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import { existsSync } from 'node:fs';
import { join } from 'node:path';
import { fileURLToPath, pathToFileURL } from 'node:url';
import { ASTRO_LOCALS_HEADER } from './adapter.js';
/**
* It generates the Vercel Edge Middleware file.
*
* It creates a temporary file, the edge middleware, with some dynamic info.
*
* Then this file gets bundled with esbuild. The bundle phase will inline the Astro middleware code.
*
* @param astroMiddlewareEntryPoint
* @param outPath
* @returns {Promise<URL>} The path to the bundled file
*/
export async function generateEdgeMiddleware(
astroMiddlewareEntryPointPath: URL,
outPath: string,
vercelEdgeMiddlewareHandlerPath: URL
): Promise<URL> {
const entryPointPathURLAsString = JSON.stringify(
fileURLToPath(astroMiddlewareEntryPointPath).replace(/\\/g, '/')
);
const code = edgeMiddlewareTemplate(entryPointPathURLAsString, vercelEdgeMiddlewareHandlerPath);
// https://vercel.com/docs/concepts/functions/edge-middleware#create-edge-middleware
const bundledFilePath = join(outPath, 'middleware.mjs');
const esbuild = await import('esbuild');
await esbuild.build({
stdin: {
contents: code,
resolveDir: process.cwd(),
},
target: 'es2020',
platform: 'browser',
// https://runtime-keys.proposal.wintercg.org/#edge-light
conditions: ['edge-light', 'worker', 'browser'],
external: ['astro/middleware'],
outfile: bundledFilePath,
allowOverwrite: true,
format: 'esm',
bundle: true,
minify: false,
});
return pathToFileURL(bundledFilePath);
}
function edgeMiddlewareTemplate(middlewarePath: string, vercelEdgeMiddlewareHandlerPath: URL) {
const filePathEdgeMiddleware = fileURLToPath(vercelEdgeMiddlewareHandlerPath);
let handlerTemplateImport = '';
let handlerTemplateCall = '{}';
if (existsSync(filePathEdgeMiddleware + '.js') || existsSync(filePathEdgeMiddleware + '.ts')) {
const stringified = JSON.stringify(filePathEdgeMiddleware.replace(/\\/g, '/'));
handlerTemplateImport = `import handler from ${stringified}`;
handlerTemplateCall = `handler({ request, context })`;
} else {
}
return `
${handlerTemplateImport}
import { onRequest } from ${middlewarePath};
import { createContext, trySerializeLocals } from 'astro/middleware';
export default async function middleware(request, context) {
const url = new URL(request.url);
const ctx = createContext({
request,
params: {}
});
ctx.locals = ${handlerTemplateCall};
const next = async () => {
const response = await fetch(url, {
headers: {
${JSON.stringify(ASTRO_LOCALS_HEADER)}: trySerializeLocals(ctx.locals)
}
});
return response;
};
return onRequest(ctx, next);
}`;
}
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