prometheus_policy_proxy/src/config.ts

import type { OptionDefinition } from "command-line-args";
import { readFile } from "node:fs/promises";
import fs from "node:fs";
import cmdline from "command-line-args";
import yaml from "js-yaml";
import { compileQuery, Query } from "./query.js";

export interface Configuration {
    bindHost: string;
    port: number;
    configFile: string;
    watchFile: boolean;
    prometheusURL: string;
    queriesAllow: string[];
    variables: AnyVariable[];
    queriesCompiled: Query[];
    labelsAllow: LabelAllow[];
}

interface LabelAllow {
    name: string;
    values?: string[];
}

interface BaseVariable<T extends string> {
    name: string;
    varType: T
}

export interface LiteralVariable extends BaseVariable<"literal"> {
    text: string;
}

export function isAnyVariable(o: any): o is AnyVariable {
    return (
        typeof o === "object" && 
        typeof o.name === "string" && 
        typeof o.varType === "string"
    );
}

interface ArrayLikeVariable<T extends string> extends BaseVariable<`${T}_array`> {
    items: string[];
    separator: string;
}

export type AnyOfItemsVariable = ArrayLikeVariable<"any_of">;
export type AllOfItemsVariable = ArrayLikeVariable<"all_of">;

export interface PatternVariable extends BaseVariable<"pattern"> {
    pattern: RegExp;
}

export type AnyVariable = LiteralVariable | AnyOfItemsVariable | AllOfItemsVariable | PatternVariable;


const optionDefinitions: OptionDefinition[] = [
    { name: "bind-host", alias: "b", type: String, defaultValue: "0.0.0.0" },
    { name: "port", alias: "p", type: Number, defaultValue: 9091 },
    { name: "config-file", alias: "c", type: String },
    { name: "watch-file", alias: "w", type: Boolean, defaultValue: false },
    { name: "prometheus-url", alias: "u", type: String },
];

const cli = cmdline(optionDefinitions);

if (!cli["prometheus-url"]) {
    throw new Error("--prometheus-url is required.");
}

const config: Configuration = {
    bindHost: cli["bind-host"],
    port: cli.port,
    configFile: cli["config-file"],
    watchFile: cli["watch-file"],
    prometheusURL: cli["prometheus-url"],
    queriesAllow: [],
    variables: [],
    queriesCompiled: [],
    labelsAllow: [],
};

function arrayProp(propName: string, target: any): string[] | undefined {
    if (!(propName in target)) {
        return;
    }
    if (!Array.isArray(target[propName])) {
        throw new Error(`property '${propName}' should be an array.`);
    }
    const badElementIndex = target[propName].findIndex(v => typeof v !== "string" && typeof v !== "number");
    if (badElementIndex !== -1) {
        throw new Error(`all elements of '${propName}' should be strings or numbers. offending element index is ${badElementIndex}.`);
    }
    return target[propName];
}

function loadConfigFileVariables(data: object): AnyVariable[] {
    const vars: AnyVariable[] = [];
    for (const [name, value] of Object.entries(data)) {
        if (typeof value === "string" || typeof value === "number") {
            vars.push({
                name,
                varType: "literal",
                text: `${value}`
            });
            continue;
        }
        if (typeof value === "object") {
            try {
                let separator = "|";
                if (typeof value.separator === "string") {
                    separator = value.separator;
                }

                let items = arrayProp("any_of", value);
                if (items) {
                    vars.push({
                        name,
                        varType: "any_of_array",
                        items,
                        separator,
                    });
                    continue;
                }

                items = arrayProp("all_of", value);
                if (items) {
                    vars.push({
                        name,
                        varType: "all_of_array",
                        items,
                        separator,
                    });
                    continue;
                }

                if (typeof value.pattern === "string") {
                    let flags = "";
                    if(typeof value.flags === "string") {
                        flags = value.flags;
                    }
            
                    vars.push({
                        name,
                        varType: "pattern",
                        pattern: new RegExp(value.pattern, flags),
                    });
                }
            } catch (e) {
                throw new Error(`failed to parse '${name}' variable: ${e}`);
            }
        }
    }
    return vars;
}

export async function loadConfigFile(filePath: string): Promise<void> {
    const doc = yaml.load(await readFile(filePath, "utf8")) as { 
        queries_allow?: any[], 
        variables?: object,
        labels_allow?: object,
    };

    if (typeof doc.variables !== "object") {
        throw new Error("'variables' defined in config file, but not a dictionary.");
    }

    if (doc.variables) {
        config.variables = loadConfigFileVariables(doc.variables);
    }

    if (typeof doc.labels_allow === "object") {
        config.labelsAllow = [];
        for(const [key, value] of Object.entries(doc.labels_allow)) {
            if (typeof value === "boolean" && value) {
                config.labelsAllow.push({ name: key });
            } else {
                const values = arrayProp(key, doc.labels_allow)!;
                config.labelsAllow.push({ name: key, values });
            }
        }
    }

    if (!Array.isArray(doc.queries_allow)) {
        throw new Error("Config file format error: no 'queries_allow' property, or not an array.");
    }

    config.queriesAllow = [];
    for (const item of doc.queries_allow) {
        if (typeof item === "string") {
            config.queriesAllow.push(item);
        }
    }

    const queries = [];
    for (const q of config.queriesAllow) {
        queries.push(compileQuery(q, config.variables));
    }
    config.queriesCompiled = queries;
}

await loadConfigFile(config.configFile);

if (config.watchFile) {
    fs.watchFile(config.configFile, async (curr, prev) => {
        if (curr.mtimeMs === prev.mtimeMs) {
            return;
        }
        console.log("[watch-file] Config file was updated. Re-reading configuration...");
        try {
            await loadConfigFile(config.configFile);
        } catch (e) {
            console.error("Failed to read config file", config.configFile, e);
        }
    });
}

export { config };