goromlagche · December 8, 2023 13:01 · Jan 26, 2022 · Jan 26, 2022
diff --git a/pagination.rb b/pagination.rb
@@ -52,7 +52,7 @@ def pagination_window
 
       def pagination_url(direction:)
         return "" if @seek == false && direction == @params[:direction]
-        return "" if @params[:cursor_created_at].blank? && direction == "prev"
+        return "" if @params[:cursor_created_at].blank? && direction == "prev" # first page
 
         cursor = direction == "prev" ?  paginated_records.first : paginated_records.last
 

diff --git a/pagination.rb b/pagination.rb
@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+# drop this file in app/lib/pagination.rb
+
+module Pagination
+  DEFAULT_PAGE_LIMIT = 10
+
+  def pages(records:, url:)
+    paginate = Paginate.new(records: records,
+                            url: url,
+                            limit: limit,
+                            params: pagination_params)
+    paginate.pages
+  end
+
+  def limit
+    return self.class::PAGE_LIMIT if defined? self.class::PAGE_LIMIT
+
+    DEFAULT_PAGE_LIMIT
+  end
+
+  def pagination_params
+    params.permit(:cursor_created_at, :direction)
+  end
+
+
+  class Paginate
+    def initialize(records:, url:, limit:, params:)
+      @records = records
+      @url = url
+      @limit = limit
+      @params = params
+    end
+
+    def pages
+      {
+        records: paginated_records,
+        next_url: pagination_url(direction: "next"),
+        prev_url: pagination_url(direction: "prev"),
+      }
+    end
+
+    private
+      def pagination_window
+        return if @params[:cursor_created_at].blank?
+
+        if @params[:direction] == "prev"
+          @records.arel_table[:created_at].gt(@params[:cursor_created_at])
+        else
+          @records.arel_table[:created_at].lt(@params[:cursor_created_at])
+        end
+      end
+
+      def pagination_url(direction:)
+        return "" if @seek == false && direction == @params[:direction]
+        return "" if @params[:cursor_created_at].blank? && direction == "prev"
+
+        cursor = direction == "prev" ?  paginated_records.first : paginated_records.last
+
+        uri = URI(@url)
+        params = Hash[URI.decode_www_form(uri.query || "")]
+                   .merge("cursor_created_at" => cursor.created_at.iso8601(6), # PG default is 6
+                          "direction" => direction)
+        uri.query = URI.encode_www_form(params)
+        uri
+      end
+
+
+      def paginated_records
+        return @paginated_records if defined? @paginated_records
+
+        @paginated_records = @records
+                               .unscope(:order)
+                               .where(pagination_window)
+                               .order(created_at: order_direction)
+                               .limit(@limit + 1)
+                               .to_a
+
+        @seek = (@paginated_records.size > @limit)
+        @paginated_records.pop if @seek == true
+        @paginated_records.reverse! if @params[:direction] == "prev"
+        @paginated_records
+      end
+
+      def order_direction
+        return :asc if @params[:direction] == "prev"
+
+        :desc
+      end
+  end
+end
diff --git a/records.js b/records.js
@@ -0,0 +1,35 @@
+class Records extends React.Component {
+  static propTypes = {
+    recordsUrl: PropTypes.string
+  };
+
+  componentDidMount() {
+    this.fetchRecords(this.props.recordsUrl);
+  }
+
+  state = {
+    records: [],
+    prevUrl: "",
+    nextUrl: ""
+  };
+
+  fetchRecords = url => {
+    fetch(url)
+      .then(data => {
+        if (data.ok) {
+          return data.json();
+        }
+        throw new Error("Network error!");
+      })
+      .then(data => {
+        this.setState({
+          records: data.records,
+          nextUrl: data.next_url,
+          prevUrl: data.prev_url,
+        });
+      })
+      .catch(err => console.log("Error: " + err));
+  };
+...
+...
+...
diff --git a/records_controller.rb b/records_controller.rb
@@ -0,0 +1,18 @@
+module Api
+  module V1
+    class RecordsController < BaseApiController
+      include Pagination
+
+      def index
+        render json: pages(records: records, url: api_v1_records_path),
+               except: [:updated_at],
+               status: :ok
+      end
+
+      private
+        def records
+          Records.with_attached_image
+        end
+    end
+  end
+end
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