refactor: add utility to access deep object properties

lib/Utils.js

@@ -3,6 +3,54 @@
 const Fs = require('fs');
 const Crypto = require('crypto');
 const UserAgent = require('user-agents');
+const Flatten = require('flat');
+
+function InnertubeError(message, info) {
+  this.info = info; 
+  this.stack = Error(message).stack; 
+}  
+
+InnertubeError.prototype = Object.create(Error.prototype);  
+InnertubeError.prototype.constructor = InnertubeError;
+
+class ParsingError extends InnertubeError {};
+class DownloadError extends InnertubeError {};
+class MissingParamError extends InnertubeError {};
+class UnavailableContentError extends InnertubeError {};
+class NoStreamingDataError extends InnertubeError {};
+
+/**
+ * Utility to help access deep properties of an object.
+ * 
+ * @param {object} obj - The object.
+ * @param {string} key - Key of the property being accessed.
+ * @param {string} target - Anything that might be inside of the property.
+ * @param {number} depth - Maximum number of nested objects to flatten.
+ * @param {boolean} safe - If set to true arrays will be preserved.
+ */
+function findNode (obj, key, target, depth, safe = true) {
+  const flat_obj = Flatten(obj, { safe, maxDepth: depth || 2 });
+  const result = Object.keys(flat_obj).find((entry) => entry.includes(key) && JSON.stringify(flat_obj[entry] || '{}').includes(target));
+  if (!result) throw new ParsingError(`Expected to find "${key}" with content "${target}" but got ${result}`, { key, target, data_snippet: `${JSON.stringify(flat_obj).slice(0, 300)}..` });
+  return flat_obj[result];
+}
+
+/**
+ * Gets a string between two delimiters.
+ *
+ * @param {string} data - The data.
+ * @param {string} start_string - Start string.
+ * @param {string} end_string - End string.
+ */
+function getStringBetweenStrings(data, start_string, end_string) {
+  const regex = new RegExp(`${escapeStringRegexp(start_string)}(.*?)${escapeStringRegexp(end_string)}`, 's');
+  const match = data.match(regex);
+  return match ? match[1] : undefined;
+}
+
+function escapeStringRegexp(string) {
+  return string.replace(/[|\\{}()[\]^$+*?.]/g, "\\$&").replace(/-/g, "\\x2d");
+}
 
 /**
  * Returns a random user agent.
@@ -38,23 +86,6 @@ function generateSidAuth(sid) {
   return ['SAPISIDHASH', [timestamp, gen_hash].join('_')].join(' ');
 }
 
-/**
- * Gets a string between two delimiters.
- *
- * @param {string} data - The data.
- * @param {string} start_string - Start string.
- * @param {string} end_string - End string.
- */
-function getStringBetweenStrings(data, start_string, end_string) {
-  const regex = new RegExp(`${escapeStringRegexp(start_string)}(.*?)${escapeStringRegexp(end_string)}`, "s");
-  const match = data.match(regex);
-  return match ? match[1] : undefined;
-}
-
-function escapeStringRegexp(string) {
-  return string.replace(/[|\\{}()[\]^$+*?.]/g, "\\$&").replace(/-/g, "\\x2d");
-}
-
 /**
  * Converts time (h:m:s) to seconds.
  * 
@@ -96,4 +127,7 @@ function refineNTokenData(data) {
     .replace(/""/g, '').replace(/length]\)}"/g, 'length])}');
 }
 
-module.exports = { getRandomUserAgent, generateSidAuth, getStringBetweenStrings, camelToSnake, timeToSeconds, refineNTokenData };
+const errors = { UnavailableContentError, ParsingError, DownloadError, InnertubeError, MissingParamError, NoStreamingDataError };
+const functions = { findNode, getRandomUserAgent, generateSidAuth, getStringBetweenStrings, camelToSnake, timeToSeconds, refineNTokenData };
+
+module.exports = { ...functions, ...errors };