summarize_json.rb

# Summarize JSON structure
# cat source.json | ruby sum_json.rb --key-pattern '\A\-|\-test\z' --format json

require 'json'
require 'yaml'

require 'getoptlong.rb'
parser = GetoptLong.new
parser.set_options(
  ['--key-pattern', '-k', GetoptLong::OPTIONAL_ARGUMENT],
  ['--format', '-f', GetoptLong::OPTIONAL_ARGUMENT],
)

@key_regexp = nil
@format = 'yaml'

begin
  parser.each_option do |name, arg|
    case name
    when '--key-pattern', '-k'
      @key_regexp = Regexp.new(arg)
    when '--format', '-f'
      @format = arg
    end
  end
rescue
   exit(1)
end

root = JSON.parse($stdin.read)

def assign(d, k, child)
  if d[k] && child
    if d[k].is_a?(Hash) && child.is_a?(Hash)
      d[k].update(child)
    else
      if d[k] != child
        if [ d[k], child ].sort != ['float64', 'int64']
          $stderr.puts("Mismatch! \n#{d[k].inspect}\n#{child.inspect}")
        end
      end
    end
  else
    d[k] ||= child
  end
end

def walk(node)
  case node
  when Hash
    node.each_with_object({}) do |(key, child), d|
      k = (@key_regexp && @key_regexp =~ key) ? '(key)' : key
      assign(d, k, walk(child))
    end
  when Array
    node.each_with_object({}) do |child, d|
      assign(d, '(index)', walk(child))
    end
  when String then 'string'
  when Integer then 'int64'
  when Float then 'float64'
  when TrueClass then 'bool'
  when FalseClass then 'bool'
  when NilClass then 'null'
  else
    $stderr.puts("unknown value: #{node.inspect}")
  end
end

r = walk(root)
output =
  case @format
  when 'yaml' then YAML.dump(r)
  when 'json' then JSON.pretty_generate(r)
  else raise "Unsupported format: #{@format.inspect}"
  end
$stdout.puts(output)