#! /usr/bin/env python

import datetime
import difflib
import gzip

# Mapping between files and their archived locations
# Must be formatted with a datestamp in the form of `YYmmdd`
ARCHIVE_CONF_FMTS = [
    ("flow.conf",         "/archive/{0}/eod/flow-eod_{0}.conf.gz"),
    ("riskmgr.conf",      "/archive/{0}/eod/riskmgr-eod_{0}.conf.gz"),
    ("risksettings.conf", "/archive/{0}/eod/risksettings-eod_{0}.conf.gz"),
]

# Returns true if the given date is a weekday (Mon-Fri)
def is_weekday(date):
    return 0 <= date.weekday() <= 4

# Gets a file's path from the archive from a specific date
def get_archive_path(fname, date):
    path = next(p for f, p in ARCHIVE_CONF_FMTS if f == fname)
    return path.format(date.strftime("%Y%m%d"))

# Read a config from the archive, returns the list of lines
def read_archived_config(fname, date):
    fpath = get_archive_path(fname, date)
    fhandle = gzip.open(fpath)
    flines = fhandle.readlines()
    fhandle.close()
    return flines

# Given a date, returns the date of the following weekday
def next_weekday(date):
    weekday = date.weekday()
    if weekday == 4: # Friday
        return date + datetime.timedelta(days=3)
    if weekday == 5: # Saturday
        return date + datetime.timedelta(days=2)
    return date + datetime.timedelta(days=1)

# Given a date, returns the date of the previous weekday
def prev_weekday(date):
    weekday = date.weekday()
    if weekday == 0: # Monday
        return date - datetime.timedelta(days=3)
    if weekday == 6: # Sunday
        return date - datetime.timedelta(days=2)
    return date - datetime.timedelta(days=1)

# Opens regular text or gzip file, returning None if failed
def open_config_file(fpath):
    try:
        if fpath.endswith(".gz"):
            return gzip.open(fpath, 'r')
        else:
            return open(fpath, 'r')
    except IOError:
        return None

# Returns the set of flows from a config file
def read_flows(fpath):
    fconf = open_config_file(fpath)
    if fconf is None:
        return []
    flows = [line for line in fconf.readlines() if line.startswith('flow')]
    fconf.close()
    return flows

# Returns the path to the config file archived on that date
def get_config_path(fname, date):
    if date == datetime.date.today():
        return "/opt/hpr/config/{0}.conf".format(fname)

    new_name = "{0}-eod_{1}.conf.gz".format(fname, date.strftime("%Y%m%d"))
    return "/archive/{0}/eod/{1}".format(date.strftime("%Y%m%d"), new_name)

# Returns the flows from a given date, going forward if none are found
def open_next_config(fnames, date):
    # Ensure the date used is a weekday
    if not is_weekday(date):
        date = next_weekday(date)

    # Open the config files
    fpaths = [get_config_path(fname, date) for fname in fnames]
    all_flows = [read_flows(fpath) for fpath in fpaths]
    filtered_flows = [flows for flows in all_flows if len(flows) != 0]

    # Either it found no flows today, or found more than one file with flows
    if len(filtered_flows) != 1:
        return open_next_config(fnames, next_weekday(date))

    return (date, filtered_flows[0])

# Returns the flows from a given date, going forward if none are found
def open_prev_config(fnames, date):
    # Ensure the date used is a weekday
    if not is_weekday(date):
        date = prev_weekday(date)

    # Open the config files
    fpaths = [get_config_path(fname, date) for fname in fnames]
    all_flows = [read_flows(fpath) for fpath in fpaths]
    filtered_flows = [flows for flows in all_flows if len(flows) != 0]

    # Either it found no flows today, or found more than one file with flows
    if len(filtered_flows) != 1:
        return open_prev_config(fnames, prev_weekday(date))

    return (date, filtered_flows[0])

# Opens the files from a given date and a month prior
def open_both_configs(fnames, date):
    pdate = date - datetime.timedelta(days=30)

    if date == datetime.date.today():
        # Not running manually; Iterate backwards
        return (open_prev_config(fnames, date), open_prev_config(fnames, pdate))
    else:
        # Running manually; Iterate forwards
        return (open_next_config(fnames, date), open_prev_config(fnames, pdate))

# Sanitize and format a flow command for presenting to client.
def format_flow(flow):
    words = flow.split()[::-1]
    sess_id = words[17]
    sess_acc = words[16]
    sess_sys = words[15]
    sess_mic = words[12]
    sess_ip = words[6]
    sess_port = words[5]
    sess_user = words[4]
    sess_pass = words[0]

    sess_socket = "{0}:{1}".format(sess_ip, sess_port)
    sess_flow = "Session: {0}".format(sess_id)
    sess_user = "Username: {0}".format(sess_user)
    sess_comp = "CompID: {0}".format(sess_pass)

    return (sess_id, "{0}\t{1}\t{2}\t{3}\t{4}\t{5}".format(sess_socket, sess_acc, sess_mic, sess_flow, sess_user, sess_comp))

def main(argv):
    date = sanitize_args(argv)
    conf_names = ["flow", "riskmgr"]
    try:
        ((cur_date, cur_flows), (old_date, old_flows)) = open_both_configs(conf_names, date)
    except RuntimeError as re:
        print("Could not find files in archive")
        sys.exit(-1)
    except IOError as io:
        print("Could not open files: {0}".format(io))
        sys.exit(-1)

    print("Comparing flows between dates {0} and {1}".format(cur_date, old_date))
    print("\n")
    print("Number of flows on {0}: {1}".format(cur_date, len(cur_flows)))
    print("Number of flows on {0}: {1}".format(old_date, len(old_flows)))
    print("\n")

    d = difflib.Differ()
    diff = list(d.compare(cur_flows, old_flows))

    possibly_added   = [format_flow(line) for line in diff if line.startswith('+')]
    possibly_removed = [format_flow(line) for line in diff if line.startswith('-')]

    possibly_added_ids = [x for (x, flow) in possibly_added]
    possibly_removed_ids = [x for (x, flow) in possibly_removed]

    actually_added = [flow for (sess_id, flow) in possibly_added if not sess_id in possibly_removed_ids]
    actually_removed = [flow for (sess_id, flow) in possibly_removed if not sess_id in possibly_added_ids]

    print("Flows removed: ({0})".format(len(actually_removed)))
    print("-" * 48)
    for line in actually_removed:
        print(line)

    # Separate by newline
    print('\n')

    print("Flows added: ({0})".format(len(actually_added)))
    print("-" * 48)
    for line in actually_added:
        print(line)

# Sanitize the CLI arguments
def sanitize_args(argv):
    # If no optional date is provided, use today
    if len(argv) < 2:
        date = datetime.date.today()

        # But make sure it's a Tuesday
        if date.weekday() != 1:
            print("Cannot run script automatically on non-Tuesdays")
            print("Supply a date to run manually")
            print("")
            print_usage_and_exit(argv[0])
    else:
        date = datetime.datetime.strptime(argv[1], '%Y%m%d').date()

    return date

def print_usage_and_exit(pname):
    print("Usage: {0} [YYYYMMDD]".format(pname))
    sys.exit(-1)

if __name__ == '__main__':
    import sys
    main(sys.argv)