Add decryptMime and refactor package structure

crypto/time.go

@@ -0,0 +1,32 @@
+package crypto
+
+import (
+	"time"
+)
+
+// UpdateTime update cached time
+func (pm *PmCrypto) UpdateTime(newTime int64) {
+	pm.latestServerTime = newTime
+	pm.latestClientTime = time.Now()
+}
+
+//GetTime get latest cached time
+func (pm *PmCrypto) GetTime() int64 {
+	return pm.getNow().Unix()
+}
+
+func (pm *PmCrypto) getNow() time.Time {
+	if pm.latestServerTime > 0 && !pm.latestClientTime.IsZero() {
+		// Sub is monotome, it uses a monotime time clock in this case instead of the wall clock
+		extrapolate := int64(pm.latestClientTime.Sub(time.Now()).Seconds())
+		return time.Unix(pm.latestServerTime + extrapolate, 0)
+	}
+
+	return time.Now()
+}
+
+func (pm *PmCrypto) getTimeGenerator() func() time.Time {
+	return func() time.Time {
+		return pm.getNow()
+	}
+}