Fixes for weight calculation

Not yet functional. Some rounding differences are still present.

src/ApiHandler.ts

@@ -130,17 +130,18 @@ export default class ApiHandler {
 			}
 		}
 
+		const fixed128 = new BN(10).pow(new BN(18))
 		const perBill = new BN(1e9);
-		const perByteFee = api.consts.transactionPayment.transactionByteFee.mul(perBill);
-		const extrinsicBaseWeight = api.consts.system.extrinsicBaseWeight.mul(perBill);
+		const perByteFee = api.consts.transactionPayment.transactionByteFee;
+		const extrinsicBaseWeight = api.consts.system.extrinsicBaseWeight;
 		// Here we assume that `weightToFee` Vec only has 1 element, which is of
 		// degree 1. FIXME Implement polynomial.
 		const coefficients = api.consts.transactionPayment.weightToFee[0];
 		const coeffFrac = coefficients.coeffFrac;
-		const coeffInt = coefficients.coeffInteger.mul(perBill);
+		const coeffInt = coefficients.coeffInteger;
 
 		// bn.js values must be < 0x20000000000000, cannot divide by 1e18 [Ref: bn.js:128]
-		const targetedFeeAdjustment = (await api.query.transactionPayment.nextFeeMultiplier.at(parentHash)).div(perBill); // FIXME This might round the number
+		const targetedFeeAdjustment = await api.query.transactionPayment.nextFeeMultiplier.at(parentHash);
 
 		// TODO: We assume that the polynomial has one positive term of degree one.
 		// const degree = coefficients.degree;
@@ -189,22 +190,21 @@ export default class ApiHandler {
 				}
 
 				// Note: we use the same variable names as in Rust
-				const len = block.extrinsics[idx].encodedLength;
-				const lenFee = perByteFee.muln(len);
+				const lenFee = perByteFee.muln(block.extrinsics[idx].encodedLength);
 
 				// weight_to_fee calculation
 				// FIXME Implement polynomial.
 				const weight = weightInfo.weight;
-				const weightedCoeffFrac = weight.mul(coeffFrac);
+				const weightedCoeffFrac = weight.mul(coeffFrac).div(perBill);
 				const weightedCoeffInt = weight.mul(coeffInt);
-				const unadjustedWeightFee = weightedCoeffInt.add(weightedCoeffFrac); // In Perbill
+				const unadjustedWeightFee = weightedCoeffInt.add(weightedCoeffFrac);
 
 				const adjustableFee = lenFee.add(unadjustedWeightFee);
-				const adjustedFee = targetedFeeAdjustment.mul(adjustableFee);
+				const adjustedFee = adjustableFee.add(targetedFeeAdjustment.mul(adjustableFee).div(fixed128));
 
 				// weight_to_fee calculation
 				// FIXME Implement polynomial.
-				const baseFeeFrac = extrinsicBaseWeight.mul(coeffFrac);
+				const baseFeeFrac = extrinsicBaseWeight.mul(coeffFrac).div(perBill);
 				const baseFeeInt = extrinsicBaseWeight.mul(coeffInt);
 				const baseFee = baseFeeInt.add(baseFeeFrac); // In Perbill
 
@@ -213,7 +213,7 @@ export default class ApiHandler {
 				extrinsics[idx].info = api.createType('RuntimeDispatchInfo', {
 					weight,
 					class: weightInfo.class,
-					partialFee: partialFee.div(perBill) // We were in Perbill-land, now back to integer
+					partialFee: partialFee
 				});
 			} catch (err) {
 				console.error(err);