const modelsDirPath = path.join(config.root, modelsDir);
+
+    const [models, dataFiles, notebooks] = await Promise.all([
+      extractModelsSchema(modelsDirPath),
+      getDataFiles(modelsDirPath),
+      getNotebooks(modelsDirPath),
+    ]);
+
+    return generateLlmsTxtContent({
+      siteTitle,
+      basePath: config.base,
+      models,
+      dataFiles,
+      notebooks,
+    });
+  }
+
+  return {
+    name: "vite-plugin-llms-txt",
+
+    configResolved(resolvedConfig) {
+      config = resolvedConfig;
+    },
+
+    // DEV MODE: Serve llms.txt dynamically
+    configureServer(server: ViteDevServer) {
+      server.middlewares.use((req, res, next) => {
+        if (req.url === "/llms.txt") {
+          void (async () => {
+            try {
+              // Regenerate on each request in dev mode for hot reloading
+              const content = await generateContent();
+              res.setHeader("Content-Type", "text/plain; charset=utf-8");
+              res.end(content);
+            } catch (error) {
+              console.error("[llms.txt] Error generating content:", error);
+              res.statusCode = 500;
+              res.end(
+                `Error generating llms.txt: ${error instanceof Error ? error.message : String(error)}`,
+              );
+            }
+          })();
+          return;
+        }
+        next();
+      });
+    },
+
+    // BUILD MODE: Generate file after bundle
+    async closeBundle() {
+      if (process.env["VITEST"] || process.env["NODE_ENV"] === "test") {
+        return;
+      }
+      if (config.command !== "build") return;
+
+      try {
+        const content = await generateContent();
+
+        const outputPath = path.join(
+          config.root,
+          config.build.outDir,
+          "llms.txt",
+        );
+        await fs.writeFile(outputPath, content, "utf-8");
+
+        console.log(`[llms.txt] Generated ${outputPath}`);
+      } catch (error) {
+        console.error("[llms.txt] Error generating file:", error);
+        throw error;
+      }
+    },
+  };
+}