Add generator for example component

lib/generators/example_component/USAGE

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+Description:
+    Generates a new component example.
+
+Example:
+    bin/rails generate example_component Cards::Responsive "Optional title"
+
+    This will create:
+        app/views/components/examples/cards/responsive_component.rb

lib/generators/example_component/example_component_generator.rb

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+class ExampleComponentGenerator < Rails::Generators::NamedBase
+  source_root File.expand_path("templates", __dir__)
+
+  argument :title, type: :string, default: "", banner: "Title of the component"
+
+  def check_for_show_view
+    unless File.exist?(show_view_path)
+      say(
+        "ShowView file not found at #{show_view_path}. Component not added. " \
+          "Run 'rails generate example_view " \
+          "#{class_path.map(&:classify).join("::")}' to create the " \
+          "ShowView file first.",
+        :red
+      )
+
+      exit 1
+    end
+  end
+
+  def create_component_file
+    template(
+      "example_component.rb.tt",
+      Rails.root.join(
+        "app",
+        "views",
+        "components",
+        "examples",
+        *file_path_parts,
+        "#{file_name}.rb"
+      )
+    )
+
+    append_component_to_show_view
+  end
+
+  private
+
+  def file_path_parts
+    class_path.map(&:underscore).map(&:pluralize)
+  end
+
+  def file_name
+    name.demodulize.underscore
+  end
+
+  def component_class_name
+    file_name.classify
+  end
+
+  def component_title
+    (title.presence || file_name).then do |result|
+      result.titleize.downcase.capitalize
+    end
+  end
+
+  def append_component_to_show_view
+    file_content = File.read(show_view_path)
+
+    # Find the indentation level from an existing line in the array.
+    #
+    # 1. render_examples \[ matches 'render_examples ['
+    # 2. \n matches the newline after the opening bracket '['
+    # 3. (\s+) captures the indentation
+    indentation = if file_content =~ /render_examples \[\n(\s+)/
+      # Retrieve the content of the first capture group from the last match.
+      # i.e. the spaces or indentation.
+      Regexp.last_match(1)
+    else
+      "  " # Fallback to 2 spaces if no indentation found.
+    end
+
+    # The regex captures the render_examples block and the content inside the
+    # array brackets.
+    #
+    # 1. render_examples \[: matches 'render_examples ['
+    # 2. ([^\]]*) a capture group that matches everything except inside the
+    #     brackets except the closing bracket ']'
+    # 3. \] matches the closing bracket ']'
+    # 4. /m is a multiline flag that allows the dot . to match newlines
+    regex = /render_examples \[([^\]]*)\]/m
+
+    gsub_file(show_view_path, regex) do |match|
+      existing_components = match.match(regex)[1]
+
+      # Format the new list with proper indentation.
+      new_component_list = existing_components
+        .split(",")
+        .map(&:strip)
+        .reject(&:empty?)
+        .push(component_class_name)
+        .map { |component| "#{indentation}#{component}" }
+        .join(",\n")
+
+      # Remove 2 spaces from the indentation for the closing bracket.
+      indentation = indentation[0..-3]
+
+      # Construct the new render_examples block with correctly indented
+      # closing bracket.
+      "render_examples [\n#{new_component_list}\n#{indentation}]"
+    end
+  end
+
+  def show_view_path
+    Rails.root.join(
+      "app",
+      "views",
+      "examples",
+      *file_path_parts,
+      "show_view.rb"
+    )
+  end
+end

lib/generators/example_component/templates/example_component.rb.tt

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+module Examples
+  module <%= class_path.map(&:classify).map(&:pluralize).join('::') %>
+    class <%= component_class_name %> < Base
+      def title
+        "<%= component_title %>"
+      end
+
+      def example
+        <%= class_path.last.classify %> do
+        end
+      end
+    end
+  end
+end

spec/generator/example_component_generator_spec.rb

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+require 'rails_helper'
+
+RSpec.describe "ExampleComponentGenerator", type: :generator do
+  pending "add some scenarios (or delete) #{__FILE__}"
+end