77 lines
2.1 KiB
Crystal
77 lines
2.1 KiB
Crystal
require "json"
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require "uri"
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private def copy_string(str : String::Builder, iter : Iterator, count : Int) : Int
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copied = 0
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while copied < count
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cp = iter.next
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break if cp.is_a?(Iterator::Stop)
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if cp == 0x26 # Ampersand (&)
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str << "&"
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elsif cp == 0x27 # Single quote (')
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str << "'"
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elsif cp == 0x22 # Double quote (")
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str << """
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elsif cp == 0x3C # Less-than (<)
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str << "<"
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elsif cp == 0x3E # Greater than (>)
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str << ">"
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else
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str << cp.chr
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end
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# A codepoint from the SMP counts twice
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copied += 1 if cp > 0xFFFF
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copied += 1
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end
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return copied
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end
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def parse_description(desc, video_id : String) : String?
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return "" if desc.nil?
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content = desc["content"].as_s
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return "" if content.empty?
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commands = desc["commandRuns"]?.try &.as_a
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return content if commands.nil?
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# Not everything is stored in UTF-8 on youtube's side. The SMP codepoints
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# (0x10000 and above) are encoded as UTF-16 surrogate pairs, which are
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# automatically decoded by the JSON parser. It means that we need to count
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# copied byte in a special manner, preventing the use of regular string copy.
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iter = content.each_codepoint
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index = 0
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return String.build do |str|
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commands.each do |command|
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cmd_start = command["startIndex"].as_i
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cmd_length = command["length"].as_i
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# Copy the text chunk between this command and the previous if needed.
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length = cmd_start - index
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index += copy_string(str, iter, length)
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# We need to copy the command's text using the iterator
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# and the special function defined above.
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cmd_content = String.build(cmd_length) do |str2|
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copy_string(str2, iter, cmd_length)
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end
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link = cmd_content
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if on_tap = command.dig?("onTap", "innertubeCommand")
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link = parse_link_endpoint(on_tap, cmd_content, video_id)
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end
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str << link
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index += cmd_length
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end
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# Copy the end of the string (past the last command).
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remaining_length = content.size - index
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copy_string(str, iter, remaining_length) if remaining_length > 0
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end
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end
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