#!/usr/bin/python3

import datetime, bisect

print("Content-type: text/html")
print("")


# Below code copied from a script from a forgotten source on the internet.


def parse_timestamp(raw_str):
    tokens = raw_str.split()
    if len(tokens) == 1:
        if tokens[0].lower() == 'never':
            return 'never';
        else:
            raise Exception('Parse error in timestamp')
    elif len(tokens) == 3:
        return datetime.datetime.strptime(' '.join(tokens[1:]),
            '%Y/%m/%d %H:%M:%S')
    else:
        raise Exception('Parse error in timestamp')

def timestamp_is_ge(t1, t2):
    if type(t2) == type(""):
        return False
    if t1 == 'never':
        return True
    elif t2 == 'never':
        return False
    else:
        return t1 >= t2

def timestamp_is_lt(t1, t2):
    if type(t2) == type(""):
        return t1 != 'never'
    if t1 == 'never':
        return False
    elif t2 == 'never':
        return t1 != 'never'
    else:
        return t1 < t2

def timestamp_is_between(t, tstart, tend):
    return timestamp_is_ge(t, tstart) and timestamp_is_lt(t, tend)

def parse_hardware(raw_str):
    tokens = raw_str.split()
    if len(tokens) == 2:
        return tokens[1]
    else:
        raise Exception('Parse error in hardware')

def strip_endquotes(raw_str):
    return raw_str.strip('"')

def identity(raw_str):
    return raw_str

def parse_binding_state(raw_str):
    tokens = raw_str.split()
    if len(tokens) == 2:
        return tokens[1]
    else:
        raise Exception('Parse error in binding state')

def parse_next_binding_state(raw_str):
    tokens = raw_str.split()
    if len(tokens) == 3:
        return tokens[2]
    else:
        raise Exception('Parse error in next binding state')

def parse_rewind_binding_state(raw_str):
    tokens = raw_str.split()
    if len(tokens) == 3:
        return tokens[2]
    else:
        raise Exception('Parse error in next binding state')

def parse_leases_file(leases_file):
    valid_keys = {
        'starts':               parse_timestamp,
        'ends':                 parse_timestamp,
        'tstp':                 parse_timestamp,
        'tsfp':                 parse_timestamp,
        'atsfp':                parse_timestamp,
        'cltt':                 parse_timestamp,
        'hardware':             parse_hardware,
        'binding':              parse_binding_state,
        'next':                 parse_next_binding_state,
        'rewind':               parse_rewind_binding_state,
        'uid':                  strip_endquotes,
        'client-hostname':      strip_endquotes,
        'option':               identity,
        'set':                  identity,
        'on':                   identity,
        'abandoned':            None,
        'bootp':                None,
        'reserved':             None,
        }
    leases_db = {}
    lease_rec = {}
    in_lease = False
    in_failover = False
    for line in leases_file:
        if line.lstrip().startswith('#'):
            continue
        tokens = line.split()
        if len(tokens) == 0:
            continue
        key = tokens[0].lower()
        if key == 'lease':
            if not in_lease:
                ip_address = tokens[1]
                lease_rec = {'ip_address' : ip_address}
                in_lease = True
            else:
                raise Exception('Parse error in leases file')
        elif key == 'failover':
            in_failover = True
        elif key == '}':
            if in_lease:
                for k in valid_keys:
                    if callable(valid_keys[k]):
                        lease_rec[k] = lease_rec.get(k, '')
                    else:
                        lease_rec[k] = False
                ip_address = lease_rec['ip_address']
                if ip_address in leases_db:
                    leases_db[ip_address].insert(0, lease_rec)
                else:
                    leases_db[ip_address] = [lease_rec]
                lease_rec = {}
                in_lease = False
            elif in_failover:
                in_failover = False
                continue
            else:
                raise Exception('Parse error in leases file')
        elif key in valid_keys:
            if in_lease:
                value = line[(line.index(key) + len(key)):]
                value = value.strip().rstrip(';').rstrip()
                if callable(valid_keys[key]):
                    lease_rec[key] = valid_keys[key](value)
                else:
                    lease_rec[key] = True
            else:
                raise Exception('Parse error in leases file')
        else:
            if in_lease:
                raise Exception('Parse error in leases file')
    if in_lease:
        raise Exception('Parse error in leases file')
    return leases_db

def round_timedelta(tdelta):
    return datetime.timedelta(tdelta.days,
        tdelta.seconds + (0 if tdelta.microseconds < 500000 else 1))

def timestamp_now():
    n = datetime.datetime.utcnow()
    return datetime.datetime(n.year, n.month, n.day, n.hour, n.minute,
        n.second + (0 if n.microsecond < 500000 else 1))

def lease_is_active(lease_rec, as_of_ts):
    return timestamp_is_between(as_of_ts, lease_rec['starts'],
        lease_rec['ends'])

def ipv4_to_int(ipv4_addr):
    parts = ipv4_addr.split('.')
    return (int(parts[0]) << 24) + (int(parts[1]) << 16) + \
        (int(parts[2]) << 8) + int(parts[3])

def select_active_leases(leases_db, as_of_ts):
    retarray = []
    sortedarray = []
    for ip_address in leases_db:
        lease_rec = leases_db[ip_address][0]
        if lease_is_active(lease_rec, as_of_ts):
            ip_as_int = ipv4_to_int(ip_address)
            insertpos = bisect.bisect(sortedarray, ip_as_int)
            sortedarray.insert(insertpos, ip_as_int)
            retarray.insert(insertpos, lease_rec)
    return retarray


# End of the other code
#############################

# Searches for insert segments in the HTML code, ex: <!-- INSERT X HERE -->
def insert_item(text, search, insert):
    parts = text.split(search, 1)
    # If this is 2 parts, then we have a split string. Otherwise, bail.
    if len(parts) == 1:
        return text
    else:
        before = parts[0].rsplit("<!--", 1)[0]
        after = parts[1].split("-->", 1)[1]
        return before + insert + after

###############################

try:
    #myfile = open('leases.leases','r')
    myfile = open('/var/lib/dhcp/dhcpd.leases', 'r')
    leases = parse_leases_file(myfile)
    myfile.close()

    now = timestamp_now()
    report_dataset = select_active_leases(leases, now)


    # read in the index file, and place it in idx
    idx_file = open("index-src.html")
    idx = ""
    for line in idx_file:
        idx += line + "\n"

    # Done reading in the file. Now to parse and replace, and return, if success

    repl = ""

    for lease in report_dataset:
        try:
            if lease['ends'] != 'never':
                expires = str(lease['ends'] - now)
            repl += "<tr><td>"
            repl += lease['ip_address']
            repl += "</td><td>"
            repl += lease['hardware']
            repl += "</td><td>"
            if lease['ends'] == 'never':
                repl += "never"
            else:
                repl += str(lease['ends'] - now)
            repl += "</td><td>"
            repl += lease['client-hostname']
            repl += "</td></tr>\n"
        except:
            pass

    active = str(len(report_dataset))
    report_gen = str(now)

    stats = "<h4>Total active leases: {}</h4><h4>Report generated {}</h4>".format(active, report_gen)

    idx = insert_item(idx, "INSERT LEASE TABLE", repl)
    idx = insert_item(idx, "INSERT STATS", stats)
    print (idx)


except Exception as e:
    print("<html><body>")
    print("There was an error on the server end. We are sorry.")
    print("Perhaps try the <a href=\"index-src.html\">static version</a> of this page.")
    print("The error encountered is listed below: <br/><br/>{}<br/>".format(str(e).replace("\n", "<br/>")))
    print("</body></html>")