#!/usr/bin/env php
<?php
use Mosquitto\Message;

define("STARTED", time());
$mqttHost = getenv("MQTT_HOST");
if (!$mqttHost) {
    echo "Please set MQTT_HOST environment variable\n";
    exit(1);
}

pcntl_signal(SIGINT, "endit");
pcntl_signal(SIGTERM, "endit");
pcntl_signal(SIGHUP, "endit");

$mqttPort = getEnvWithDefaultInt("MQTT_PORT", 1883);

$mqttUser = getEnvWithDefaultStr("MQTT_USER", "");
$mqttPass = getEnvWithDefaultStr("MQTT_PASS", "");
$mqttClientId = getEnvWithDefaultStr("MQTT_CLIENT_ID", "mqtt2prometheus");
$mqttTopic = getEnvWithDefaultStr("MQTT_TOPIC", "prometheus");
$qos = getEnvWithDefaultInt("MQTT_QOS", 2);
$ignoreRetained = getEnvWithDefaultInt("IGNORE_RETAINED", 1) ? 1 : 0;

$mqtt = new Mosquitto\Client($mqttClientId);

$data = [];
$mqtt->setCredentials($mqttUser, $mqttPass);

$usedConfig = [
    "MQTT_HOST" => $mqttHost,
    "MQTT_PORT" => $mqttPort,
    "MQTT_USER" => $mqttUser,
    "MQTT_PASS" => $mqttPass,
    "MQTT_CLIENT_ID" => $mqttClientId,
    "MQTT_TOPIC" => $mqttTopic,
    "MQTT_QOS" => $qos,
    "IGNORE_RETAINED" => $ignoreRetained,
];

$padLength = max(array_map("strlen", array_keys($usedConfig)));

echo "Using the following config:\n";
foreach ($usedConfig as $key => $value) {
    echo str_pad($key, $padLength) . ": $value\n";
}

echo "Connecting to $mqttHost:$mqttPort";
$mqtt->connect($mqttHost, $mqttPort);
echo "Connected\n";

$data = [];
$stats = [
    "messages" => [],
    "errors" => [],
    "metrics" => [],
];
$news = true;
$isRunning = true;
$globalCounter = 0;
$mqtt->onMessage(function ($message) use (
    &$data,
    &$stats,
    &$news,
    &$globalCounter,
    &$isRunning,
    $mqttTopic
) {
    if ($mqttTopic . "/restart" === $message->topic) {
        $isRunning = false;
        return;
    }
    $globalCounter++;
    $stats["messages"][] = time();
    if (!precheck($message)) {
        $stats["errors"][] = time();
        return;
    }
    $stats["metrics"][] = time();
    $payload = (array) json_decode($message->payload, true);

    $payload["timestamp"] = time();
    $data[] = $payload;
    $news = true;
});

echo "Subscribing to $mqttTopic with QoS $qos ";
$mqtt->subscribe($mqttTopic, $qos);
$mqtt->subscribe($mqttTopic . "/restart", $qos);
echo "Subscribed\n";

$timer = 0;

echo "Started listening for incoming messages\n will wait 60 seconds before starting to export data\n";
$realStart = time() + 15;
echo "waiting till " .
    date("Y-m-d H:i:s", $realStart) .
    " that's in " .
    ($realStart - time()) .
    " seconds\n";
while (time() < $realStart) {
    $wait = time() + 5;
    $mqtt->loop(5000);
    sleep($wait - time());
    echo "Still waiting...\n";
}
echo "\n Starting to export data\n";

while ($isRunning) {
    $mqtt->loop(1000);
    if ($news || time() - $timer > 15) {
        output();
        $news = false;
        $timer = time();
    }
}
$mqtt->disconnect();
$mqtt->loop();
exit();

function error(string $msg): void
{
    global $mqtt, $mqttTopic;
    $mqtt->publish($mqttTopic . "/error", $msg, 2);
    fwrite(STDERR, "ERROR: " . $msg . "\n");
}
function precheck(Message $message): bool
{
    global $ignoreRetained;
    if ($ignoreRetained && $message->retain) {
        error("Ignoring retained message");
        return false;
    }
    $payloadRaw = $message->payload;
    $payload = json_decode($payloadRaw, true);
    if (json_last_error() != JSON_ERROR_NONE) {
        error(
            "Invalid json: $message->payload (" . json_last_error_msg() . ")"
        );
        return false;
    }
    if (!is_array($payload)) {
        error("Payload is not an object: $payloadRaw");
        return false;
    }

    if (!isset($payload["name"]) || !isset($payload["value"])) {
        error(
            "Invalid payload, at least name and value is needed: $payloadRaw"
        );
        return false;
    }
    if (!preg_match('/^[a-zA-Z_][a-zA-Z0-9_]*$/', $payload["name"])) {
        error("Invalid name: " . $payload["name"]);
        return false;
    }
    if (!is_numeric($payload["value"])) {
        error("Value is not a number: $payloadRaw");
        return false;
    }
    $payload["labels"] = $payload["labels"] ?? [];
    if (!is_array($payload["labels"])) {
        error("Labels must be an object: $payloadRaw");
        return false;
    }
    foreach ($payload["labels"] as $labelName => $labelValue) {
        if (!is_string($labelName) || !is_scalar($labelValue)) {
            error("Label names and values must be strings: $payloadRaw");
            return false;
        }
        if (!preg_match('/^[a-zA-Z_][a-zA-Z0-9_]*$/', $labelName)) {
            error("Invalid label name: $labelName");
            return false;
        }
    }

    if (!isset($payload["valid_seconds"])) {
        $payload["valid_seconds"] = 60;
    }
    if (!is_numeric($payload["valid_seconds"])) {
        error("valid_seconds must be a number");
        return false;
    }
    if ($payload["valid_seconds"] < 1) {
        error("valid_seconds must be at least 1");
        return false;
    }
    if ($payload["valid_seconds"] > 60 * 60 * 48) {
        error("valid_seconds must be at most 48 hours");
        return false;
    }

    foreach (array_keys($payload) as $key) {
        if (!in_array($key, ["name", "value", "labels", "valid_seconds"])) {
            error("Unknown key: $key");
            return false;
        }
    }
    return true;
}

function output(): void
{
    filter();
    global $data, $stats, $globalCounter;
    $t = time();
    $json = [];
    $prom = "";
    $prom .=
        "# service started at             : " .
        STARTED .
        " / " .
        date("Y-m-d H:i:s", intval(STARTED)) .
        "\n";
    $prom .=
        "# exported at                    : $t / " .
        date("Y-m-d H:i:s", intval($t)) .
        "\n";
    $prom .= "# \n";
    $prom .=
        "# mem usage                      : " .
        round(memory_get_usage() / 1024 / 1024, 1) .
        " / " .
        round(memory_get_usage(true) / 1024 / 1024, 1) .
        " MB\n";
    $prom .=
        "# mem usage peak                 : " .
        round(memory_get_peak_usage() / 1024 / 1024, 1) .
        " / " .
        round(memory_get_peak_usage(true) / 1024 / 1024, 1) .
        " MB\n";
    $timeframe = [
        60 => "Minute",
        300 => "5 Minutes",
        900 => "15 Minutes",
        1800 => "30 Minutes",
        3600 => "Hour",
        21600 => "6 Hours",
        43200 => "12 Hours",
        86400 => "Day",
    ];
    foreach ($stats as $key => $values) {
        $prom .= "# \n";
        foreach ($timeframe as $time => $name) {
            $count = count(
                array_filter($values, function ($v) use ($time) {
                    return $v > time() - $time;
                })
            );
            $fkey = str_pad($key, 8);
            $fname = str_pad($name, 10);
            $prom .= "# $fkey in the last $fname: $count\n";
        }
    }
    $prom .= "# \n";
    $prom .= "# global counter                 : $globalCounter\n\n";

    $filteredData = [];

    foreach ($data as $entry) {
        $sort = $entry["labels"] ?? [];
        ksort($sort);
        $sort[] = $entry["name"];
        $hash = md5(strval(json_encode($sort)));

        $filteredData[$hash] = $entry;
    }

    foreach ($filteredData as $entry) {
        $labels = [];
        if (isset($entry["labels"])) {
            ksort($entry["labels"]);
            foreach ($entry["labels"] as $labelName => $labelValue) {
                $labels[] =
                    "$labelName=" .
                    json_encode(
                        strval($labelValue),
                        JSON_UNESCAPED_UNICODE + JSON_UNESCAPED_SLASHES
                    );
            }
        }
        $json[] = [
            "name" => $entry["name"],
            "labels" => $entry["labels"] ?? [],
            "value" => $entry["value"],
        ];
        $labels = implode(", ", $labels);
        if ($labels != "") {
            $labels = "{" . $labels . "}";
        }

        $prom .= $entry["name"] . $labels . " " . $entry["value"] . "\n";
    }

    $prom .= "\n\n# internals\n";
    $prom .=
        "memory_usage_current{unit=\"bytes\"} " . memory_get_usage() . "\n";
    $prom .=
        "memory_usage_peak{unit=\"bytes\"} " . memory_get_peak_usage() . "\n";

    $prom .=
        "memory_usage_current_allocated{unit=\"bytes\"} " .
        memory_get_usage(true) .
        "\n";
    $prom .=
        "memory_usage_peak_allocated{unit=\"bytes\"} " .
        memory_get_peak_usage(true) .
        "\n";

    file_put_contents("/www/metrics/new.prom", $prom);
    file_put_contents(
        "/www/metrics/new.json",
        json_encode(
            $json,
            JSON_PRETTY_PRINT + JSON_UNESCAPED_SLASHES + JSON_UNESCAPED_UNICODE
        )
    );
    rename("/www/metrics/new.json", "/www/metrics/metrics.json");
    rename("/www/metrics/new.prom", "/www/metrics/index.prom");
    // return $prom;
}

function filter(): void
{
    global $data, $stats;
    $data = array_filter($data, function ($entry) {
        return $entry["timestamp"] > time() - $entry["valid_seconds"];
    });
    // remove stats older than 24h
    foreach ($stats as $key => $values) {
        $stats[$key] = array_filter($values, function ($v) {
            return $v > time() - 24 * 60 * 60;
        });
    }
}

function getEnvWithDefaultStr(string $key, string $default): string
{
    return strval(getEnvWithDefault($key, $default));
}

function getEnvWithDefaultInt(string $key, int $default): int
{
    return intval(getEnvWithDefault($key, $default));
}
function getEnvWithDefault(
    string $key,
    bool|string|int $default
): bool|string|int {
    $value = getenv($key);
    if (!is_scalar($value)) {
        return $default;
    }
    if ($value === false) {
        return $default;
    }
    if (is_numeric($default)) {
        return intval($value);
    }
    return strval($value);
}

function endit(): void
{
    global $mqtt;
    global $isRunning;
    $isRunning = false;
    error("Exiting");
}