To use the Config file, one needs to give the fully qualified path to the configuration file

For example: Config.load(/user/bin/example/xyz.txt, "production", "staging");

Config class uses HashMap of HashMap and returns the Config object which can be called by calling get(String key) method to fetch the values. It will return null if can't find a valid configuration value for the given set of overrides.

Assumptions:

1. Only those configuration values are persisted which are in the override
2. Sequential processing of the configuration file ensures the override will happen on the last seen value.
3. Configuration file size with valid configuration key value pairs for a system are within the memory limit.
4. Integers and Strings at the moment are treated as same.
5. A String is defined if it starts with ' “ ' and ends with ' ” '
6. An array is defined as the value which is not a string and has a ',' in it.
7. Default values are overridden by the overrides and if there are two overrides present for the same key than the last seen one is picked up.
8. For boolean values it returns what is mentioned in the configuration file which could be yes, no, true or false, 0 or 1
9. For all the queries after pre-processing, access time is O(1);
10. Incorrect entries in the configuration files are ignored at the moment.
11. Returns null for any configuration key which cannot be found.
12. For section details without a valid section, error is thrown.

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Configuration Loader Every large software project has its share of configuration files to control settings, execution, etc. Let’s contemplate a config file format that looks a lot like standard PHP .ini files, but with a few tweaks. A config file will appear as follows: [common] basic_size_limit = 26214400 student_size_limit = 52428800 paid_users_size_limit = 2147483648 path = /srv/var/tmp/ path = /srv/tmp/ [ftp] name = “hello there, ftp uploading” path = /tmp/ path = /srv/var/tmp/ path = /srv/uploads/ path = /etc/var/uploads enabled = no ; This is a comment [http] name = “http uploading” path = /tmp/ path = /srv/var/tmp/ path = /srv/uploads/; This is another comment params = array,of,values Where ● “[group]” denotes the start of a group of related config options ● “setting = value“ denotes a standard setting name and associated default value ● “setting = value2” denotes the value for the setting if the given override is enabled ● If multiple enabled overrides are defined on a setting, the one defined last will have priority.

Objective: To write a function that parses this format and returns an object that can be queried for “group.variable” or “group”.

• Note that overrides can be passed as String array A sample in java would be: Config conf = Config.load(“/path/to/config_file”, new String(){“ubuntu”, “production” })

Config.get(“common.paid_users_size_limit”);

returns 2147483648

Config.get("ftp.name”);

returns “hello there, ftp uploading”

Config.get("http.params”)

returns [“array”, “of”, “values”]

Config.get("ftp.lastname”);

returns null

Config.get("ftp.enabled”);

returns false (permitted bool values are “yes”, “no”, “true”,

“false”, 1, 0)

Config.get("ftp.path”);

returns “/etc/var/uploads”

Config.get("ftp

returns a symbolized hashmap:

{ “name” == “http uploading”, “path” == “/etc/var/uploads”, “enabled” == false }

Design Considerations

1. Config.load() will be called at boot time, and thus should be as fast as possible. Conf files can get quite lengthy there can be an arbitrary number of groups and number of settings within each group.
2. Config.get() will be queried throughout the program’s execution, so each query should be very fast as well.
3. Certain queries will be made very often (thousands of times), others pretty rarely.
4. If the conf file is not well formed, it is acceptable to print an error and exit from within Config.load(). Once the object is returned, however, it is not permissible to exit or crash no matter what the query is. Returning NULL/NIL is acceptable.