require 'sqlite3/errors'
require 'sqlite3/resultset'

class String
  def to_blob
    SQLite3::Blob.new( self )
  end
end

module SQLite3
  # A statement represents a prepared-but-unexecuted SQL query. It will rarely
  # (if ever) be instantiated directly by a client, and is most often obtained
  # via the Database#prepare method.
  class Statement
    include Enumerable

    # This is any text that followed the first valid SQL statement in the text
    # with which the statement was initialized. If there was no trailing text,
    # this will be the empty string.
    attr_reader :remainder

    # Binds the given variables to the corresponding placeholders in the SQL
    # text.
    #
    # See Database#execute for a description of the valid placeholder
    # syntaxes.
    #
    # Example:
    #
    #   stmt = db.prepare( "select * from table where a=? and b=?" )
    #   stmt.bind_params( 15, "hello" )
    #
    # See also #execute, #bind_param, Statement#bind_param, and
    # Statement#bind_params.
    def bind_params( *bind_vars )
      index = 1
      bind_vars.flatten.each do |var|
        if Hash === var
          var.each { |key, val| bind_param key, val }
        else
          bind_param index, var
          index += 1
        end
      end
    end

    # Execute the statement. This creates a new ResultSet object for the
    # statement's virtual machine. If a block was given, the new ResultSet will
    # be yielded to it; otherwise, the ResultSet will be returned.
    #
    # Any parameters will be bound to the statement using #bind_params.
    #
    # Example:
    #
    #   stmt = db.prepare( "select * from table" )
    #   stmt.execute do |result|
    #     ...
    #   end
    #
    # See also #bind_params, #execute!.
    def execute( *bind_vars )
      reset! if active? || done?

      bind_params(*bind_vars) unless bind_vars.empty?
      @results = ResultSet.new(@connection, self)

      step if 0 == column_count

      yield @results if block_given?
      @results
    end

    # Execute the statement. If no block was given, this returns an array of
    # rows returned by executing the statement. Otherwise, each row will be
    # yielded to the block.
    #
    # Any parameters will be bound to the statement using #bind_params.
    #
    # Example:
    #
    #   stmt = db.prepare( "select * from table" )
    #   stmt.execute! do |row|
    #     ...
    #   end
    #
    # See also #bind_params, #execute.
    def execute!( *bind_vars, &block )
      execute(*bind_vars)
      block_given? ? each(&block) : to_a
    end

    # Returns true if the statement is currently active, meaning it has an
    # open result set.
    def active?
      !done?
    end

    # Return an array of the column names for this statement. Note that this
    # may execute the statement in order to obtain the metadata; this makes it
    # a (potentially) expensive operation.
    def columns
      get_metadata unless @columns
      return @columns
    end

    def each
      loop do
        val = step
        break self if done?
        yield val
      end
    end

    # Return an array of the data types for each column in this statement. Note
    # that this may execute the statement in order to obtain the metadata; this
    # makes it a (potentially) expensive operation.
    def types
      must_be_open!
      get_metadata unless @types
      @types
    end

    # A convenience method for obtaining the metadata about the query. Note
    # that this will actually execute the SQL, which means it can be a
    # (potentially) expensive operation.
    def get_metadata
      @columns = []
      @types = []

      column_count.times do |column|
        @columns << column_name(column)
        @types << column_decltype(column)
      end

      @columns.freeze
      @types.freeze
    end
    private :get_metadata

    # Performs a sanity check to ensure that the statement is not
    # closed. If it is, an exception is raised.
    def must_be_open! # :nodoc:
      if closed?
        raise SQLite3::Exception, "cannot use a closed statement"
      end
    end
  end
end
