package library

import (
	"context"
	"encoding/json"
	"errors"
	"time"

	"github.com/libp2p/go-libp2p/core/peer"
	"github.com/waku-org/go-waku/waku/v2/protocol"
	"github.com/waku-org/go-waku/waku/v2/protocol/filter"
	"github.com/waku-org/go-waku/waku/v2/protocol/subscription"
)

type filterArgument struct {
	PubsubTopic   string   `json:"pubsubTopic,omitempty"`
	ContentTopics []string `json:"contentTopics,omitempty"`
}

func toContentFilter(filterJSON string) (protocol.ContentFilter, error) {
	var f filterArgument
	err := json.Unmarshal([]byte(filterJSON), &f)
	if err != nil {
		return protocol.ContentFilter{}, err
	}

	return protocol.ContentFilter{
		PubsubTopic:   f.PubsubTopic,
		ContentTopics: protocol.NewContentTopicSet(f.ContentTopics...),
	}, nil
}

type subscribeResult struct {
	Subscriptions []*subscription.SubscriptionDetails `json:"subscriptions"`
	Error         string                              `json:"error,omitempty"`
}

// FilterSubscribe is used to create a subscription to a filter node to receive messages
func FilterSubscribe(instance *WakuInstance, filterJSON string, peerID string, ms int) (string, error) {
	cf, err := toContentFilter(filterJSON)
	if err != nil {
		return "", err
	}

	if err := validateInstance(instance, MustBeStarted); err != nil {
		return "", err
	}

	var ctx context.Context
	var cancel context.CancelFunc

	if ms > 0 {
		ctx, cancel = context.WithTimeout(instance.ctx, time.Duration(int(ms))*time.Millisecond)
		defer cancel()
	} else {
		ctx = instance.ctx
	}

	var fOptions []filter.FilterSubscribeOption
	if peerID != "" {
		p, err := peer.Decode(peerID)
		if err != nil {
			return "", err
		}
		fOptions = append(fOptions, filter.WithPeer(p))
	} else {
		fOptions = append(fOptions, filter.WithAutomaticPeerSelection())
	}

	subscriptions, err := instance.node.FilterLightnode().Subscribe(ctx, cf, fOptions...)
	if err != nil && subscriptions == nil {
		return "", err
	}

	for _, subscriptionDetails := range subscriptions {
		go func(subscriptionDetails *subscription.SubscriptionDetails) {
			for envelope := range subscriptionDetails.C {
				send(instance, "message", toSubscriptionMessage(envelope))
			}
		}(subscriptionDetails)
	}
	var subResult subscribeResult
	subResult.Subscriptions = subscriptions
	if err != nil {
		subResult.Error = err.Error()
	}

	return marshalJSON(subResult)
}

// FilterPing is used to determine if a peer has an active subscription
func FilterPing(instance *WakuInstance, peerID string, ms int) error {
	if err := validateInstance(instance, MustBeStarted); err != nil {
		return err
	}

	var ctx context.Context
	var cancel context.CancelFunc

	if ms > 0 {
		ctx, cancel = context.WithTimeout(instance.ctx, time.Duration(int(ms))*time.Millisecond)
		defer cancel()
	} else {
		ctx = instance.ctx
	}

	var pID peer.ID
	var err error
	if peerID != "" {
		pID, err = peer.Decode(peerID)
		if err != nil {
			return err
		}
	} else {
		return errors.New("peerID is required")
	}

	return instance.node.FilterLightnode().Ping(ctx, pID)
}

// FilterUnsubscribe is used to remove a filter criteria from an active subscription with a filter node
func FilterUnsubscribe(instance *WakuInstance, filterJSON string, peerID string, ms int) error {
	cf, err := toContentFilter(filterJSON)
	if err != nil {
		return err
	}

	if err := validateInstance(instance, MustBeStarted); err != nil {
		return err
	}

	var ctx context.Context
	var cancel context.CancelFunc

	if ms > 0 {
		ctx, cancel = context.WithTimeout(instance.ctx, time.Duration(int(ms))*time.Millisecond)
		defer cancel()
	} else {
		ctx = instance.ctx
	}

	var fOptions []filter.FilterSubscribeOption
	if peerID != "" {
		p, err := peer.Decode(peerID)
		if err != nil {
			return err
		}
		fOptions = append(fOptions, filter.WithPeer(p))
	} else {
		return errors.New("peerID is required")
	}

	result, err := instance.node.FilterLightnode().Unsubscribe(ctx, cf, fOptions...)
	if err != nil {
		return err
	}

	errs := result.Errors()
	if len(errs) == 0 {
		return nil
	}
	return errs[0].Err
}

type unsubscribeAllResult struct {
	PeerID string `json:"peerID"`
	Error  string `json:"error"`
}

// FilterUnsubscribeAll is used to remove an active subscription to a peer. If no peerID is defined, it will stop all active filter subscriptions
func FilterUnsubscribeAll(instance *WakuInstance, peerID string, ms int) (string, error) {
	if err := validateInstance(instance, MustBeStarted); err != nil {
		return "", err
	}

	var ctx context.Context
	var cancel context.CancelFunc

	if ms > 0 {
		ctx, cancel = context.WithTimeout(instance.ctx, time.Duration(int(ms))*time.Millisecond)
		defer cancel()
	} else {
		ctx = instance.ctx
	}

	var fOptions []filter.FilterSubscribeOption
	if peerID != "" {
		p, err := peer.Decode(peerID)
		if err != nil {
			return "", err
		}
		fOptions = append(fOptions, filter.WithPeer(p))
	} else {
		fOptions = append(fOptions, filter.UnsubscribeAll())
	}

	result, err := instance.node.FilterLightnode().UnsubscribeAll(ctx, fOptions...)
	if err != nil {
		return "", err
	}

	var unsubscribeResult []unsubscribeAllResult

	for _, err := range result.Errors() {
		ur := unsubscribeAllResult{
			PeerID: err.PeerID.String(),
		}
		if err.Err != nil {
			ur.Error = err.Err.Error()
		}
		unsubscribeResult = append(unsubscribeResult, ur)
	}

	return marshalJSON(unsubscribeResult)
}