# frozen_string_literal: true

require 'tempfile'

# Provide a diff between two strings.
module Puppet::Util::Diff
  include Puppet::Util::Execution
  require 'tempfile'

  def diff(old, new)
    diff_cmd = Puppet[:diff]
    return '' unless diff_cmd && diff_cmd != ""

    command = [diff_cmd]
    args = Puppet[:diff_args]
    if args && args != ""
      args.split(' ').each do |arg|
        command << arg
      end
    end
    command << old << new
    Puppet::Util::Execution.execute(command, :failonfail => false, :combine => false)
  end

  module_function :diff

  # return diff string of two input strings
  # format defaults to unified
  # context defaults to 3 lines
  def lcs_diff(data_old, data_new, format = :unified, context_lines = 3)
    unless Puppet.features.diff?
      Puppet.warning _("Cannot provide diff without the diff/lcs Ruby library")
      return ""
    end
    data_old = data_old.split(/\n/).map! { |e| e.chomp }
    data_new = data_new.split(/\n/).map! { |e| e.chomp }

    output = ''.dup

    diffs = ::Diff::LCS.diff(data_old, data_new)
    return output if diffs.empty?

    oldhunk = hunk = nil
    file_length_difference = 0

    diffs.each do |piece|
      begin
        hunk = ::Diff::LCS::Hunk.new(
          data_old, data_new, piece,
          context_lines,
          file_length_difference
        )
        file_length_difference = hunk.file_length_difference
        next unless oldhunk

        # Hunks may overlap, which is why we need to be careful when our
        # diff includes lines of context. Otherwise, we might print
        # redundant lines.
        if (context_lines > 0) and hunk.overlaps?(oldhunk)
          hunk.unshift(oldhunk)
        else
          output << oldhunk.diff(format)
        end
      ensure
        oldhunk = hunk
        output << "\n"
      end
    end

    # Handle the last remaining hunk
    output << oldhunk.diff(format) << "\n"
  end

  def string_file_diff(path, string)
    tempfile = Tempfile.new("puppet-diffing")
    tempfile.open
    tempfile.print string
    tempfile.close
    notice "\n" + diff(path, tempfile.path)
    tempfile.delete
  end
end