require "sqlite3/constants"
require "sqlite3/errors"

module SQLite3

  # The ResultSet object encapsulates the enumerability of a query's output.
  # It is a simple cursor over the data that the query returns. It will
  # very rarely (if ever) be instantiated directly. Instead, client's should
  # obtain a ResultSet instance via Statement#execute.
  class ResultSet
    include Enumerable

    # The class of which we return an object in case we want an Array as
    # result. (ArrayFields is installed.)
    class ArrayWithTypes < Array
      attr_accessor :types
    end

    # The class of which we return an object in case we want an Array as
    # result. (ArrayFields is not installed.)
    class ArrayWithTypesAndFields < Array
      attr_accessor :types
      attr_accessor :fields
    end

    # The class of which we return an object in case we want a Hash as
    # result.
    class HashWithTypes < Hash
      attr_accessor :types
    end

    # Create a new ResultSet attached to the given database, using the
    # given sql text.
    def initialize(db, stmt)
      @db = db
      @driver = @db.driver
      @stmt = stmt
      commence
    end

    # A convenience method for compiling the virtual machine and stepping
    # to the first row of the result set.
    def commence
      result = @driver.step(@stmt.handle)
      if result == Constants::ErrorCode::ERROR
        @driver.reset(@stmt.handle)
      end
      check result
      @first_row = true
    end
    private :commence

    def check(result)
      @eof = (result == Constants::ErrorCode::DONE)
      found = (result == Constants::ErrorCode::ROW)
      Error.check(result, @db) unless @eof || found
    end
    private :check

    # Reset the cursor, so that a result set which has reached end-of-file
    # can be rewound and reiterated.
    def reset(*bind_params)
      @stmt.must_be_open!
      @stmt.reset!(false)
      @driver.reset(@stmt.handle)
      @stmt.bind_params(*bind_params)
      @eof = false
      commence
    end

    # Query whether the cursor has reached the end of the result set or not.
    def eof?
      @eof
    end

    # Obtain the next row from the cursor. If there are no more rows to be
    # had, this will return +nil+. If type translation is active on the
    # corresponding database, the values in the row will be translated
    # according to their types.
    #
    # The returned value will be an array, unless Database#results_as_hash has
    # been set to +true+, in which case the returned value will be a hash.
    #
    # For arrays, the column names are accessible via the +fields+ property,
    # and the column types are accessible via the +types+ property.
    #
    # For hashes, the column names are the keys of the hash, and the column
    # types are accessible via the +types+ property.
    def next
      return nil if @eof

      @stmt.must_be_open!

      unless @first_row
        result = @driver.step(@stmt.handle)
        check result
      end

      @first_row = false

      unless @eof
        row = []
        @driver.data_count(@stmt.handle).times do |column|
          type  = @driver.column_type(@stmt.handle, column)

          if type == Constants::ColumnType::TEXT
            row << @driver.column_text(@stmt.handle, column)
          elsif type == Constants::ColumnType::NULL
            row << nil
          elsif type == Constants::ColumnType::BLOB
            row << @driver.column_blob(@stmt.handle, column)
          else
            row << @driver.column_text(@stmt.handle, column)
          end
        end

        if @db.type_translation
          row = @stmt.types.zip(row).map do |type, value|
            @db.translator.translate(type, value)
          end
        end

        if @db.results_as_hash
          new_row = HashWithTypes[ *(@stmt.columns.zip(row).to_a.flatten) ]
          row.each_with_index { |value,idx| new_row[idx] = value }
          row = new_row
        else
          if row.respond_to?(:fields)
            row = ArrayWithTypes.new(row)
          else
            row = ArrayWithTypesAndFields.new(row)
          end
          row.fields = @stmt.columns
        end

        row.types = @stmt.types

        return row
      end

      nil
    end

    # Required by the Enumerable mixin. Provides an internal iterator over the
    # rows of the result set.
    def each
      while row=self.next
        yield row
      end
    end

    # Closes the statement that spawned this result set.
    # <em>Use with caution!</em> Closing a result set will automatically
    # close any other result sets that were spawned from the same statement.
    def close
      @stmt.close
    end

    # Queries whether the underlying statement has been closed or not.
    def closed?
      @stmt.closed?
    end

    # Returns the types of the columns returned by this result set.
    def types
      @stmt.types
    end

    # Returns the names of the columns returned by this result set.
    def columns
      @stmt.columns
    end

  end

end