Script to automatically generate migrations for Ruby on Rails, based on changes in schema.rb file

north.rb

#!/usr/bin/env ruby

require 'fileutils'

help = view = gen = apply = edit = del = restore = false
letters = ''    
ARGV.each do |arg|
  if arg[1] == '-'
    help ||= arg == '--help'
    view ||= arg == '--view'
    gen ||= arg == '--generate'
    apply ||= arg == '--apply'
    edit ||= arg == '--edit'
    del ||= arg == '--delete'
    restore ||= arg == '--restore'
  else
    letters += arg[1..999]
  end
end
letters.chars.each do |arg|
  arg = '-'+arg
  help ||= (arg == '-h') || (arg == '-?')
  view ||= arg == '-v' 
  gen ||= arg == '-g'
  apply ||= arg == '-a'
  edit ||= arg == '-e'
  del ||= arg == '-d'
  restore ||= arg == '-r'
end    

puts 'view' if view
puts 'generate' if gen
puts 'apply' if apply
puts 'edit' if edit
puts 'delete' if del
puts 'restore' if restore

def parse_tabs(fn)
  tab_lines = []
  line_num = 0
  text = File.open(fn).read
  #text.gsub!(/\r\n?/, "\n")
  tab_name = ''
  text.each_line do |line|
    if /create_table/ =~ line
      m = (/^.*create_table \"(.*)\".*$/.match line )
      tab_name = m[1]
      puts "parsed tab #{tab_name} @ #{line_num}"      
    end
    tab_lines[line_num] = tab_name
    #print "#{tab_name} #{line_num} #{line}"
    line_num += 1
  end  
  tab_lines
end



def last_mig_file    
  Dir.chdir File.expand_path 'db/migrate'      
  migfiles = Dir.glob('*.rb')
  lastfile = nil
  lasttime = Time.new(1999,01,01)
  migfiles.each do |migfile|
    f = File.open(migfile)
    #puts 'seach last mig... '+f.path+' '+f.mtime.to_s
    if f.mtime > lasttime
      lastfile = f
      lasttime = f.mtime
    end
  end
  Dir.chdir File.expand_path '../..'      
  if lastfile 
    #puts 'found last mig:   '+lastfile.path+' '+lasttime.to_s
    './db/migrate/'+lastfile.path
  else
    ''
  end      
end

#    f = last_mig_file
#class ChangeOrderOfProductChars < ActiveRecord::Migration
#  def change
#    change_column :iproduct_chars, :order, :integer, null: true
#  end
#end    

if help 
  puts 'north.rb <[email protected]>'
  puts ' -g, --generate : generate migrations'
  puts ' -a, --apply : apply generated migrations'
  puts ' -v, --view : view last migration'
  puts ' -e, --edit : edit last migration'
  puts ' -d, --delete : delete last migration'
  puts ' -r, --restore : restore schema.rb (for testing)'
end

if gen

  puts 'copy schema'
  FileUtils.cp File.expand_path('db/schema.rb'), File.expand_path('db/schema_north.rb')
  `rake db:schema:dump`

  tab_lines = parse_tabs('db/schema.rb')
  #puts tab_lines

  puts 'generate migrations'
  migrations = []    
  diff = `diff -bBE db/schema.rb db/schema_north.rb`

  puts ''
  puts diff
  puts ''

  tab_name = ''
  
  line_num = 0
  diff.each_line do |line|
    ss = line.split    

    if ss.length >= 2      
      s = ss[2]
      field = (/.*['\"](.*)['\"].*/.match s)
      if not field.nil?
        field = field[1]
        s = ss[1].strip
        type_name = s[2..s.length-1]      
        sss = line.split ','
        field_opts = sss[1..sss.length-1].join(',').strip
      else
        field = ''
        type_name = ''
        field_opts = ''
      end
    end
    
    if line[0] == '<' and field.to_s != ''and tab_name.to_s != ''
      #puts "del field #{field}"
      migrations.push({action: 'remove', line_num: line_num, tab_name: tab_name, field: field, type_name: type_name, field_opts: field_opts})
      puts "migration remove_#{field}_to_#{tab_name} #{field}:#{type_name}"
    elsif line[0] == '>' and field.to_s != '' and tab_name.to_s != ''
      #puts "add field #{field} type #{type_name}"
      migrations.push({action: 'add', line_num: line_num, tab_name: tab_name, field: field, type_name: type_name, field_opts: field_opts})        
      puts "migration add_#{field}_to_#{tab_name} #{field}:#{type_name}, #{field_opts}"
    elsif line[0] != '-'
      line_num = line.to_i
      tab_name = tab_lines[line_num]
      puts "at #{line_num} tab #{tab_name} "
    end
  
  end  

  # generate change commands from remove+add
  migrations.each do |m|
    migrations.each do |m2|
      if (m[:tab_name] == m2[:tab_name]) && (m[:field] == m2[:field])
        if (m[:action] == 'add') && (m2[:action] == 'remove')
          m[:action] = 'change'
          m2[:action] = ''
          puts "CHANGE"
        elsif (m[:action] == 'remove') && (m2[:action] == 'add')
          m2[:action] = 'change'
          m[:action] = ''
          puts "CHANGE"
        end
      elsif m[:line_num] == m2[:line_num] && m[:field] != m2[:field] && m[:type_name] == m2[:type_name] && m[:field_opts] == m2[:field_opts]
        if (m[:action] == 'add') && (m2[:action] == 'remove')
          m[:action] = ''
          m2[:action] = 'rename'
          m2[:new_field] = m[:field]
          puts "RENAME"
        elsif (m[:action] == 'remove') && (m2[:action] == 'add')
          m2[:action] = ''
          m[:action] = 'rename'
          m[:new_field] = m2[:field]
          puts "RENAME"
        end
      end
    end
  end      
  
  # generate and apply commands
  migrations.each do |m|
    a = m[:action]
    tab_name = m[:tab_name]
    field = m[:field]
    type_name = m[:type_name]
    field_opts = m[:field_opts]
    if a == 'add'
      code = "rails g migration add_#{field}_to_#{tab_name} #{field}:#{type_name}"   
      puts code
      if gen
        system(code)
        if field_opts != ''
          fn = last_mig_file
          first_line = ''
          File.open(fn, "r").each_line do |line|
            first_line = line
            break
          end
          File.open(fn, "w") do |file|
            file.write(first_line)
            file.write("  def change\n")
            if field_opts == ''
              file.write("    add_column :#{tab_name}, :#{field}, :#{type_name}\n")
            else
              file.write("    add_column :#{tab_name}, :#{field}, :#{type_name}, #{field_opts}\n") 
            end
            file.write("  end\n")
            file.write("end\n")
          end
        end
      end
    elsif a == 'remove'
      code = "rails g migration remove_#{field}_from_#{tab_name} #{field}:#{type_name}"
      puts code
      system(code) if gen
    elsif a == 'change'
      code = "rails g migration change_#{field}_in_#{tab_name} #{field}:#{type_name}"
      puts code
      if gen
        system(code)
        fn = last_mig_file
        first_line = ''
        File.open(fn, "r").each_line do |line|
          first_line = line
          break
        end
        File.open(fn, "w") do |file|
          file.write(first_line)
          file.write("  def change\n")
          if field_opts == ''
            file.write("    change_column :#{tab_name}, :#{field}, :#{type_name}\n")
          else
            file.write("    change_column :#{tab_name}, :#{field}, :#{type_name}, #{field_opts}\n") 
          end
          file.write("  end\n")
          file.write("end\n")
        end
      end
    elsif a == 'rename'
      new_field = m[:new_field]
      code = "rails g migration rename_#{field}_of_#{tab_name} #{new_field}:#{type_name}"
      puts code
      if gen
        system(code)
        fn = last_mig_file
        first_line = ''
        File.open(fn, "r").each_line do |line|
          first_line = line
          break
        end
        File.open(fn, "w") do |file|
          file.write(first_line)
          file.write("  def change\n")
          file.write("    rename_column :#{tab_name}, :#{field}, :#{new_field}\n")
          file.write("  end\n")
          file.write("end\n")
        end
      end        
    end
  end   
end

if view 
  puts 'view'
  lastfile = last_mig_file
  system('cat', lastfile)
end

if edit
  puts 'edit'
  lastfile = last_mig_file
  system('editor', lastfile)
end

if del
  puts 'delete'
  lastfile = last_mig_file
  system('rm', lastfile)
end

if restore  
  # restore schema
  puts 'restore schema'
  FileUtils.cp File.expand_path('db/schema_north.rb'), File.expand_path('db/schema.rb')  
end

if apply
  # rake db:migrate here
  puts 'apply (not implemented)'
end