#!/usr/bin/env python3
NUM_SECS_IN_DAY=86400

import json
import time
from datetime import datetime
from argparse import ArgumentParser
from slackclient import SlackClient

parser = ArgumentParser(description="Read messages from the specified slack channel")
parser.add_argument("-t", "--slack-token", action="store", dest="slack_token", required=True,
                    help="Slack API Token")
parser.add_argument("-c", "--channel-id", action="store", dest="channel_id", required=True,
                    help=("Channel ID - obtained for a channel by reading URL when"
                          " accessing channel in Slack Client."))
parser.add_argument("-n", "--number-messages-to-read", action="store",
                    dest="number_messages_to_read",
                    default=100,
                    help="Number of messages to read in an attempt")
parser.add_argument("-u", "--username", action="store",
                    dest="username_to_filter_by",
                    help="Filter messages by username (generally used for apps)")
parser.add_argument("-uid", "--user-id", action="store",
                    dest="userid_to_filter_by",
                    help="Filter messages by userid (generally used by users)")
parser.add_argument("-d", "--days", action="store",
                    dest="days_to_filter_by",
                    help="Filter messages to show only ones posted in last X days")
parser.add_argument("-o", "--outfile", action="store", dest="outfile",
                    default="out-messages-in-channel.txt",
                    help="Output file for storing messages in channel")
args = parser.parse_args()
channel_id = args.channel_id
number_messages_to_read = args.number_messages_to_read
slack_token = args.slack_token
username_to_filter_by = args.username_to_filter_by
userid_to_filter_by = args.userid_to_filter_by
days_to_filter_by = args.days_to_filter_by
outfile = args.outfile

print("[*] Initializing Slack Client with the slack token provided")
sc = SlackClient(slack_token)

print("[*] Reading {} messages from channel: {} via SlackClient's channel:history function".format(number_messages_to_read, channel_id))
out = sc.api_call("channels.history", channel=channel_id, count=number_messages_to_read)

print("[*] Parsing response to ensure that there were not errors")
if "ok" in out:

    if out["ok"] == True:

        print("[+] Messages downloaded ok.")
        if "messages" in out:
            out_messages = out["messages"]
        else:
            out_messages = []

        if username_to_filter_by:
            print("[*] Filtering messages by username: {}".format(username_to_filter_by))

            out_with_username = []

            num_messages_found_matching_criteria = 0
            for message in out_messages:
                if "username" in message and message["username"].lower() == username_to_filter_by.lower():
                    num_messages_found_matching_criteria += 1
                    out_with_username.append(message)

            print("[+] Number of messages found matching username: {} criteria: {}".format(username_to_filter_by, num_messages_found_matching_criteria))

            out_messages = out_with_username

        if userid_to_filter_by:
            print("[*] Filtering messages by userid: {}".format(userid_to_filter_by))

            out_with_userid = []

            num_messages_found_matching_criteria = 0
            for message in out_messages:
                if "user" in message and message["user"].lower() == userid_to_filter_by.lower():
                    num_messages_found_matching_criteria += 1
                    out_with_userid.append(message)

            print("[+] Number of messages found matching user: {} criteria: {}".format(userid_to_filter_by, num_messages_found_matching_criteria))

            out_messages = out_with_userid

        if days_to_filter_by:
            now = datetime.now()
            now_epoch = time.mktime(now.timetuple())

            print("[*] Filtering messages for ones posted in the last {} days".format(days_to_filter_by))

            out_within_specified_days = []

            num_messages_found_matching_criteria = 0
            for message in out_messages:
                message_epoch_time = float(message["ts"])
#               print("[v] message_epoch_time = {}, now_epoch = {}".format(message_epoch_time, now_epoch))

                if (now_epoch - message_epoch_time) < (int(days_to_filter_by) * NUM_SECS_IN_DAY):
                    num_messages_found_matching_criteria += 1
                    out_within_specified_days.append(message)

            print("[+] Number of messages found matching days to filter by: {} criteria: {}".format(days_to_filter_by, num_messages_found_matching_criteria))
            out_messages = out_within_specified_days

        print("[*] Writing messages in output as JSON to file: {}".format(outfile))
        formatted_out = json.dumps(out_messages, indent=4)
        with open(outfile, "w+") as f:
            f.write(formatted_out)
    else:

        print("[-] Error occurred when downloading the messages from channel: {}".format(channel_id))
        if "error" in out:
            error = out["error"]
            print("[-] Error that occurred: {}".format(error))
        else:

            print("[-] No 'error' key status returned in JSON output - something went wrong.")
            print("[-] Dumping the entire response: ")
            formatted_out = json.dumps(out, indent=4)
            print("{}".format(formatted_out))

else:

    print("[-] No 'ok' key status returned in JSON output - something went wrong.")
    print("[-] Dumping the entire response: ")
    formatted_out = json.dumps(out, indent=4)
    print("{}".format(formatted_out))