initial commit

.editorconfig

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+[*.cr]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true

.gitignore

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+/doc/
+/lib/
+/bin/
+/.shards/
+
+# Libraries don't need dependency lock
+# Dependencies will be locked in application that uses them
+/shard.lock

.travis.yml

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+language: crystal

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2017 Sam Eaton
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# Cache Hash
+
+A simple key value store where pairs can expire after a set interval
+
+## Installation
+
+Add this to your application's `shard.yml`:
+
+```yaml
+dependencies:
+  cache_hash:
+    github: samueleaton/cache_hash
+```
+
+## Usage
+
+```ruby
+require "cache_hash"
+
+# (Hours, Minutes, Seconds), caching 2 seconds
+cache_interval = Time::Span.new(0, 0, 2)
+
+cache_hash = CacheHash(String, String).new(cache_interval)
+cache_hash["key1"] = "Value 1"
+sleep 1 # one second elapsed
+cache_hash["key2"] = "Value 2"
+sleep 1 # two seconds elapsed
+
+cache_hash["key1"] #=> nil
+cache_hash["key2"] #=> "Value 2"
+```
+
+## Contributing
+
+1. Fork it ( https://github.com/[your-github-name]/cache_hash/fork )
+2. Create your feature branch (git checkout -b my-new-feature)
+3. Commit your changes (git commit -am 'Add some feature')
+4. Push to the branch (git push origin my-new-feature)
+5. Create a new Pull Request
+
+## Contributors
+
+- [Sam Eaton](https://github.com/samueleaton) - creator, maintainer

shard.yml

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+name: cache_hash
+version: 0.1.0
+
+authors:
+  - Sam Eaton <same@qualtrics.com>
+
+crystal: 0.23.1
+
+license: MIT

spec/cache_hash_spec.cr

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+require "./spec_helper"
+
+describe CacheHash do
+  it "saves key value pairs" do
+    hash = CacheHash(String, String).new(Time::Span.new(0,0,4))
+    hash["city_1"] = "Seattle"
+    hash["city_2"] = "Honk Kong"
+    hash["city_3"] = "Sacramento"
+    hash["city_1"].should eq("Seattle")
+    hash["city_2"].should eq("Honk Kong")
+    hash["city_3"].should eq("Sacramento")
+  end
+
+  it "removes stale kv pairs on lookup" do
+    hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+    hash["city_1"] = "Seattle"
+    sleep 1
+    hash["city_2"] = "Honk Kong"
+    sleep 1
+    hash["city_3"] = "Sacramento"
+    sleep 1
+    hash["city_4"] = "Salt Lake City"
+    sleep 1
+    hash["city_5"] = "Denver"
+    sleep 1
+
+    hash.raw["city_1"].should eq("Seattle")
+    hash.raw["city_2"].should eq("Honk Kong")
+    hash.raw["city_3"].should eq("Sacramento")
+    hash.raw["city_4"].should eq("Salt Lake City")
+    hash.raw["city_5"].should eq("Denver")
+
+    hash["city_1"].should be_nil
+    hash["city_2"].should be_nil
+    hash["city_3"].should be_nil
+    hash["city_4"].should eq("Salt Lake City")
+    hash["city_5"].should eq("Denver")
+
+    hash.raw["city_1"]?.should be_nil
+    hash.raw["city_2"]?.should be_nil
+    hash.raw["city_3"]?.should be_nil
+    hash.raw["city_4"]?.should eq("Salt Lake City")
+    hash.raw["city_5"]?.should eq("Denver")
+  end
+
+  describe "#purge_stale" do
+    it "removes all stale, expired values from the hash" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+      hash["city_1"] = "Seattle"
+      sleep 1
+      hash["city_2"] = "Honk Kong"
+      sleep 1
+      hash["city_3"] = "Sacramento"
+      sleep 1
+      hash["city_4"] = "Salt Lake City"
+      sleep 1
+      hash["city_5"] = "Denver"
+      sleep 1
+      hash.raw["city_1"].should eq("Seattle")
+      hash.raw["city_2"].should eq("Honk Kong")
+      hash.raw["city_3"].should eq("Sacramento")
+      hash.raw["city_4"].should eq("Salt Lake City")
+      hash.raw["city_5"].should eq("Denver")
+      hash.purge_stale
+      hash.raw["city_1"]?.should be_nil
+      hash.raw["city_2"]?.should be_nil
+      hash.raw["city_3"]?.should be_nil
+      hash.raw["city_4"]?.should eq("Salt Lake City")
+      hash.raw["city_5"]?.should eq("Denver")
+    end
+  end
+
+  describe "#fresh" do
+    it "purges all stale values and returns the IDs of non-stale kv pairs" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+      hash["city_1"] = "Seattle"
+      sleep 1
+      hash["city_2"] = "Honk Kong"
+      sleep 1
+      hash["city_3"] = "Sacramento"
+      sleep 1
+      hash["city_4"] = "Salt Lake City"
+      sleep 1
+      hash["city_5"] = "Denver"
+      sleep 1
+
+      hash.raw["city_1"].should eq("Seattle")
+      hash.raw["city_2"].should eq("Honk Kong")
+      hash.raw["city_3"].should eq("Sacramento")
+      hash.raw["city_4"].should eq("Salt Lake City")
+      hash.raw["city_5"].should eq("Denver")
+
+      hash.fresh.should eq(["city_4", "city_5"])
+
+      hash.raw["city_1"]?.should be_nil
+      hash.raw["city_2"]?.should be_nil
+      hash.raw["city_3"]?.should be_nil
+      hash.raw["city_4"]?.should eq("Salt Lake City")
+      hash.raw["city_5"]?.should eq("Denver")
+    end
+  end
+
+  describe "#fresh?" do
+    it "returns a true if the kv pair is not stale" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+      hash["city_1"] = "Seattle"
+      sleep 1
+      hash["city_2"] = "Honk Kong"
+      sleep 1
+      hash["city_3"] = "Sacramento"
+      sleep 1
+      hash["city_4"] = "Salt Lake City"
+      sleep 1
+      hash["city_5"] = "Denver"
+      sleep 1
+
+      hash.fresh?("city_1").should be_false
+      hash.fresh?("city_4").should be_true
+      hash.fresh?("xxxxx").should be_false
+      sleep 2
+      hash.fresh?("city_4").should be_false
+    end
+
+    it "removes deletes the kv pair if it is stale" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+      hash["city_1"] = "Seattle"
+      sleep 1
+      hash["city_2"] = "Honk Kong"
+      sleep 1
+      hash["city_3"] = "Sacramento"
+      sleep 1
+      hash["city_4"] = "Salt Lake City"
+      sleep 1
+      hash["city_5"] = "Denver"
+      sleep 1
+
+      hash.raw["city_1"].should eq("Seattle")
+      hash.raw["city_2"].should eq("Honk Kong")
+      hash.raw["city_3"].should eq("Sacramento")
+      hash.raw["city_4"].should eq("Salt Lake City")
+      hash.raw["city_5"].should eq("Denver")
+
+      (hash.fresh?("city_1")).should be_false
+      hash.raw["city_1"]?.should be_nil
+    end
+  end
+
+  describe "#time" do
+    it "returns a time if the kv pair is not stale" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+
+      t = Time.now
+      hash["city_1"] = "Seattle"
+      hash.time("city_1").class.should eq(Time)
+
+      city_1_time = hash.time("city_1").not_nil!
+      (city_1_time > t && city_1_time < Time.now).should be_true
+    end
+
+    it "delete the kv pair if it is stale" do
+      hash = CacheHash(String, String).new(Time::Span.new(0,0,3))
+      hash["city_1"] = "Seattle"
+      sleep 1
+      hash["city_2"] = "Honk Kong"
+      sleep 1
+      hash["city_3"] = "Sacramento"
+      sleep 1
+      hash["city_4"] = "Salt Lake City"
+      sleep 1
+      hash["city_5"] = "Denver"
+      sleep 1
+
+      hash.raw["city_1"].should eq("Seattle")
+      hash.raw["city_2"].should eq("Honk Kong")
+      hash.raw["city_3"].should eq("Sacramento")
+      hash.raw["city_4"].should eq("Salt Lake City")
+      hash.raw["city_5"].should eq("Denver")
+
+      hash.time("city_1").should be_nil
+      hash.raw["city_1"]?.should be_nil
+    end
+  end
+end

spec/spec_helper.cr

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+require "spec"
+require "../src/cache_hash"
+
+class CacheHash
+  def raw
+    @kv_hash
+  end
+end

src/cache_hash.cr

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+class CacheHash(K, T)
+  def initialize(@cache_time_span : Time::Span)
+    @kv_hash = {} of K => String
+    @time_hash = {} of K => Time
+  end
+
+  def [](key)
+    if cached_time = @time_hash[key]?
+      if cached_time > Time.now - @cache_time_span
+        @kv_hash[key]
+      else
+        delete key
+        nil
+      end
+    end
+  end
+
+  def []=(key, val : T)
+    @time_hash[key] = Time.now
+    @kv_hash[key] = val
+  end
+
+  private def delete(key) : String | Nil
+    @time_hash.delete key
+    @kv_hash.delete key
+    nil
+  end
+
+  def purge_stale()
+    @kv_hash.select! do |k, v|
+      if cached_time = @time_hash[k]?
+        cached_time > Time.now - @cache_time_span
+      end
+    end
+    nil
+  end
+
+  def fresh
+    purge_stale
+    @kv_hash.keys
+  end
+
+  def fresh?(k)
+    if cached_time = @time_hash[k]?
+      if cached_time > Time.now - @cache_time_span
+        true
+      else
+        delete k
+        false
+      end
+    else
+      false
+    end
+  end
+
+  def time(k)
+    if cached_time = @time_hash[k]?
+      if cached_time > Time.now - @cache_time_span
+        cached_time
+      else
+        delete k
+      end
+    end
+  end
+end