# -*- coding: utf-8 -*-

module ErbTeX
  class NoInputFile < StandardError; end

  class CommandLine
    attr_reader :erbtex_name, :tex_program, :tex_options
    attr_reader :tex_commands, :input_file

    def initialize(argv)
      # Note: argv will be the command line arguments after processing by the
      # shell, so if we see things such as '&', '~', '\' in the args, these were
      # quoted by the user on the command-line and need no special treatment
      # here. For example, '~/junk' on the commandline will show up here as
      # '/home/ded/junk'. If we see '~/junk', that means the user has quoted the
      # ~ on the command line with something like '\~junk', so we should assume
      # that the user wants to keep it that way. Likewise, an arg with spaces in
      # it will have been quoted by the user to be seen as a single argument.
      # When we output these for use by the shell in the system command, we
      # should apply shellquote to everything so that the receiving shell sees
      # the args in the same way.

      @erbtex_name = File.basename($0)

      # Find the tex_commands
      @tex_commands = []
      if argv.any? { |a| a =~ /\A\\/ }
        # All args after first starting with '\' should be interpreted as TeX
        # commands, even if they don't start with '\'
        @tex_commands = argv.drop_while { |a| a !~ /\A\\/ }
        first_tex_command_k = argv.size - @tex_commands.size
        argv = argv[0..first_tex_command_k - 1]
      end

      # Look for our --invoke=tex_command option
      @tex_program = 'pdflatex'
      if argv.any? { |a| a =~ /\A--invoke=(\w+)/ }
        @tex_program = $1
        argv.reject! { |a| a =~ /\A--invoke=(\w+)/ }
      end

      # The last argument, assuming it does not start with a '-' or '&', is
      # assumed to be the name of the input_file.
      if !argv.empty? && argv[-1] !~ /\A[-&]/
        @input_file = CommandLine.expand_input_file(argv.pop)
      end

      # What remains in argv should be the tex program's '-options', which
      # should be passed through untouched. So, can form the full command line
      # for tex_processing
      @tex_options = argv.dup
    end

    def tex_command(tex_file = input_file)
      "#{tex_program} " \
      "#{tex_options.shelljoin} " \
      "#{tex_commands.shelljoin} " \
      "#{tex_file}"
        .strip.squeeze(' ')
    end

    # Return the name of the input file based on the name given in the command
    # line. Try to find the right extension for the input file if none is given.
    def self.expand_input_file(input_file)
      full_ext = input_file[/\A(.*)(\.[\w.]+)\z/, 2]
      if full_ext.nil? || full_ext.empty?
        if File.exist?("#{input_file}.tex.erb")
          "#{input_file}.tex.erb"
        elsif File.exist?("#{input_file}.tex")
          "#{input_file}.tex"
        elsif File.exist?("#{input_file}.erb")
          "#{input_file}.erb"
        else
          input_file
        end
      else
        input_file
      end
    end
  end
end

# NOTES:
# The following text is from the Web2C documentation at
# http://tug.org/texinfohtml/web2c.html#Output-file-location
#
# 4.1 TeX invocation
#
#   TeX, Metafont, and MetaPost process the command line (described here)
#   and determine their memory dump (fmt) file in the same way (*note Memory
#   dumps::).  Synopses:
#
#   tex [OPTION]... [TEXNAME[.tex]] [TEX-COMMANDS]
#   tex [OPTION]... \FIRST-LINE
#   tex [OPTION]... &FMT ARGS
#
#   TeX searches the usual places for the main input file TEXNAME (*note
#   (kpathsea)Supported file formats::), extending TEXNAME with '.tex' if
#   necessary.  To see all the relevant paths, set the environment variable
#   'KPATHSEA_DEBUG' to '-1' before running the program.
#
#   After TEXNAME is read, TeX processes any remaining TEX-COMMANDS on
#   the command line as regular TeX input.  Also, if the first non-option
#   argument begins with a TeX escape character (usually '\'), TeX processes
#   all non-option command-line arguments as a line of regular TeX input.

# 3.4 Output file location
#
# All the programs generally follow the usual convention for output
# files. Namely, they are placed in the directory current when the
# program is run, regardless of any input file location; or, in a few
# cases, output is to standard output.

# For example, if you run ‘tex /tmp/foo’, for example, the output will
# be in ./foo.dvi and ./foo.log, not /tmp/foo.dvi and /tmp/foo.log.

# You can use the ‘-output-directory’ option to cause all output files
# that would normally be written in the current directory to be written
# in the specified directory instead. See Common options.

# If the current directory is not writable, and ‘-output-directory’ is
# not specified, the main programs (TeX, Metafont, MetaPost, and BibTeX)
# make an exception: if the config file or environment variable value
# TEXMFOUTPUT is set (it is not by default), output files are written to
# the directory specified.

# TEXMFOUTPUT is also checked for input files, as TeX often generates
# files that need to be subsequently read; for input, no suffixes (such
# as ‘.tex’) are added by default and no exhaustive path searching is
# done, the input name is simply checked as given.