[#473] Implement EigenTrust calculations

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/reputation/eigentrust/controller/deps.go

@@ -0,0 +1,35 @@
+package eigentrustctrl
+
+import (
+	"context"
+)
+
+// IterationContext is a context of the i-th
+// stage of iterative EigenTrust algorithm.
+type IterationContext interface {
+	context.Context
+
+	// Must return epoch number to select the values
+	// for global trust calculation.
+	Epoch() uint64
+
+	// Must return the sequence number of the iteration.
+	I() uint32
+
+	// Must return true if I() is the last iteration.
+	Last() bool
+}
+
+// DaughtersTrustCalculator is an interface of entity
+// responsible for calculating the global trust of
+// daughter nodes in terms of EigenTrust algorithm.
+type DaughtersTrustCalculator interface {
+	// Must perform the iteration step of the loop
+	// for computing the global trust of all daughter
+	// nodes and sending intermediate values
+	// according to EigenTrust description
+	// http://ilpubs.stanford.edu:8090/562/1/2002-56.pdf Ch.5.1.
+	//
+	// Execution should be interrupted if ctx.Last().
+	Calculate(ctx IterationContext)
+}