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archivist.js
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archivist.js
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import hasha from 'hasha';
import {URL} from 'url';
import path from 'path';
import args from './args.js';
import {context, sleep, DEBUG} from './common.js';
import {connect} from './protocol.js';
// cache is a simple map
// that holds the serialized requests
// that are saved on disk
const Cache = new Map();
const State = {
Cache
}
const Archivist = {
collect, getMode, changeMode
}
const NEVER_CACHE = new Set([
`http://localhost:${args.server_port}`,
`http://localhost:${args.chrome_port}`
]);
const CACHE_FILE = path.resolve(args.library_path, 'cache.json');
const TBL = /:\/\//g;
const HASH_OPTS = {algorithm: 'sha1'};
const UNCACHED_BODY = b64('We have not saved this data');
const UNCACHED_CODE = 404;
const UNCACHED_HEADERS = [
{ name: 'Content-type', value: 'text/plain' },
{ name: 'Content-length', value: '26' }
];
const UNCACHED = {
body:UNCACHED_BODY, responseCode:UNCACHED_CODE, responseHeaders:UNCACHED_HEADERS
}
let Fs, Mode, Close;
export default Archivist;
async function collect({chrome_port:port, mode} = {}) {
if ( context == 'node' ) {
const {default:fs} = await import('fs');
Fs = fs;
}
const {library_path} = args;
const {send, on, close} = await connect({port});
Close = close;
Mode = mode;
// send commands and listen to events
// so that we can intercept every request
// and cache it and if it's in cache then we
// can pause the request (so it does not go to network)
// and serve from cache
// effectively off-lining the site
// question
// can we attach to browser target and catch everything
// or do we need to handle sessions ?
let requestStage;
try {
if ( !Fs.existsSync(CACHE_FILE) ) {
console.log(`Cache file does not exist, creating...`);
Fs.writeFileSync(CACHE_FILE, JSON.stringify([]));
console.log(`Created!`);
}
State.Cache = new Map(JSON.parse(Fs.readFileSync(CACHE_FILE)));
} catch(e) {
DEBUG && console.warn(e);
State.Cache = new Map();
}
if ( Mode == 'save' ) {
requestStage = "Response";
process.on('SIGINT', () => {
saveCache();
process.exit(0);
});
setInterval(saveCache, 10000);
} else if ( Mode == 'serve' ) {
requestStage = "Request";
DEBUG && console.log(State.Cache);
} else {
throw new TypeError(`Must specify mode`);
}
send("Fetch.enable", {
patterns: [
{
urlPattern: "http*://*",
requestStage
}
]
});
on("Fetch.requestPaused", cacheRequest);
async function cacheRequest(pausedRequest) {
const {requestId, request, responseStatusCode, responseHeaders} = pausedRequest;
if ( dontCache(request) ) {
DEBUG && console.log("Not caching", request);
return send("Fetch.continueRequest", {requestId});
}
const key = serializeRequest(request);
if ( Mode == 'serve' ) {
if ( State.Cache.has(key) ) {
let {body, responseCode, responseHeaders} = await getResponseData(State.Cache.get(key));
responseCode = responseCode || 200;
DEBUG && console.log("Fulfilling", key, responseCode, responseHeaders, body.slice(0,140));
await send("Fetch.fulfillRequest", {
requestId, body, responseCode, responseHeaders
});
} else {
DEBUG && console.log("Sending cache stub", key);
await send("Fetch.fulfillRequest", {
requestId, ...UNCACHED
});
}
} else if ( Mode == 'save' ) {
if ( responseStatusCode == 302 ) {
return send("Fetch.continueRequest", {requestId});
}
const response = {key, responseCode: responseStatusCode, responseHeaders};
let resp = await send("Fetch.getResponseBody", {requestId});
if ( ! resp ) {
DEBUG && console.warn("get response body error", key, responseStatusCode, responseHeaders, pausedRequest.responseErrorReason);
return send("Fetch.continueRequest", {requestId});
}
if ( !! resp ) {
let {body, base64Encoded} = resp;
if ( ! base64Encoded ) {
body = b64(body);
}
response.body = body;
} else {
response.body = '';
}
const responsePath = await saveResponseData(key, request.url, response);
State.Cache.set(key, responsePath);
await send("Fetch.continueRequest", {requestId});
}
}
function dontCache(request) {
const origin = new URL(request.url).origin;
return NEVER_CACHE.has(origin);
}
async function getResponseData(path) {
try {
return JSON.parse(await Fs.promises.readFile(path));
} catch(e) {
console.warn(`Error with ${path}`, e);
return UNCACHED;
}
}
async function saveResponseData(key, url, response) {
const origin = (new URL(url).origin);
let originDir = State.Cache.get(origin);
if ( ! originDir ) {
originDir = path.resolve(library_path, origin.replace(TBL, '_'));
try {
await Fs.promises.mkdir(originDir, {recursive:true});
} catch(e) {
console.warn(`Issue with origin directory ${path.dirname(responsePath)}`, e);
}
State.Cache.set(origin, originDir);
}
const fileName = `${await hasha(key, HASH_OPTS)}.json`;
const responsePath = path.resolve(originDir, fileName);
await Fs.promises.writeFile(responsePath, JSON.stringify(response));
return responsePath;
}
function serializeRequest(request) {
const {url, urlFragment, method, headers, postData, hasPostData} = request;
/**
let sortedHeaders = '';
for( const key of Object.keys(headers).sort() ) {
sortedHeaders += `${key}:${headers[key]}/`;
}
**/
return `${method}${url}`;
//return `${url}${urlFragment}:${method}:${sortedHeaders}:${postData}:${hasPostData}`;
}
}
function getMode() { return Mode; }
async function changeMode(mode) {
DEBUG && console.log({modeChange:mode});
saveCache();
Close && Close();
Mode = mode;
await collect({chrome_port:args.chrome_port, mode});
}
function saveCache() {
if ( context == 'node' ) {
Fs.writeFileSync(CACHE_FILE, JSON.stringify([...State.Cache.entries()]));
}
}
function b64(s) {
if ( context == 'node' ) {
return Buffer.from(s).toString('base64');
} else {
return btoa(s);
}
}