#This class can be used to make SQL-dumps of databases, tables or however you want it.
class Baza::Dump
  #Constructor.
  #===Examples
  # dump = Baza::Dump.new(:db => db)
  def initialize(args)
    @args = args
    @debug = @args[:debug]
  end
  
  #Method used to update the status.
  def update_status
    return nil if !@on_status
    rows_count = Knj::Locales.number_out(@rows_count, 0)
    rows_count_total = Knj::Locales.number_out(@rows_count_total, 0)
    percent = (@rows_count.to_f / @rows_count_total.to_f) * 100
    percent_text = Knj::Locales.number_out(percent, 1)
    @on_status.call(:text => "Dumping table: '#{@table_obj.name}' (#{rows_count}/#{rows_count_total} - #{percent_text}%).")
  end
  
  #Dumps all tables into the given IO.
  def dump(io)
    print "Going through tables.\n" if @debug
    @rows_count = 0
    
    if @args[:tables]
      tables = @args[:tables]
    else
      tables = @args[:db].tables.list.values
    end
    
    if @on_status
      @on_status.call(:text => "Preparing.")
      
      @rows_count_total = 0
      tables.each do |table_obj|
        @rows_count_total += table_obj.rows_count
      end
    end
    
    tables.each do |table_obj|
      table_obj = @args[:db].tables[table_obj] if table_obj.is_a?(String) or table_obj.is_a?(Symbol)
      next if table_obj.native?
      
      #Figure out keys.
      @keys = []
      table_obj.columns do |col|
        @keys << col.name
      end
      
      @table_obj = table_obj
      self.update_status
      puts "Dumping table: '#{table_obj.name}'." if @debug
      self.dump_table(io, table_obj)
    end
  end
  
  #A block can be executed when a new status occurs.
  def on_status(&block)
    @on_status = block
  end
  
  #Dumps the given table into the given IO.
  def dump_table(io, table_obj)
    create_data = table_obj.data
    create_data.delete(:name)
    
    #Get SQL for creating table and add it to IO.
    sqls = @args[:db].tables.create(table_obj.name, create_data, :return_sql => true)
    sqls.each do |sql|
      io.write("#{sql};\n")
    end
    
    
    #Try to find a primary column in the table.
    prim_col = nil
    table_obj.columns do |col|
      if col.primarykey?
        prim_col = col
        break
      end
    end
    
    
    #Set up rows and way to fill rows.
    rows = []
    block_data = proc do |row|
      rows << row
      @rows_count += 1
      
      if rows.length >= 1000
        self.update_status
        self.dump_insert_multi(io, table_obj, rows)
      end
    end
    
    
    #If a primary column is found then use IDQuery. Otherwise use cloned unbuffered query.
    args = {:idquery => prim_col.name.to_sym} if prim_col
    
    
    #Clone the connecting with array-results and execute query.
    @args[:db].clone_conn(:result => "array") do |db|
      db.select(table_obj.name, nil, args, &block_data)
    end
    
    
    #Dump the last rows if any.
    self.dump_insert_multi(io, table_obj, rows) if !rows.empty?
  end
  
  #Dumps the given rows from the given table into the given IO.
  def dump_insert_multi(io, table_obj, rows)
    print "Inserting #{rows.length} into #{table_obj.name}.\n" if @debug
    sqls = @args[:db].insert_multi(table_obj.name, rows, :return_sql => true, :keys => @keys)
    sqls.each do |sql|
      io.write("#{sql};\n")
    end
    
    rows.clear
    
    #Ensure garbage collection or we might start using A LOT of memory.
    GC.start
  end
end