#!/usr/bin/env python3

# Compare the items defined in a Zabbix template with the metrics defined in a config file.

import sys

import yaml

# Special built in metrics
SPECIAL = {
    "agent_version",
    "latest_version_info"
}


class NonMetricItemError(Exception):
    """
    A given item does not directly use a metric
    """


def read_metrics(file):
    """
    Read the metrics from a config file and return the list of names

    params:
        file: the name of the file to read

    returns:
        list of metric named defined in the file

    raises:
        yaml.parser.ParserError: invalid yaml file
    """
    names = set()
    config = None

    with open(file, "r", encoding="utf-8") as f:
        config = yaml.safe_load(f)

    try:
        for m in config["metrics"].keys():
            names.add(m)
    except KeyError:
        pass

    return names


def extract_metric(item):
    """
    Extract the metric from an item definition

    params:
        item: the item/discovery/prototype definition dict

    returns:
        the name of the metric used in the item

    raises:
        NonMetricItemError: the item does not directly use a metric
    """
    try:
        if item["type"] == "HTTP_AGENT":
            url = item["url"]
            if url.startswith("http://localhost:{$AGENT_PORT}"):
                return url.split("/")[-1]
    except KeyError:
        raise NonMetricItemError()

    raise NonMetricItemError()


def read_template(file):
    """
    Read the items from a Zabbix template and return the list of metric names

    params:
        file: the name of the file to read

    returns:
        list of metric named used in the file

    raises:
        yaml.parser.ParserError: invalid yaml file
    """
    names = set()
    config = None

    with open(file, "r", encoding="utf-8") as f:
        config = yaml.safe_load(f)

    try:
        for template in config["zabbix_export"]["templates"]:
            for item in template["items"]:
                try:
                    names.add(extract_metric(item))
                except NonMetricItemError:
                    pass

            for rule in template["discovery_rules"]:
                try:
                    names.add(extract_metric(rule))
                except NonMetricItemError:
                    pass

                for proto in rule["item_prototypes"]:
                    try:
                        names.add(extract_metric(proto))
                    except NonMetricItemError:
                        pass
    except KeyError:
        pass

    return names


if __name__ == '__main__':
    config_file = sys.argv[1]
    config_metrics = read_metrics(config_file)

    template_file = sys.argv[2]
    template_metrics = read_template(template_file) - SPECIAL

    config_only = config_metrics - template_metrics
    template_only = template_metrics - config_metrics

    print("Config only: {}".format(sorted(list(config_only))))
    print("Template only: {}".format(sorted(list(template_only))))