#!/usr/local/bin/python

import jinja2
import os
import sys
import subprocess
import glob
import codecs


# Utility functions
def log(txt):
    print(txt, file=sys.stderr)


def error(txt):
    log(txt)
    sys.exit(2)


def convert(src, dst, environ):
    """Generate a file from a template

    Args:
        src (str): path to input file
        dst (str): path to file to write
        environ (dict): environment dictionary, for replacement mappings.
    """
    with open(src) as infile:
        template = infile.read()
    rendered = jinja2.Template(template).render(**environ)
    with open(dst, "w") as outfile:
        outfile.write(rendered)


def check_arguments(environ, args):
    for argument in args:
        if argument not in environ:
            error("Environment variable %s is mandatory, exiting." % argument)


def generate_config_from_template(environ, ownership):
    """Generate a homeserver.yaml from environment variables

    Args:
        environ (dict): environment dictionary
        ownership (str): "<user>:<group>" string which will be used to set
            ownership of the generated configs

    Returns:
        path to generated config file
    """
    for v in ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS"):
        if v not in environ:
            error(
                "Environment variable '%s' is mandatory when generating a config "
                "file on-the-fly." % (v,)
            )

    # populate some params from data files (if they exist, else create new ones)
    environ = environ.copy()
    secrets = {
        "registration": "SYNAPSE_REGISTRATION_SHARED_SECRET",
        "macaroon": "SYNAPSE_MACAROON_SECRET_KEY",
    }

    for name, secret in secrets.items():
        if secret not in environ:
            filename = "/data/%s.%s.key" % (environ["SYNAPSE_SERVER_NAME"], name)

            # if the file already exists, load in the existing value; otherwise,
            # generate a new secret and write it to a file

            if os.path.exists(filename):
                with open(filename) as handle:
                    value = handle.read()
            else:
                log("Generating a random secret for {}".format(name))
                value = codecs.encode(os.urandom(32), "hex").decode()
                with open(filename, "w") as handle:
                    handle.write(value)
            environ[secret] = value

    environ["SYNAPSE_APPSERVICES"] = glob.glob("/data/appservices/*.yaml")
    if not os.path.exists("/compiled"):
        os.mkdir("/compiled")

    config_path = "/compiled/homeserver.yaml"

    # Convert SYNAPSE_NO_TLS to boolean if exists
    if "SYNAPSE_NO_TLS" in environ:
        tlsanswerstring = str.lower(environ["SYNAPSE_NO_TLS"])
        if tlsanswerstring in ("true", "on", "1", "yes"):
            environ["SYNAPSE_NO_TLS"] = True
        else:
            if tlsanswerstring in ("false", "off", "0", "no"):
                environ["SYNAPSE_NO_TLS"] = False
            else:
                error(
                    'Environment variable "SYNAPSE_NO_TLS" found but value "'
                    + tlsanswerstring
                    + '" unrecognized; exiting.'
                )

    convert("/conf/homeserver.yaml", config_path, environ)
    convert("/conf/log.config", "/compiled/log.config", environ)
    subprocess.check_output(["chown", "-R", ownership, "/data"])
    return config_path


# Prepare the configuration
mode = sys.argv[1] if len(sys.argv) > 1 else None
ownership = "{}:{}".format(environ.get("UID", 991), environ.get("GID", 991))
args = ["python", "-m", "synapse.app.homeserver"]

# In generate mode, generate a configuration, missing keys, then exit
if mode == "generate":
    check_arguments(
        environ, ("SYNAPSE_SERVER_NAME", "SYNAPSE_REPORT_STATS", "SYNAPSE_CONFIG_PATH")
    )
    args += [
        "--server-name",
        environ["SYNAPSE_SERVER_NAME"],
        "--report-stats",
        environ["SYNAPSE_REPORT_STATS"],
        "--config-path",
        environ["SYNAPSE_CONFIG_PATH"],
        "--generate-config",
    ]
    os.execv("/usr/local/bin/python", args)

# In normal mode, generate missing keys if any, then run synapse
else:
    if "SYNAPSE_CONFIG_PATH" in environ:
        config_path = environ["SYNAPSE_CONFIG_PATH"]
    else:
        config_path = generate_config_from_template(environ, ownership)

    args += [
        "--config-path",
        config_path,
        # tell synapse to put any generated keys in /data rather than /compiled
        "--keys-directory",
        "/data",
    ]

    # Generate missing keys and start synapse
    subprocess.check_output(args + ["--generate-keys"])
    os.execv("/sbin/su-exec", ["su-exec", ownership] + args)