bio-miga/miga

# @package MiGA
# @license Artistic-2.0

require 'sqlite3'

##
# SQLite3 wrapper for MiGA.
class MiGA::SQLite < MiGA::MiGA
  class << self
    ##
    # Default parsing options. Supported +opts+ keys:
    # - +:busy_attempts+: Number of times to retry when database is busy
    #   (default: 3)
    def default_opts(opts = {})
      opts[:busy_attempts] ||= 3
      opts
    end
  end

  ##
  # Options hash
  attr :opts

  ##
  # Database absolute path
  attr :path

  ##
  # Create MiGA::SQLite with database in +path+ (without opening a connection)
  # and options +opts+ (see +.default_opts+)
  def initialize(path, opts = {})
    @opts = MiGA::SQLite.default_opts(opts)
    @path = File.absolute_path(path)
    MiGA::MiGA.DEBUG("Accessing database: #{path}")
  end

  ##
  # Executes +cmd+ and returns the result. Alternatively, if a block is
  # passed, the commands are ignored and the block is executed with a
  # single parameter of the database connection
  def run(*cmd)
    if block_given?
      run_block { |conn| yield(conn) }
    else
      y = nil
      run_block { |conn| y = conn.execute(*cmd) }
      y
    end
  end

  ##
  # Executes +blk+ that accepts a single parameter for the database
  # connection
  def run_block(&blk)
    busy_attempts ||= 0
    io_attempts ||= 0
    SQLite3::Database.new(path) { |conn| blk[conn] }
  rescue SQLite3::BusyException => e
    busy_attempts += 1
    raise "Database busy #{path}: #{e.message}" if busy_attempts >= 3

    sleep(1)
    retry
  rescue SQLite3::IOException => e
    io_attempts += 1
    raise "Database I/O error #{path}: #{e.message}" if io_attempts >= 3

    sleep(1)
    retry
  end
end