#399

backend/app/services/post_metadata_fetcher.rb

@@ -1,4 +1,9 @@
 class PostMetadataFetcher
+  TIMESTAMP_PATTERN =
+      /\A(\d{4})-(\d{2})-(\d{2})T(\d{2})/ \
+      /(?::(\d{2})(?::(\d{2})(?:\.(\d+))?)?)?/ \
+      /(Z|[+-]\d{2}:?\d{2})?\z/
+
   def self.fetch raw_url
     uri, = Preview::UrlSafety.validate(raw_url)
     response = Preview::HttpFetcher.fetch(
@@ -37,25 +42,76 @@ class PostMetadataFetcher
     return nil if value.blank?
 
     raw = value.to_s.strip
-    from = Time.zone.parse(raw)
-    zone = '(?:Z|[+-]\d{2}:?\d{2})?'
-    before =
-      case raw
-      when /\A\d{4}\z/ then from + 1.year
-      when /\A\d{4}-\d{2}\z/ then from + 1.month
-      when /\A\d{4}-\d{2}-\d{2}\z/ then from + 1.day
-      when /\A\d{4}-\d{2}-\d{2}T\d{2}#{ zone }\z/ then from + 1.hour
-      when /\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}#{ zone }\z/ then from + 1.minute
-      when /\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}#{ zone }\z/ then from + 1.second
-      when /\A\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.(\d+)#{ zone }\z/
-        from + (10**(-Regexp.last_match(1).length))
-      else
-        return nil
-      end
+    from, before =
+        case raw
+        when /\A(\d{4})\z/
+          year = Regexp.last_match(1).to_i
+          from = Time.zone.local(year, 1, 1)
+          [from, from + 1.year]
+        when /\A(\d{4})-(\d{2})\z/
+          year = Regexp.last_match(1).to_i
+          month = Regexp.last_match(2).to_i
+          from = Time.zone.local(year, month, 1)
+          [from, from + 1.month]
+        when /\A(\d{4})-(\d{2})-(\d{2})\z/
+          year = Regexp.last_match(1).to_i
+          month = Regexp.last_match(2).to_i
+          day = Regexp.last_match(3).to_i
+          from = Time.zone.local(year, month, day)
+          [from, from + 1.day]
+        else
+          parse_timestamp_range(raw)
+        end
+    return nil if from.nil? || before.nil?
+
     [from, before]
   rescue ArgumentError, TypeError
     nil
   end
 
-  private_class_method :platform_tags, :original_created_range
+  def self.parse_timestamp_range raw
+    match = raw.match(TIMESTAMP_PATTERN)
+    return nil unless match
+
+    year = match[1].to_i
+    month = match[2].to_i
+    day = match[3].to_i
+    hour = match[4].to_i
+    minute = match[5]&.to_i || 0
+    second = match[6]&.to_i || 0
+    fraction = match[7]
+    offset = parse_offset(match[8])
+    from = Time.new(year, month, day, hour, minute, second + fractional_seconds(fraction), offset)
+              .in_time_zone
+    before =
+        if fraction.present?
+          from + (10**(-fraction.length))
+        elsif match[6].present?
+          from + 1.second
+        elsif match[5].present?
+          from + 1.minute
+        else
+          from + 1.hour
+        end
+    [from, before]
+  end
+
+  def self.parse_offset value
+    return Time.zone.formatted_offset if value.blank?
+    return '+00:00' if value == 'Z'
+
+    value.match?(/\A[+-]\d{2}:\d{2}\z/) ? value : "#{ value[0, 3] }:#{ value[3, 2] }"
+  end
+
+  def self.fractional_seconds value
+    return 0 if value.blank?
+
+    Rational(value.to_i, 10**value.length)
+  end
+
+  private_class_method :platform_tags,
+                       :original_created_range,
+                       :parse_timestamp_range,
+                       :parse_offset,
+                       :fractional_seconds
 end