82 行
2.3 KiB
Crystal
82 行
2.3 KiB
Crystal
# Namespace for logic relating to generating WebVTT files
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#
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# Probably not compliant to WebVTT's specs but it is enough for Invidious.
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module WebVTT
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# A WebVTT builder generates WebVTT files
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private class Builder
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# See https://developer.mozilla.org/en-US/docs/Web/API/WebVTT_API#cue_payload
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private ESCAPE_SUBSTITUTIONS = {
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'&' => "&",
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'<' => "<",
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'>' => ">",
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'\u200E' => "‎",
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'\u200F' => "‏",
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'\u00A0' => " ",
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}
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def initialize(@io : IO)
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end
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# Writes an vtt cue with the specified time stamp and contents
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def cue(start_time : Time::Span, end_time : Time::Span, text : String)
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timestamp(start_time, end_time)
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@io << self.escape(text)
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@io << "\n\n"
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end
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private def timestamp(start_time : Time::Span, end_time : Time::Span)
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timestamp_component(start_time)
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@io << " --> "
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timestamp_component(end_time)
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@io << '\n'
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end
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private def timestamp_component(timestamp : Time::Span)
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@io << timestamp.hours.to_s.rjust(2, '0')
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@io << ':' << timestamp.minutes.to_s.rjust(2, '0')
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@io << ':' << timestamp.seconds.to_s.rjust(2, '0')
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@io << '.' << timestamp.milliseconds.to_s.rjust(3, '0')
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end
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private def escape(text : String) : String
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return text.gsub(ESCAPE_SUBSTITUTIONS)
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end
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def document(setting_fields : Hash(String, String)? = nil, &)
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@io << "WEBVTT\n"
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if setting_fields
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setting_fields.each do |name, value|
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@io << name << ": " << value << '\n'
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end
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end
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@io << '\n'
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yield
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end
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end
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# Returns the resulting `String` of writing WebVTT to the yielded `WebVTT::Builder`
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#
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# ```
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# string = WebVTT.build do |vtt|
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# vtt.cue(Time::Span.new(seconds: 1), Time::Span.new(seconds: 2), "Line 1")
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# vtt.cue(Time::Span.new(seconds: 2), Time::Span.new(seconds: 3), "Line 2")
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# end
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#
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# string # => "WEBVTT\n\n00:00:01.000 --> 00:00:02.000\nLine 1\n\n00:00:02.000 --> 00:00:03.000\nLine 2\n\n"
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# ```
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#
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# Accepts an optional settings fields hash to add settings attribute to the resulting vtt file.
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def self.build(setting_fields : Hash(String, String)? = nil, &)
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String.build do |str|
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builder = Builder.new(str)
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builder.document(setting_fields) do
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yield builder
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end
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end
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end
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end
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