Add experimental basic quote post authoring (#35355)

app/models/concerns/status/interaction_policy_concern.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+module Status::InteractionPolicyConcern
+  extend ActiveSupport::Concern
+
+  QUOTE_APPROVAL_POLICY_FLAGS = {
+    unknown: (1 << 0),
+    public: (1 << 1),
+    followers: (1 << 2),
+    followed: (1 << 3),
+  }.freeze
+
+  def quote_policy_as_keys(kind)
+    case kind
+    when :automatic
+      policy = quote_approval_policy >> 16
+    when :manual
+      policy = quote_approval_policy & 0xFFFF
+    end
+
+    QUOTE_APPROVAL_POLICY_FLAGS.keys.select { |key| policy.anybits?(QUOTE_APPROVAL_POLICY_FLAGS[key]) }.map(&:to_s)
+  end
+
+  # Returns `:automatic`, `:manual`, `:unknown` or `:denied`
+  def quote_policy_for_account(other_account, preloaded_relations: {})
+    return :denied if other_account.nil?
+
+    following_author = nil
+
+    # Post author is always allowed to quote themselves
+    return :automatic if account_id == other_account.id
+
+    automatic_policy = quote_approval_policy >> 16
+    manual_policy = quote_approval_policy & 0xFFFF
+
+    # Checking for public policy first because it's less expensive than looking at mentions
+    return :automatic if automatic_policy.anybits?(QUOTE_APPROVAL_POLICY_FLAGS[:public])
+
+    # Mentioned users are always allowed to quote
+    if active_mentions.loaded?
+      return :automatic if active_mentions.any? { |mention| mention.account_id == other_account.id }
+    elsif active_mentions.exists?(account: other_account)
+      return :automatic
+    end
+
+    if automatic_policy.anybits?(QUOTE_APPROVAL_POLICY_FLAGS[:followers])
+      following_author = preloaded_relations[:following] ? preloaded_relations[:following][account_id] : other_account.following?(account) if following_author.nil?
+      return :automatic if following_author
+    end
+
+    # We don't know we are allowed by the automatic policy, considering the manual one
+    return :manual if manual_policy.anybits?(QUOTE_APPROVAL_POLICY_FLAGS[:public])
+
+    if manual_policy.anybits?(QUOTE_APPROVAL_POLICY_FLAGS[:followers])
+      following_author = preloaded_relations[:following] ? preloaded_relations[:following][account_id] : other_account.following?(account) if following_author.nil?
+      return :manual if following_author
+    end
+
+    return :unknown if (automatic_policy | manual_policy).anybits?(QUOTE_APPROVAL_POLICY_FLAGS[:unknown])
+
+    :denied
+  end
+end