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         /Title (Integrating Instamojo)
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\title{Integrating Instamojo}
\date{\today \\Version 1.2}
\hyphenation{Instamojo}

\begin{document}
\maketitle

\tableofcontents

\newpage
\section{Introduction}
\paragraph{}
This document guides you through the process of creating a tighter integration
between your web-application and Instamojo.

Should you have any questions about what the most appropriate workflow is for
you or for your customers, please feel free to call us at
\href{tel:+918880110011}{+91-8880-110-011} or email us at
\href{mailto:support@instamojo.com}{support@instamojo.com}.

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\section{Basic features}

\paragraph{}
There are several ways for you and your customers to interact with
\mbox{Instamojo}. The simplest way is for you to create and share an Instamojo
link with your customers.

\paragraph{}
Instamojo links support a host of very powerful features. \uline{Please review
and take advantage of these features before considering our more advanced
features}, described in the next section.

\begin{description}
\item[Smart descriptions] The description section of your payment link supports
a subset\footnote{Not all features of Markdown are supported. In particularly,
any HTML or Javascript added will be removed} of Markdown\footnote{Syntax:
\url{http://daringfireball.net/projects/markdown/syntax}}, that allows you to
add beautiful formatting to the text you add. Also, if you add a link to media
content from selected popular rich media sites\footnote{This includes services
like Youtube, Flickr, Vimeo, Slideshare, Scribd, Instagram, SoundCloud, Twitter
and many more} on its own line, the link is automatically converted into an
embed.  No need to fumble around and search for embed code.

Example:  \url{https://www.instamojo.com/instamojo/integration-documentation/}
\item[Custom fields] These allow you to specify extra fields of data that you
would like your user to enter during the checkout process. The default fields
available in a payment link are the name, the email address and the phone
number of the buyer. You may request for more information, such as the company
name, age, etc. according to your needs.

Example: \url{https://www.instamojo.com/demo/demo-custom-fields/}
\item[Discount codes] These allow you to provide some of your users with
discount codes. You have the option to render a discount code box on your
payment link where users can enter their code manually (Eg:
\url{https://www.instamojo.com/demo/demo-payment-features/}) or,
you can share a link with a discount directly with your users (Eg:
\url{https://www.instamojo.com/demo/demo-payment-features/?discount=off15}).
\item[Variants] If you have multiple variants/tiers/options/colours of the same
product or service that you're selling, you don't need to create individual
links for each of them. You can add these variants to the same Instamojo link.
You can specify limits to the quantity of each variant being sold, if you
choose.

Example: \url{https://www.instamojo.com/demo/demo-payment-features/}
\item[Custom notes] You can add a custom note to a payment link. This note is
only shown to a user at the end of a successful purchase. This is displayed in
the post-purchase success page and in the email that is sent to the buyer after
a purchase. You can include a thank-you message, instructions to get started,
any keys or passwords required, etc.

Example:  \url{https://www.instamojo.com/instamojo/integration-documentation/}
\item[Quantity limits] You can restrict the number of items that can be
purchased for a given link.
\item[Socialpay] If you'd like to give something away for free, you can accept
social payments in the form of a Tweet or Facebook post.

Example:  \url{https://www.instamojo.com/instamojo/integration-documentation/}
\item[Digital downloads] If you'd like to sell your music, e-books, or other
digital content, you can take advantage of our \emph{Digital Goods} links. You
can upload the file to our servers and we take care of hosting, bandwidth, user
downloads, future retrievals, etc.

Example:  \url{https://www.instamojo.com/instamojo/integration-documentation/}
\item[Affiliate system] We have an affiliate system in place where you can
invite your affiliates to help you increase your sales. We'll handle their
payouts and KYC procedures so you don't have to.
\end{description}

We offer all of the above features and many more that are being added every
day. If you have any questions about whether we can support your use cases or
workflow, or if you're having difficulties finding any of the above features in
your account, please do not hesitate to reach out to the Instamojo team.


\newpage
\section{Advanced features}
If the features in the previous section do not meet your needs, or if you need
a tighter integration between your website and Instamojo, we provide several
integration options:

\begin{description}

\item[Before a payment]
Before a customer reaches an Instamojo page, you can specify the behaviour of
the Instamojo page through URL query-string parameters. 
\begin{itemize}
\item \emph{Pre-fill} any or all of the fields in the payment form.
\item Make any of the fields \emph{read-only} and \emph{tamper-proof}.
\item If it isn't a fixed price payment, pass the \emph{amount} at the time of
the payment.
\item Send us any \emph{custom data} (such as an order ID or a username) that
you'd like us to \emph{send back} after the payment.
\item Specify the \emph{layout} of the Instamojo page.
\end{itemize}

\item[After a payment]
After a payment successfully ends, there are several ways in which you can
choose to be notified:

\begin{itemize}
\item We can \emph{redirect} the customer to a URL that you specify.
\item You can query our \emph{API} to get details about a specific transaction
(read below).
\item We can send you a \emph{webhook notification} to your server.
\end{itemize}

\item[Instamojo APIs]
We have the following APIs that permit programmatic access:

\begin{itemize}
\item \emph{Payment API}: Get details about a specific payment or all your payments
programmatically.
\item \emph{Link API}: View, create or edit links in your account programmatically.
\end{itemize}

\end{description}

\newpage
\section{Before a payment}

There are several ways in which you can customize a payment link using URL
query-string parameters. Please do not forget to \uline{URL encode} any
parameters you send.


\subsection{Pre-filling the payment form}
Every Instamojo link contains a payment form that will contain, at the very
least, fields to ask for the buyer's \emph{name}, \emph{email address} and
\emph{phone number}. If you have these details before they arrive on this page,
you can send the values across so that they don't have to fill it up again.

\begin{tabular}{| l | l | r |}
\hline
Field & Key & Character limit \\ \hline \hline
Name & \verb+data_name+ & 20 \\
Email address & \verb+data_email+ & 75 \\
Phone number & \verb+data_phone+ & 20 \\ \hline
\end{tabular}

\begin{flushleft}
Example:

\url{https://www.instamojo.com/demo/demo-offer/?data_name=Aditya+Sengupta&data_email=aditya@instamojo.com&data_phone=9821485060}
\end{flushleft}

\subsection{Passing the amount at the time of the payment}
By default, links on Instamojo have a fixed price. If you would like to pass
the amount at the time the transaction is taking place, you'll need to first
edit the link and make the following changes:

\begin{enumerate}
\item Ensure the price is greater than 0 (say Rs. 10).
\item Enable the \emph{``pay what you want"} option.
\end{enumerate}

\begin{flushleft}
Once you have done this, you can pass the price using the following URL query parameter:
\end{flushleft}

\begin{tabular}{| l | l | r |}
\hline
Field & Key & Character limit \\ \hline \hline
Amount & \verb+data_amount+ & Any number up to 2 decimal places \\ \hline
\end{tabular}

\begin{flushleft}
Example:

\url{https://www.instamojo.com/demo/demo-offer/?data_amount=123.45}
\end{flushleft}

\subsection{Making fields read-only}

\textbf{Note}: This section only describes how to specify read-only fields.
Fields specified as read-only will have the HTML \texttt{readonly} attribute
added to them. A savvy user can still edit the URL or the HTML and change the
values being sent. \uline{Please read section \ref{subsec:tamper_proof} to find
out how to make a read-only field tamper proof.}

You can make any of the payment form fields read-only by passing the name of
that field as a value to the key \verb+data_readonly+. If there are multiple
fields you would like to make read-only, simply repeat this for every field (in
the same way you would use an HTML select-multiple field\footnote{HTML
select-multiple field:
\url{http://www.w3schools.com/tags/att_select_multiple.asp}}).

\begin{flushleft}
Example:

\url{https://www.instamojo.com/demo/demo-offer/?data_name=Aditya+Sengupta&data_email=aditya@instamojo.com&data_readonly=data_name&data_readonly=data_email}
\end{flushleft}

\subsection{Making fields tamper-proof}
\label{subsec:tamper_proof}
To ensure that your read-only fields cannot be tampered with, you can sign your links using the procedure below.

\textbf{Note 1}: To do this, you'll need the \textbf{salt} for your Instamojo
account. You can get this by logging into your Instamojo account and visiting
the \href{https://www.instamojo.com/developers}{Developers page}.

\textbf{Note 2}: \uline{You will need to contact the Instamojo team to enable
permanent tamper-proofing for your link}. If you do not, anyone can remove the
URL query-string parameters and be able to make a payment with a value that is
less than what you expect. Once permanent tamper-proofing is enabled, we will refuse to accept payments on links that are not signed.

For the purpose of this example, we assume you're trying to make the following link tamper-proof:

\begin{flushleft}
\url{https://www.instamojo.com/demo/demo-offer/?data_name=Aditya+Sengupta&data_email=aditya@instamojo.com&data_phone=9821485060&data_amount=123.45&data_readonly=data_name&data_readonly=data_email&data_readonly=data_phone&data_readonly=data_amount}
\end{flushleft}

\begin{enumerate}
\item Arrange the \textbf{read-only} fields in the alphabetical order of their
keys. If you have any keys with upper-case letters, convert them to lower-case
letters first.

In this example, you would get the following order:
\begin{enumerate}
\item \verb+data_amount+
\item \verb+data_email+
\item \verb+data_name+
\item \verb+data_phone+
\end{enumerate}

\item Using the order above, replace the keys by their respective values.

In this example, you would get the values below in the following order:
\begin{enumerate}
\item \verb+123.45+
\item \verb+aditya@instamojo.com+
\item \verb+Aditya Sengupta+
\item \verb+9821485060+
\end{enumerate}
\item Concatenate the above values into a single string, with each value separated by a pipe character, i.e, the $\vert$ character.

Using the above example, you get the following string:
\begin{verbatim}
123.45|aditya@instamojo.com|Aditya Sengupta|9821485060
\end{verbatim}
\item Use the above string as the message for the HMAC-SHA1
algorithm\footnote{Hash-based Message Authentication Code:
\url{http://en.wikipedia.org/wiki/Hash-based_message_authentication_code}} and
the salt for your Instamojo account as the salt for the algorithm. The output
of this will be the signature we need.

For example, if your salt is ``abcde", the signature you would generate using the string from the previous step as the message is:
\begin{verbatim}
6f905be9811990707f9d833da8e93bfebb23abbc
\end{verbatim}
\end{enumerate}

% Add point about URL encoding/escaping the querystring

Once you have the signature using the above procedure, you add it as the value of the \verb+data_sign+ key in the URL. The URL would then be:

\begin{flushleft}
\url{https://www.instamojo.com/demo/demo-offer/?data_readonly=data_name&data_readonly=data_email&data_readonly=data_phone&data_readonly=data_amount&data_sign=6f905be9811990707f9d833da8e93bfebb23abbc&data_email=aditya@instamojo.com&data_amount=123.45&data_name=Aditya+Sengupta&data_phone=9821485060}
\end{flushleft}

Note that the above URL will not actually work since the salt for the demo account is not actually ``abcde".

Don't forget to URL encode the query-string parameters!

\subsection{Passing custom data}
You may want to pass custom data to Instamojo at the beginning of a payment
that you would like to retrieve at the end of a payment, such as an order ID,
or a username of someone on your application.
\begin{enumerate}
\item Open your Instamojo dashboard and search for the link you would like to
add custom data to. (Don't click the link).
\item Below the link, you'll find the option to add and edit \emph{``Custom
Fields"}. Click on this.
\item Add the approprate fields. You can add as many as you like.
\item For each field that you would like to pass the data for in the URL,
you'll need the identifier of that field. You can find the identifier by using
the mouse to hover over the field name you've just created and the identifier
will appear. It will look like \verb+Field_<number>+, where \verb+<number>+
will be a number. Note down the identifiers for each custom field you define.
\item The data key for the query-string parameter will be generated by
prefacing the identifier with \verb+data_+. For example, if the identifier is
\verb+Field_12345+, the data key would be \verb+data_Field_12345+. Note the
placement of the underscores and the case sensitivity.
\item You can add your custom data using the data keys above. Here is an example:

\url{https://www.instamojo.com/demo/demo-custom-fields/?data_Field_70240=27&data_Field_70241=Instamojo&intent=buy}

\end{enumerate}

Note that custom data fields can be made read-only and signed using the same
procedure described in section \ref{subsec:tamper_proof}.

\subsection{Hiding custom data}
You may want to hide the custom data (such as order IDs or internal usernames)
that is displayed in the payment form, especially if it is not of immediate
obvious use to the buyer. To do this:

\begin{enumerate}
\item Add the key \verb+data_hidden+ as a query-string parameter to the URL.
\item Use the data key of the custom field as the value of the \verb+data_hidden+ parameter.
\item Repeat for all the custom fields you want to hide.
\end{enumerate}

Example: \url{https://www.instamojo.com/demo/demo-custom-fields/?data_Field_70240=27&data_Field_70241=Instamojo&intent=buy&data_hidden=data_Field_70240&data_hidden=data_Field_70241}

\subsection{Specifying the layout}
There are four layouts that are provided by Instamojo.
\begin{description}
\item[Default layout]

This is the default layout you see when you open an Instamojo link.
\item[Payment button]

You can make the Instamojo payment link appear as part of your web-application
by using our payment button. You can customize your payment button and generate
the embed code by searching for your Instamojo link in your dashboard and
clicking on the \emph{``Payment button"} option below your link.

The \emph{``Redirect"} style will simply open the Instamojo link in a new tab
and allow the payment to take place there.

The \emph{``Remote checkout"} style will open a modal overlay on your
web-application and allow the payment process to seamlessly integrate with your
site.

\item[Form open]

If you're pre-filling the payment form, you may want to keep the payment form
open by default, so the buyer is saved an extra click of having to open the
form. You can do this by adding the query-string parameter, \verb+intent=buy+
to your Instamojo link.

Example: \url{https://www.instamojo.com/demo/demo-offer/?intent=buy}
\item[Minimal link]

If you want to embed the Instamojo link in an iframe, you may want a minimal
version of the Instamojo page to appear. To do this, simply add the
query-string parameter, \verb+embed=form+ to your Instamojo link and you'll get
a skinned version of the Instamojo link that consists only of the payment
forms.

Example: \url{https://www.instamojo.com/demo/demo-offer/?embed=form}
\end{description}

\subsection{Error codes}

If you've made an error with one of the query parameters, you may see one or more of the following error codes:

\begin{tabular}{| l | l | r |}
\hline
Error code & Error description \\ \hline
QF1 & Name is not valid \\
QF2 & Email is not valid \\
QF3 & Phone is not valid \\
QF4 & Amount is not valid \\
QF5 & Readonly fields are not valid \\
QF6 & Hidden fields are not valid \\
QF7 & Signature is not valid \\
QF10 & Custom field is not valid \\
QF11 & Signature not specified for link that requires signature \\
QF12 & Readonly fields not specified for link that requires signature \\
QF13 & Data to sign invalid for link that requires signature \\
QF14 & Data to sign not specified for link that requires signature \\
QF15 & Signature not valid \\
\hline
\end{tabular}

\newpage
\section{After a payment}

There are several ways in which you can process a successful transaction.

\subsection{Redirect}
\label{subsec:redirect}

At the end of each transaction on a given link, the user can be redirected to a
link that you specify. You can specify this link in the \emph{``Advanced
settings"} section while creating or editing a link. While we redirect the
user, we also add the payment ID as a query parameter (using the key
\verb+payment_id+) to your redirect link.

You can use the payment ID to query our Payment API (described in section
\ref{subsec:payment_api} on page \pageref{subsec:payment_api}) to verify the
status of the payment and retrieve other details, such as the amount, the
custom data, the buyer's details, etc. More on this in the next section.

\subsection{Payment API}

The payment API allows you to do the following:

\begin{enumerate}
\item Retrieve a list of payments associated with your Instamojo account.
\item Given a payment ID, retrieve the data associated with a specific payment.
\end{enumerate}

The details of this are provided in section \ref{subsec:payment_api} on
page \pageref{subsec:payment_api}.

\subsection{Webhook notification}

At the end of a successful payment, we can initiate a server to server POST
request that sends you all the data associated with that payment. You can
specify the URL to which we send the webhook request in the \emph{``Advanced
settings"} section while creating or editing a link. We send the following
data with each webhook request:

\begin{flushleft}
The following parameters are always sent:
\end{flushleft}

\begin{tabular}{| l | l | r |}
\hline
Variable & Key \\ \hline
Payment ID & \verb+payment_id+ \\
Status & \verb+status+ \\
Slug of the link & \verb+offer_slug+ \\
Title of the link & \verb+offer_title+ \\
Buyer's email address & \verb+buyer+ \\
Buyer's name & \verb+buyer_name+ \\
Buyer's phone number & \verb+buyer_phone+ \\
Currency & \verb+currency+ \\
Quantity of items purchased & \verb+quantity+ \\
Price of each item & \verb+unit_price+ \\
Total amount paid & \verb+amount+ \\
Fees charged by Instamojo & \verb+fees+ \\
Message authentication code & \verb+mac+ \\
\hline
\end{tabular}

\begin{flushleft}
The following parameters are only sent when applicable:
\end{flushleft}

\begin{tabular}{| l | l | r |}
\hline
Variable & Key \\ \hline
Shipping address specified & \verb+shipping_address+ \\
Shipping city & \verb+shipping_city+ \\
Shipping state & \verb+shipping_state+ \\
Shipping postal code & \verb+shipping_zip+ \\
Shipping country & \verb+shipping_country+ \\
Discount code used & \verb+discount_code+ \\
Amount discounted & \verb+discount_amount_off+ \\
Variant options specified & \verb+variants+ \\
Custom fields (JSON blob) & \verb+custom_fields+ \\
\hline
\end{tabular}

\subsubsection{How is the webhook different from the redirect?}

A webhook notification is an HTTP \emph{POST} request that is made from our
server. A redirect is an HTTP \emph{GET} request that is made from the buyer's
web browser.

In a webhook notification, we send along all the data of the payment. In a
redirect, we only send the payment ID of the transaction as a URL query-string
parameter. The redirect is typically used in conjunction with the API (by
making use of the payment ID as the key to poll the payment API with) while the
webhook is often used independently.

\subsubsection{What comes first, the redirect or the webhook?}
The webhook request is asynchronous with the redirect. The redirect takes
place on the user's browser while the webhook request is initiated from our
server. Therefore, there is no guarantee that you will receive one before the
other.

\subsubsection{How do I test whether webhook notifications are working?}
\label{subsubsec:webhook_testing}
To check whether webhook requests are being sent from Instamojo's servers or to see what what data is being sent through the webhook request, you can use \url{requestb.in}. Simply create a new Requestb.in URL and paste the URL in the webhook URL field of your Instamojo link. 

To view the data sent to the webhook URL, open the Requestb.in URL in your
browser after adding \verb+?inspect+ to the URL. For instance, if the URL you
enter in the webhook field is \verb+http://requestb.in/example+, you'll need to
open \verb+http://requestb.in/example?inspect+ in your browser to view requests
sent to this URL. Of course, to send data to this URL, simply make a
transaction on the Instamojo link that you've set up with this Requestb.in URL.

Remember that webhooks work with free links too, so you can create a link
priced at Rs. 0 for testing purposes and it'll still work.

\subsubsection{I'm not getting any webhook requests on my server}
There are several reasons for which you may not be receiving any webhook requests.
\begin{itemize}
\item Webhooks requests are made though a deferred task queue, so they may not
fire immediately as a payment happens. There may be a delay of a few seconds if
our servers are under heavy task loads. You can read
\ref{subsubsec:webhook_testing} to verify whether the webhook requests are
being made from Instamojo's servers.
\item Certain web servers block out requests made using non-browser query
strings. You'll need to whitelist the user agent that Instamojo uses to send
webhook requests if this is the case.
\item Our webhook requests currently time out after 5 seconds, if no response
is received from your server.
\item You may not have configured your webhook receiver correctly. Read
\ref{subsubsec:simulate} to see how to simulate a webhook request.
\item Our webhook request need a publicly accessible URL to work. They won't
work with localhost URLs and local IP address ranges.
\end{itemize}

\subsubsection{How do I verify that Instamojo is sending me the webhook request}
Every webhook request includes a field named \verb+mac+, which is the message
authentication code. This code is generated using the content of the message
and a secret salt that is accessible only to you and to Instamojo. You should
check every webhook request against the message authentication code included
and verify that it is the same as the code that you are able to generate using
the content of the message and your salt\footnote{You'll find your salt here
once you log into your Instamojo account: \\
\url{https://www.instamojo.com/developers/}}.

The procedure for calculating the webhook MAC is similar to the procedure
described in section \ref{subsec:tamper_proof}. Simply use all the fields of
the message except the \verb+mac+ field itself for generating the message
authentication code and verify it against the one you've received\footnote{The
procedure is described in detail here: \\
\url{http://support.instamojo.com/support/solutions/articles/139575-what-is-the-message-authentication-code-in}}.

\subsubsection{Should I use the webhook or the API?}

To decide whether you should use the webhook or the API, you'll need to keep in
mind that webhooks are asynchronous and deferred.

\begin{itemize}
\item If you need the transaction details immediately after redirecting the
buyer to your site, then you'll need to use the API.
\item If you need to show a custom page to the buyer after the payment that
depends on the transaction details, then you'll need to use the API.
\item If you only need to update your database or send an email to the buyer
after a transaction, then you can use the webhook.
\end{itemize}

\subsubsection{Can you provide a way to simulate a webhook request?}
\label{subsubsec:simulate}

In order to simulate a webhook request by yourself for testing or debugging purposes, you can issue the following curl request:

\begin{flushleft}
\verb+curl --data "param1=val1&param2=val2" http://your-webhook-url.com/endpoint/+
\end{flushleft}

\newpage
\section{Instamojo APIs}

Instamojo primarily provides the two following REST APIs- the Payment API and
the Link API. To use either of these APIs, you'll need a private API key and
auth token. You can view these credentials by logging into your Instamojo
account and then visiting \url{https://www.instamojo.com/developers/}.

Documentation for the Instamojo APIs is provided at
\url{https://www.instamojo.com/developers/rest/}. A summary is provided below.

\subsection{Payment API}
\label{subsec:payment_api}
This API can be used to retrieve all the details of a specific payment or a
list of payments made to your Instamojo account. This is typically used at the
end of a payment to verify the status of a payment. You can retrieve a payment
ID from a redirected URL as described in section \ref{subsec:redirect} on page
\pageref{subsec:redirect}.

\uline{Note}: You must verify the status of every payment using the API or by
logging into your Instamojo account if you're using a redirect based workflow
to check whether a payment is successful or not.

\subsection{Link API}
\label{subsec:link_api}
This API can be used to create and edit links in your Instamojo account. This
is typically used when you need to  upload a large number of products to your
Instamojo account.

If you have any questions on which API you should use, please don't hesitate to
reach out to the Instamojo team.

% \section{Use cases}

\newpage
\section{Tools and libraries}
\label{sec:tools}

\begin{description}
\item [Python API wrapper]

This is an implementation of the Instamojo REST API in Python.

    \url{https://github.com/Instamojo/instamojo-py}

\item [PHP API wrapper]

This is an implementation of the Instamojo REST API in PHP.

    \url{https://github.com/Instamojo/instamojo-php}

\item [Prestashop plugin]

If you use Prestashop for your shopping cart needs, then this plugin allows you to set up Instamojo for checkout.

    \url{https://github.com/Instamojo/instamojo-prestashop}

\item [Wordpress plugin]

This is a sample Wordpress plugin and can be used to showcase your Instamojo
links on Wordpress.

    \url{https://github.com/Instamojo/instamojo-wordpress-plugin}

\item [IM Tools]

This repository contains a few useful Instamojo tools- such as a sample Webhook
receiver and a command line tool to generate pre-filled and signed links on
Instamojo. To use the link tool, simply download the Python file to your computer, open a command line shell and execute the following command for a tutorial on how to use the tool:

\verb+python link.py -h+

\url{https://github.com/Instamojo/instamojo-wordpress-plugin}
\end{description}


\newpage
\section{Change Log}
\label{sec:changelog}

\begin{description}
\item [Version 1.1: \date{November 11, 2014}] \hfill \\

The first version of this document was released.

\item [Version 1.2: \date{April 6, 2014}] \hfill \\

\begin{enumerate}
\item Updated the support phone number.
\item Fixed an incorrect URL in an example.
\item Added a cautionary note for aforementioned example.
\item Added this change log and document version number.
\end{enumerate}

\end{description}

\end{document}