vector-im-hydrogen-web/scripts/build-plugins/service-worker.js

const path = require("path");
const xxhash = require("xxhashjs");

function contentHash(str) {
    var hasher = new xxhash.h32(0);
    hasher.update(str);
    return hasher.digest();
}

function injectServiceWorker(
    swFile,
    findUnhashedFileNamesFromBundle,
    placeholdersPerChunk
) {
    const swName = path.basename(swFile);
    let version;
    let logger;
    let mode;

    return {
        name: "hydrogen:injectServiceWorker",
        apply: "build",
        enforce: "post",

        buildStart() {
            this.emitFile({
                type: "chunk",
                fileName: swName,
                id: swFile,
            });
        },

        configResolved: (config) => {
            mode = config.mode;
            version = JSON.parse(config.define.DEFINE_VERSION); // unquote
            logger = config.logger;
        },

        generateBundle: async function (options, bundle) {
            const otherUnhashedFiles = findUnhashedFileNamesFromBundle(bundle);
            const unhashedFilenames = [swName].concat(otherUnhashedFiles);
            const unhashedFileContentMap = unhashedFilenames.reduce(
                (map, fileName) => {
                    const chunkOrAsset = bundle[fileName];
                    if (!chunkOrAsset) {
                        throw new Error(
                            "could not get content for uncached asset or chunk " +
                                fileName
                        );
                    }
                    map[fileName] = chunkOrAsset.source || chunkOrAsset.code;
                    return map;
                },
                {}
            );
            const assets = Object.values(bundle);
            const hashedFileNames = assets
                .map((o) => o.fileName)
                .filter((fileName) => !unhashedFileContentMap[fileName]);
            const globalHash = getBuildHash(
                hashedFileNames,
                unhashedFileContentMap
            );
            const placeholderValues = {
                DEFINE_GLOBAL_HASH: `"${globalHash}"`,
                ...getCacheFileNamePlaceholderValues(
                    swName,
                    unhashedFilenames,
                    assets,
                    mode
                ),
            };
            replacePlaceholdersInChunks(
                assets,
                placeholdersPerChunk,
                placeholderValues
            );
            logger.info(`\nBuilt ${version} (${globalHash})`);
        },
    };
}

function getBuildHash(hashedFileNames, unhashedFileContentMap) {
    const unhashedHashes = Object.entries(unhashedFileContentMap).map(
        ([fileName, content]) => {
            return `${fileName}-${contentHash(Buffer.from(content))}`;
        }
    );
    const globalHashAssets = hashedFileNames.concat(unhashedHashes);
    globalHashAssets.sort();
    return contentHash(globalHashAssets.join(",")).toString();
}

const NON_PRECACHED_JS = [
    "hydrogen-legacy",
    "olm_legacy.js",
    // most environments don't need the worker
    "main.js",
];

function isPreCached(asset) {
    const { name, fileName } = asset;
    return (
        name?.endsWith(".svg") ||
        name?.endsWith(".png") ||
        name?.endsWith(".css") ||
        name?.endsWith(".wasm") ||
        name?.endsWith(".html") ||
        // the index and vendor chunks don't have an extension in `name`, so check extension on `fileName`
        (fileName.endsWith(".js") &&
            !NON_PRECACHED_JS.includes(path.basename(name)))
    );
}

function getCacheFileNamePlaceholderValues(
    swName,
    unhashedFilenames,
    assets,
    mode
) {
    const unhashedPreCachedAssets = [];
    const hashedPreCachedAssets = [];
    const hashedCachedOnRequestAssets = [];

    if (mode === "production") {
        for (const asset of assets) {
            const { name, fileName } = asset;
            // the service worker should not be cached at all,
            // it's how updates happen
            if (fileName === swName) {
                continue;
            } else if (unhashedFilenames.includes(fileName)) {
                unhashedPreCachedAssets.push(fileName);
            } else if (isPreCached(asset)) {
                hashedPreCachedAssets.push(fileName);
            } else {
                hashedCachedOnRequestAssets.push(fileName);
            }
        }
    }

    return {
        DEFINE_UNHASHED_PRECACHED_ASSETS: JSON.stringify(
            unhashedPreCachedAssets
        ),
        DEFINE_HASHED_PRECACHED_ASSETS: JSON.stringify(hashedPreCachedAssets),
        DEFINE_HASHED_CACHED_ON_REQUEST_ASSETS: JSON.stringify(
            hashedCachedOnRequestAssets
        ),
    };
}

function replacePlaceholdersInChunks(
    assets,
    placeholdersPerChunk,
    placeholderValues
) {
    for (const [name, placeholderMap] of Object.entries(placeholdersPerChunk)) {
        const chunk = assets.find((a) => a.type === "chunk" && a.name === name);
        if (!chunk) {
            throw new Error(
                `could not find chunk ${name} to replace placeholders`
            );
        }
        for (const [placeholderName, placeholderLiteral] of Object.entries(
            placeholderMap
        )) {
            const replacedValue = placeholderValues[placeholderName];
            const oldCode = chunk.code;
            chunk.code = chunk.code.replaceAll(
                placeholderLiteral,
                replacedValue
            );
            if (chunk.code === oldCode) {
                throw new Error(
                    `Could not replace ${placeholderName} in ${name}, looking for literal ${placeholderLiteral}`
                );
            }
        }
    }
}

/** creates a value to be include in the `define` build settings,
 * but can be replace at the end of the build in certain chunks.
 * We need this for injecting the global build hash and the final
 * filenames in the service worker and index chunk.
 * These values are only known in the generateBundle step, so we
 * replace them by unique strings wrapped in a prompt call so no
 * transformation will touch them (minifying, ...) and we can do a
 * string replacement still at the end of the build. */
function definePlaceholderValue(mode, name, devValue) {
    if (mode === "production" || mode === "sdk") {
        // note that `prompt(...)` will never be in the final output, it's replaced by the final value
        // once we know at the end of the build what it is and just used as a temporary value during the build
        // as something that will not be transformed.
        // I first considered Symbol but it's not inconceivable that babel would transform this.
        return `prompt(${JSON.stringify(name)})`;
    } else {
        return JSON.stringify(devValue);
    }
}

/**
 * Returns the short sha for the latest git commit
 * @see https://stackoverflow.com/a/35778030
 */
function getLatestGitCommitHash() {
    try {
        return require("child_process")
            .execSync("git rev-parse --short HEAD")
            .toString()
            .trim();
    } catch {
        return "could_not_fetch_sha";
    }
}

function createPlaceholderValues(mode) {
    return {
        DEFINE_GLOBAL_HASH: definePlaceholderValue(
            mode,
            "DEFINE_GLOBAL_HASH",
            `git commit: ${getLatestGitCommitHash()}`
        ),
        DEFINE_UNHASHED_PRECACHED_ASSETS: definePlaceholderValue(
            mode,
            "UNHASHED_PRECACHED_ASSETS",
            []
        ),
        DEFINE_HASHED_PRECACHED_ASSETS: definePlaceholderValue(
            mode,
            "HASHED_PRECACHED_ASSETS",
            []
        ),
        DEFINE_HASHED_CACHED_ON_REQUEST_ASSETS: definePlaceholderValue(
            mode,
            "HASHED_CACHED_ON_REQUEST_ASSETS",
            []
        ),
    };
}

module.exports = { injectServiceWorker, createPlaceholderValues };