feat: add valkey backed store

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/policy/passratechecker.go

@@ -0,0 +1,47 @@
+package policy
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/TecharoHQ/anubis/internal"
+	"github.com/TecharoHQ/anubis/internal/store/valkey"
+)
+
+type PassRateChecker struct {
+	store  *valkey.Store
+	header string
+	rate   float64
+}
+
+func NewPassRateChecker(store *valkey.Store, rate float64) Checker {
+	return &PassRateChecker{
+		store:  store,
+		rate:   rate,
+		header: "User-Agent",
+	}
+}
+
+func (prc *PassRateChecker) Hash() string {
+	return internal.SHA256sum(fmt.Sprintf("pass rate checker::%s", prc.header))
+}
+
+func (prc *PassRateChecker) Check(r *http.Request) (bool, error) {
+	data, err := prc.store.MultiGetInt(r.Context(), [][]string{
+		{"pass_rate", prc.header, r.Header.Get(prc.header), "pass"},
+		{"pass_rate", prc.header, r.Header.Get(prc.header), "challenges_issued"},
+		{"pass_rate", prc.header, r.Header.Get(prc.header), "fail"},
+	})
+	if err != nil {
+		return false, err
+	}
+
+	passCount, challengeCount, failCount := data[0], data[1], data[2]
+	passRate := float64(passCount-failCount) / float64(challengeCount)
+
+	if passRate >= prc.rate {
+		return true, nil
+	}
+
+	return false, nil
+}