add contract deployment page

src/pages/docs/interacting-with-geth/javascript-console_contracts.md

@@ -0,0 +1,116 @@
+---
+title: JavaScript Console 2: Contracts
+description: Instructions for working with contracts in the Javascript console.
+---
+
+The [Introduction to the Javascript console](src/pages/docs/interacting-with-geth/javascript-console.md) page outlined how a Javascript console can be attached to Geth to provide a more user-friendly interface to Ethereum than interacting directly with the JSON-RPC API. This page will describe how to deploy contracts and interact with contracts using the attached console. This page will assume the Javascript console is attached to a running Geth instance using IPC. Clef should be used to manage accounts. 
+
+## Deploying a contract
+
+First we need a contract to deploy. We can use the well-known `Storage.sol` contract written in Solidity. The following Solidity code can be copied and pasted into a text editor and saved as `go-ethereum/storage-contract/Storage.sol`.
+
+```Solidity
+// SPDX License-Identifier: GPL 3.0
+
+pragma solidity ^0.8.0;
+
+contract Storage{
+
+    uint256 value = 5;
+    
+    function set(uint256 number) public{
+        value = number;
+    }
+
+    function retrieve() public view returns (uint256){
+        return value;
+    }
+}
+```
+
+The contract needs to be compiled before Geth can understand it. Compiling the contract creates an [Application Binary Interface](src/pages/docs/tools/abigen.md) and the contract bytecode. This requires a Solidity compiler (e.g. `solc`) to be installed on the local machine. Then, compile and save the ABI and bytecode to a new `build` subdirectory using the following terminal commands:
+
+```sh
+cd ~/go-ethereum/storage-contract
+solc --bin Storage.sol -o build
+solc --abi Storage.sol -o build
+```
+
+The outputs look as follows:
+
+```sh
+# build/Storage.bin
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
+```
+
+```json
+# Storage.abi
+[{"inputs":[],"name":"retrieve","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"number","type":"uint256"}],"name":"store","outputs":[],"stateMutability":"nonpayable","type":"function"}]
+```
+
+These are all the data required to deploy the contract using the Geth Javascript console. Open the Javascript console using `./geth attach geth.ipc`. 
+
+Now, for convenice we can store the abi and bytecode in variables in the console:
+
+```js
+var abi = [{"inputs":[],"name":"retrieve","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"number","type":"uint256"}],"name":"store","outputs":[],"stateMutability":"nonpayable","type":"function"}]
+
+var bytecode = "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"
+```
+
+The ABI can be used to create an instance of the contract:
+
+```js
+var contract = eth.contract(abi)
+```
+
+This contract instance can then be deployed to the blockchain. This is done using `eth.sendTransaction`, passing the contract bytecode in the `data` field. For convenience we can create a transaction JSON object first, then pass it to `eth.sendTransaction` later. Let's use the first account in `eth.accounts` as the sender. The amount of gas to include can be determined using `eth.estimateGas`:
+
+```js
+var gas = eth.estimateGas({data: bytecode})
+```
+
+Note that each command that touches accounts will require approval in Clef unless a custom rule has been implemented.
+
+```js
+var tx = {'from': eth.accounts[0], data: bytecode, gas: gas}
+var deployed_contract = contract.new(tx)
+```
+
+The transaction hash and deployment address can now been viewed in the console by entering the variable name (in this case `deployed_contract`):
+
+```js
+{
+  abi:[{
+    inputs: [],
+    name: "retrieve",
+    outputs: [{...}],
+    stateMutability: "view",
+    type: "function"
+  },{
+    inputs: [],
+    name: "store",
+    outputs: [{...}],
+    stateMutability: "nonpayable",
+    type: "function"
+  }],
+  address: "0x2d6505f8b1130a22a5998cd31788bf6c751247f",
+  transactionHash: "0x5040a8916b23b76696ea9eba5b072546e1112cc481995219081fc86f5b911bf3",
+  allEvents: function bound(),
+  retrieve: function bound(),
+  store: function bound()
+}
+```
+
+Passing the transaction hash to `eth.getTransaction()` returns the deployment transaction details including the contract bytecode in the `input` field. To interact with the contract, create an instance by passing the deployment address to `contract.at` then call the methods.
+
+```js
+var instance = contract.at("0x2d6505f8b1130a22a5998cd31788bf6c751247f")
+// store() alters the state and therefore requires sendTransaction()
+contract.set.sendTransaction(42, {from: eth.accounts[0], gas: 1000000})
+// retrieve does not alter state so it can be executed using call()
+contract.retrieve().call()
+
+>> 2
+```
+