Data store coding test

Introduction

Your task is to implement a simple data store with JSON-like structure, e.g.:

{
    foo: {
        bar: {
            baz: 42
        },
        hello: 'world'
    }
}

The data store interface is specified in src/dataStore.ts and it consists of 3 asynchronous methods:

• read(path: string) - should return a Promise with data located at path. Path is a concatenated list of keys separated with ., for example foo.bar.baz references data located at key baz of object bar nested in object foo. Duplicated . should not matter. If there's no value at path the method should return Promise with undefined.

• write(path: string, value: StoredValue) - should write value at given path. Value could be a primitive value (string, number, boolean), an object (with primitive values or other objects) or an undefined value. If path doesn't exist yet in the store it should be created. Writing at root path (empty string or .) should not be allowed.

• observe(path: string, callback: ObserverCallback) - should register a callback that will be called every time the value at path or any sub-paths is modified. It should be also called immediately after registering with the current value. For example if observer is registered for foo.bar path and later foo.bar.baz value is written the callback should be called.

For example, given the data structure shown above we should expect the following results:

• read('foo.bar.baz') // 42
• read('foo.bar') // { baz: 42 }
• write('foo.bar', 'test'); read('foo') // { bar: 'test', hello: 'world' }

Implementation

There are three classes to be implemented:

• InMemoryStore - should keep the data in-memory.
• FileStore - should read and write the data to file.
• TypedStore - read should return values with types depending on provided schema

Tests

There are ordered test files in tests/ folder, we strongly suggest that you fix them one by one:

1. 01.read.test - tests read method of InMemoryStore
2. 02.write.test - tests write method of InMemoryStore
3. 03.observe.test - tests observe method of InMemoryStore
4. 04.file.test - tests reading and saving to file by FileStore
5. 05.typed.test - tests checking if types returned by TypedStore are correct