Implement CustomRegex detector

[mcastorina]

This detector uses webhooks for verification.

[ahrav]

This is gonna be huge win for the product. Nice job

[ahrav]

Very useful comment 🙌

[ahrav]

question: is this used anywhere? I don't see any reference to it. Also it looks like we are returning an unexported type from an exported function, is that on purpose? Or could we maybe make them both exported.

[mcastorina]

It's not used anywhere yet. The intention is to use it in the engine once the functionality is implemented here.

I did intentionally return an unexported type from the exported function to control initialization. The idea being if a variable exists as that type, the values must have been validated.

[mcastorina]

I'll add some comments to make that clear for the function.

[ahrav]

suggestion: If we do some precomputations up front we get a nice little speed up.

// Find the max length and total number of permutations.
	maxLength := 0
	t := 1
	for _, l := range lengths {
		t *= l
		if l > maxLength {
			maxLength = l
		}
	}
	result := make([][]int, 0, t)
	for r := range result {
		result[r] = make([]int, 0, maxLength)
	}

	for _, length := range lengths {
		var nextResult [][]int
		for i := 0; i < length; i++ {
			// Append index to all existing results.
			for _, curResult := range result {
				nextResult = append(nextResult, append(curResult, i))
				if len(nextResult) >= maxTotalMatches {
					return nextResult
				}
			}
		}
		result = nextResult
	}
	return result

Using:

func BenchmarkProductIndices(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = productIndices(3, 2, 6)
	}
}

With just 2,3,2 as the input:

[mcastorina]

Nice, that's way better!

[mcastorina]

I ended up implementing a different algorithm that's a bit faster and still passes the tests:

» go test -bench . ./pkg/custom_detectors
BenchmarkProductIndices-8         512116              2325 ns/op

» go test -bench . ./pkg/custom_detectors
BenchmarkProductIndices-8        1355827               890.8 ns/op

I think the 126 ns/op you were getting was because it was always returning an empty result.. (also explains the 1 alloc).