Handle edge case for dlmm zapin

programs/zap/src/math/price_math.rs

@@ -20,7 +20,7 @@ pub fn get_price_from_id(active_id: i32, bin_step: u16) -> Result<u128> {
 
 // get price base factor
 pub fn get_price_base_factor(bin_step: u16) -> Result<u128> {
-    // Make bin_step into Q64x64, and divided by BASIS_POINT_MAX. If bin_step = 1, we get 0.0001 in Q64x64
+    // Make bin_step into Q64x64, and divided by MAX_BASIS_POINT. If bin_step = 1, we get 0.0001 in Q64x64
     let bps = u128::from(bin_step)
         .safe_shl(SCALE_OFFSET.into())?
         .safe_div(MAX_BASIS_POINT as u128)?;

programs/zap/src/utils/dlmm_utils.rs

@@ -308,10 +308,7 @@ impl StrategyHandler for CurveHandler {
 
         if min_delta_id == max_delta_id {
             let bin_id = active_id.safe_add(min_delta_id)?;
-            let pm = U256::from(get_price_from_id(bin_id, bin_step)?);
-            let x0 = U256::from(amount_x).safe_mul(pm)?.safe_shr(64)?;
-            let x0: i128 = x0.try_into().map_err(|_| ZapError::TypeCastFailed)?;
-            return Ok((x0, 0));
+            return find_x0_and_delta_x_single_bin(bin_id, bin_step, amount_x);
         }
 
         let mut b = U256::ZERO;
@@ -405,14 +402,11 @@ impl StrategyHandler for BidAskHandler {
         // C = (m1 * p(m1) + ... + m2 * p(m2))
         // delta_x = sum(amounts) / (C-B)
         // note: in bid ask strategy: x0 <= 0 and delta_x >= 0
+        // except for the case min_delta_id == max_delta_id, x0 > 0 and delta_x = 0 (using the same result from curve strategy)
 
         if min_delta_id == max_delta_id {
             let bin_id = active_id.safe_add(min_delta_id)?;
-            let pm = get_price_from_id(bin_id.neg(), bin_step)?;
-            let denominator = U256::from(min_delta_id).safe_mul(U256::from(pm))?;
-            let delta_x = U256::from(amount_x).safe_shl(64)?.safe_div(denominator)?;
-            let delta_x: i128 = delta_x.try_into().map_err(|_| ZapError::TypeCastFailed)?;
-            return Ok((0, delta_x));
+            return find_x0_and_delta_x_single_bin(bin_id, bin_step, amount_x);
         }
 
         let mut b = U256::ZERO;
@@ -443,3 +437,14 @@ impl StrategyHandler for BidAskHandler {
         Ok((x0, delta_x))
     }
 }
+
+fn find_x0_and_delta_x_single_bin(
+    bin_id: i32,
+    bin_step: u16,
+    amount_x: u64,
+) -> Result<(i128, i128)> {
+    let pm = U256::from(get_price_from_id(bin_id, bin_step)?);
+    let x0 = U256::from(amount_x).safe_mul(pm)?.safe_shr(64)?;
+    let x0: i128 = x0.try_into().map_err(|_| ZapError::TypeCastFailed)?;
+    return Ok((x0, 0));
+}

tests/test_zapin/zapin_dlmm_initialize_position.test.ts

@@ -233,6 +233,66 @@ describe("Zapin DLMM with initialize position", () => {
     });
   });
 
+  it("Zapin dlmm single bin with Curve strategy", async () => {
+    await initializeBinArrayBitmapExtension(svm, lbPair, admin);
+    const position = await createDlmmPosition(svm, user, lbPair, lowerBinId);
+
+    const amountTokenA = new BN(LAMPORTS_PER_SOL);
+    const amountSwap = amountTokenA.divn(2);
+
+    const binArrays = getBinArrayAccountMetaByBinRange(
+      lbPair,
+      new BN(lowerBinId),
+      new BN(upperBinId)
+    );
+
+    await zapInDlmmFullFlow({
+      svm,
+      user,
+      lbPair,
+      position,
+      inputTokenMint: tokenXMint,
+      outputTokenMint: tokenYMint,
+      totalAmount: amountTokenA,
+      amountSwap,
+      minDeltaId: 0,
+      maxDeltaId: 0,
+      strategy: StrategyType.Curve,
+      binArrays,
+      remainingAccountInfo: { slices: [] },
+    });
+  });
+
+  it("Zapin dlmm single bin with Bid/ask strategy", async () => {
+    await initializeBinArrayBitmapExtension(svm, lbPair, admin);
+    const position = await createDlmmPosition(svm, user, lbPair, lowerBinId);
+
+    const amountTokenA = new BN(LAMPORTS_PER_SOL);
+    const amountSwap = amountTokenA.divn(2);
+
+    const binArrays = getBinArrayAccountMetaByBinRange(
+      lbPair,
+      new BN(lowerBinId),
+      new BN(upperBinId)
+    );
+
+    await zapInDlmmFullFlow({
+      svm,
+      user,
+      lbPair,
+      position,
+      inputTokenMint: tokenXMint,
+      outputTokenMint: tokenYMint,
+      totalAmount: amountTokenA,
+      amountSwap,
+      minDeltaId: 0,
+      maxDeltaId: 0,
+      strategy: StrategyType.BidAsk,
+      binArrays,
+      remainingAccountInfo: { slices: [] },
+    });
+  });
+
   it("Zapin dlmm without bin array bitmap extension", async () => {
     const position = await createDlmmPosition(svm, user, lbPair, lowerBinId);
     const amountTokenA = new BN(LAMPORTS_PER_SOL);
@@ -370,5 +430,12 @@ async function zapInDlmmFullFlow(params: {
   expect(result).instanceOf(TransactionMetadata);
 
   let liquidities = getPositionTotalLiquidityAllBin(svm, position);
-  console.log(babar(liquidities));
+  if (liquidities.length > 1) {
+    // there is a bug in babar that we could draw single bin
+    console.log(babar(liquidities));
+  } else {
+    console.log("Liquidity distribution (bin_index, liquidity)");
+    console.log(liquidities);
+  }
+
 }