livecheck: CPAN strategy

Library/Homebrew/livecheck/strategy.rb

@@ -86,6 +86,7 @@ end
 
 require_relative "strategy/apache"
 require_relative "strategy/bitbucket"
+require_relative "strategy/cpan"
 require_relative "strategy/git"
 require_relative "strategy/github_latest"
 require_relative "strategy/gnome"

Library/Homebrew/livecheck/strategy/cpan.rb

@@ -0,0 +1,67 @@
+# typed: false
+# frozen_string_literal: true
+
+require "uri"
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The {Cpan} strategy identifies versions of software at
+      # cpan.metacpan.org by checking directory listing pages.
+      #
+      # CPAN URLs take the following format:
+      #
+      # * `https://cpan.metacpan.org/authors/id/M/MI/MIYAGAWA/Carton-v1.0.34.tar.gz`
+      #
+      # @api public
+      class Cpan
+        NICE_NAME = "CPAN"
+
+        # The allowlist used to determine if the strategy applies to the URL.
+        HOST_ALLOWLIST = ["cpan.metacpan.org"].freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        #
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          uri = URI.parse url
+          HOST_ALLOWLIST.include? uri.host
+        rescue URI::InvalidURIError
+          false
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to {PageMatch.find_versions} to identify versions in the content.
+        #
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{
+            /authors/id/(?<author_path>(?:[^/](?:/[^/]+){2})) # The author path (e.g. M/MI/MIYAGAWA)
+            /(?<package_path>.+) # The package path (e.g. Carton-v1.0.34.tar.gz)
+          }ix =~ url
+
+          # We need a Pathname because we've monkeypatched extname to support
+          # double extensions (e.g. tar.gz).
+          pathname = Pathname.new(package_path)
+
+          # Exteract package name
+          /^(?<package_name>.+)-v?\d+/ =~ pathname.basename(pathname.extname)
+          # Use `\.t` instead of specific tarball extensions (e.g. .tar.gz)
+          suffix = pathname.extname.sub!(/\.t(?:ar\..+|[a-z0-9]+)$/i, "\.t")
+
+          # A page containing a directory listing of the latest source tarball
+          package_dir = Pathname.new(author_path).join(pathname.dirname)
+          page_url = "https://cpan.metacpan.org/authors/id/#{package_dir}/"
+
+          # Example regex: `%r{href=.*?Carton-v?(\d+(?:\.\d+)*).t}i`
+          regex ||= /href=.*?#{package_name}-v?(\d+(?:\.\d+)*)#{Regexp.escape(suffix)}/i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/cpan_spec.rb

@@ -0,0 +1,21 @@
+# typed: false
+# frozen_string_literal: true
+
+require "livecheck/strategy/cpan"
+
+describe Homebrew::Livecheck::Strategy::Cpan do
+  subject(:cpan) { described_class }
+
+  let(:cpan_url) { "https://cpan.metacpan.org/authors/id/M/MI/MIYAGAWA/Carton-v1.0.34.tar.gz" }
+  let(:non_cpan_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a CPAN URL" do
+      expect(cpan.match?(cpan_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a CPAN URL" do
+      expect(cpan.match?(non_cpan_url)).to be false
+    end
+  end
+end