setupHeaders.js

const { join } = require("path");
const { existsSync, readFileSync, writeFileSync } = require("fs-extra");
const { logTitle, logItem } = require("../helpers/logger");
const { CUSTOM_HEADERS_PATH } = require("../config");

// Setup _headers file to override specific header rules for next assets
const setupHeaders = (publishPath) => {
  logTitle("🔀 Setting up headers");

  // Collect custom redirects defined by the user
  const headers = [];
  if (existsSync(CUSTOM_HEADERS_PATH)) {
    logItem("# Prepending custom headers");
    headers.push(readFileSync(CUSTOM_HEADERS_PATH, "utf8"));
  }

  // Add NoN section heading
  headers.push("# Next-on-Netlify Headers");

  // Add rule to override cache control for static chunks
  const indentNewLine = (s) => `\n  ${s}`;
  const staticChunkRule = [
    `/*/_next/static/chunks/*`,
    indentNewLine(`cache-control: public`),
    indentNewLine(`cache-control: max-age=31536000`),
    indentNewLine(`cache-control: immutable`),
  ].join("");
  headers.push(staticChunkRule);

  // Write redirects to _redirects file
  writeFileSync(join(publishPath, "_headers"), headers.join("\n"));
};

module.exports = setupHeaders;