[#428] reputation: Implement local trust controller

Implement `Controller` designed to analyze the values collected by the local
node (the source is hidden behind Writer/WriterProvider interfaces) and
transfer them to the destination (hidden behind Iterator / IteratorProvider
interface).

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

pkg/services/reputation/local/controller/controller.go

@@ -0,0 +1,82 @@
+package trustcontroller
+
+import (
+	"context"
+	"fmt"
+	"sync"
+)
+
+// Prm groups the required parameters of the Controller's constructor.
+//
+// All values must comply with the requirements imposed on them.
+// Passing incorrect parameter values will result in constructor
+// failure (error or panic depending on the implementation).
+type Prm struct {
+	// Iterator over the reputation values
+	// collected by the node locally.
+	//
+	// Must not be nil.
+	LocalTrustSource IteratorProvider
+
+	// Place of recording the local values of
+	// the used space of containers.
+	//
+	// Must not be nil.
+	LocalTrustTarget WriterProvider
+}
+
+// Controller represents main handler for starting
+// and interrupting the reporting local trust values.
+//
+// It binds the interfaces of the local value stores
+// to the target storage points. Controller is abstracted
+// from the internal storage device and the network location
+// of the connecting components. At its core, it is a
+// high-level start-stop trigger for reporting.
+//
+// For correct operation, the controller must be created
+// using the constructor (New) based on the required parameters
+// and optional components. After successful creation,
+// the constructor is immediately ready to work through
+// API of external control of calculations and data transfer.
+type Controller struct {
+	prm Prm
+
+	opts *options
+
+	mtx  sync.Mutex
+	mCtx map[uint64]context.CancelFunc
+}
+
+const invalidPrmValFmt = "invalid parameter %s (%T):%v"
+
+func panicOnPrmValue(n string, v interface{}) {
+	panic(fmt.Sprintf(invalidPrmValFmt, n, v, v))
+}
+
+// New creates a new instance of the Controller.
+//
+// Panics if at least one value of the parameters is invalid.
+//
+// The created Controller does not require additional
+// initialization and is completely ready for work
+func New(prm Prm, opts ...Option) *Controller {
+	switch {
+	case prm.LocalTrustSource == nil:
+		panicOnPrmValue("LocalTrustSource", prm.LocalTrustSource)
+	case prm.LocalTrustTarget == nil:
+		panicOnPrmValue("LocalTrustTarget", prm.LocalTrustTarget)
+	}
+
+	o := defaultOpts()
+
+	for _, opt := range opts {
+		opt(o)
+	}
+
+	return &Controller{
+		prm:  prm,
+		opts: o,
+		mCtx: make(map[uint64]context.CancelFunc),
+	}
+}