Add method to construct WebVTT files

Similar to JSON.Build
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syeopite 2023-08-24 14:58:50 -07:00
parent bb14f79496
commit 54fa59cbb0
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require "../../spec_helper.cr"
MockLines = [
{
"start_time": Time::Span.new(seconds: 1),
"end_time": Time::Span.new(seconds: 2),
"text": "Line 1",
},
{
"start_time": Time::Span.new(seconds: 2),
"end_time": Time::Span.new(seconds: 3),
"text": "Line 2",
},
]
Spectator.describe "WebVTT::Builder" do
it "correctly builds a vtt file" do
result = WebVTT.build do |vtt|
MockLines.each do |line|
vtt.line(line["start_time"], line["end_time"], line["text"])
end
end
expect(result).to eq([
"WEBVTT",
"",
"00:00:01.000 --> 00:00:02.000",
"Line 1",
"",
"00:00:02.000 --> 00:00:03.000",
"Line 2",
"",
"",
].join('\n'))
end
it "correctly builds a vtt file with setting fields" do
setting_fields = {
"Kind" => "captions",
"Language" => "en",
}
result = WebVTT.build(setting_fields) do |vtt|
MockLines.each do |line|
vtt.line(line["start_time"], line["end_time"], line["text"])
end
end
expect(result).to eq([
"WEBVTT",
"Kind: captions",
"Language: en",
"",
"00:00:01.000 --> 00:00:02.000",
"Line 1",
"",
"00:00:02.000 --> 00:00:03.000",
"Line 2",
"",
"",
].join('\n'))
end
end

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# Namespace for logic relating to generating WebVTT files
#
# Probably not compliant to WebVTT's specs but it is enough for Invidious.
module WebVTT
# A WebVTT builder generates WebVTT files
private class Builder
def initialize(@io : IO)
end
# Writes an vtt line with the specified time stamp and contents
def line(start_time : Time::Span, end_time : Time::Span, text : String)
timestamp(start_time, end_time)
@io << text
@io << "\n\n"
end
private def timestamp(start_time : Time::Span, end_time : Time::Span)
add_timestamp_component(start_time)
@io << " --> "
add_timestamp_component(end_time)
@io << '\n'
end
private def add_timestamp_component(timestamp : Time::Span)
@io << timestamp.hours.to_s.rjust(2, '0')
@io << ':' << timestamp.minutes.to_s.rjust(2, '0')
@io << ':' << timestamp.seconds.to_s.rjust(2, '0')
@io << '.' << timestamp.milliseconds.to_s.rjust(3, '0')
end
def document(setting_fields : Hash(String, String)? = nil, &)
@io << "WEBVTT\n"
if setting_fields
setting_fields.each do |name, value|
@io << "#{name}: #{value}\n"
end
end
@io << '\n'
yield
end
end
# Returns the resulting `String` of writing WebVTT to the yielded WebVTT::Builder
#
# ```
# string = WebVTT.build do |io|
# vtt.line(Time::Span.new(seconds: 1), Time::Span.new(seconds: 2), "Line 1")
# vtt.line(Time::Span.new(seconds: 2), Time::Span.new(seconds: 3), "Line 2")
# end
#
# 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"
# ```
#
# Accepts an optional settings fields hash to add settings attribute to the resulting vtt file.
def self.build(setting_fields : Hash(String, String)? = nil, &)
String.build do |str|
builder = Builder.new(str)
builder.document(setting_fields) do
yield builder
end
end
end
end