# frozen_string_literal: true

module Linguist

class Shebang

# Public: Use shebang to detect language of the blob.

#

# blob - An object that quacks like a blob.

# candidates - A list of candidate languages.

#

# Examples

#

# Shebang.call(FileBlob.new("path/to/file"))

#

# Returns an array of languages from the candidate list for which the

# blob's shebang is valid. Returns an empty list if there is no shebang.

# If the candidate list is empty, any language is a valid candidate.

def self.call(blob, candidates)

return [] if blob.symlink?

languages = Language.find_by_interpreter interpreter(blob.data)

candidates.any? ? candidates & languages : languages

end

# Public: Get the interpreter from the shebang

#

# Returns a String or nil

def self.interpreter(data)

# First line must start with #!

return unless data.start_with?("#!")

shebang = data[0, data.index($/) || data.length]

s = StringScanner.new(shebang)

# There was nothing after the #!

return unless path = s.scan(/^#!\s*\S+/)

# Keep going

script = path.split('/').last

# if /usr/bin/env type shebang then walk the string

if script == 'env'

s.scan(/\s+/)

while s.scan(/((-[i0uCSv]*|--\S+)\s+)+/) || # skip over optional arguments e.g. -vS

s.scan(/(\S+=\S+\s+)+/) # skip over variable arguments e.g. foo=bar

# do nothing

end

script = s.scan(/\S+/)

end

# Interpreter was /usr/bin/env with no arguments

return unless script

# "python2.6" -> "python2"

script.sub!(/(\.\d+)$/, '')

# #! perl -> perl

script.sub!(/^#!\s*/, '')

# Check for multiline shebang hacks that call `exec`

if script == 'sh' &&

data.lines.first(5).any? { |l| l.match(/exec (\w+)[\s"']+\$0[\s"']+\$@/) }

script = $1

end

# osascript can be called with an optional `-l <language>` argument, which may not be a language with an interpreter.

# In this case, return and rely on the subsequent strategies to determine the language.

if script == 'osascript'

return if s.scan_until(/\-l\s?/)

end

File.basename(script)

end

end

end