Add Completions for storing and navigating completion suggestions

lib/tty/reader.rb

@@ -4,6 +4,7 @@
 require "tty-screen"
 require "wisper"
 
+require_relative "reader/completions"
 require_relative "reader/history"
 require_relative "reader/line"
 require_relative "reader/key_event"

lib/tty/reader/completions.rb

@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+require "forwardable"
+
+module TTY
+  class Reader
+    # Responsible for storing and navigating completion suggestions
+    #
+    # @api private
+    class Completions
+      include Enumerable
+      extend Forwardable
+
+      def_delegators :@completions, :size, :empty?
+
+      # Create a Completions collection
+      #
+      # @api public
+      def initialize
+        @completions = []
+        @index = 0
+      end
+
+      # Clear current completions
+      #
+      # @api public
+      def clear
+        @completions.clear
+        @index = 0
+      end
+
+      # Check whether the current index is at the first completion or not
+      #
+      # @return [Boolean]
+      #
+      # @api public
+      def first?
+        @index.zero?
+      end
+
+      # Check whether the current index is at the last completion or not
+      #
+      # @return [Boolean]
+      #
+      # @api public
+      def last?
+        @index == size - 1
+      end
+
+      # Add completion suggestions
+      #
+      # @param [Array<String>] suggestions
+      #   the suggestions to add
+      #
+      # @api public
+      def concat(suggestions)
+        suggestions.each { |suggestion| @completions << suggestion.dup }
+      end
+
+      # Iterate over all completions
+      #
+      # @api public
+      def each(&block)
+        if block_given?
+          @completions.each(&block)
+        else
+          @completions.to_enum
+        end
+      end
+
+      # Retrieve completion at the current index
+      #
+      # @return [String]
+      #
+      # @api public
+      def get
+        @completions[@index]
+      end
+
+      # Move index to the next completion
+      #
+      # @api public
+      def next
+        return if size.zero?
+
+        if @index == size - 1
+          @index = 0
+        else
+          @index += 1
+        end
+      end
+
+      # Move index to the previous completion
+      #
+      # @api public
+      def previous
+        return if size.zero?
+
+        if @index.zero?
+          @index = size - 1
+        else
+          @index -= 1
+        end
+      end
+    end # Completions
+  end # Reader
+end # TTY

spec/unit/completions_spec.rb

@@ -0,0 +1,100 @@
+# frozen_string_literal: true
+
+RSpec.describe TTY::Reader::Completions do
+  it "has no suggestions by default" do
+    completions = described_class.new
+
+    expect(completions.empty?).to eq(true)
+    expect(completions.size).to eq(0)
+  end
+
+  it "adds suggestions making copies of each one" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+
+    completions.concat(suggestions)
+
+    suggestions[0] = "ax"
+
+    expect(completions.to_a).to eq(%w[aa ab ac])
+    expect(completions.to_a).to_not eq(suggestions)
+  end
+
+  it "clears all suggestions" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+
+    completions.concat(suggestions)
+
+    expect(completions.empty?).to eq(false)
+    expect(completions.size).to eq(3)
+
+    completions.clear
+
+    expect(completions.empty?).to eq(true)
+    expect(completions.size).to eq(0)
+  end
+
+  it "navigates to the next completion" do
+    completions = described_class.new
+    completions.concat(%w[aa ab ac])
+
+    expect(completions.get).to eq("aa")
+
+    completions.next
+    expect(completions.get).to eq("ab")
+  end
+
+  it "navigates to the previous completion" do
+    completions = described_class.new
+    completions.concat(%w[aa ab ac])
+
+    completions.next
+    expect(completions.get).to eq("ab")
+
+    completions.previous
+    expect(completions.get).to eq("aa")
+  end
+
+  it "cycles through completions forward" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+    completions.concat(suggestions)
+
+    suggestions.size.times { completions.next }
+
+    expect(completions.get).to eq("aa")
+  end
+
+  it "cycles through completions backward" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+    completions.concat(suggestions)
+
+    suggestions.size.times { completions.previous }
+
+    expect(completions.get).to eq("aa")
+  end
+
+  it "checks whether index is at the first completion" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+    completions.concat(suggestions)
+
+    expect(completions.first?).to eq(true)
+
+    completions.next
+    expect(completions.first?).to eq(false)
+  end
+
+  it "checks whether index is at the last completion" do
+    completions = described_class.new
+    suggestions = %w[aa ab ac]
+    completions.concat(suggestions)
+
+    expect(completions.last?).to eq(false)
+
+    2.times { completions.next }
+    expect(completions.last?).to eq(true)
+  end
+end