lnav2

#!/usr/bin/ruby
#
# Wrapper around lnav which adds some handy extra options / features:
#
#   - make r/R hotkeys default to navigating one minute forward/back
#
#   - --hide-before option to ignore lines before a certain time
#
#   - --start-at option to jump to a specific time on startup
#
#   - if --start-at is not given, places the first error (roughly)
#     in the middle of the screen

require 'time'
require 'optparse'
require 'optparse/time'
require 'pp'

ENV['LANG'] = "C"

class OptionParser
  # Like order!, but leave any unrecognized --switches alone
  # https://stackoverflow.com/a/40434335/179332
  def order_recognized!(args=ARGV)
    extra_opts = []
    begin
      order!(args) { |a| extra_opts << a }
    rescue OptionParser::InvalidOption => e
      extra_opts << e.args[0]
      retry
    end
    args[0, 0] = extra_opts
  end
end

def main
  options = parse_options

  args = [
    # hack to make r/R hotkeys default to navigating one minute forward/back
    # https://github.com/tstack/lnav/issues/382
    "-c", ":goto 1 min later",
  ]

  if options[:hide_before]
    args += [ "-c", ":hide-lines-before +#{options[:hide_before]}" ]
  end

  if options[:start_at]
    args += [ "-c", ":goto +#{options[:start_at]}" ]
  else
    # put first error in middle of display
    args += [
      '-c', ':goto 0',
      '-c', ':next-mark error',
      '-c', ':relative-goto -20',
    ]
  end

  args += ARGV

  puts "Running lnav with args:"
  args.each { |arg| puts "  " + arg.inspect }

  system 'lnav', *args
end

def parse_options
  {}.tap do |options|
    parser = OptionParser.new do |opts|
      opts.banner = "Usage: #$0 [options] [args]"

      opts.on("-h", "--help", "Show this help") do
        puts parser
        puts "\nOther options and arguments are passed on to lnav:\n\n"
        system "lnav", "-h"
        exit
      end

      opts.on("--hide-before TIME", Time, "Hide lines before TIME") do |time|
        options[:hide_before] = time.strftime("%s")
      end

      opts.on("--start-at TIME", Time, "Start viewing at TIME") do |time|
        options[:start_at] = time.strftime("%s")
      end
    end

    parser.order_recognized!
  end
end

main