From b3f47d385695210e2bff276a300d3f55246f158c Mon Sep 17 00:00:00 2001
From: Konstantin Haase <konstantin.mailinglists@googlemail.com>
Date: Fri, 21 Aug 2015 17:04:12 +0200
Subject: [PATCH] v3: add pagination

---
 lib/travis/api/v3/access_control/anonymous.rb |  4 +
 lib/travis/api/v3/paginator.rb                | 42 ++++++++
 lib/travis/api/v3/paginator/url_generator.rb  | 95 +++++++++++++++++++
 .../api/v3/renderer/collection_renderer.rb    | 35 +++++--
 lib/travis/api/v3/result.rb                   | 13 ++-
 lib/travis/api/v3/service.rb                  | 23 ++++-
 lib/travis/api/v3/services/builds/find.rb     |  2 +
 7 files changed, 199 insertions(+), 15 deletions(-)
 create mode 100644 lib/travis/api/v3/paginator.rb
 create mode 100644 lib/travis/api/v3/paginator/url_generator.rb

diff --git a/lib/travis/api/v3/access_control/anonymous.rb b/lib/travis/api/v3/access_control/anonymous.rb
index c41df37f..08300b33 100644
--- a/lib/travis/api/v3/access_control/anonymous.rb
+++ b/lib/travis/api/v3/access_control/anonymous.rb
@@ -2,6 +2,10 @@ require 'travis/api/v3/access_control/generic'
 
 module Travis::API::V3
   class AccessControl::Anonymous < AccessControl::Generic
+    def self.new
+      @instace ||= super
+    end
+
     # use when Authorization header is not set
     auth_type(nil)
 
diff --git a/lib/travis/api/v3/paginator.rb b/lib/travis/api/v3/paginator.rb
new file mode 100644
index 00000000..26503c2d
--- /dev/null
+++ b/lib/travis/api/v3/paginator.rb
@@ -0,0 +1,42 @@
+module Travis::API::V3
+  class Paginator
+    attr_accessor :default_limit, :max_limit
+
+    def initialize(default_limit: 25, max_limit: 100)
+      @default_limit = default_limit
+      @max_limit     = max_limit
+    end
+
+    def paginate(result, limit: nil, offset: nil, access_control: AccessControl::Anonymous.new)
+      limit &&= Integer(limit, :limit)
+      limit ||= default_limit
+      limit   = default_limit if limit < 0
+
+      unless access_control.full_access?
+        limit = max_limit if limit > max_limit or limit < 1
+      end
+
+      offset &&= Integer(offset, :offset)
+      offset   = 0 if offset.nil? or offset < 0
+
+      count = result.resource ? result.resource.count : 0
+      result.resource &&= result.resource.limit(limit)   unless limit  == 0
+      result.resource &&= result.resource.offset(offset) unless offset == 0
+
+      pagination_info = {
+        limit:  limit,
+        offset: offset,
+        count:  count,
+      }
+
+      result.meta_data[:pagination] = pagination_info
+      result
+    end
+
+    def Integer(value, key)
+      super(value)
+    rescue ArgumentError
+      raise WrongParams, "#{key} must be an integer"
+    end
+  end
+end
diff --git a/lib/travis/api/v3/paginator/url_generator.rb b/lib/travis/api/v3/paginator/url_generator.rb
new file mode 100644
index 00000000..da29c34e
--- /dev/null
+++ b/lib/travis/api/v3/paginator/url_generator.rb
@@ -0,0 +1,95 @@
+require "addressable/uri"
+
+module Travis::API::V3
+  class Paginator
+    class URLGenerator
+      class FancyParser
+        def initialize(href)
+          @uri = Addressable::URI.parse(href)
+        end
+
+        def generate(offset, limit)
+          uri = @uri.dup
+          uri.query_values = uri.query_values.merge("offset".freeze => offset, "limit".freeze => limit)
+          uri.to_s
+        end
+      end
+
+      class FastParser
+        PATTERN = /\?(?:&?(?:limit|offset)=[^=]*)*\Z/
+
+        def self.can_handle?(href)
+          return true unless href.include? ??.freeze
+          href =~ PATTERN
+        end
+
+        def initialize(href)
+          @path_info = href.split(??.freeze, 2).first
+        end
+
+        def generate(offset, limit)
+          "#{@path_info}?limit=#{limit}&offset=#{offset}"
+        end
+      end
+
+      def initialize(href, limit: 0, offset: 0, count: 0, **)
+        @parser = FastParser.can_handle?(href) ? FastParser.new(href) : FancyParser.new(href)
+        @href   = href
+        @limit  = limit
+        @offset = offset
+        @count  = count
+      end
+
+      def last?
+        @count <= @offset + @limit
+      end
+
+      def first?
+        @offset == 0
+      end
+
+      def next_info
+        info(offset: @offset + @limit) unless last?
+      end
+
+      def previous_info
+        return if @offset == 0
+        @offset <= @limit ? info(offset: 0, limit: @offset) : info(offset: @offset - @limit, limit: @limit)
+      end
+
+      def first_info
+        info(offset: 0)
+      end
+
+      def last_info
+        offset = @count / @limit * @limit
+        offset -= @limit if offset == @count
+        info(offset: offset)
+      end
+
+      def info(offset: @offset, limit: @limit)
+        {
+          :@href  => uri_with(offset, limit),
+          :offset => offset,
+          :limit  => limit
+        }
+      end
+
+      def to_h
+        {
+          is_first: first?,
+          is_last:  last?,
+          next:     next_info,
+          prev:     previous_info,
+          first:    first_info,
+          last:     last_info
+        }
+      end
+
+      def uri_with(offset, limit)
+        return @href if offset == @offset and limit == @limit
+        @parser.generate(offset, limit)
+      end
+    end
+  end
+end
diff --git a/lib/travis/api/v3/renderer/collection_renderer.rb b/lib/travis/api/v3/renderer/collection_renderer.rb
index 1be17af6..461c7353 100644
--- a/lib/travis/api/v3/renderer/collection_renderer.rb
+++ b/lib/travis/api/v3/renderer/collection_renderer.rb
@@ -17,19 +17,34 @@ module Travis::API::V3
       available_attributes << value
     end
 
-    def initialize(list, href: nil, included: [], **options)
-      @href     = href
-      @options  = options
-      @list     = list
-      @included = included
+    attr_reader :href, :options, :list, :included, :meta_data
+
+    def initialize(list, href: nil, included: [], meta_data: {}, **options)
+      @href      = href
+      @options   = options
+      @list      = list
+      @included  = included
+      @meta_data = meta_data
+    end
+
+    def fields
+      fields              = { :"@type" => type }
+      fields[:@href]      = href if href
+      fields[:pagination] = pagination_info if meta_data.include? :pagination
+      fields
+    end
+
+    def pagination_info
+      return meta_data[:@pagination] unless href
+      generator = V3::Paginator::URLGenerator.new(href, **meta_data[:pagination])
+      meta_data[:pagination].merge generator.to_h
     end
 
     def render
-      result                 = { :"@type" => type }
-      result[:@href]         = @href if @href
-      included               = @included.dup
-      result[collection_key] = @list.map do |entry|
-        rendered = render_entry(entry, included: included, mode: :standard, **@options)
+      result                 = fields
+      included               = self.included.dup
+      result[collection_key] = list.map do |entry|
+        rendered = render_entry(entry, included: included, mode: :standard, **options)
         included << entry
         rendered
       end
diff --git a/lib/travis/api/v3/result.rb b/lib/travis/api/v3/result.rb
index 1cf5733b..7f8d2b0d 100644
--- a/lib/travis/api/v3/result.rb
+++ b/lib/travis/api/v3/result.rb
@@ -1,9 +1,9 @@
 module Travis::API::V3
   class Result
-    attr_accessor :access_control, :type, :resource, :status, :href
+    attr_accessor :access_control, :type, :resource, :status, :href, :meta_data
 
-    def initialize(access_control, type, resource = [], status: 200)
-      @access_control, @type, @resource, @status = access_control, type, resource, status
+    def initialize(access_control, type, resource = [], status: 200, **meta_data)
+      @access_control, @type, @resource, @status, @meta_data = access_control, type, resource, status, meta_data
     end
 
     def respond_to_missing?(method, *)
@@ -19,7 +19,12 @@ module Travis::API::V3
       href    = self.href
       href    = V3.location(env) if href.nil? and env['REQUEST_METHOD'.freeze] == 'GET'.freeze
       include = params['include'.freeze].to_s.split(?,.freeze)
-      Renderer[type].render(resource, href: href, script_name: env['SCRIPT_NAME'.freeze], include: include, access_control: access_control)
+      Renderer[type].render(resource,
+        href:           href,
+        script_name:    env['SCRIPT_NAME'.freeze],
+        include:        include,
+        access_control: access_control,
+        meta_data:      meta_data)
     end
 
     def method_missing(method, *args)
diff --git a/lib/travis/api/v3/service.rb b/lib/travis/api/v3/service.rb
index c8c90249..2a0011e0 100644
--- a/lib/travis/api/v3/service.rb
+++ b/lib/travis/api/v3/service.rb
@@ -24,6 +24,19 @@ module Travis::API::V3
       @params
     end
 
+    def self.paginate(**options)
+      params("limit".freeze, "offset".freeze)
+      @paginator = Paginator.new(**options)
+    end
+
+    def self.paginator
+      @paginator ||= nil
+    end
+
+    def self.paginate?
+      !!@paginator if defined? @paginator
+    end
+
     attr_accessor :access_control, :params
 
     def initialize(access_control, params)
@@ -68,7 +81,15 @@ module Travis::API::V3
     def run
       not_found unless result = run!
       result = result(result_type, result) unless result.is_a? Result
-      result
+      self.class.paginate? ? paginate(result) : result
+    end
+
+    def paginate(result)
+      p params
+      self.class.paginator.paginate(result,
+        limit:          params['limit'.freeze],
+        offset:         params['offset'.freeze],
+        access_control: access_control)
     end
 
     def params_for?(prefix)
diff --git a/lib/travis/api/v3/services/builds/find.rb b/lib/travis/api/v3/services/builds/find.rb
index 48354927..9c2a69f9 100644
--- a/lib/travis/api/v3/services/builds/find.rb
+++ b/lib/travis/api/v3/services/builds/find.rb
@@ -1,5 +1,7 @@
 module Travis::API::V3
   class Services::Builds::Find < Service
+    paginate
+
     def run!
       query.find(find(:repository))
     end