#!/usr/bin/env python3

#   -------------------------------------------------------------
#   Resolve docker-compose containers names
#   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#   Project:        Nasqueron
#   Description:    Guess by naive heuristics the containers
#                   run from a docker-compose YAML configuration.
#
#                   As Docker doesn't record any link between
#                   a docker compose or stack information and the
#                   running containers, the approach consist to
#                   compare the containers names in a config file,
#                   with the running containers on the machine.
#   License:        BSD-2-Clause
#   -------------------------------------------------------------


import subprocess
import sys
import yaml


#   -------------------------------------------------------------
#   Parse docker-compose.yml
#   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


def parse_compose_config(config_path):
    with open(config_path) as fd:
        return yaml.safe_load(fd)


def resolve_container_prefix(service, image):
    image_short = image.split("/")[1]
    return image_short + "_" + service + "_"


def resolve_containers_prefix(compose_config):
    return [
        resolve_container_prefix(name, args["image"])
        for name, args in compose_config["services"].items()
    ]


#   -------------------------------------------------------------
#   Interact with Docker CLI
#
#   This avoid to have to deal with version conflicts with docker
#   Python libraries.
#   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


def get_running_container_names():
    process = subprocess.run(["docker", "ps"], capture_output=True)

    if process.returncode != 0:
        raise RuntimeError("Can't get containers: " + process.stderr.decode().strip())

    # The output of docker ps starts by an header line to skip.
    # Then the last column contains the container name.
    docker_ps_lines = process.stdout.decode().strip().split("\n")[1:]
    return [line.split()[-1] for line in docker_ps_lines]


#   -------------------------------------------------------------
#   Cross config file and running Docker information
#   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


def is_container_name_match(config_container, running_container):
    # The service web for the image acme/foo is foo_web_1:
    # <image name>_<service name>_<number>
    n = len(config_container)
    return (
        running_container.startswith(config_container)
        and running_container[n:].isnumeric()
    )


def resolve_docker_compose_containers_name(config_path):
    config = parse_compose_config(config_path)

    config_containers = resolve_containers_prefix(config)
    running_containers = get_running_container_names()

    return [
        running_container
        for config_container in config_containers
        for running_container in running_containers
        if is_container_name_match(config_container, running_container)
    ]


#   -------------------------------------------------------------
#   Application entry point
#   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


def run(config_path):
    containers = resolve_docker_compose_containers_name(config_path)
    print(" ".join(containers))


if __name__ == "__main__":
    argc = len(sys.argv)

    if argc < 2:
        print(f"Usage: {sys.argv[0]} <path to docker-compose.yml>", file=sys.stderr)
        sys.exit(1)

    run(sys.argv[1])