feat: add Prism and I18n

lib/prism/i18n.rb

@@ -0,0 +1,124 @@
+require_relative 'i18n/backend'
+require_relative 'i18n/translator'
+
+module Prism
+  # Rails-i18n-like translation API: JSON translation files (this Ruby
+  # build has no psych/libyaml, so YAML is not an option), a per-thread
+  # current locale, fallback chains, and Accept-Language negotiation.
+  module I18n
+    class << self
+      def backend
+        @backend ||= Backend.new
+      end
+
+      def default_locale
+        @default_locale ||= :en
+      end
+
+      def default_locale=(locale)
+        @translator = nil
+        @default_locale = locale.to_sym
+      end
+
+      def fallbacks
+        @fallbacks ||= {}
+      end
+
+      def fallbacks=(hash)
+        @translator = nil
+        @fallbacks = hash
+      end
+
+      def locale
+        Thread.current[:prism_i18n_locale] || default_locale
+      end
+
+      def locale=(new_locale)
+        Thread.current[:prism_i18n_locale] = new_locale&.to_sym
+      end
+
+      def with_locale(new_locale)
+        previous = locale
+        self.locale = new_locale
+        yield
+      ensure
+        self.locale = previous
+      end
+
+      def load_path
+        @load_path ||= []
+      end
+
+      def load_translations!
+        load_path.each do |path|
+          Dir.glob(File.join(path, '**', '*.json')).sort.each { |file| backend.load_file(file) }
+        end
+        @translator = nil
+      end
+
+      def store_translations(locale, data)
+        @translator = nil
+        backend.store_translations(locale, data)
+      end
+
+      def available_locales
+        backend.locales
+      end
+
+      def translate(key, **options)
+        options[:locale] ||= locale
+        translator.translate(key, **options)
+      end
+      alias_method :t, :translate
+
+      def localize(value, **options)
+        options[:locale] ||= locale
+        translator.localize(value, **options)
+      end
+      alias_method :l, :localize
+
+      # Picks the first locale in the client's Accept-Language header that
+      # this app has translations for, honoring q-values (like
+      # Mime.best_from_accept but for BCP-47 language tags, matching on
+      # the primary subtag: "en-US" negotiates against an :en backend).
+      def best_locale_from_accept(header, available: available_locales)
+        return nil if header.nil? || header.strip.empty?
+        wanted = available.map(&:to_s)
+        parse_accept_language(header).each do |tag|
+          exact = wanted.find { |candidate| candidate.casecmp?(tag) }
+          return exact.to_sym if exact
+          primary = tag.split('-').first
+          match = wanted.find { |candidate| candidate.casecmp?(primary) }
+          return match.to_sym if match
+        end
+        nil
+      end
+
+      def reset!
+        @backend = nil
+        @translator = nil
+        @default_locale = nil
+        @fallbacks = nil
+        @load_path = nil
+        Thread.current[:prism_i18n_locale] = nil
+      end
+
+      private
+
+      def translator
+        @translator ||= Translator.new(backend, default_locale: default_locale, fallbacks: fallbacks)
+      end
+
+      def parse_accept_language(header)
+        entries = header.split(',').filter_map do |part|
+          tag, *params = part.strip.split(';').map(&:strip)
+          next if tag.nil? || tag.empty?
+          quality = 1.0
+          params.each { |param| quality = param.sub('q=', '').to_f if param.start_with?('q=') }
+          [tag, quality]
+        end
+        entries.sort_by.with_index { |(_, quality), index| [-quality, index] }.map(&:first)
+      end
+    end
+  end
+end