package beaconclient

import (
	"context"
	"fmt"

	"github.com/r3labs/sse"
	log "github.com/sirupsen/logrus"
	"github.com/vulcanize/ipld-ethcl-indexer/pkg/database/sql"
)

// TODO: Use prysms config values instead of hardcoding them here.
var (
	bcHealthEndpoint     = "/eth/v1/node/health"               // Endpoint used for the healthcheck
	BcHeadTopicEndpoint  = "/eth/v1/events?topics=head"        // Endpoint used to subscribe to the head of the chain
	bcReorgTopicEndpoint = "/eth/v1/events?topics=chain_reorg" // Endpoint used to subscribe to the head of the chain
	BcBlockQueryEndpoint = "/eth/v2/beacon/blocks/"            // Endpoint to query individual Blocks
	BcStateQueryEndpoint = "/eth/v2/debug/beacon/states/"      // Endpoint to query individual States
	BcSyncStatusEndpoint = "/eth/v1/node/syncing"
	BcBlockRootEndpoint  = func(slot string) string {
		return "/eth/v1/beacon/blocks/" + slot + "/root"
	}
	bcSlotsPerEpoch = 32 // Number of slots in a single Epoch
	//bcSlotPerHistoricalVector = 8192                                // The number of slots in a historic vector.
	//bcFinalizedTopicEndpoint  = "/eth/v1/events?topics=finalized_checkpoint" // Endpoint used to subscribe to the head of the chain
)

// A structure utilized for keeping track of various metrics. Currently, mostly used in testing.
type BeaconClientMetrics struct {
	HeadTrackingInserts   uint64 // Number of head events we successfully wrote to the DB.
	HeadTrackingReorgs    uint64 // Number of reorg events we successfully wrote to the DB.
	HeadTrackingKnownGaps uint64 // Number of known_gaps we successfully wrote to the DB.
}

// A struct that capture the Beacon Server that the Beacon Client will be interacting with and querying.
type BeaconClient struct {
	Context                     context.Context      // A context generic context with multiple uses.
	ServerEndpoint              string               // What is the endpoint of the beacon server.
	PerformHistoricalProcessing bool                 // Should we perform historical processing?
	Db                          sql.Database         // Database object used for reads and writes.
	Metrics                     *BeaconClientMetrics // An object used to keep track of certain BeaconClient Metrics.
	KnownGapTableIncrement      int                  // The max number of slots within a single known_gaps table entry.

	// Used for Head Tracking
	PerformHeadTracking bool                   // Should we track head?
	StartingSlot        int                    // If we're performing head tracking. What is the first slot we processed.
	PreviousSlot        int                    // Whats the previous slot we processed
	PreviousBlockRoot   string                 // Whats the previous block root, used to check the next blocks parent.
	CheckKnownGaps      bool                   // Should we check for gaps at start up.
	HeadTracking        *SseEvents[Head]       // Track the head block
	ReOrgTracking       *SseEvents[ChainReorg] // Track all Reorgs
	//FinalizationTracking        *SseEvents[FinalizedCheckpoint] // Track all finalization checkpoints
}

// A struct to keep track of relevant the head event topic.
type SseEvents[P ProcessedEvents] struct {
	Endpoint   string          // The endpoint for the subscription. Primarily used for logging
	MessagesCh chan *sse.Event // Contains all the messages from the SSE Channel
	ErrorCh    chan *SseError  // Contains any errors while SSE streaming occurred
	ProcessCh  chan *P         // Used to capture processed data in its proper struct.
	SseClient  *sse.Client     // sse.Client object that is used to interact with the SSE stream
}

// An object to capture any errors when turning an SSE message to JSON.
type SseError struct {
	err error
	msg []byte
}

// A Function to create the BeaconClient.
func CreateBeaconClient(ctx context.Context, connectionProtocol string, bcAddress string, bcPort int) *BeaconClient {
	endpoint := fmt.Sprintf("%s://%s:%d", connectionProtocol, bcAddress, bcPort)
	log.Info("Creating the BeaconClient")
	return &BeaconClient{
		Context:        ctx,
		ServerEndpoint: endpoint,
		HeadTracking:   createSseEvent[Head](endpoint, BcHeadTopicEndpoint),
		ReOrgTracking:  createSseEvent[ChainReorg](endpoint, bcReorgTopicEndpoint),
		Metrics: &BeaconClientMetrics{
			HeadTrackingInserts: 0,
			HeadTrackingReorgs:  0,
		},
		//FinalizationTracking: createSseEvent[FinalizedCheckpoint](endpoint, bcFinalizedTopicEndpoint),
	}
}

// Create all the channels to handle a SSE events
func createSseEvent[P ProcessedEvents](baseEndpoint string, path string) *SseEvents[P] {
	endpoint := baseEndpoint + path
	sseEvents := &SseEvents[P]{
		Endpoint:   endpoint,
		MessagesCh: make(chan *sse.Event, 1),
		ErrorCh:    make(chan *SseError),
		ProcessCh:  make(chan *P),
		SseClient: func(endpoint string) *sse.Client {
			log.WithFields(log.Fields{"endpoint": endpoint}).Info("Creating SSE client")
			return sse.NewClient(endpoint)
		}(endpoint),
	}
	return sseEvents
}