#!/usr/bin/env ruby
# List all foreign key constraints for *_id columns.
# Use --only-no-constraint to list *_id has no constraint.

gem "activerecord", ">= 4.2.1"
gem "mysql2"

require "optparse"
require "active_record"
require "mysql2"

def stringify_keys_deeply(obj)
  case obj
  when Hash
    obj.inject({}) do |h, (k, v)|
      h[k.to_s] = stringify_keys_deeply(v)
      h
    end
  when Array
    obj.map{|e| stringify_keys_deeply(e) }
  else
    obj
  end
end

if ARGV.empty?
  puts <<-EOS
Usage: #{$0} [--environment=development] path/to/database.yml
       #{$0} --username=USERNAME --password=PASSWORD ...
EOS

  exit 1
end

options = {
  environment: "development",
  only_no_constraint: false,
}

conn_options = {
  adapter: "mysql2",
  encoding: "utf8",
}

OptionParser.new do |o|
  o.banner = <<-EOS
Usage: #{$0} [--environment=development] path/to/database.yml
       #{$0} --database=DATABASE --username=USERNAME ...
EOS
  o.on("-e", "--environment KEY_ON_DATABASE_YML") {|e| options[:environment] = e }
  o.on("--only-no-constraint"){|e| options[:only_no_constraint] = true }
  o.on("--database DATABASE"){|s| conn_options[:database] = s }
  o.on("--host HOST"){|s| conn_options[:host] = s }
  o.on("--port PORT"){|s| conn_options[:port] = s }
  o.on("--username USERNAME"){|s| conn_options[:username] = s }
  o.on("--password [PASSWORD]"){|s|
    unless s
      print "password: "
      s = gets.chomp
    end
    conn_options[:password] = s
  }
  o.on("--encoding ENCODING"){|s| conn_options[:encoding] = s }
  o.on("--socket SOCKET"){|s| conn_options[:socket] = s }
  o.parse!(ARGV)
end

if ARGV[0]
  require "yaml"
  require "erb"
  database_yml = YAML.load(ERB.new(File.read(ARGV[0])).result)
  database_yml = database_yml[options[:environment]]
  conn_options = database_yml.merge(conn_options)
end

ActiveRecord::Base.establish_connection(conn_options)
conn = ActiveRecord::Base.connection

foreign_key_columns = Hash.new{|h, k| h[k] = {} }

conn.data_sources.each do |table_name|
  next if table_name == "schema_migrations"
  fks = conn.foreign_keys(table_name).map{|struct| stringify_keys_deeply(struct.to_h) }
  conn.columns(table_name).each do |column|
    column_name = column.name.to_s
    next unless column_name =~ /_id$/

    fks_for_column = fks.select{|fk| (fk["options"] || {})["column"] == column_name }
    next if options[:only_no_constraint] && fks_for_column.any?

    foreign_key_columns[table_name][column_name] = fks_for_column
  end
end

puts YAML.dump(foreign_key_columns)