add helper functions (#9)

helpers.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"github.com/decred/dcrd/chaincfg/v3"
+	"github.com/decred/dcrd/dcrutil/v3"
+)
+
+func currentVoteVersion(params *chaincfg.Params) uint32 {
+	var latestVersion uint32
+	for version := range params.Deployments {
+		if latestVersion < version {
+			latestVersion = version
+		}
+	}
+	return latestVersion
+}
+
+// isValidVoteBits returns an error if voteBits are not valid for agendas
+func isValidVoteBits(params *chaincfg.Params, voteVersion uint32, voteBits uint16) bool {
+	if !dcrutil.IsFlagSet16(voteBits, dcrutil.BlockValid) {
+		return false
+	}
+	voteBits &= ^uint16(dcrutil.BlockValid)
+
+	var availVoteBits uint16
+	for _, vote := range params.Deployments[voteVersion] {
+		availVoteBits |= vote.Vote.Mask
+
+		isValid := false
+		maskedBits := voteBits & vote.Vote.Mask
+		for _, c := range vote.Vote.Choices {
+			if c.Bits == maskedBits {
+				isValid = true
+				break
+			}
+		}
+		if !isValid {
+			return false
+		}
+	}
+	return true
+}

helpers_test.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/decred/dcrd/chaincfg/v3"
+	"github.com/decred/dcrd/dcrutil/v3"
+)
+
+func TestVoteBits(t *testing.T) {
+	var tests = []struct {
+		voteBits uint16
+		isValid  bool
+	}{
+		{0, false},
+		{dcrutil.BlockValid, true},
+		{dcrutil.BlockValid | 0x0002, true},
+		{dcrutil.BlockValid | 0x0003, true},
+		{dcrutil.BlockValid | 0x0004, true},
+		{dcrutil.BlockValid | 0x0005, true},
+		{dcrutil.BlockValid | 0x0006, false},
+		{dcrutil.BlockValid | 0x0007, false},
+		{dcrutil.BlockValid | 0x0008, true},
+	}
+
+	params := chaincfg.MainNetParams()
+	voteVersion := currentVoteVersion(params)
+	for _, test := range tests {
+		isValid := isValidVoteBits(params, voteVersion, test.voteBits)
+		if isValid != test.isValid {
+			t.Fatalf("isValidVoteBits failed for votebits '%d': want %v, got %v",
+				test.voteBits, test.isValid, isValid)
+		}
+	}
+}