require 'active_record/connection_adapters/mysql_adapter'

ActiveRecord::ConnectionAdapters::MysqlAdapter.class_eval do
  include SpatialAdapter

  def supports_geographic?
    false
  end
  
  alias :original_native_database_types :native_database_types
  def native_database_types
    original_native_database_types.merge!(geometry_data_types)
  end
 
  alias :original_quote :quote
  #Redefines the quote method to add behaviour for when a Geometry is encountered ; used when binding variables in find_by methods
  def quote(value, column = nil)
    if value.kind_of?(GeoRuby::SimpleFeatures::Geometry)
      "GeomFromWKB(0x#{value.as_hex_wkb},#{value.srid})"
    else
      original_quote(value,column)
    end
  end
  
  #Redefinition of columns to add the information that a column is geometric
  def columns(table_name, name = nil)#:nodoc:
    sql = "SHOW FIELDS FROM #{quote_table_name(table_name)}"
    columns = []
    result = execute(sql, name)
    result.each do |field|
      klass = field[1] =~ /geometry|point|linestring|polygon|multipoint|multilinestring|multipolygon|geometrycollection/i ? ActiveRecord::ConnectionAdapters::SpatialMysqlColumn : ActiveRecord::ConnectionAdapters::MysqlColumn
      columns << klass.new(field[0], field[4], field[1], field[2] == "YES")
    end
    result.free
    columns
  end


  #operations relative to migrations

  #Redefines add_index to support the case where the index is spatial
  #If the :spatial key in the options table is true, then the sql string for a spatial index is created
  def add_index(table_name,column_name,options = {})
    index_name = options[:name] || index_name(table_name,:column => Array(column_name))
    
    if options[:spatial]
      execute "CREATE SPATIAL INDEX #{index_name} ON #{table_name} (#{Array(column_name).join(", ")})"
    else
      super
    end
  end

  #Check the nature of the index : If it is SPATIAL, it is indicated in the IndexDefinition object (redefined to add the spatial flag in spatial_adapter_common.rb)
  def indexes(table_name, name = nil)#:nodoc:
    indexes = []
    current_index = nil
    execute("SHOW KEYS FROM #{table_name}", name).each do |row|
      if current_index != row[2]
        next if row[2] == "PRIMARY" # skip the primary key
        current_index = row[2]
        indexes << ActiveRecord::ConnectionAdapters::IndexDefinition.new(row[0], row[2], row[1] == "0", [], row[10] == "SPATIAL")
      end
      indexes.last.columns << row[4]
    end
    indexes
  end
        
  #Get the table creation options : Only the engine for now. The text encoding could also be parsed and returned here.
  def options_for(table)
    result = execute("show table status like '#{table}'")
    engine = result.fetch_row[1]
    if engine !~ /inno/i #inno is default so do nothing for it in order not to clutter the migration
      "ENGINE=#{engine}" 
    else
      nil
    end
  end
end


module ActiveRecord
  module ConnectionAdapters
    class SpatialMysqlColumn < MysqlColumn
      include SpatialAdapter::SpatialColumn
      
      #MySql-specific geometry string parsing. By default, MySql returns geometries in strict wkb format with "0" characters in the first 4 positions.
      def self.string_to_geometry(string)
        return string unless string.is_a?(String)
        begin
          GeoRuby::SimpleFeatures::Geometry.from_ewkb(string[4..-1])
        rescue Exception => exception
          nil
        end
      end
    end
  end
end