Adds set_purge_interval method

README.md

@@ -61,6 +61,22 @@ Removes all key/value pairs from the hash.
 
 Removes all stale key/value pairs from the hash.
 
+### `.set_purge_interval(interval : Time::Span, stale_only : Bool = true)`
+
+Sets an interval where key/value pairs will automatically be purged.
+
+**Example:**
+
+```ruby
+cache_hash = CacheHash(String).new(1.minute)
+cache_hash.set_purge_interval(10.minutes) # stale_only defaults to true
+```
+
+```ruby
+cache_hash = CacheHash(String).new(1.minute)
+cache_hash.set_purge_interval(10.minutes, stale_only: false) # deletes all values, not just stale ones
+```
+
 ### `.keys() : Array(String)`
 
 Runs `purge_stale` and returns an array of all the the non-stale keys.

spec/cache_hash_spec.cr

@@ -165,14 +165,17 @@ describe CacheHash do
 
   describe "#time" do
     it "returns a time if the kv pair is not stale" do
-      hash = CacheHash(String).new(Time::Span.new(0, 0, 3))
-
-      t = Time.now
+      time_before = Time.now
+      sleep 1
+      hash = CacheHash(String).new(3.seconds)
       hash.set "city_1", "Seattle"
-      hash.time("city_1").class.should eq(Time)
+      sleep 1
+      time_after = Time.now
 
       city_1_time = hash.time("city_1").not_nil!
-      (city_1_time > t && city_1_time < Time.now).should be_true
+      city_1_time.class.should eq(Time)
+      (city_1_time > time_before).should be_true
+      (city_1_time < time_after).should be_true
     end
 
     it "delete the kv pair if it is stale" do
@@ -278,4 +281,55 @@ describe CacheHash do
       hash.raw.empty?.should be_true
     end
   end
+
+  describe "#set_purge_interval" do
+    it "purges stale values from hash" do
+      hash = CacheHash(String).new(4.seconds)
+      hash.set_purge_interval(3.seconds)
+      hash.set "city_1", "Seattle"
+      hash.set "city_2", "Hong Kong"
+      hash.set "city_3", "Sacramento"
+
+      hash.get("city_1").should eq("Seattle")
+      hash.get("city_2").should eq("Hong Kong")
+      hash.get("city_3").should eq("Sacramento")
+      hash.raw.empty?.should be_false
+      sleep 4
+      hash.get("city_1").should be_nil
+      hash.get("city_2").should be_nil
+      hash.get("city_3").should be_nil
+      hash.raw.empty?.should be_true
+
+      hash.set "city_1", "Seattle"
+      sleep 2
+      hash.set "city_2", "Hong Kong"
+      hash.get("city_1").should eq("Seattle")
+      hash.get("city_2").should eq("Hong Kong")
+      sleep 2
+      hash.get("city_1").should be_nil
+      hash.get("city_2").should eq("Hong Kong")
+      sleep 2
+      hash.get("city_1").should be_nil
+      hash.get("city_2").should be_nil
+      hash.raw.empty?.should be_true
+    end
+
+    it "purges all values from hash if specified" do
+      hash = CacheHash(String).new(5.seconds)
+      hash.set_purge_interval(3.seconds, stale_only: false)
+      hash.set "city_1", "Seattle"
+      hash.set "city_2", "Hong Kong"
+      hash.set "city_3", "Sacramento"
+
+      hash.get("city_1").should eq("Seattle")
+      hash.get("city_2").should eq("Hong Kong")
+      hash.get("city_3").should eq("Sacramento")
+      hash.raw.empty?.should be_false
+      sleep 4
+      hash.get("city_1").should be_nil
+      hash.get("city_2").should be_nil
+      hash.get("city_3").should be_nil
+      hash.raw.empty?.should be_true
+    end
+  end
 end

src/cache_hash.cr

@@ -2,6 +2,7 @@ class CacheHash(V)
   def initialize(@cache_time_span : Time::Span)
     @kv_hash = {} of String => V
     @time_hash = {} of String => Time
+    @is_purge_interval_running = false
   end
 
   def get(key : String)
@@ -83,4 +84,31 @@ class CacheHash(V)
       end
     end
   end
+
+  def set_purge_interval(interval : Time::Span, stale_only = true)
+    @purge_interval = interval
+    @purge_interval_stale_only = stale_only
+    unless @is_purge_interval_running
+      spawn do
+        run_purge_interval_loop
+      end
+    end
+  end
+
+  private def run_purge_interval_loop
+    return if @is_purge_interval_running
+
+    @is_purge_interval_running = true
+    loop do
+      stale_only = @purge_interval_stale_only
+      if (interval = @purge_interval).is_a?(Time::Span)
+        sleep interval.as(Time::Span)
+        if stale_only
+          purge_stale
+        else
+          purge
+        end
+      end
+    end
+  end
 end