package dag

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"sync"
	"time"

	"golang.org/x/time/rate"

	"github.com/oarkflow/mq"
	"github.com/oarkflow/mq/consts"
)

type EdgeType int

func (c EdgeType) IsValid() bool { return c >= Simple && c <= Iterator }

const (
	Simple EdgeType = iota
	Iterator
)

type Node struct {
	processor mq.Processor
	Name      string
	Key       string
	Edges     []Edge
	isReady   bool
}

func (n *Node) ProcessTask(ctx context.Context, msg *mq.Task) mq.Result {
	return n.processor.ProcessTask(ctx, msg)
}

func (n *Node) Close() error {
	return n.processor.Close()
}

type Edge struct {
	Label string
	From  *Node
	To    []*Node
	Type  EdgeType
}

type (
	FromNode string
	When     string
	Then     string
)

type DAG struct {
	nodes         map[string]*Node
	server        *mq.Broker
	consumer      *mq.Consumer
	taskContext   map[string]*TaskManager
	conditions    map[FromNode]map[When]Then
	pool          *mq.Pool
	taskCleanupCh chan string
	name          string
	key           string
	startNode     string
	consumerTopic string
	opts          []mq.Option
	mu            sync.RWMutex
	paused        bool
}

func (tm *DAG) SetKey(key string) {
	tm.key = key
}

func (tm *DAG) GetType() string {
	return tm.key
}

func (tm *DAG) listenForTaskCleanup() {
	for taskID := range tm.taskCleanupCh {
		if tm.server.Options().CleanTaskOnComplete() {
			tm.taskCleanup(taskID)
		}
	}
}

func (tm *DAG) taskCleanup(taskID string) {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	delete(tm.taskContext, taskID)
	log.Printf("DAG - Task %s cleaned up", taskID)
}

func (tm *DAG) Consume(ctx context.Context) error {
	if tm.consumer != nil {
		tm.server.Options().SetSyncMode(true)
		return tm.consumer.Consume(ctx)
	}
	return nil
}

func (tm *DAG) Stop(ctx context.Context) error {
	for _, n := range tm.nodes {
		err := n.processor.Stop(ctx)
		if err != nil {
			return err
		}
	}
	return nil
}

func (tm *DAG) GetKey() string {
	return tm.key
}

func (tm *DAG) AssignTopic(topic string) {
	tm.consumer = mq.NewConsumer(topic, topic, tm.ProcessTask, mq.WithRespondPendingResult(false))
	tm.consumerTopic = topic
}

func NewDAG(name, key string, opts ...mq.Option) *DAG {
	callback := func(ctx context.Context, result mq.Result) error { return nil }
	d := &DAG{
		name:          name,
		key:           key,
		nodes:         make(map[string]*Node),
		taskContext:   make(map[string]*TaskManager),
		conditions:    make(map[FromNode]map[When]Then),
		taskCleanupCh: make(chan string),
	}
	opts = append(opts, mq.WithCallback(d.onTaskCallback), mq.WithConsumerOnSubscribe(d.onConsumerJoin), mq.WithConsumerOnClose(d.onConsumerClose))
	d.server = mq.NewBroker(opts...)
	d.opts = opts
	options := d.server.Options()
	d.pool = mq.NewPool(options.NumOfWorkers(), options.QueueSize(), options.MaxMemoryLoad(), d.ProcessTask, callback, options.Storage())
	d.pool.Start(d.server.Options().NumOfWorkers())
	go d.listenForTaskCleanup()
	return d
}

func (tm *DAG) callbackToConsumer(ctx context.Context, result mq.Result) {
	if tm.consumer != nil {
		result.Topic = tm.consumerTopic
		if tm.consumer.Conn() == nil {
			tm.onTaskCallback(ctx, result)
		} else {
			tm.consumer.OnResponse(ctx, result)
		}
	}
}

func (tm *DAG) onTaskCallback(ctx context.Context, result mq.Result) mq.Result {
	if taskContext, ok := tm.taskContext[result.TaskID]; ok && result.Topic != "" {
		return taskContext.handleCallback(ctx, result)
	}
	return mq.Result{}
}

func (tm *DAG) onConsumerJoin(_ context.Context, topic, _ string) {
	if node, ok := tm.nodes[topic]; ok {
		log.Printf("DAG - CONSUMER ~> ready on %s", topic)
		node.isReady = true
	}
}

func (tm *DAG) onConsumerClose(_ context.Context, topic, _ string) {
	if node, ok := tm.nodes[topic]; ok {
		log.Printf("DAG - CONSUMER ~> down on %s", topic)
		node.isReady = false
	}
}

func (tm *DAG) SetStartNode(node string) {
	tm.startNode = node
}

func (tm *DAG) GetStartNode() string {
	return tm.startNode
}

func (tm *DAG) Start(ctx context.Context, addr string) error {
	if !tm.server.SyncMode() {
		go func() {
			err := tm.server.Start(ctx)
			if err != nil {
				panic(err)
			}
		}()
		for _, con := range tm.nodes {
			go func(con *Node) {
				limiter := rate.NewLimiter(rate.Every(1*time.Second), 1) // Retry every second
				for {
					err := con.processor.Consume(ctx)
					if err != nil {
						log.Printf("[ERROR] - Consumer %s failed to start: %v", con.Key, err)
					} else {
						log.Printf("[INFO] - Consumer %s started successfully", con.Key)
						break
					}
					limiter.Wait(ctx) // Wait with rate limiting before retrying
				}
			}(con)
		}
	}
	log.Printf("DAG - HTTP_SERVER ~> started on %s", addr)
	tm.Handlers()
	config := tm.server.TLSConfig()
	if config.UseTLS {
		return http.ListenAndServeTLS(addr, config.CertPath, config.KeyPath, nil)
	}
	return http.ListenAndServe(addr, nil)
}

func (tm *DAG) AddDAGNode(name string, key string, dag *DAG, firstNode ...bool) {
	dag.AssignTopic(key)
	tm.mu.Lock()
	defer tm.mu.Unlock()
	tm.nodes[key] = &Node{
		Name:      name,
		Key:       key,
		processor: dag,
		isReady:   true,
	}
	if len(firstNode) > 0 && firstNode[0] {
		tm.startNode = key
	}
}

func (tm *DAG) AddNode(name, key string, handler mq.Processor, firstNode ...bool) *DAG {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	con := mq.NewConsumer(key, key, handler.ProcessTask, tm.opts...)
	tm.nodes[key] = &Node{
		Name:      name,
		Key:       key,
		processor: con,
		isReady:   true,
	}
	if len(firstNode) > 0 && firstNode[0] {
		tm.startNode = key
	}
	return tm
}

func (tm *DAG) AddDeferredNode(name, key string, firstNode ...bool) error {
	if tm.server.SyncMode() {
		return fmt.Errorf("DAG cannot have deferred node in Sync Mode")
	}
	tm.mu.Lock()
	defer tm.mu.Unlock()
	tm.nodes[key] = &Node{
		Name: name,
		Key:  key,
	}
	if len(firstNode) > 0 && firstNode[0] {
		tm.startNode = key
	}
	return nil
}

func (tm *DAG) IsReady() bool {
	tm.mu.RLock()
	defer tm.mu.RUnlock()
	for _, node := range tm.nodes {
		if !node.isReady {
			return false
		}
	}
	return true
}

func (tm *DAG) AddCondition(fromNode FromNode, conditions map[When]Then) *DAG {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	tm.conditions[fromNode] = conditions
	return tm
}

func (tm *DAG) AddIterator(label, from string, targets ...string) *DAG {
	tm.addEdge(Iterator, label, from, targets...)
	return tm
}

func (tm *DAG) AddEdge(label, from string, targets ...string) *DAG {
	tm.addEdge(Simple, label, from, targets...)
	return tm
}

func (tm *DAG) addEdge(edgeType EdgeType, label, from string, targets ...string) {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	fromNode, ok := tm.nodes[from]
	if !ok {
		return
	}
	var nodes []*Node
	for _, target := range targets {
		toNode, ok := tm.nodes[target]
		if !ok {
			return
		}
		nodes = append(nodes, toNode)
	}
	edge := Edge{From: fromNode, To: nodes, Type: edgeType, Label: label}
	fromNode.Edges = append(fromNode.Edges, edge)
}

func (tm *DAG) ProcessTask(ctx context.Context, task *mq.Task) mq.Result {
	tm.mu.Lock()
	taskID := mq.NewID()
	manager := NewTaskManager(tm, taskID)
	manager.createdAt = task.CreatedAt
	tm.taskContext[taskID] = manager
	tm.mu.Unlock()

	if tm.consumer != nil {
		initialNode, err := tm.parseInitialNode(ctx)
		if err != nil {
			return mq.Result{Error: err}
		}
		task.Topic = initialNode
	}
	return manager.processTask(ctx, task.Topic, task.Payload)
}

func (tm *DAG) Process(ctx context.Context, payload []byte) mq.Result {
	tm.mu.RLock()
	if tm.paused {
		tm.mu.RUnlock()
		return mq.Result{Error: fmt.Errorf("unable to process task, error: DAG is not accepting any task")}
	}
	tm.mu.RUnlock()
	if !tm.IsReady() {
		return mq.Result{Error: fmt.Errorf("unable to process task, error: DAG is not ready yet")}
	}
	initialNode, err := tm.parseInitialNode(ctx)
	if err != nil {
		return mq.Result{Error: err}
	}
	if tm.server.SyncMode() {
		ctx = mq.SetHeaders(ctx, map[string]string{consts.AwaitResponseKey: "true"})
	}
	task := mq.NewTask(mq.NewID(), payload, initialNode)
	awaitResponse, _ := mq.GetAwaitResponse(ctx)
	if awaitResponse != "true" {
		headers, ok := mq.GetHeaders(ctx)
		ctxx := context.Background()
		if ok {
			ctxx = mq.SetHeaders(ctxx, headers.AsMap())
		}
		if err := tm.pool.EnqueueTask(ctxx, task, 0); err != nil {
			return mq.Result{CreatedAt: task.CreatedAt, TaskID: task.ID, Topic: initialNode, Status: "FAILED", Error: err}
		}
		return mq.Result{CreatedAt: task.CreatedAt, TaskID: task.ID, Topic: initialNode, Status: "PENDING"}
	}
	return tm.ProcessTask(ctx, task)
}

func (tm *DAG) ScheduleTask(ctx context.Context, payload []byte, opts ...mq.SchedulerOption) mq.Result {
	tm.mu.RLock()
	if tm.paused {
		tm.mu.RUnlock()
		return mq.Result{Error: fmt.Errorf("unable to process task, error: DAG is not accepting any task")}
	}
	tm.mu.RUnlock()
	if !tm.IsReady() {
		return mq.Result{Error: fmt.Errorf("unable to process task, error: DAG is not ready yet")}
	}
	initialNode, err := tm.parseInitialNode(ctx)
	if err != nil {
		return mq.Result{Error: err}
	}
	if tm.server.SyncMode() {
		ctx = mq.SetHeaders(ctx, map[string]string{consts.AwaitResponseKey: "true"})
	}
	task := mq.NewTask(mq.NewID(), payload, initialNode)
	headers, ok := mq.GetHeaders(ctx)
	ctxx := context.Background()
	if ok {
		ctxx = mq.SetHeaders(ctxx, headers.AsMap())
	}
	tm.pool.Scheduler().AddTask(ctxx, task, opts...)
	return mq.Result{CreatedAt: task.CreatedAt, TaskID: task.ID, Topic: initialNode, Status: "PENDING"}
}

func (tm *DAG) parseInitialNode(ctx context.Context) (string, error) {
	tm.mu.RLock()
	defer tm.mu.RUnlock()

	val := ctx.Value("initial_node")
	initialNode, ok := val.(string)
	if ok {
		return initialNode, nil
	}
	if tm.startNode == "" {
		firstNode := tm.findStartNode()
		if firstNode != nil {
			tm.startNode = firstNode.Key
		}
	}

	if tm.startNode == "" {
		return "", fmt.Errorf("initial node not found")
	}
	return tm.startNode, nil
}

func (tm *DAG) findStartNode() *Node {
	incomingEdges := make(map[string]bool)
	connectedNodes := make(map[string]bool)
	for _, node := range tm.nodes {
		for _, edge := range node.Edges {
			if edge.Type.IsValid() {
				connectedNodes[node.Key] = true
				for _, to := range edge.To {
					connectedNodes[to.Key] = true
					incomingEdges[to.Key] = true
				}
			}
		}
		if cond, ok := tm.conditions[FromNode(node.Key)]; ok {
			for _, target := range cond {
				connectedNodes[string(target)] = true
				incomingEdges[string(target)] = true
			}
		}
	}
	for nodeID, node := range tm.nodes {
		if !incomingEdges[nodeID] && connectedNodes[nodeID] {
			return node
		}
	}
	return nil
}

func (tm *DAG) Pause(_ context.Context) error {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	tm.paused = true
	return nil
}

func (tm *DAG) Resume(_ context.Context) error {
	tm.mu.Lock()
	defer tm.mu.Unlock()
	tm.paused = false
	return nil
}

func (tm *DAG) Close() error {
	for _, n := range tm.nodes {
		err := n.Close()
		if err != nil {
			return err
		}
	}
	return nil
}

func (tm *DAG) PauseConsumer(ctx context.Context, id string) {
	tm.doConsumer(ctx, id, consts.CONSUMER_PAUSE)
}

func (tm *DAG) ResumeConsumer(ctx context.Context, id string) {
	tm.doConsumer(ctx, id, consts.CONSUMER_RESUME)
}

func (tm *DAG) doConsumer(ctx context.Context, id string, action consts.CMD) {
	if node, ok := tm.nodes[id]; ok {
		switch action {
		case consts.CONSUMER_PAUSE:
			err := node.processor.Pause(ctx)
			if err == nil {
				node.isReady = false
				log.Printf("[INFO] - Consumer %s paused successfully", node.Key)
			} else {
				log.Printf("[ERROR] - Failed to pause consumer %s: %v", node.Key, err)
			}
		case consts.CONSUMER_RESUME:
			err := node.processor.Resume(ctx)
			if err == nil {
				node.isReady = true
				log.Printf("[INFO] - Consumer %s resumed successfully", node.Key)
			} else {
				log.Printf("[ERROR] - Failed to resume consumer %s: %v", node.Key, err)
			}
		}
	} else {
		log.Printf("[WARNING] - Consumer %s not found", id)
	}
}