package common

/*
 * This file is part of Autogits.
 *
 * Copyright © 2024 SUSE LLC
 *
 * Autogits is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 2 of the License, or (at your option) any later
 * version.
 *
 * Autogits is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * Foobar. If not, see <https://www.gnu.org/licenses/>.
 */

import (
	"crypto/tls"
	"fmt"
	"net/url"
	"runtime/debug"
	"slices"
	"strings"
	"time"

	rabbitmq "github.com/rabbitmq/amqp091-go"
)

const RequestType_CreateBrachTag = "create"
const RequestType_DeleteBranchTag = "delete"
const RequestType_Fork = "fork"
const RequestType_Issue = "issues"
const RequestType_IssueAssign = "issue_assign"
const RequestType_IssueComment = "issue_comment"
const RequestType_IssueLabel = "issue_label"
const RequestType_IssueMilestone = "issue_milestone"
const RequestType_Push = "push"
const RequestType_Repository = "repository"
const RequestType_Release = "release"
const RequestType_PR = "pull_request"
const RequestType_PRAssign = "pull_request_assign"
const RequestType_PRLabel = "pull_request_label"
const RequestType_PRComment = "pull_request_comment"
const RequestType_PRMilestone = "pull_request_milestone"
const RequestType_PRSync = "pull_request_sync"
const RequestType_PRReviewAccepted = "pull_request_review_approved"
const RequestType_PRReviewRejected = "pull_request_review_rejected"
const RequestType_PRReviewRequest = "pull_request_review_request"
const RequestType_PRReviewComment = "pull_request_review_comment"
const RequestType_Wiki = "wiki"

type RequestProcessor interface {
	ProcessFunc(*Request) error
}

type ListenDefinitions struct {
	RabbitURL *url.URL // amqps://user:password@host/queue

	GitAuthor string
	Handlers  map[string]RequestProcessor
	Orgs      []string

	topics          []string
	topicSubChanges chan string // +topic = subscribe, -topic = unsubscribe
}

type RabbitMessage rabbitmq.Delivery

func (l *ListenDefinitions) processTopicChanges(ch *rabbitmq.Channel, queueName string) {
	for {
		topic, ok := <-l.topicSubChanges
		if !ok {
			return
		}

		LogDebug("    topic change:", topic)
		switch topic[0] {
		case '+':
			if err := ch.QueueBind(queueName, topic[1:], "pubsub", false, nil); err != nil {
				LogError(err)
			}
		case '-':
			if err := ch.QueueUnbind(queueName, topic[1:], "pubsub", nil); err != nil {
				LogError(err)
			}
		default:
			LogInfo("Ignoring unknown topic change:", topic)
		}
	}
}

func (l *ListenDefinitions) processRabbitMQ(msgCh chan<- RabbitMessage) error {
	queueName := l.RabbitURL.Path
	l.RabbitURL.Path = ""

	if len(queueName) > 0 && queueName[0] == '/' {
		queueName = queueName[1:]
	}

	connection, err := rabbitmq.DialTLS(l.RabbitURL.String(), &tls.Config{
		ServerName: l.RabbitURL.Hostname(),
	})
	if err != nil {
		return fmt.Errorf("Cannot connect to %s . Err: %w", l.RabbitURL.Hostname(), err)
	}
	defer connection.Close()

	ch, err := connection.Channel()
	if err != nil {
		return fmt.Errorf("Cannot create a channel. Err: %w", err)
	}
	defer ch.Close()

	if err = ch.ExchangeDeclarePassive("pubsub", "topic", true, false, false, false, nil); err != nil {
		return fmt.Errorf("Cannot find pubsub exchange? Err: %w", err)
	}

	var q rabbitmq.Queue
	if len(queueName) == 0 {
		q, err = ch.QueueDeclare("", false, true, true, false, nil)
	} else {
		q, err = ch.QueueDeclarePassive(queueName, true, false, true, false, nil)
		if err != nil {
			LogInfo("queue not found .. trying to create it:", err)
			if ch.IsClosed() {
				ch, err = connection.Channel()
				if err != nil {
					return fmt.Errorf("Channel cannot be re-opened. Err: %w", err)
				}
			}
			q, err = ch.QueueDeclare(queueName, true, false, true, false, nil)

			if err != nil {
				LogInfo("can't create persistent queue ... falling back to temporaty queue:", err)
				if ch.IsClosed() {
					ch, err = connection.Channel()
					return fmt.Errorf("Channel cannot be re-opened. Err: %w", err)
				}
				q, err = ch.QueueDeclare("", false, true, true, false, nil)
			}
		}
	}
	if err != nil {
		return fmt.Errorf("Cannot declare queue. Err: %w", err)
	}
	//	log.Printf("queue: %s:%d", q.Name, q.Consumers)

	LogDebug(" -- listening to topics:")
	l.topicSubChanges = make(chan string)
	defer close(l.topicSubChanges)
	go l.processTopicChanges(ch, q.Name)

	for _, topic := range l.topics {
		l.topicSubChanges <- "+" + topic
	}

	msgs, err := ch.Consume(q.Name, "", true, true, false, false, nil)
	if err != nil {
		return fmt.Errorf("Cannot start consumer. Err: %w", err)
	}
	//	log.Printf("queue: %s:%d", q.Name, q.Consumers)

	for {
		msg, ok := <-msgs
		if !ok {
			return fmt.Errorf("channel/connection closed?\n")
		}

		msgCh <- RabbitMessage(msg)
	}
}

func (l *ListenDefinitions) connectAndProcessRabbitMQ(ch chan<- RabbitMessage) {
	defer func() {
		if r := recover(); r != nil {
			LogError(r)
			LogError("'crash' RabbitMQ worker. Recovering... reconnecting...")
			time.Sleep(5 * time.Second)
			go l.connectAndProcessRabbitMQ(ch)
		}
	}()

	for {
		err := l.processRabbitMQ(ch)
		if err != nil {
			LogError("Error in RabbitMQ connection. %#v", err)
			LogInfo("Reconnecting in 2 seconds...")
			time.Sleep(2 * time.Second)
		}
	}
}

func (l *ListenDefinitions) connectToRabbitMQ() chan RabbitMessage {
	ch := make(chan RabbitMessage, 100)
	go l.connectAndProcessRabbitMQ(ch)

	return ch
}

func ProcessEvent(f RequestProcessor, request *Request) {
	defer func() {
		if r := recover(); r != nil {
			LogError("panic caught")
			if err, ok := r.(error); !ok {
				LogError(err)
			}
			LogError(string(debug.Stack()))
		}
	}()

	if err := f.ProcessFunc(request); err != nil {
		LogError(err)
	}

}

func (l *ListenDefinitions) generateTopics() []string {
	topics := make([]string, 0, len(l.Handlers)*len(l.Orgs))
	scope := "suse"
	if l.RabbitURL.Hostname() == "rabbit.opensuse.org" {
		scope = "opensuse"
	}

	for _, org := range l.Orgs {
		for requestType, _ := range l.Handlers {
			topics = append(topics, fmt.Sprintf("%s.src.%s.%s.#", scope, org, requestType))
		}
	}

	slices.Sort(topics)
	return slices.Compact(topics)
}

func (l *ListenDefinitions) UpdateTopics() {
	newTopics := l.generateTopics()

	j := 0
next_new_topic:
	for i := 0; i < len(newTopics); i++ {
		topic := newTopics[i]

		for j < len(l.topics) {
			cmp := strings.Compare(topic, l.topics[j])

			if cmp == 0 {
				j++
				continue next_new_topic
			}

			if cmp < 0 {
				l.topicSubChanges <- "+" + topic
				break
			}

			l.topicSubChanges <- "-" + l.topics[j]
			j++
		}

		if j == len(l.topics) {
			l.topicSubChanges <- "+" + topic
		}
	}

	for j < len(l.topics) {
		l.topicSubChanges <- "-" + l.topics[j]
		j++
	}

	l.topics = newTopics
}

func (l *ListenDefinitions) ProcessRabbitMQEvents() error {
	LogInfo("RabbitMQ connection:", l.RabbitURL.String())
	LogDebug("# Handlers:", len(l.Handlers))
	LogDebug("# Orgs:", len(l.Orgs))

	l.RabbitURL.User = url.UserPassword(rabbitUser, rabbitPassword)
	l.topics = l.generateTopics()
	ch := l.connectToRabbitMQ()

	for {
		msg, ok := <-ch
		if !ok {
			return nil
		}

		LogDebug("event:", msg.RoutingKey)

		route := strings.Split(msg.RoutingKey, ".")
		if len(route) > 3 {
			reqType := route[3]
			org := route[2]

			if !slices.Contains(l.Orgs, org) {
				LogInfo("Got event for unhandeled org:", org)
				continue
			}

			LogDebug("org:", org, "type:", reqType)
			if handler, found := l.Handlers[reqType]; found {
				/*				h, err := CreateRequestHandler()
								if err != nil {
									log.Println("Cannot create request handler", err)
									continue
								}
				*/
				req, err := ParseRequestJSON(reqType, msg.Body)
				if err != nil {
					LogError("Error parsing request JSON:", err)
					continue
				} else {
					LogDebug("processing req", req.Type)
					//					h.Request = req
					ProcessEvent(handler, req)

				}
			}
		}
	}
}