feat: Constant Product Amm

NethermindEth · Oct 5, 2023 · f896d74 · f896d74
1 parent 9da1312
commit f896d74
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Showing 3 changed files with 42 additions and 5 deletions.
diff --git a/listings/ch02-applications/constant_product_amm/src/constant_product_amm.cairo b/listings/ch02-applications/constant_product_amm/src/constant_product_amm.cairo
@@ -256,7 +256,7 @@ mod ConstantProductAmm {
         }
     }
 }
-// ANCHOR_END: StoreArrayContract
+// ANCHOR_END: ConstantProductAmmContract
 
 #[cfg(test)]
 mod tests {
@@ -285,7 +285,6 @@ mod tests {
     #[derive(Drop, Copy)]
     struct Deployment {
         contract: IConstantProductAmmDispatcher,
-        contract_address: ContractAddress,
         token0: IERC20Dispatcher,
         token1: IERC20Dispatcher
     }
@@ -315,7 +314,6 @@ mod tests {
         let contract_address = utils::deploy(ConstantProductAmm::TEST_CLASS_HASH, calldata);
         Deployment {
             contract: IConstantProductAmmDispatcher { contract_address },
-            contract_address,
             token0,
             token1
         }
@@ -327,8 +325,8 @@ mod tests {
         let provider: ContractAddress = BANK.try_into().unwrap();
         set_contract_address(provider);
 
-        deploy.token0.approve(deploy.contract_address, amount);
-        deploy.token1.approve(deploy.contract_address, amount);
+        deploy.token0.approve(deploy.contract.contract_address, amount);
+        deploy.token1.approve(deploy.contract.contract_address, amount);
 
         deploy.contract.add_liquidity(amount, amount)
     }
@@ -367,4 +365,33 @@ mod tests {
         assert(deploy.token0.balance_of(provider) == INITIAL_SUPPLY, 'Wrong balance token0');
         assert(deploy.token1.balance_of(provider) == INITIAL_SUPPLY, 'Wrong balance token1');
     }
+
+    #[test]
+    #[available_gas(20000000)]
+    fn should_swap() {
+        let deploy = setup();
+        let shares = add_liquidity(deploy, INITIAL_SUPPLY / 2);
+
+        let provider: ContractAddress = BANK.try_into().unwrap();
+        let user = contract_address_const::<0x1>();
+
+        // Provider send some token0 to user
+        set_contract_address(provider);
+        let amount = deploy.token0.balance_of(provider) / 2;
+        deploy.token0.transfer(user, amount);
+
+        // user swap for token1 using AMM liquidity
+        set_contract_address(user);
+        deploy.token0.approve(deploy.contract.contract_address, amount);
+        deploy.contract.swap(deploy.token0.contract_address, amount);
+        let amount_token1_received = deploy.token1.balance_of(user);
+        assert(amount_token1_received > 0, 'Swap: wrong balance token1');
+
+        // User can swap back token1 to token0
+        // As each swap has a 0.3% fee, user will receive less token0
+        deploy.token1.approve(deploy.contract.contract_address, amount_token1_received);
+        deploy.contract.swap(deploy.token1.contract_address, amount_token1_received);
+        let amount_token0_received = deploy.token0.balance_of(user);
+        assert(amount_token0_received < amount, 'Swap: wrong balance token0');
+    }
 }
diff --git a/src/SUMMARY.md b/src/SUMMARY.md
@@ -26,6 +26,7 @@ Summary
 
   - [Upgradeable Contract](./ch02-01-upgradeable_contract.md)
   - [Defi Vault](./ch02-02-simple_vault.md)
+  - [Constant Product AMM](./ch02-03-constant-product-amm.md)
 
 - [Optimisations](./ch03-00-optimisations.md)
 

diff --git a/src/ch02-03-constant-product-amm.md b/src/ch02-03-constant-product-amm.md
@@ -0,0 +1,9 @@
+# Constant Product AMM
+
+This is the Cairo adaptation of the [Solidity by example Constant Product AMM](https://solidity-by-example.org/defi/constant-product-amm/).
+
+```rust
+{{#include ../listings/ch02-applications/constant_product_amm/src/constant_product_amm.cairo:ConstantProductAmmContract}}
+```
+
+Play with this contract in [Remix](https://remix.ethereum.org/?#activate=Starknet&url=https://github.com/NethermindEth/StarknetByExample/blob/main/listings/ch02-applications/constant_product_amm/src/constant_product_amm.cairo).