#!/usr/bin/env ruby

def try_require(name, version=nil)
  gem name, version if version
  require name
rescue LoadError
  if version
    STDERR.puts "Unable to load gem #{name} (#{version})"
    STDERR.puts "to install, type: gem install #{name} -v '#{version}'"
  else
    STDERR.puts "Unable to load gem #{name}"
    STDERR.puts "to install, type: gem install #{name}"
  end
  exit 1
end

try_require 'slop', '~> 4.2.0'
try_require 'awesome_print'
try_require 'json'

require 'pathname'
require 'erb'

VERSION = '0.1.0'

def test_erb_with_params(erbfile, params = {})
  local_binding = binding.clone

  params.each do |param, value|
    local_binding.eval("@#{param} = #{value.inspect}")
  end

  begin
    erb = ERB.new(IO.read(erbfile.to_s), nil, '-')
    erb.filename = erbfile.to_s
    erb.result(local_binding)
  rescue StandardError => e
    file_and_line = e.backtrace.first.split(':')[0..1].join(':')
    STDERR.puts "#{file_and_line}: #{e.message}"
    exit 1
  end
end

module Slop
  class PathOption < Option
    def call(value)
      Pathname.new(value)
    end
  end

  class DictOption < Option
    def call(value)
      raise ArgumentError, 'Hash option requires colon delimited key/value pair' unless value.include? ':'
      @value ||= {}
      @value.merge(Hash[ [value.split(':', 2)] ])
    end
  end
end

slop_opts = Slop::Options.new
slop_opts.banner = "usage: #{File.basename($0)} [options]"
slop_opts.path '-F', '--file', 'file to erbify'
slop_opts.dict '-p', '--params', 'colon delimited key:value pair to add as local variables for the erb (use json notation for complex values)'
slop_opts.on('-V', '--version', 'show version') { STDERR.puts VERSION; exit 0 }
slop_opts.on('-h', '--help', 'show help') { STDERR.puts slop_opts; exit 0 }

opts = Slop::Parser.new(slop_opts).parse(ARGV)

if opts[:file].nil? && !opts.arguments.empty?
  opts[:file] = Pathname.new File.expand_path(opts.arguments.first)
end

if opts.to_hash.values.all?(&:nil?)
  STDERR.puts slop_opts
  exit 1
end

if opts[:file].nil?
  STDERR.puts "Missing required option \`file'"
  STDERR.puts slop_opts
  exit 1
elsif ! opts[:file].exist?
  STDERR.puts "Unable to find file #{opts[:file].to_s}"
  STDERR.puts slop_opts
  exit 1
end

params = (opts[:params] || {}).each_with_object({}) do |(key, value), params|
  params[key] = value =~ /[\{\[]/ ? ( JSON.parse(value) rescue value) : value
end

STDERR.puts params

STDOUT.puts test_erb_with_params(opts[:file], params)