#!/usr/bin/python3.4

import os
import sys
import http.client
import json
import signal
from string import Template

target_path="/tmp/nginx"
pid_file="/run/nginx.pid"
non_location_template = """server {
    listen $listen;
    server_name $name;
    location / {
        proxy_set_header X-Real-IP  $$remote_addr;
        proxy_set_header X-Forwarded-For $$remote_addr;
        proxy_set_header Host $$host;
        proxy_pass http://$ip:$port/;      
    }
}
"""

location_template="""server {
    listen $listen;
    server_name $name;
    location / {
        return 301 $$scheme://$name/$location;
    }
    location /$location {
        proxy_set_header X-Real-IP  $$remote_addr;
        proxy_set_header X-Forwarded-For $$remote_addr;
        proxy_set_header Host $$host;
        proxy_pass http://$ip:$port/;      
    }
}
"""

def get_pid():
    with open(pid_file, 'r') as file:
        return int(file.read())

def get_container_data():
    conn = http.client.HTTPConnection("localhost:2375")
    conn.request("GET", "/containers/json")
    response = conn.getresponse()
    data = response.read().decode("UTF-8")
    data = json.loads(data)
#    print(json.dumps(data, sort_keys=True, indent=4))
    conn.close()
    return data

def inspect_container(container_id):
    conn = http.client.HTTPConnection("localhost:2375")
    conn.request("GET", "/containers/"+str(container_id)+"/json")
    response = conn.getresponse()
    data = response.read().decode("UTF-8")
    data = json.loads(data)
#    print(json.dumps(data, sort_keys=True, indent=4))
    conn.close()
    return data

def analyse_env_vars(data):
    env_data = {}
    for env_var in data:
        t = env_var.split("=")
        env_data[t[0]] = t[1]
    return env_data

def analyse_proxy_data(data):
    proxy_data = {}
    for proxy_var in data.split(','):
        t = proxy_var.split(":")
        proxy_data[t[0]] = t[1]
    return proxy_data

def handle_event(event):
    files = os.listdir(target_path)
    print('deleting files')
    for file in files:
        if file.startswith('proxy_'):
            os.remove(target_path+'/'+file)
    event_data = json.loads(event)
    containers_data = get_container_data()
    for container_data in containers_data:
        inspect_data = inspect_container(container_data['Id'])
        env_data = analyse_env_vars(inspect_data['Config']['Env'])
        if 'PROXY_DATA' in env_data:
            container_id = container_data['Id']
            ip = inspect_data['NetworkSettings']['IPAddress']
            proxy_data = analyse_proxy_data(env_data['PROXY_DATA'])

            server_name = ''
            if 'server_name' in proxy_data:
                server_name = proxy_data['server_name']
            
            port = 0
            if 'port' in proxy_data:
                port = proxy_data['port']

            location = ''
            if 'location' in proxy_data:
                location = proxy_data['location']

            listen ='*:80'
            if 'ip' in proxy_data:
                listen = proxy_data['ip']+':80'

            print('writing /tmp/nginx/proxy_'+container_id)
            with open('/tmp/nginx/proxy_'+container_id, 'w') as file:
                if location == '':
                    s = Template(non_location_template)                
                    file.write(s.substitute(name=server_name,ip=ip,port=port,listen=listen))
                else:
                    s = Template(location_template)            
                    file.write(s.substitute(name=server_name,ip=ip,port=port,listen=listen,location=location))
            print('HUPing nginx')
            os.kill(pid, signal.SIGHUP)

if not os.path.exists(target_path):
    os.mkdir(target_path)

pid = get_pid()

conn = http.client.HTTPConnection("localhost:2375")
try:
	conn.request("GET", "/events")
except ConnectionRefusedError:
	print('Docker does not expose events on its REST-API. Perhaps it is not running?')
	sys.exit(-1)

response = conn.getresponse()

events = ""
while not response.closed:
    data = response.read(80)
    if len(data) != 0:
        events += data.decode("UTF-8")
        if events.find("{") != -1:
            open_pos = events.index("{")
            if events.find("}", open_pos) != -1:
                close_pos = events.index("}", open_pos)+1
                handle_event(events[open_pos:close_pos])
                events = events[close_pos:]