Merge pull request github#126 from osowskit/master

Add Ruby webhook server to dismiss reviews

hooks/ruby/dismiss-review-server/Gemfile

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+source "http://rubygems.org"
+
+gem "json",        "~> 1.8"
+gem 'sinatra',     '~> 1.3.5'
+gem 'rest-client'

hooks/ruby/dismiss-review-server/Gemfile.lock

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+GEM
+  remote: http://rubygems.org/
+  specs:
+    domain_name (0.5.20161129)
+      unf (>= 0.0.5, < 1.0.0)
+    http-cookie (1.0.3)
+      domain_name (~> 0.5)
+    json (1.8.6)
+    mime-types (3.1)
+      mime-types-data (~> 3.2015)
+    mime-types-data (3.2016.0521)
+    netrc (0.11.0)
+    rack (1.6.5)
+    rack-protection (1.5.3)
+      rack
+    rest-client (2.0.1)
+      http-cookie (>= 1.0.2, < 2.0)
+      mime-types (>= 1.16, < 4.0)
+      netrc (~> 0.8)
+    sinatra (1.3.6)
+      rack (~> 1.4)
+      rack-protection (~> 1.3)
+      tilt (~> 1.3, >= 1.3.3)
+    tilt (1.4.1)
+    unf (0.1.4)
+      unf_ext
+    unf_ext (0.0.7.2)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  json (~> 1.8)
+  rest-client
+  sinatra (~> 1.3.5)
+
+BUNDLED WITH
+   1.14.4

hooks/ruby/dismiss-review-server/README.md

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+# Dismiss Review Server
+
+A ruby server that listens for GitHub webhook `push` events, based on [the documentation](https://developer.github.com/webhooks/configuring/#writing-the-server), that will dismiss any `APPROVED` [Pull Request Reviews](https://help.github.com/articles/about-pull-request-reviews/).
+
+## Configuration
+
+Follow the [instructions](https://developer.github.com/webhooks/) of setting up a Webhook on GitHub to this server. Set the following environment variables:
+- GITHUB_API_TOKEN - (Required) [OAuth token](https://developer.github.com/v3/#authentication) with write access to the repository.
+- SECRET_TOKEN - (Optional) [Shared secret token](https://developer.github.com/webhooks/securing/#validating-payloads-from-github) between the GitHub Webhook and this application. Leave this unset if not using a secret token.

hooks/ruby/dismiss-review-server/server.rb

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+require 'sinatra'
+require 'json'
+require 'rest-client'
+
+$github_api_token = ENV['GITHUB_API_TOKEN']
+$github_secret_token = ENV['SECRET_TOKEN']
+
+post '/payload' do
+
+  # Only validate secret token if set 
+  if !$github_secret_token.nil?
+    payload_body = request.body.read
+    verify_signature(payload_body)
+  end
+
+  github_event = request.env['HTTP_X_GITHUB_EVENT']
+  if github_event == "push"
+    request.body.rewind
+    parsed = JSON.parse(request.body.read)
+
+    # Get branch information
+    branch_name = parsed['ref']
+    removed_slice = branch_name.slice!("refs/heads/")
+    if removed_slice.nil?
+      return "Not a branch. Nothing to do."
+    end
+
+    # Get Repository owner
+    repo_owner = parsed["repository"]["owner"]["name"]
+
+    # Create URL to look up Pull Requests for this branch
+    # e.g. https://api.github.com/repos/baxterthehacker/public-repo/pulls{/number}
+    pulls_url = parsed['repository']['pulls_url']
+
+    # Pull off the "{/number}" and search for all Pull Requests
+    # that include the branch
+    pulls_url_filtered = pulls_url.split('{').first + "?head=#{repo_owner}:#{branch_name}"
+    pulls = get(pulls_url_filtered)
+
+    # parse pull requests
+    if pulls.empty?
+      puts "empty"
+    else
+      pulls.each do |pull_request|
+
+        # Get all Reviews for a Pull Request via API
+        review_url_orig = pull_request["url"] + "/reviews"
+        reviews = get(review_url_orig)
+
+        reviews.each do |review|
+
+          # Dismiss all Reviews in 'APPROVED' state via API
+          if review["state"] == "APPROVED"
+            puts "INFO: found an approved Review"
+            review_id = review["id"]
+            dismiss_url = review_url_orig + "/#{review_id}/dismissals"
+            put(dismiss_url)
+          end
+        end.empty? and begin
+          puts "no reviews"
+        end
+      end
+    end
+  elsif github_event == "ping"
+    puts github_event
+  else
+    puts github_event
+  end
+  "message received"
+end
+
+def put(url)
+  jdata = JSON.generate({ message: "Auto-dismissing"})
+  headers = {
+    params:
+      {
+        access_token: $github_api_token
+      },
+    accept: "application/vnd.github.black-cat-preview+json"
+  }
+  response = RestClient.put(url, jdata, headers)
+  JSON.parse(response.body)
+end
+
+def get(url)
+  headers = {
+    params: {
+      access_token:  $github_api_token
+    },
+    accept: "application/vnd.github.black-cat-preview+json"
+  }
+  response = RestClient.get(url, headers)
+  JSON.parse(response.body)
+end
+
+def verify_signature(payload_body)
+  signature = 'sha1=' + OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha1'), ENV['SECRET_TOKEN'], payload_body)
+  return halt 500, "Signatures didn't match!" unless Rack::Utils.secure_compare(signature, request.env['HTTP_X_HUB_SIGNATURE'])
+end