zkoss/zk

// Adapted from tsdoc/eslint-plugin/src/ConfigCache.ts
import { TSDocConfigFile } from '@microsoft/tsdoc-config';
import * as path from 'path';

interface ICachedConfig {
    loadTimeMs: number;
    lastCheckTimeMs: number;
    configFile: TSDocConfigFile;
}

// How often to check for modified input files. Evict the cache entry when a file's modification timestamp has changed.
const CACHE_CHECK_INTERVAL_MS = 3_000;
// Evict old entries from the cache after this much time, regardless of whether the file was detected as being modified or not.
const CACHE_EXPIRE_MS = 20_000;
// If this many objects accumulate in the cache, then it is cleared to avoid a memory leak.
const CACHE_MAX_SIZE = 100;
// configFilePath -> config
const cachedConfigs = new Map<string, ICachedConfig>();

/**
 * Node.js equivalent of performance.now().
 */
function getTimeInMs(): number {
    const [seconds, nanoseconds] = process.hrtime();
    return seconds * 1_000 + nanoseconds / 1_000_000;
}

export function getForSourceFile(sourceFilePath: string): TSDocConfigFile {
    const sourceFileFolder = path.dirname(path.resolve(sourceFilePath));
    // First, determine the file to be loaded. If not found, the configFilePath will be an empty string.
    const configFilePath = TSDocConfigFile.findConfigPathForFolder(sourceFileFolder);
    // If configFilePath is an empty string, then we'll use the folder of sourceFilePath as our cache key.
    const cacheKey = configFilePath || sourceFileFolder + '/';
    const nowMs = getTimeInMs();

    let cachedConfig = cachedConfigs.get(cacheKey);
    if (cachedConfig) {
        const loadAgeMs = nowMs - cachedConfig.loadTimeMs;
        const lastCheckAgeMs = nowMs - cachedConfig.lastCheckTimeMs;

        // Is the cached object still valid?
        if (loadAgeMs < 0 || CACHE_EXPIRE_MS < loadAgeMs) {
            cachedConfig = undefined;
            cachedConfigs.delete(cacheKey);
        } else if (lastCheckAgeMs < 0 || CACHE_CHECK_INTERVAL_MS < lastCheckAgeMs) {
            cachedConfig.lastCheckTimeMs = nowMs;
            if (cachedConfig.configFile.checkForModifiedFiles()) {
                // Invalidate the cache because it failed to load completely
                cachedConfig = undefined;
                cachedConfigs.delete(cacheKey);
            }
        }
    }

    // Load the object
    if (!cachedConfig) {
        if (cachedConfigs.size > CACHE_MAX_SIZE) {
            cachedConfigs.clear(); // avoid a memory leak
        }
        cachedConfig = {
            configFile: TSDocConfigFile.loadFile(configFilePath),
            lastCheckTimeMs: nowMs,
            loadTimeMs: nowMs
        };
        cachedConfigs.set(cacheKey, cachedConfig);
    }

    return cachedConfig.configFile;
}