ruby : output format (#3237)

* Fix a typo

* Don't allocate output string unless needed

* Add methods to output SRT and WebVTT

* Add tests for output methods

* Make constants for output private

* Add signatures for output methods

* Add document on output methods

* Fix method name: Segment#speaker_next_turn? -> #speacker_turn_next?

* Add Whisper::Segment#descotruct_keys

* Add test for Whisper::Context#descotruct_keys

* Add signature of Whisper::Segment#deconstruct_keys

* Use parentheses to suppress warning

* Update date

bindings/ruby/lib/whisper/segment.rb

@@ -0,0 +1,58 @@
+module Whisper
+  class Segment
+    SRT_ESCAPES = {
+      "&" => "&",
+      "<" => "&lt;",
+      ">" => "&gt;",
+    }
+    SRT_ESCAPES_RE = Regexp.union(SRT_ESCAPES.keys)
+    private_constant :SRT_ESCAPES, :SRT_ESCAPES_RE
+
+    def to_srt_cue
+      "#{srt_start_time} --> #{srt_end_time}\n#{srt_text}\n"
+    end
+
+    def to_webvtt_cue
+      "#{webvtt_start_time} --> #{webvtt_end_time}\n#{webvtt_text}\n"
+    end
+
+    private
+
+    def time_to_a(time)
+      sec, decimal_part = time.divmod(1000)
+      min, sec = sec.divmod(60)
+      hour, min = min.divmod(60)
+      [hour, min, sec, decimal_part]
+    end
+
+    def srt_time(time)
+      "%02d:%02d:%02d,%03d" % time_to_a(time)
+    end
+
+    def srt_start_time
+      srt_time(start_time)
+    end
+
+    def srt_end_time
+      srt_time(end_time)
+    end
+
+    def srt_text
+      text.gsub(SRT_ESCAPES_RE, SRT_ESCAPES)
+    end
+
+    def webvtt_time(time)
+      "%02d:%02d:%02d.%03d" % time_to_a(time)
+    end
+
+    def webvtt_start_time
+      webvtt_time(start_time)
+    end
+
+    def webvtt_end_time
+      webvtt_time(end_time)
+    end
+
+    alias webvtt_text srt_text
+  end
+end