lib/gen_arg.py

#!/usr/bin/env python

r"""
This module provides valuable argument processing functions like gen_get_options and sprint_args.
"""

import sys
try:
    import __builtin__
except ImportError:
    import builtins as __builtin__
import atexit
import signal
import argparse

import gen_print as gp
import gen_valid as gv

default_string = '  The default value is "%(default)s".'


def gen_get_options(parser,
                    stock_list=[]):
    r"""
    Parse the command line arguments using the parser object passed and return True/False (i.e. pass/fail).
    However, if gv.exit_on_error is set, simply exit the program on failure.  Also set the following built in
    values:

    __builtin__.quiet      This value is used by the qprint functions.
    __builtin__.test_mode  This value is used by command processing functions.
    __builtin__.debug      This value is used by the dprint functions.
    __builtin__.arg_obj    This value is used by print_program_header, etc.
    __builtin__.parser     This value is used by print_program_header, etc.

    Description of arguments:
    parser                          A parser object.  See argparse module documentation for details.
    stock_list                      The caller can use this parameter to request certain stock parameters
                                    offered by this function.  For example, this function will define a
                                    "quiet" option upon request.  This includes stop help text and parm
                                    checking.  The stock_list is a list of tuples each of which consists of
                                    an arg_name and a default value.  Example: stock_list = [("test_mode",
                                    0), ("quiet", 1), ("debug", 0)]
    """

    # This is a list of stock parms that we support.
    master_stock_list = ["quiet", "test_mode", "debug", "loglevel"]

    # Process stock_list.
    for ix in range(0, len(stock_list)):
        if len(stock_list[ix]) < 1:
            error_message = "Programmer error - stock_list[" + str(ix) +\
                            "] is supposed to be a tuple containing at" +\
                            " least one element which is the name of" +\
                            " the desired stock parameter:\n" +\
                            gp.sprint_var(stock_list)
            return gv.process_error_message(error_message)
        if isinstance(stock_list[ix], tuple):
            arg_name = stock_list[ix][0]
            default = stock_list[ix][1]
        else:
            arg_name = stock_list[ix]
            default = None

        if arg_name not in master_stock_list:
            error_message = "Programmer error - arg_name \"" + arg_name +\
                            "\" not found found in stock list:\n" +\
                            gp.sprint_var(master_stock_list)
            return gv.process_error_message(error_message)

        if arg_name == "quiet":
            if default is None:
                default = 0
            parser.add_argument(
                '--quiet',
                default=default,
                type=int,
                choices=[1, 0],
                help='If this parameter is set to "1", %(prog)s'
                     + ' will print only essential information, i.e. it will'
                     + ' not echo parameters, echo commands, print the total'
                     + ' run time, etc.' + default_string)
        elif arg_name == "test_mode":
            if default is None:
                default = 0
            parser.add_argument(
                '--test_mode',
                default=default,
                type=int,
                choices=[1, 0],
                help='This means that %(prog)s should go through all the'
                     + ' motions but not actually do anything substantial.'
                     + '  This is mainly to be used by the developer of'
                     + ' %(prog)s.' + default_string)
        elif arg_name == "debug":
            if default is None:
                default = 0
            parser.add_argument(
                '--debug',
                default=default,
                type=int,
                choices=[1, 0],
                help='If this parameter is set to "1", %(prog)s will print'
                     + ' additional debug information.  This is mainly to be'
                     + ' used by the developer of %(prog)s.' + default_string)
        elif arg_name == "loglevel":
            if default is None:
                default = "info"
            parser.add_argument(
                '--loglevel',
                default=default,
                type=str,
                choices=['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL',
                         'debug', 'info', 'warning', 'error', 'critical'],
                help='If this parameter is set to "1", %(prog)s will print'
                     + ' additional debug information.  This is mainly to be'
                     + ' used by the developer of %(prog)s.' + default_string)

    arg_obj = parser.parse_args()

    __builtin__.quiet = 0
    __builtin__.test_mode = 0
    __builtin__.debug = 0
    __builtin__.loglevel = 'WARNING'
    for ix in range(0, len(stock_list)):
        if isinstance(stock_list[ix], tuple):
            arg_name = stock_list[ix][0]
            default = stock_list[ix][1]
        else:
            arg_name = stock_list[ix]
            default = None
        if arg_name == "quiet":
            __builtin__.quiet = arg_obj.quiet
        elif arg_name == "test_mode":
            __builtin__.test_mode = arg_obj.test_mode
        elif arg_name == "debug":
            __builtin__.debug = arg_obj.debug
        elif arg_name == "loglevel":
            __builtin__.loglevel = arg_obj.loglevel

    __builtin__.arg_obj = arg_obj
    __builtin__.parser = parser

    # For each command line parameter, create a corresponding global variable and assign it the appropriate
    # value.  For example, if the command line contained "--last_name='Smith', we'll create a global variable
    # named "last_name" with the value "Smith".
    module = sys.modules['__main__']
    for key in arg_obj.__dict__:
        setattr(module, key, getattr(__builtin__.arg_obj, key))

    return True


def set_pgm_arg(var_value,
                var_name=None):
    r"""
    Set the value of the arg_obj.__dict__ entry named in var_name with the var_value provided.  Also, set
    corresponding global variable.

    Description of arguments:
    var_value                       The value to set in the variable.
    var_name                        The name of the variable to set.  This defaults to the name of the
                                    variable used for var_value when calling this function.
    """

    if var_name is None:
        var_name = gp.get_arg_name(None, 1, 2)

    arg_obj.__dict__[var_name] = var_value
    module = sys.modules['__main__']
    setattr(module, var_name, var_value)
    if var_name == "quiet":
        __builtin__.quiet = var_value
    elif var_name == "debug":
        __builtin__.debug = var_value
    elif var_name == "test_mode":
        __builtin__.test_mode = var_value


def sprint_args(arg_obj,
                indent=0):
    r"""
    sprint_var all of the arguments found in arg_obj and return the result as a string.

    Description of arguments:
    arg_obj                         An argument object such as is returned by the argparse parse_args()
                                    method.
    indent                          The number of spaces to indent each line of output.
    """

    col1_width = gp.dft_col1_width + indent

    buffer = ""
    for key in arg_obj.__dict__:
        buffer += gp.sprint_varx(key, getattr(arg_obj, key), 0, indent,
                                 col1_width)
    return buffer


module = sys.modules["__main__"]


def gen_exit_function(signal_number=0,
                      frame=None):
    r"""
    Execute whenever the program ends normally or with the signals that we catch (i.e. TERM, INT).
    """

    gp.dprint_executing()
    gp.dprint_var(signal_number)

    # ignore_err influences the way shell_cmd processes errors.  Since we're doing exit processing, we don't
    # want to stop the program due to a shell_cmd failure.
    ignore_err = 1

    # Call the main module's exit_function if it is defined.
    exit_function = getattr(module, "exit_function", None)
    if exit_function:
        exit_function(signal_number, frame)

    gp.qprint_pgm_footer()


def gen_signal_handler(signal_number,
                       frame):
    r"""
    Handle signals.  Without a function to catch a SIGTERM or SIGINT, the program would terminate immediately
    with return code 143 and without calling the exit_function.
    """

    # The convention is to set up exit_function with atexit.register() so there is no need to explicitly
    # call exit_function from here.

    gp.dprint_executing()

    # Calling exit prevents control from returning to the code that was running when the signal was received.
    exit(0)


def gen_post_validation(exit_function=None,
                        signal_handler=None):
    r"""
    Do generic post-validation processing.  By "post", we mean that this is to be called from a validation
    function after the caller has done any validation desired.  If the calling program passes exit_function
    and signal_handler parms, this function will register them.  In other words, it will make the
    signal_handler functions get called for SIGINT and SIGTERM and will make the exit_function function run
    prior to the termination of the program.

    Description of arguments:
    exit_function                   A function object pointing to the caller's exit function.  This defaults
                                    to this module's gen_exit_function.
    signal_handler                  A function object pointing to the caller's signal_handler function.  This
                                    defaults to this module's gen_signal_handler.
    """

    # Get defaults.
    exit_function = exit_function or gen_exit_function
    signal_handler = signal_handler or gen_signal_handler

    atexit.register(exit_function)
    signal.signal(signal.SIGINT, signal_handler)
    signal.signal(signal.SIGTERM, signal_handler)


def gen_setup():
    r"""
    Do general setup for a program.
    """

    # Set exit_on_error for gen_valid functions.
    gv.set_exit_on_error(True)

    # Get main module variable values.
    parser = getattr(module, "parser")
    stock_list = getattr(module, "stock_list")
    validate_parms = getattr(module, "validate_parms", None)

    gen_get_options(parser, stock_list)

    if validate_parms:
        validate_parms()
    gen_post_validation()

    gp.qprint_pgm_header()