From ad938f5d05651e70d8911ccd8221c9a46790e9de Mon Sep 17 00:00:00 2001
From: Oliver <oliver.lokhandwala@gmail.com>
Date: Mon, 1 Jan 2024 19:56:40 -0800
Subject: [PATCH] first iteration of lockmanager with tests

---
 util/lockmanager.go      | 56 ++++++++++++++++++++++++++++++++++++++++
 util/lockmanager_test.go | 51 ++++++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+)
 create mode 100644 util/lockmanager.go
 create mode 100644 util/lockmanager_test.go

diff --git a/util/lockmanager.go b/util/lockmanager.go
new file mode 100644
index 00000000..32be5c26
--- /dev/null
+++ b/util/lockmanager.go
@@ -0,0 +1,56 @@
+package util
+
+import (
+	"fmt"
+	"log"
+	"sync"
+	"time"
+)
+
+type Lock struct {
+	key string;
+	timestamp time.Time;
+}
+
+type LockManager struct {
+	locks map[string]*Lock;
+	mutex sync.Mutex;
+	staleDuration time.Duration;
+}
+
+func NewLockManager(staleDuration time.Duration) *LockManager {
+	lm := &LockManager{
+		locks: make(map[string]*Lock),
+		staleDuration: staleDuration,
+	}
+	go lm.removeStaleLocks();
+	return lm;
+}
+
+func (lm *LockManager) Lock(key string) {
+	lm.mutex.Lock();
+	lm.locks[key] = &Lock{key: key, timestamp: time.Now()};
+}
+
+func (lm *LockManager) Unlock(key string) error {
+	// Check if key exists in the lock map
+	_, ok := lm.locks[key];
+	if ok {
+		defer lm.mutex.Unlock();
+		delete(lm.locks, key);
+		return nil;
+	} else {
+		log.Fatal("Key not found.")
+		return fmt.Errorf("Error. Key not found.");
+	}
+}
+
+func (lm *LockManager) removeStaleLocks() {
+	time.Sleep(lm.staleDuration);
+	for key, lock := range lm.locks {
+		if time.Since(lock.timestamp) > lm.staleDuration {
+			delete(lm.locks, key);
+			lm.mutex.Unlock();
+		}
+	}
+}
\ No newline at end of file
diff --git a/util/lockmanager_test.go b/util/lockmanager_test.go
new file mode 100644
index 00000000..36b0b948
--- /dev/null
+++ b/util/lockmanager_test.go
@@ -0,0 +1,51 @@
+package util
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+
+func TestLockAcquisition(t *testing.T) {
+	lm := NewLockManager(3 * time.Second);
+	key := "testkey"
+	fmt.Println("Main Thread!")
+	lm.Lock(key)
+	lm.Lock(key)
+
+	fmt.Println("Got past the first lock from removeStaleLocks go routine")
+
+	go func() {
+		fmt.Println("1st Go Routine Started")
+
+		startTime := time.Now();
+		lm.Lock(key)
+		lockWaitDuration := time.Since(startTime);
+		fmt.Printf("Waited %v long to aquire the lock in the 1st go routine\n", lockWaitDuration);
+
+		go func() {
+			fmt.Println("2nd Go Routine Started")
+			startTime := time.Now();
+			lm.Lock(key);
+			lockWaitDuration := time.Since(startTime);
+			fmt.Printf("Waited %v long to aquire the lock in the 2nd go routine\n", lockWaitDuration);
+			defer lm.Unlock(key);
+			fmt.Println("2nd Go Routine Done")
+		}()
+
+		
+		defer lm.Unlock(key)
+		fmt.Println("1st Go Routine Done")
+		time.Sleep(3 * time.Second)
+	}()
+
+	fmt.Println("Main Thread Almost Done")
+	time.Sleep(1 * time.Second)
+	lm.Unlock(key)
+
+	time.Sleep(4 * time.Second)
+
+	fmt.Println("Main Thread Done!")
+
+}
\ No newline at end of file