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/*******************************************************************************
 *   © 2019-2024 SAP SE or an SAP affiliate company. All rights reserved.
 ******************************************************************************/

package com.sap.cloud.mt.runtime;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static java.lang.StackWalker.Option.RETAIN_CLASS_REFERENCE;

public class TenantOverwrite implements AutoCloseable {
	private static final Logger logger = LoggerFactory.getLogger(TenantOverwrite.class);
	private static final ThreadLocal overwritePerThread = new ThreadLocal<>();

	public TenantOverwrite(String tenantId) {
		if (logger.isDebugEnabled()) {
			logger.debug("Tenant overwrite called with tenant id {}", tenantId);
			var walker = StackWalker.getInstance(RETAIN_CLASS_REFERENCE);
			var frame = walker.walk(stream -> stream.skip(1).findFirst().orElse(null));
			if (frame != null) {
				logger.debug("class={} method={}", frame.getClassName(), frame.getMethodName());
			}
		}
		TenantAndCount tenantAndCount = overwritePerThread.get();
		if (tenantAndCount != null) {
			logger.debug("There is already a tenant overwrite with count {}", tenantAndCount.callDepth);
			if (!tenantAndCount.getTenantId().equals(tenantId)) {
				throw new UnsupportedOperationException("It is not supported to stack overwrites with different tenants");//NOSONAR
			}
		} else {
			tenantAndCount = new TenantAndCount(tenantId);
			overwritePerThread.set(tenantAndCount);
		}
		tenantAndCount.inc();
	}

	public static boolean isOverwritten() {
		return (overwritePerThread.get() != null);
	}

	public static String getTenantId() {
		return overwritePerThread.get() != null ? overwritePerThread.get().getTenantId() : null;
	}

	@Override
	public void close() {
		logger.debug("Tenant overwrite close called");
		if (overwritePerThread.get() != null) {
			overwritePerThread.get().dec();
			if (overwritePerThread.get().counterIsZero()) {
				logger.debug("Tenant overwrite is deleted");
				overwritePerThread.remove();
			}
		}
	}

	private static class TenantAndCount {
		private String tenantId;
		private int callDepth = 0;

		public TenantAndCount(String tenantId) {
			this.tenantId = tenantId;
		}

		public void inc() {
			callDepth++;
		}

		public void dec() {
			callDepth--;
		}

		public boolean counterIsZero() {
			return callDepth == 0;
		}

		public String getTenantId() {
			return tenantId;
		}
	}
}