"""This plugin provides ``--pdb`` and ``--pdb-failures`` options. The ``--pdb``
option will drop the test runner into pdb when it encounters an error. To
drop into pdb on failure, use ``--pdb-failures``."""
import pdb
from nose.plugins.base import Plugin


class Pdb(Plugin):
    """Provides --pdb and --pdb-failures options that cause the test runner to
    drop into pdb if it encounters an error or failure, respectively."""
    enabled_for_errors = False
    enabled_for_failures = False
    score = 5  # Run last among builtins

    def options(self, parser, env):
        """Register commandline options."""
        parser.add_option(
            "--pdb", action="store_true", dest="debugBoth",
            default=env.get('NOSE_PDB', False),
            help="Drop into debugger on failures or errors")
        parser.add_option(
            "--pdb-failures", action="store_true", dest="debugFailures",
            default=env.get('NOSE_PDB_FAILURES', False),
            help="Drop into debugger on failures")
        parser.add_option(
            "--pdb-errors", action="store_true", dest="debugErrors",
            default=env.get('NOSE_PDB_ERRORS', False),
            help="Drop into debugger on errors")

    def configure(self, options, conf):
        """Configure which kinds of exceptions trigger plugin."""
        self.conf = conf
        self.enabled_for_errors = options.debugErrors or options.debugBoth
        self.enabled_for_failures = options.debugFailures or options.debugBoth
        self.enabled = self.enabled_for_failures or self.enabled_for_errors

    def addError(self, test, err):
        """Enter pdb if configured to debug errors."""
        if not self.enabled_for_errors:
            return
        self.debug(err)

    def addFailure(self, test, err):
        """Enter pdb if configured to debug failures."""
        if not self.enabled_for_failures:
            return
        self.debug(err)

    def debug(self, err):
        import sys
        ec, ev, tb = err
        stdout = sys.stdout
        sys.stdout = sys.__stdout__
        try:
            pdb.post_mortem(tb)
        finally:
            sys.stdout = stdout