Add indexing API docs

Author: anttiai

README.md

@@ -7,7 +7,7 @@ with JavaScript on web browsers or from Node.js.
 ## Quick Start
 The library is available on the global CDN [jsDelivr:](https://www.jsdelivr.com/package/npm/addsearch-js-client)
 ```html
-<script src="https://cdn.jsdelivr.net/npm/addsearch-js-client@0.4/dist/addsearch-js-client.min.js"></script>
+<script src="https://cdn.jsdelivr.net/npm/addsearch-js-client@0.5/dist/addsearch-js-client.min.js"></script>
 ```
 Or install the library locally to use it with Node.js:
 ```sh
@@ -40,9 +40,10 @@ var cb = function(res) {
 client.search('keyword', cb);
 ```
 
-## Publicly accessible functions
+## Search API
 
-The client provides the following functions.
+The client provides following functions to execute search queries. To use the client library for indexing, 
+see [Indexing API](https://github.com/AddSearch/js-client-library#indexing-api) section.
 
 #### Fetch search results
 ```js
@@ -305,14 +306,177 @@ client.setJWT(token);
 client.setThrottleTime(500);
 ```
 
+## Indexing API
+The Indexing API allows for retrieving documents, creating documents, updating single documents and batches of 
+documents, as well as deleting single documents and batches of documents.
+
+Following indexing API functions are meant to be used in Node.js. Never expose your
+secret key in your website code.
+
+```js
+// Create client with your 32-character keys
+var client = new AddSearchClient('YOUR PUBLIC SITEKEY', 'YOUR SECRET KEY');
+```
+
+The secret key can be found from AddSearch Dashboard's "Setup" > "Keys and installation" page.
+Always keep the key secret.
+
+Indexing API functions return promises.
+
+
+### Document ID
+
+Document ID can be defined by the user, or it can be autogenerated when a document is added to the index.
+
+```js
+// ID defined by the user
+const doc = {
+  id: '1234',
+  ...
+}
+
+// ID created from the URL field (md5 sum)
+const doc = {
+  url: 'https://..', // id will be md5('https://..')
+  ...
+}
+
+// ID will be generated automatically
+const doc = {
+  // No id or url fields
+  ...
+}
+```
+
+
+### Document structure
+Documents have schemaless data structures. Data fields should be defined under custom_fields key.
+
+```js
+// Create client with your 32-character keys
+const doc = {
+  id: '1234',
+  custom_fields: {
+    'name': 'Example product',
+    'description': 'Description for example product',
+    'price_cents': 599,
+    'average_customer_rating': 4.5,
+    'release_date': 1589200255
+  }
+}
+```
+
+Data types for custom fields are automatically detected from the content. Supported data types are:
+
+- text
+- integer
+- double
+
+Dates should be defined as UNIX timestamps with integer values.
+
+
+### Save document
+Add or update a document in the index.
+
+```js
+const doc = {
+  id: '1234',
+  custom_fields: {
+    'name': 'Example product'
+  }
+};
+
+// Save document
+client.saveDocument(doc)
+  .then(response => {
+    console.log(response);
+  })
+  .catch(error => {
+    console.log(error);
+  });
+```
+
+
+### Get document by ID
+```js
+client.getDocument(id)
+  .then(response => {
+    console.log(response);
+  })
+  .catch(error => {
+    console.log(error);
+  });
+```
+
+
+### Delete document by ID
+```js
+client.deleteDocument(id)
+  .then(response => {
+    console.log(response);
+  })
+  .catch(error => {
+    console.log(error);
+  });
+```
+
+
+### Save batch of documents
+```js
+const batch = {
+  documents: [
+    {
+      id: '1234',
+      custom_fields: {
+        'name': 'Product 1'
+      }
+    },
+    {
+      id: '5678',
+      custom_fields: {
+        'name': 'Product 2'
+      }
+    }
+  ]
+};
+
+// Save batch of documents
+client.saveDocumentsBatch(batch)
+  .then(response => {
+    console.log(response);
+  })
+  .catch(error => {
+    console.log(error);
+  });
+```
+
+
+### Delete batch of documents
+```js
+// Array of document IDs
+const batch = {
+  documents: ["1234", "5678"]
+};
+
+// Delete batch of documents
+client.deleteDocumentsBatch(batch)
+  .then(response => {
+    console.log(response);
+  })
+  .catch(error => {
+    console.log(error);
+  });
+```
+
+
 ## Supported web browsers and node.js versions
 The client is tested on
 - Chrome
 - Firefox
 - Edge
 - Safari 6.1+
 - Internet Explorer 10+
-- Node.js 4+
+- Node.js
 
 
 ## Development