mukan-consensus/internal/indexer/indexer_utils.go

package indexer

import (
	"fmt"
	"math/big"

	"git.cw.tr/mukan-network/mukan-consensus/state/indexer"
)

// If the actual event value is a float, we get the condition and parse it as a float
// to compare against
func compareFloat(op1 *big.Float, op2 interface{}) (int, bool, error) {
	switch opVal := op2.(type) {
	case *big.Int:
		vF := new(big.Float)
		vF.SetInt(opVal)
		cmp := op1.Cmp(vF)
		return cmp, false, nil

	case *big.Float:
		return op1.Cmp(opVal), true, nil
	default:
		return -1, false, fmt.Errorf("unable to parse arguments, bad type: %T", op2)
	}
}

// If the event value we compare against the condition (op2) is an integer
// we convert the int to float with a precision equal to the number of bits
// needed to represent the integer to avoid rounding issues with floats
// where 100 would equal to 100.2 because 100.2 is rounded to 100, while 100.7
// would be rounded to 101.
func compareInt(op1 *big.Int, op2 interface{}) (int, bool, error) {

	switch opVal := op2.(type) {
	case *big.Int:
		return op1.Cmp(opVal), false, nil
	case *big.Float:
		vF := new(big.Float)
		vF.SetInt(op1)
		return vF.Cmp(opVal), true, nil
	default:
		return -1, false, fmt.Errorf("unable to parse arguments, unexpected type: %T", op2)
	}
}

func CheckBounds(ranges indexer.QueryRange, v interface{}) (bool, error) {
	// These functions fetch the lower and upper bounds of the query
	// It is expected that for x > 5, the value of lowerBound is 6.
	// This is achieved by adding one to the actual lower bound.
	// For a query of x < 5, the value of upper bound is 4.
	// This is achieved by subtracting one from the actual upper bound.

	// For integers this behavior will work. However, for floats, we cannot simply add/sub 1.
	// Query :x < 5.5 ; x = 5 should match the query. If we subtracted one as for integers,
	// the upperBound would be 4.5 and x would not match.  Thus we do not subtract anything for
	// floating point bounds.

	// We can rewrite these functions to not add/sub 1 but the function handles also time arguments.
	// To be sure we are not breaking existing queries that compare time, and as we are planning to replace
	// the indexer in the future, we adapt the code here to handle floats as a special case.
	lowerBound := ranges.LowerBoundValue()
	upperBound := ranges.UpperBoundValue()

	// *Explanation for the isFloat condition below.*
	// In LowerBoundValue(), for floating points, we cannot simply add 1 due to the reasons explained in
	// in the comment at the beginning. The same is true for subtracting one for UpperBoundValue().
	// That means that for integers, if the condition is >=, cmp will be either 0 or 1
	// ( cmp == -1 should always be false).
	// 	But if the lowerBound is a float, we have not subtracted one, so returning a 0
	// is correct only if ranges.IncludeLowerBound is true.
	// example int: x < 100; upperBound = 99; if x.Cmp(99) == 0 the condition holds
	// example float: x < 100.0; upperBound = 100.0; if x.Cmp(100) ==0 then returning x
	// would be wrong.
	switch vVal := v.(type) {
	case *big.Int:
		if lowerBound != nil {
			cmp, isFloat, err := compareInt(vVal, lowerBound)
			if err != nil {
				return false, err
			}
			if cmp == -1 || (isFloat && cmp == 0 && !ranges.IncludeLowerBound) {
				return false, err
			}
		}
		if upperBound != nil {
			cmp, isFloat, err := compareInt(vVal, upperBound)
			if err != nil {
				return false, err
			}
			if cmp == 1 || (isFloat && cmp == 0 && !ranges.IncludeUpperBound) {
				return false, err
			}
		}

	case *big.Float:
		if lowerBound != nil {
			cmp, isFloat, err := compareFloat(vVal, lowerBound)
			if err != nil {
				return false, err
			}
			if cmp == -1 || (cmp == 0 && isFloat && !ranges.IncludeLowerBound) {
				return false, err
			}
		}
		if upperBound != nil {
			cmp, isFloat, err := compareFloat(vVal, upperBound)
			if err != nil {
				return false, err
			}
			if cmp == 1 || (cmp == 0 && isFloat && !ranges.IncludeUpperBound) {
				return false, err
			}
		}

	default:
		return false, fmt.Errorf("invalid argument type in query: %T", v)
	}
	return true, nil
}