/*
 *      Copyright (c) 2018-2028, DreamLu All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice,
 *  this list of conditions and the following disclaimer.
 *  Redistributions in binary form must reproduce the above copyright
 *  notice, this list of conditions and the following disclaimer in the
 *  documentation and/or other materials provided with the distribution.
 *  Neither the name of the dreamlu.net developer nor the names of its
 *  contributors may be used to endorse or promote products derived from
 *  this software without specific prior written permission.
 *  Author: DreamLu 卢春梦 (596392912@qq.com)
 */
package org.springblade.core.prometheus.endpoint;

import lombok.RequiredArgsConstructor;
import org.springblade.core.auto.annotation.AutoIgnore;
import org.springblade.core.prometheus.data.Service;
import org.springblade.core.prometheus.data.ServiceHealth;
import org.springblade.core.prometheus.service.RegistrationService;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.Assert;
import org.springframework.util.MultiValueMap;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Mono;

import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static java.util.stream.Collectors.toList;

/**
 * consul catalog api
 *
 * @author L.cm
 */
@AutoIgnore
@RestController
@RequiredArgsConstructor
public class ServiceEndpoint {
	private static final String CONSUL_IDX_HEADER = "X-Consul-Index";
	private static final String QUERY_PARAM_WAIT = "wait";
	private static final String QUERY_PARAM_INDEX = "index";
	private static final Pattern WAIT_PATTERN = Pattern.compile("(\\d*)(m|s|ms|h)");
	private final RegistrationService registrationService;

	@GetMapping(value = "/v1/catalog/services", produces = MediaType.APPLICATION_JSON_VALUE)
	public Mono<ResponseEntity<Map<String, String[]>>> getServiceNames(
		@RequestParam(name = QUERY_PARAM_WAIT, required = false) String wait,
		@RequestParam(name = QUERY_PARAM_INDEX, required = false) Long index) {
		return registrationService.getServiceNames(getWaitMillis(wait), index)
			.map(item -> createResponseEntity(item.getItem(), item.getChangeIndex()));
	}

	@GetMapping(value = "/v1/catalog/service/{appName}", produces = MediaType.APPLICATION_JSON_VALUE)
	public Mono<ResponseEntity<List<Service>>> getService(@PathVariable("appName") String appName,
														  @RequestParam(value = QUERY_PARAM_WAIT, required = false) String wait,
														  @RequestParam(value = QUERY_PARAM_INDEX, required = false) Long index) {
		Objects.requireNonNull(appName, "service name can not be null");
		return registrationService.getService(appName, getWaitMillis(wait), index)
			.map(item -> createResponseEntity(item.getItem(), item.getChangeIndex()));
	}

	@GetMapping(value = "/v1/health/service/{appName}", produces = MediaType.APPLICATION_JSON_VALUE)
	public Mono<ResponseEntity<List<ServiceHealth>>> getServiceHealth(@PathVariable("appName") String appName,
																	  @RequestParam(value = QUERY_PARAM_WAIT, required = false) String wait,
																	  @RequestParam(value = QUERY_PARAM_INDEX, required = false) Long index) {
		Assert.isTrue(appName != null, "service name can not be null");
		return registrationService.getService(appName, getWaitMillis(wait), index)
			.map(item -> {
				List<ServiceHealth> services = item.getItem().stream()
					.map(registrationService::getServiceHealth).collect(toList());
				return createResponseEntity(services, item.getChangeIndex());
			});
	}

	private static MultiValueMap<String, String> createHeaders(long index) {
		HttpHeaders headers = new HttpHeaders();
		headers.add(CONSUL_IDX_HEADER, String.valueOf(index));
		return headers;
	}

	private static <T> ResponseEntity<T> createResponseEntity(T body, long index) {
		return new ResponseEntity<>(body, createHeaders(index), HttpStatus.OK);
	}

	/**
	 * Details to the wait behaviour can be found
	 * https://www.consul.io/api/index.html#blocking-queries
	 */
	private static long getWaitMillis(String wait) {
		// default from consul docu
		long millis = TimeUnit.MINUTES.toMillis(5);
		if (wait != null) {
			Matcher matcher = WAIT_PATTERN.matcher(wait);
			if (matcher.matches()) {
				long value = Long.parseLong(matcher.group(1));
				TimeUnit timeUnit = parseTimeUnit(matcher.group(2));
				millis = timeUnit.toMillis(value);
			} else {
				throw new IllegalArgumentException("Invalid wait pattern");
			}
		}
		return millis + ThreadLocalRandom.current().nextInt(((int) millis / 16) + 1);
	}

	private static TimeUnit parseTimeUnit(String unit) {
		switch (unit) {
			case "h":
				return TimeUnit.HOURS;
			case "m":
				return TimeUnit.MINUTES;
			case "s":
				return TimeUnit.SECONDS;
			case "ms":
				return TimeUnit.MILLISECONDS;
			default:
				throw new IllegalArgumentException("No valid time unit");
		}
	}
}