Experiment the Pair contract

Once you are inside the soroban-preview-9 container (by bash quickstart.sh and bash run.sh) you can start experimenting with the SoroswapPair contract.

1. Open and read the contract:

Open in your favourite IDE or text editor, and check the pair folder:

In the pair/src folder you will find:

• The lib.rs file with the SoroswapPair functions

• The token folder, which is a fork of the token contract from soroban-examples, with two added functions: The internal_burn and the internal_mint function. As the SoroswapPair contract is a token itself, if it's not making a cross-contract call to iself in order to mint or burn tokens, it will have problems with require_auth. Read more about this in the following issue: #16

• The test.rs.

• The events.rs to emmit events

• The factory.rs used as a Interface of some of the factory functions

• The create folder, that contains the create mod, used in testings in order to create the pair contract.

Also, you will see that in the root folder, there is a ./soroban_token_contract.wasm file. This was taken by compiling the []soroban-examples/token contract v0.8.4](https://github.com/stellar/soroban-examples/releases/tag/v0.8.4)

2. Compile the contract

We can compile both contracts by just calling make build from the root directory, however, we can go contract by contract:

cd pair
make build

3. Read and run the tests:

make test

4.- Experiment with the SoroswapFactory contract using the soroban CLI:

You can see the followng step-by-step. However, if you decide you can read and just run the initialize_factory.sh contract:

bash initialize_pair.sh

1.- First, set your enviromental variables

Here, as we are using the soroban-network docker network, containers can call each other just using their name. In the case of the stellar quickstart container, it's name is stellar:

Choose your network. In this example we will use standalone, but you can also use futurenet:

NETWORK="standalone"

Then:

SOROBAN_RPC_HOST="http://stellar:8000"
SOROBAN_RPC_URL="$SOROBAN_RPC_HOST/soroban/rpc"
SOROBAN_NETWORK_PASSPHRASE="Standalone Network ; February 2017"
FRIENDBOT_URL="$SOROBAN_RPC_HOST/friendbot"

echo Add the $NETWORK network to cli client
  soroban config network add "$NETWORK" \
    --rpc-url "$SOROBAN_RPC_URL" \
    --network-passphrase "$SOROBAN_NETWORK_PASSPHRASE"

echo Create the token-admin identity
  soroban config identity generate token-admin

TOKEN_ADMIN_SECRET="$(soroban config identity show token-admin)"
TOKEN_ADMIN_ADDRESS="$(soroban config identity address token-admin)"

echo "We are using the following TOKEN_ADMIN_ADDRESS: $TOKEN_ADMIN_ADDRESS"
echo "$TOKEN_ADMIN_SECRET" > .soroban/token_admin_secret
echo "$TOKEN_ADMIN_ADDRESS" > .soroban/token_admin_address

echo Fund token-admin account from friendbot
  echo This will fail if the account already exists, but it\' still be fine.
  curl  -X POST "$FRIENDBOT_URL?addr=$TOKEN_ADMIN_ADDRESS"

ARGS="--network $NETWORK --source token-admin"
echo "Using ARGS: $ARGS"

2.- Let's create two dummy tokens:

We need to create 2 tokens in order to interact with the Pair contract

mkdir -p .soroban
PAIR_WASM="pair/target/wasm32-unknown-unknown/release/soroswap_pair_contract.wasm"
TOKEN_WASM="soroban_token_contract.wasm"

echo Deploying TOKEN_A
  TOKEN_A_ID="$( soroban contract deploy $ARGS --wasm $TOKEN_WASM)"

echo "Initializing TOKEN_A. Executing:
    fn initialize(e: Env, admin: Address, decimal: u32, name: Bytes,symbol: Bytes)"

  soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM \
  --id $TOKEN_A_ID \
  -- \
  initialize \
  --admin "$TOKEN_ADMIN_ADDRESS" \
  --decimal 7 \
  --name 'AA' \
  --symbol 'AA'
  echo "--"
  echo "--"


echo Deploying TOKEN_B
  TOKEN_B_ID="$(soroban contract deploy $ARGS --wasm $TOKEN_WASM)"
  
echo Initializing TOKEN_B

  soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM \
  --id $TOKEN_B_ID \
  -- \
  initialize \
  --admin "$TOKEN_ADMIN_ADDRESS" \
  --decimal 7 \
  --name 'BB' \
  --symbol 'BB'
  echo "--"
  echo "--"

echo Current TOKEN_A_ID: $TOKEN_A_ID
echo Current TOKEN_B_ID: $TOKEN_B_ID

Because the Pair token always uses token_a and token_b so token_a<token_b, this is something we need to check before initializing the pair contract with our two tokens. Later, this is something that will be done automatically by the Factory contract:

if [[ "$TOKEN_B_ID" > "$TOKEN_A_ID" ]]; then
  echo "TOKEN_B_ID is greater than TOKEN_A_ID"
  echo "This is the correct order"
else
  echo "TOKEN_B_ID is less than or equal to TOKEN_A_ID"
  echo "We will invert the order of the tokens"
  TOKEN_A_ID_NEW=$TOKEN_B_ID
  TOKEN_B_ID=$TOKEN_A_ID
  TOKEN_A_ID=$TOKEN_A_ID_NEW

fi
echo Current TOKEN_A_ID: $TOKEN_A_ID
echo Current TOKEN_B_ID: $TOKEN_B_ID
  echo "--"
  echo "--"


echo -n "$TOKEN_A_ID" > .soroban/token_a_id
echo -n "$TOKEN_B_ID" > .soroban/token_b_id

3.- Build, deploy and initialize the Pair contract

echo Build the SoroswapPair contract
    cd pair
    make build
    cd ..
    PAIR_WASM="pair/target/wasm32-unknown-unknown/release/soroswap_pair_contract.wasm"
echo "--"

echo Deploy the Pair 
    PAIR_ID="$(soroban contract deploy $ARGS --wasm $PAIR_WASM)"
echo "$PAIR_ID" > .soroban/pair_wasm_hash
echo "SoroswapPair deployed succesfully with PAIR_ID: $PAIR_ID"
echo "--"

echo "Initialize the Pair contract using the Admin address as Factory"
echo "Calling: fn initialize_pair( e: Env, factory: Address, token_a: BytesN<32>, token_b: BytesN<32>);"

soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM \
  --id $PAIR_ID \
  -- \
  initialize_pair \
  --factory "$TOKEN_ADMIN_ADDRESS" \
  --token_a "$TOKEN_A_ID" \
  --token_b "$TOKEN_B_ID" 

4.- Creare a USER account and mint tokens to that account.

echo In the following we are going to use a new USER account:
  echo Creating the user identity
  soroban config identity generate user
  USER_SECRET="$(soroban config identity show user)"
  USER_ADDRESS="$(soroban config identity address user)"
  echo "We are using the following USER_ADDRESS: $USER_ADDRESS"
  echo "$USER_SECRET" > .soroban/user_secret
  echo "$USER_ADDRESS" > .soroban/user_address

echo Fund user account from friendbot
    echo This will fail if the account already exists, but it\' still be fine.
    curl  -X POST "$FRIENDBOT_URL?addr=$USER_ADDRESS"

  
echo "Mint 1000 units of token A user -- calling from TOKEN_ADMIN"

soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM \
  --id $TOKEN_A_ID \
  -- \
  mint \
  --admin "$TOKEN_ADMIN_ADDRESS" \
  --to "$USER_ADDRESS" \
  --amount "1000" 

echo "Mint 1000 units of token B to user"

soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM \
  --id $TOKEN_B_ID \
  -- \
  mint \
  --admin "$TOKEN_ADMIN_ADDRESS" \
  --to "$USER_ADDRESS" \
  --amount "1000" 

echo "Check that user has 1000 units of each token"
echo "Check TOKEN_A"
soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM\
  --id $TOKEN_A_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo "Check TOKEN_A"
soroban contract invoke \
  $ARGS \
  --wasm $TOKEN_WASM\
  --id $TOKEN_B_ID \
  -- \
  balance \
  --id $USER_ADDRESS

5.- Deposit tokens in the PAIR contract

Now is the fun part! Interacting with our pair contract!!!

echo "Deposit these tokens into the Pool contract"
    echo "This will be called by the user"
    ARGS_USER="--network $NETWORK --source user"
    echo "Hence we use ARG_USER: $ARGS_USER"
echo "Calling: fn deposit( e: Env, 
                to: Address,
                desired_a: i128, 
                min_a: i128, 
                desired_b: i128, 
                min_b: i128)"

soroban contract invoke \
  $ARGS_USER \
  --wasm $PAIR_WASM \
  --id $PAIR_ID \
  -- \
  deposit \
  --to "$USER_ADDRESS" \
  --desired_a 100 \
  --min_a 100 \
  --desired_b 100 \
  --min_b 100

After this, you should receive a sucess message... But how do we know that we actually deposited 100 units of each token? The user shoud have new pair tokens, and it should have 100 token_a less and 100 token_b less!

echo Check that the user\'s pair tokens balance is 100

echo "Check PAIR_ID"
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $PAIR_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo Now the user should have: 900 units of TOKEN_A
echo "Check user\'s TOKEN_A balance"
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_A_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo Now the user should have: 900 units of TOKEN_B
echo "Check user\'s TOKEN_B balance"
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_B_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo And the Pair contract should hold:
PAIR_CONTRACT_ADDRESS="{\"address\": {\"contract\":\"$PAIR_ID\"}}"

echo 100 tokens of TOKEN_A
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_A_ID \
  -- \
  balance \
  --id "$PAIR_CONTRACT_ADDRESS"

echo 100 tokens of TOKEN_B
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_B_ID \
  -- \
  balance \
  --id "$PAIR_CONTRACT_ADDRESS"


echo And none of its own tokens -- the pair tokens --
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $PAIR_ID \
  -- \
  balance \
  --id "$PAIR_CONTRACT_ADDRESS"
echo "--"
echo "--"
echo "--"
echo "--"

6.- Swap tokens.

Once the SoroswapPair contract (which is a liquidity pool) has been initialized with some units of token_a and token_b, any user can perform a trade executing the swap function.

Here we will call the fn swap(e: Env, to: Address, buy_a: bool, out: i128, in_max: i128) function. If "buy_a" is true, the swap will buy token_a and sell token_b. This is flipped if "buy_a" is false "out" is the amount being bought, with in_max being a safety to make sure you receive at least that amount. The swap function will transfer the selling token "to" to this contract, and then the contract will transfer the buying token to "to".

echo Now we will SWAP 

soroban contract invoke \
  $ARGS_USER \
  --wasm $PAIR_WASM \
  --id $PAIR_ID \
  -- \
  swap \
  --to "$USER_ADDRESS" \
  --out 49 \
  --in_max 100 


echo Now the user should have:
echo 803 units of TOKEN_A
echo "Check user\'s TOKEN_A balance"
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_A_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo 949 units of TOKEN_B
echo "Check user\'s TOKEN_B balance"
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_B_ID \
  -- \
  balance \
  --id $USER_ADDRESS

echo And the Pair contract should hold:
PAIR_CONTRACT_ADDRESS="{\"address\": {\"contract\":\"$PAIR_ID\"}}"

echo 197 tokens of TOKEN_A
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_A_ID \
  -- \
  balance \
  --id "$PAIR_CONTRACT_ADDRESS"

echo 51 tokens of TOKEN_B
soroban contract invoke \
  $ARGS \
  --wasm $PAIR_WASM\
  --id $TOKEN_B_ID \
  -- \
  balance \
  --id "$PAIR_CONTRACT_ADDRESS"

7.- The final part: Withdraw

The final test is when the user want's to exit the liquidity pool and withdraw its tokens by giving back the pair_tokens that it has:

The function here will be

fn withdraw(    e: Env,
                to: Address,
                share_amount: i128, 
                min_a: i128, 
                min_b: i128) -> (i128, i128)

soroban contract invoke \
  $ARGS_USER \
  --wasm $PAIR_WASM \
  --id $PAIR_ID \
  -- \
  withdraw \
  --to "$USER_ADDRESS" \
  --share_amount 100 \
  --min_a 197 \
  --min_b 51 

If you want to continue experimenting directly with the CLI, here aresome env variable setting that might be useful <3

ARGS="--network $NETWORK --source token-admin"
PAIR_WASM="pair/target/wasm32-unknown-unknown/release/soroswap_pair_contract.wasm"
PAIR_ID=$(cat .soroban/pair_wasm_hash)
TOKEN_ADMIN_ADDRESS=$(cat .soroban/token_admin_address)
USER_ADDRESS=$(cat .soroban/user_address)
TOKEN_A_ID=$(cat .soroban/token_a_id)
TOKEN_B_ID=$(cat .soroban/token_b_id)
ARGS_USER="--network $NETWORK --source user"


echo In the next we will use:
echo ARGS = $ARGS
echo ARGS_USER = $ARGS_USER
echo PAIR_WASM = $PAIR_WASM
echo PAIR_ID = $PAIR_ID
echo TOKEN_ADMIN_ADDRESS = $TOKEN_ADMIN_ADDRESS
echo USER_ADDRESS = $USER_ADDRESS
echo TOKEN_A_ID = $TOKEN_A_ID
echo TOKEN_B_ID = $TOKEN_B_ID
echo "--"
echo "--"

---

You can go through all this steps just by doing:

bash initialize_pair.sh

---

In the next, we will experiment the creation of Pair contracts through the SoroswapFactory contract!