From b293acc89bc1dbc1c8bde6c40cd7dd0bc0cc745c Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Sat, 12 Dec 2020 21:56:33 +0100
Subject: [PATCH] Add `FollowRedirection` livecheck strategy.

---
 Library/Homebrew/livecheck/strategy.rb        |  1 +
 .../livecheck/strategy/follow_redirection.rb  | 47 +++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 Library/Homebrew/livecheck/strategy/follow_redirection.rb

diff --git a/Library/Homebrew/livecheck/strategy.rb b/Library/Homebrew/livecheck/strategy.rb
index f368479843..158fede7bd 100644
--- a/Library/Homebrew/livecheck/strategy.rb
+++ b/Library/Homebrew/livecheck/strategy.rb
@@ -110,5 +110,6 @@ require_relative "strategy/launchpad"
 require_relative "strategy/npm"
 require_relative "strategy/page_match"
 require_relative "strategy/pypi"
+require_relative "strategy/follow_redirection"
 require_relative "strategy/sourceforge"
 require_relative "strategy/xorg"
diff --git a/Library/Homebrew/livecheck/strategy/follow_redirection.rb b/Library/Homebrew/livecheck/strategy/follow_redirection.rb
new file mode 100644
index 0000000000..f27e6176d3
--- /dev/null
+++ b/Library/Homebrew/livecheck/strategy/follow_redirection.rb
@@ -0,0 +1,47 @@
+# typed: false
+# frozen_string_literal: true
+
+require_relative "page_match"
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The {FollowRedirection} strategy follows all URL redirections and scans
+      # the final URL for matching text using the provided regex.
+      #
+      # @api private
+      class FollowRedirection
+        extend T::Sig
+
+        NICE_NAME = "Follow HTTP Redirection"
+
+        # We set the priority to zero since this cannot
+        # be detected automatically.
+        PRIORITY = 0
+
+        # Whether the strategy can be applied to the provided URL.
+        # FollowRedirection will technically match any HTTP URL but is
+        # only usable with a `livecheck` block containing a regex.
+        sig { params(url: String).returns(T::Boolean) }
+        def self.match?(url)
+          url.match?(%r{^https?://})
+        end
+
+        # Checks the final URL for new versions after following all redirections,
+        # using the provided regex for matching.
+        sig { params(url: String, regex: T.nilable(Regexp)).returns(T::Hash[Symbol, T.untyped]) }
+        def self.find_versions(url, regex)
+          raise ArgumentError, "A regular expression is required for the #{NICE_NAME} strategy." if regex.nil?
+
+          match_data = { matches: {}, regex: regex, url: url }
+
+          if (location = Strategy.page_headers(url)["location"]) && (match = location[regex, 1])
+            match_data[:matches][match] = Version.new(match)
+          end
+
+          match_data
+        end
+      end
+    end
+  end
+end