Using The Contract Simulator
============================

-  We recommend that you prepare a `solc
   compiler <https://solidity.readthedocs.io/en/develop/installing-solidity.html>`__
   before using the contract simulator.
-  If you do not want to prepare the solc compiler, it is necessary to
   prepare a Remix `online <http://remix.ethereum.org/>`__ environment
   or Remix local browser.

Example
-------

Compile the contract simulator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The code is in ``https://github.com/seeleteam/go-seele``

::

   git clone https://github.com/seeleteam/go-seele.git

   cd go-seele/cmd/vm
   go build

Copy the solc compiler to this path, and copy the solidity file in it
too.

I. A simple smart contract example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Smart contract source code:
^^^^^^^^^^^^^^^^^^^^^^^^^^^

SimpleStorage.sol:

::

   pragma solidity >=0.4.0 <0.6.0;

   contract SimpleStorage {
       uint storedData;

       function set(uint x) public {
           storedData = x;
       }

       function get() public view returns (uint) {
           return storedData;
       }
   }

Create the contract in the simulator with solidity file
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

::

   // Request
   ./vm create -f simpleStorage.sol

   // Response
   Succeed to create contract!
   Contract address: 0x9dfba51a3302c45310534a80bfc7874a09c10022

When a smart contract created successfully, the contract address will be
stored.

Call the contract in simulator
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Use the global contract address (if -c not specified) and set(21)
function to call contract.

::

   // Request
   vm call -m set 21

   // Response
   Succeed to call contract!

Verify the set function:

::

   // Request
   vm call -m get

   // Response
   Succeed to call contract!
   Result (raw): [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 21]
   Result (hex): 0x0000000000000000000000000000000000000000000000000000000000000015
   Result (big): 21

II. A simple smart contract example that relies on Remix
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Prepare Remix
^^^^^^^^^^^^^^^^

Remix-IDE is a browser based IDE for solidity development, you can use
the online version at http://remix.ethereum.org/, or download it from
https://github.com/ethereum/remix-ide to install it locally.

The following demonstration is done using the online version.

2. Compile Contract
^^^^^^^^^^^^^^^^^^^

Prepare the smart contract source code:

::

   pragma solidity >=0.4.0 <0.6.0;

   contract SimpleStorage {
       uint storedData;

       function set(uint x) public {
           storedData = x;
       }

       function get() public view returns (uint) {
           return storedData;
       }
   }

And copy the smart contract source code to the text area.

|image0|

Choose the appropriate compiler and click the Start to compile on the
right to start compile.

3. Deploy Contract
^^^^^^^^^^^^^^^^^^

Select Run on the right, as shown in the picture with an arrow point to
it. Click the Deploy button at the middle section of the page at the
right.

|image1|

After successful deployment as shown in picture, open the log detail
section for log details, click on input to copy the Bytecode to the
clipboard.

|image2| Copy the content in the Input section, as below

::

   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

4. Create and deploy contract in contract simulator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Run the following commands to change into go-seele/cmd/vm directory,
then run the command go build.

::

   cd go-seele/cmd/vm
   go build

Create and deploy contract using the input hex string acquired from step
three.

::

   // Request
   vm create -c 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

   // Response
   Succeed to create contract!
   Contract address: 0x7729861639f2a54efa89b0e4095303bb464b0012

The string “Succeed to create contract!” means creation is successful,
the deployment address might be different from the address above but
that will not affect anything.

5. Test Set Function
^^^^^^^^^^^^^^^^^^^^

Pick a random number such as 21 for testing. You could pick any number
that you like. Enter the number at the right side in the Set field.
|image3|

The execution log will show up in the area marked grey. Click on this
log line item for detail.

|image4|

Copy the content in the Input field.

::

   0x60fe47b10000000000000000000000000000000000000000000000000000000000000015

Then switch back to the contract simulator to execute the contract.

::

   // Request
   vm call -c 0x7729861639f2a54efa89b0e4095303bb464b0012 -i 0x60fe47b10000000000000000000000000000000000000000000000000000000000000015

   // Response
   Succeed to call contract!

The string “Succeed to call contract!” indicates function call
successful.

6. Test get Function
^^^^^^^^^^^^^^^^^^^^

Similar to set function, click on the get button.

|image5|

If the log shows up in the log field then means the function call is
successful. Click on the log line item for detail.

|image6|

Copy the content from the input field.

::

   0x6d4ce63c

Switch to contract simulator, then call the get function.

::

   // Request
   vm call -c 0x7729861639f2a54efa89b0e4095303bb464b0012 -i 0x6d4ce63c

   // Response
   Succeed to call contract!
   Result (raw): [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 21]
   Result (hex): 0x0000000000000000000000000000000000000000000000000000000000000015
   Result (big): 21

When the string “Succeed to call contract!” is shown and the result is
21, then the function is running correctly!

.. |image0| image:: ../img/remix1.png
.. |image1| image:: ../img/remix2.png
.. |image2| image:: ../img/remix3.png
.. |image3| image:: ../img/remix4.png
.. |image4| image:: ../img/remix5.png
.. |image5| image:: ../img/remix6.png
.. |image6| image:: ../img/remix7.png