From a1342c23fbd100db482b8592e1b97cf2286454d8 Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Mon, 14 Oct 2019 15:17:25 +0100
Subject: [PATCH] add mutex lock implementation

---
 sync/lock/lock.go        |   5 ++
 sync/lock/mutex/mutex.go | 142 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 147 insertions(+)
 create mode 100644 sync/lock/mutex/mutex.go

diff --git a/sync/lock/lock.go b/sync/lock/lock.go
index 8be6629f..c21a9125 100644
--- a/sync/lock/lock.go
+++ b/sync/lock/lock.go
@@ -2,9 +2,14 @@
 package lock
 
 import (
+	"errors"
 	"time"
 )
 
+var (
+	ErrLockTimeout = errors.New("lock timeout")
+)
+
 // Lock is a distributed locking interface
 type Lock interface {
 	// Acquire a lock with given id
diff --git a/sync/lock/mutex/mutex.go b/sync/lock/mutex/mutex.go
new file mode 100644
index 00000000..81059ab3
--- /dev/null
+++ b/sync/lock/mutex/mutex.go
@@ -0,0 +1,142 @@
+// Package mutex provides a sync.Mutex implementation of the lock for local use
+package mutex
+
+import (
+	"sync"
+	"time"
+
+	lock "github.com/micro/go-micro/sync/lock"
+)
+
+type mutexLock struct {
+	sync.RWMutex
+	locks map[string]*mlock
+}
+
+type mlock struct {
+	id      string
+	time    time.Time
+	ttl     time.Duration
+	release chan bool
+}
+
+func (m *mutexLock) Acquire(id string, opts ...lock.AcquireOption) error {
+	// lock our access
+	m.Lock()
+
+	var options lock.AcquireOptions
+	for _, o := range opts {
+		o(&options)
+	}
+
+	lk, ok := m.locks[id]
+	if !ok {
+		m.locks[id] = &mlock{
+			id:      id,
+			time:    time.Now(),
+			ttl:     options.TTL,
+			release: make(chan bool),
+		}
+		// unlock
+		m.Unlock()
+		return nil
+	}
+
+	m.Unlock()
+
+	// set wait time
+	var wait <-chan time.Time
+	var ttl <-chan time.Time
+
+	// decide if we should wait
+	if options.Wait > time.Duration(0) {
+		wait = time.After(options.Wait)
+	}
+
+	// check the ttl of the lock
+	if lk.ttl > time.Duration(0) {
+		// time lived for the lock
+		live := time.Since(lk.time)
+
+		// set a timer for the leftover ttl
+		if live > lk.ttl {
+			// release the lock if it expired
+			m.Release(id)
+		} else {
+			ttl = time.After(live)
+		}
+	}
+
+lockLoop:
+	for {
+		// wait for the lock to be released
+		select {
+		case <-lk.release:
+			m.Lock()
+
+			// someone locked before us
+			lk, ok = m.locks[id]
+			if ok {
+				m.Unlock()
+				continue
+			}
+
+			// got chance to lock
+			m.locks[id] = &mlock{
+				id:      id,
+				time:    time.Now(),
+				ttl:     options.TTL,
+				release: make(chan bool),
+			}
+
+			m.Unlock()
+
+			break lockLoop
+		case <-ttl:
+			// ttl exceeded
+			m.Release(id)
+			// TODO: check the ttl again above
+			ttl = nil
+			// try acquire
+			continue
+		case <-wait:
+			return lock.ErrLockTimeout
+		}
+	}
+
+	return nil
+}
+
+func (m *mutexLock) Release(id string) error {
+	m.Lock()
+	defer m.Unlock()
+
+	lk, ok := m.locks[id]
+	// no lock exists
+	if !ok {
+		return nil
+	}
+
+	// delete the lock
+	delete(m.locks, id)
+
+	select {
+	case <-lk.release:
+		return nil
+	default:
+		close(lk.release)
+	}
+
+	return nil
+}
+
+func NewLock(opts ...lock.Option) lock.Lock {
+	var options lock.Options
+	for _, o := range opts {
+		o(&options)
+	}
+
+	return &mutexLock{
+		locks: make(map[string]*mlock),
+	}
+}