From 476349dd1c77e7bd9064293ce3eb7ac6efbabab6 Mon Sep 17 00:00:00 2001
From: Leonard Lyubich <leonard@nspcc.ru>
Date: Thu, 21 Jan 2021 19:32:41 +0300
Subject: [PATCH] [#324] ir/timers: Implement chain block timer

Implement a timer that can tick chain blocks and perform actions at time
intervals in the blocks.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
---
 pkg/innerring/timers/block.go      | 114 +++++++++++++++++++++++++++++
 pkg/innerring/timers/block_test.go |  56 ++++++++++++++
 2 files changed, 170 insertions(+)
 create mode 100644 pkg/innerring/timers/block.go
 create mode 100644 pkg/innerring/timers/block_test.go

diff --git a/pkg/innerring/timers/block.go b/pkg/innerring/timers/block.go
new file mode 100644
index 000000000..b0aebd48c
--- /dev/null
+++ b/pkg/innerring/timers/block.go
@@ -0,0 +1,114 @@
+package timers
+
+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 {
+	mtx *sync.Mutex
+
+	dur BlockMeter
+
+	mul, div uint32
+
+	cur, tgt uint32
+
+	h BlockTickHandler
+
+	ps []BlockTimer
+}
+
+// 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,
+	}
+}
+
+// OnDelta registers handler which is executed every (mul / div * BlockMeter()) block.
+func (t *BlockTimer) OnDelta(mul, div uint32, h BlockTickHandler) {
+	t.ps = append(t.ps, BlockTimer{
+		mul: mul,
+		div: div,
+		h:   h,
+	})
+}
+
+// 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.reset(d)
+	t.mtx.Unlock()
+
+	return nil
+}
+
+func (t *BlockTimer) reset(dur uint32) {
+	delta := t.mul * dur / t.div
+	if delta == 0 {
+		delta = 1
+	}
+
+	t.tgt = delta
+	t.cur = 0
+
+	for i := range t.ps {
+		t.ps[i].reset(dur)
+	}
+}
+
+// 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 {
+		t.cur = 0
+
+		// 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()
+	}
+
+	for i := range t.ps {
+		t.ps[i].tick()
+	}
+}
diff --git a/pkg/innerring/timers/block_test.go b/pkg/innerring/timers/block_test.go
new file mode 100644
index 000000000..da677a581
--- /dev/null
+++ b/pkg/innerring/timers/block_test.go
@@ -0,0 +1,56 @@
+package timers_test
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-node/pkg/innerring/timers"
+	"github.com/stretchr/testify/require"
+)
+
+func tickN(t *timers.BlockTimer, n uint32) {
+	for i := uint32(0); i < n; i++ {
+		t.Tick()
+	}
+}
+
+func TestBlockTimer(t *testing.T) {
+	blockDur := uint32(10)
+	baseCallCounter := uint32(0)
+
+	bt := timers.NewBlockTimer(timers.StaticBlockMeter(blockDur), func() {
+		baseCallCounter++
+	})
+
+	require.NoError(t, bt.Reset())
+
+	intervalNum := uint32(7)
+
+	tickN(bt, intervalNum*blockDur)
+
+	require.Equal(t, intervalNum, uint32(baseCallCounter))
+
+	// add half-interval handler
+	halfCallCounter := uint32(0)
+
+	bt.OnDelta(1, 2, func() {
+		halfCallCounter++
+	})
+
+	// add double interval handler
+	doubleCallCounter := uint32(0)
+
+	bt.OnDelta(2, 1, func() {
+		doubleCallCounter++
+	})
+
+	require.NoError(t, bt.Reset())
+
+	baseCallCounter = 0
+	intervalNum = 20
+
+	tickN(bt, intervalNum*blockDur)
+
+	require.Equal(t, intervalNum*2, uint32(halfCallCounter))
+	require.Equal(t, intervalNum, uint32(baseCallCounter))
+	require.Equal(t, intervalNum/2, uint32(doubleCallCounter))
+}