[#479] morph/timer: Move block timer to morph package

Block timer is going to be reused in storage node to tick
EigenTrust calculation rounds.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/morph/timer/block.go

@@ -0,0 +1,168 @@
+package timer
+
+import (
+	"sync"
+)
+
+// BlockMeter calculates block time interval dynamically.
+type BlockMeter func() (uint32, error)
+
+// BlockTickHandler is a callback of a certain block advance.
+type BlockTickHandler func()
+
+// BlockTimer represents block timer.
+//
+// It can tick the blocks and perform certain actions
+// on block time intervals.
+type BlockTimer struct {
+	rolledBack bool
+
+	mtx *sync.Mutex
+
+	dur BlockMeter
+
+	baseDur uint32
+
+	mul, div uint32
+
+	cur, tgt uint32
+
+	h BlockTickHandler
+
+	ps []BlockTimer
+
+	deltaCfg
+}
+
+// DeltaOption is an option of delta-interval handler.
+type DeltaOption func(*deltaCfg)
+
+type deltaCfg struct {
+	pulse bool
+}
+
+// WithPulse returns option to call delta-interval handler multiple
+// times
+func WithPulse() DeltaOption {
+	return func(c *deltaCfg) {
+		c.pulse = true
+	}
+}
+
+// StaticBlockMeter returns BlockMeters that always returns (d, nil).
+func StaticBlockMeter(d uint32) BlockMeter {
+	return func() (uint32, error) {
+		return d, nil
+	}
+}
+
+// NewBlockTimer creates a new BlockTimer.
+//
+// Reset should be called before timer ticking.
+func NewBlockTimer(dur BlockMeter, h BlockTickHandler) *BlockTimer {
+	return &BlockTimer{
+		mtx: new(sync.Mutex),
+		dur: dur,
+		mul: 1,
+		div: 1,
+		h:   h,
+		deltaCfg: deltaCfg{
+			pulse: true,
+		},
+	}
+}
+
+// OnDelta registers handler which is executed on (mul / div * BlockMeter()) block
+// after basic interval reset.
+//
+// If WithPulse option is provided, handler is executed (mul / div * BlockMeter()) block
+// during base interval.
+func (t *BlockTimer) OnDelta(mul, div uint32, h BlockTickHandler, opts ...DeltaOption) {
+	c := deltaCfg{
+		pulse: false,
+	}
+
+	for i := range opts {
+		opts[i](&c)
+	}
+
+	t.ps = append(t.ps, BlockTimer{
+		mul: mul,
+		div: div,
+		h:   h,
+
+		deltaCfg: c,
+	})
+}
+
+// Reset resets previous ticks of the BlockTimer.
+//
+// Returns BlockMeter's error upon occurrence.
+func (t *BlockTimer) Reset() error {
+	d, err := t.dur()
+	if err != nil {
+		return err
+	}
+
+	t.mtx.Lock()
+
+	t.resetWithBaseInterval(d)
+
+	for i := range t.ps {
+		t.ps[i].resetWithBaseInterval(d)
+	}
+
+	t.mtx.Unlock()
+
+	return nil
+}
+
+func (t *BlockTimer) resetWithBaseInterval(d uint32) {
+	t.rolledBack = false
+	t.baseDur = d
+	t.reset()
+}
+
+func (t *BlockTimer) reset() {
+	mul, div := t.mul, t.div
+
+	if !t.pulse && t.rolledBack && mul < div {
+		mul, div = 1, 1
+	}
+
+	delta := mul * t.baseDur / div
+	if delta == 0 {
+		delta = 1
+	}
+
+	t.tgt = delta
+	t.cur = 0
+}
+
+// Tick ticks one block in the BlockTimer.
+//
+// Executes all callbacks which are awaiting execution at the new block.
+func (t *BlockTimer) Tick() {
+	t.mtx.Lock()
+	t.tick()
+	t.mtx.Unlock()
+}
+
+func (t *BlockTimer) tick() {
+	t.cur++
+
+	if t.cur == t.tgt {
+		// it would be advisable to optimize such execution, for example:
+		//   1. push handler to worker pool t.wp.Submit(h);
+		//   2. call t.tickH(h)
+		t.h()
+
+		t.cur = 0
+		t.rolledBack = true
+		t.reset()
+	}
+
+	for i := range t.ps {
+		t.ps[i].tick()
+	}
+}