Gittr: A Git key/value store

README.md

Gittr.rb

Git as a key-value store! Build with Grit, it supports SET, GET, KEYS, and DELETE operations. In addition, we can also get the change history of key/values.

And since it's Git, we can easily enhance it to include other awesome Git features such as branches, diffs, reverting, and more!

Example:

@store = Gittr.new(:repo => File.expand_path('..', __FILE__))
@store.clear  # Deletes all keys/values from the store

# SET
@store['lady'] = "gaga"

# GET
@store['lady'] #=> "gaga"

# KEYS
@store.keys  #=> ['lady']

# DELETE
@store.delete('lady') #=> 'gaga'

# LOG
@store.log('key')

# Produces:
[
 {"message"=>"all clear","committer"=>{"name"=>"Matt Sears", "email"=>"[email protected]"}, "committed_date"=>"..."},
 {"message"=>"set 'lady' ", "committer"=>{"name"=>"Matt Sears", "email"=>"[email protected]"}, "committed_date"=>"..."}
 {"message"=>"delete 'lady' ", "committer"=>{"name"=>"Matt Sears", "email"=>"[email protected]"}, "committed_date"=>"..."}
]

gittr.rb

require 'yaml'
require 'grit'

class Gittr

  def initialize(options = {})
    @options = options
    unless ::File.exists?(File.join(path,'.git'))
      Grit::Repo.init(path)
    end
  end

  # Add the value to the to the store
  #
  # Example
  #   @store.set('key', 'value')
  #
  # Returns nothing
  def set(key, value)
    save("set '#{key}'") do |index|
      index.add(key_for(key), encode(value))
    end
  end

  # Shortcut for #set
  #
  # Example:
  #  @store[key] = 'value'
  #
  def []=(key, value)
    set(key, value)
  end

  # Retrieve the value for the given key with a default value
  #
  # Example:
  #  @store.get(key)  #=> value
  #
  # Returns the object found in the repo matching the key
  def get(key, value = nil, *)
    if head && blob = head.commit.tree / key_for(key)
      decode(blob.data)
    end
  end

  # Shortcut for #get
  #
  # Example:
  #   @store['key']  #=> value
  #
  def [](key)
    get(key)
  end

  # Returns an array of key names contained in store
  #
  # Example:
  #  @store.keys  #=> ['key1', 'key2']
  #
  def keys
    head.commit.tree.contents.map{|blob| deserialize(blob.name) }
  end

  # Deletes commits matching the given key
  #
  # Example:
  #  @store.delete('key')
  #
  # Returns nothing
  def delete(key, *)
    self[key].tap do
      save("deleted #{key}") {|index| index.delete(key_for(key)) }
    end
  end

  # Deletes all contents of the store
  #
  # Returns nothing
  def clear
    save("all clear") do |index|
      if tree = index.current_tree
        tree.contents.each do |entry|
          index.delete(key_for(entry.name))
        end
      end
    end
  end

  # The commit log for the given key
  #
  # Example:
  #  @store.log('key') #=> [{"message"=>"Updated key"...}]
  #
  # Returns Array of commit data
  def log(key)
    git.log(branch, key_for(key)).map{ |commit| commit.to_hash }
  end

  # Find the key if exists in the git repo
  #
  # Example:
  #  @store.key? 'key'  #=> true
  #
  # Returns true if found; false if not found
  def key?(key)
    !(head && head.commit.tree / key_for(key)).nil?
  end

  private

  # Format the given key so that it ensures it's git worthy
  def key_for(key)
    key.is_a?(String) ? key : serialize(key)
  end

  # Given the file path, return a new Grit::Repo if found
  def git
    @git ||= Grit::Repo.new(path)
  end

  # The git branch to use for this store
  def branch
    @options[:branch] || 'master'
  end

  # Checks out the branch on the repo
  def head
    git.get_head(branch)
  end

  # Commits the the value into the git repository with the given commit message
  def save(message)
    index = git.index
    if head
      commit = head.commit
      index.current_tree = commit.tree
    end
    yield index
    index.commit(message, :parents => Array(commit), :head => branch) if index.tree.any?
  end

  # Converts the value to yaml format
  def encode(value)
    value.to_yaml
  end

  # Loads value as a Yaml structure
  def decode(value)
    YAML.load(value)
  end

  # Convert value to byte stream. This allows keys to be objects too
  def serialize(value)
    Marshal.dump(value)
  end

  # Converts value back to an object.
  def deserialize(value)
    Marshal.restore(value) rescue value
  end

  # Given that repo path set in the options, return the expanded file path
  def path(key = '')
    @path ||= File.join(File.expand_path(@options[:repo]), key)
  end

end

gittr_test.rb

require 'minitest/autorun'
require File.join(File.dirname(__FILE__), 'gittr.rb')

describe Gittr do

  @types = {
    "String" => ["lady", "gaga"],
    "Object" => [{:lady => :gaga}, {:gaga => :ohai}]
  }

  before do
    @store = Gittr.new(:repo => File.expand_path('..', __FILE__))
    @store.clear
  end

  @types.each do |type, (key, key2)|

    it "writes String values to keys" do
      @store[key] = "value"
      @store[key].must_equal "value"
    end

    it "reads from keys" do
      @store[key].must_be_nil
    end

    it "returns a list of keys" do
      @store[key] = "value"
      @store.keys.must_include(key)
    end

    it "guarantees that a different String value is retrieved" do
      value = "value"
      @store[key] = value
      @store[key].wont_be_same_as(value)
    end

    it "writes Object values to keys" do
      @store[key] = {:foo => :bar}
      @store[key].must_equal({:foo => :bar})
    end

    it "guarantees that a different Object value is retrieved" do
      value = {:foo => :bar}
      @store[key] = value
      @store[key].wont_be_same_as(:foo => :bar)
    end

    it "returns false from key? if a key is not available" do
      @store.key?(key).must_equal false
    end

    it "returns true from key? if a key is available" do
      @store[key] = "value"
      @store.key?(key).must_equal true
    end

    it "removes and return an element with a key from the store via delete if it exists" do
      @store[key] = "value"
      @store.delete(key).must_equal "value"
      @store.key?(key).must_equal false
    end

    it "returns nil from delete if an element for a key does not exist" do
      @store.delete(key).must_be_nil
    end

    it "removes all keys from the store with clear" do
      @store[key] = "value"
      @store[key2] = "value2"
      @store.clear
      @store.key?(key).wont_equal true
      @store.key?(key2).wont_equal true
    end

    it "does not run the block if the #{type} key is available" do
      @store[key] = "value"
      unaltered = "unaltered"
      @store.get(key) { unaltered = "altered" }
      unaltered.must_equal "unaltered"
    end

    it "stores #{key} values with #set" do
      @store.set(key, "value")
      @store[key].must_equal "value"
    end

    it "returns a list of commit history for the key" do
      @store.log(key).wont_be_empty
    end
  end

end

Nice one! A was thinking about creating same thing!

This is awesome, you should turn it into a gem after the contest is over! :D

Nifty :-)