package httpapi

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
	"net/http/pprof"
	"slices"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/bluesky-social/indigo/atproto/atcrypto"
	"github.com/cometbft/cometbft/node"
	"github.com/did-method-plc/go-didplc"
	"github.com/google/uuid"
	cbornode "github.com/ipfs/go-ipld-cbor"
	"github.com/palantir/stacktrace"
	"github.com/rs/cors"
	"github.com/samber/lo"

	"tangled.org/gbl08ma.com/didplcbft/abciapp"
	"tangled.org/gbl08ma.com/didplcbft/plc"
	"tangled.org/gbl08ma.com/didplcbft/transaction"
)

// Server represents the HTTP server for the PLC directory.
type Server struct {
	txFactory      *transaction.Factory
	plc            plc.ReadPLC
	router         *http.ServeMux
	node           *node.Node
	srv            http.Server
	handlerTimeout time.Duration
	proto          string
	addr           string

	started  atomic.Bool
	exitDone sync.WaitGroup
}

// NewServer creates a new instance of the Server.
func NewServer(txFactory *transaction.Factory, plc plc.ReadPLC, node *node.Node, listenAddr string, handlerTimeout time.Duration) (*Server, error) {
	s := &Server{
		txFactory:      txFactory,
		plc:            plc,
		router:         http.NewServeMux(),
		node:           node,
		srv:            http.Server{Addr: listenAddr},
		handlerTimeout: handlerTimeout,
	}
	s.setupRoutes()

	handler := cors.Default().Handler(s.router)

	timeoutMsg, _ := json.Marshal(map[string]string{"message": "Internal server timeout"})

	handler = http.TimeoutHandler(handler, s.handlerTimeout, string(timeoutMsg))

	s.srv.Handler = handler

	parts := strings.SplitN(listenAddr, "://", 2)
	if len(parts) != 2 {
		return nil, stacktrace.NewError(
			"invalid listening address %s (use fully formed addresses, including the tcp:// or unix:// prefix)",
			listenAddr,
		)
	}
	s.proto, s.addr = parts[0], parts[1]

	return s, nil
}

// setupRoutes configures the routes for the server.
func (s *Server) setupRoutes() {
	s.router.HandleFunc("GET /{did}", s.makeDIDHandler(s.handleResolveDID))
	s.router.HandleFunc("POST /{did}", s.makeDIDHandler(s.handleCreatePLC))
	s.router.HandleFunc("GET /{did}/log", s.makeDIDHandler(s.handleGetPLCLog))
	s.router.HandleFunc("GET /{did}/log/audit", s.makeDIDHandler(s.handleGetPLCAuditLog))
	s.router.HandleFunc("GET /{did}/log/last", s.makeDIDHandler(s.handleGetLastOp))
	s.router.HandleFunc("GET /{did}/data", s.makeDIDHandler(s.handleGetPLCData))
	s.router.HandleFunc("GET /export", s.handleExport)

	s.router.HandleFunc("/debug/pprof/", pprof.Index)
	s.router.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
	s.router.HandleFunc("/debug/pprof/profile", pprof.Profile)
	s.router.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
	s.router.HandleFunc("/debug/pprof/trace", pprof.Trace)

	// Register handlers for specific profiles
	s.router.Handle("/debug/pprof/heap", pprof.Handler("heap"))
	s.router.Handle("/debug/pprof/goroutine", pprof.Handler("goroutine"))
	s.router.Handle("/debug/pprof/block", pprof.Handler("block"))
	s.router.Handle("/debug/pprof/threadcreate", pprof.Handler("threadcreate"))
}

// makeDIDHandler creates a wrapper handler that extracts DID from URL path
func (s *Server) makeDIDHandler(handler func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		handler(w, r, r.PathValue("did"))
	}
}

func (s *Server) Start() error {
	if !s.started.CompareAndSwap(false, true) {
		return stacktrace.NewError("server already started")
	}

	s.exitDone.Add(1)

	listener, err := net.Listen(s.proto, s.addr)
	if err != nil {
		return stacktrace.Propagate(err, "failed to listen on %v", s.addr)
	}

	go func() {
		defer s.exitDone.Done()

		if err := s.srv.Serve(listener); !errors.Is(err, http.ErrServerClosed) {
			log.Fatalf("ListenAndServe(): %v", err)
		}
	}()
	return nil
}

func (s *Server) Stop() error {
	ctx, cancel := context.WithTimeout(context.Background(), s.handlerTimeout)
	defer cancel()
	if err := s.srv.Shutdown(ctx); err != nil {
		return stacktrace.Propagate(err, "")
	}
	return nil
}

func (s *Server) Wait() {
	s.exitDone.Wait()
}

// handleResolveDID handles the GET /{did} endpoint.
func (s *Server) handleResolveDID(w http.ResponseWriter, r *http.Request, did string) {
	ctx := context.Background()
	doc, err := s.plc.Resolve(ctx, s.txFactory.ReadCommitted(), did)
	if handlePLCError(w, err, did) {
		return
	}

	wrapper := struct {
		Context []string `json:"@context"`
		didplc.Doc
	}{
		Context: []string{
			"https://www.w3.org/ns/did/v1",
			"https://w3id.org/security/multikey/v1",
		},
		Doc: doc,
	}

	for _, method := range doc.VerificationMethod {
		pub, err := atcrypto.ParsePublicMultibase(method.PublicKeyMultibase)
		if err != nil {
			// not the time to be doubting what the PLC implementation is giving us, just ignore
			continue
		}
		jwk, err := pub.JWK()
		if err != nil {
			// not the time to be doubting what the PLC implementation is giving us, just ignore
			continue
		}
		addToContext := ""
		switch jwk.Curve {
		case "P-256":
			addToContext = "https://w3id.org/security/suites/ecdsa-2019/v1"
		case "secp256k1":
			addToContext = "https://w3id.org/security/suites/secp256k1-2019/v1"
		default:
			continue
		}
		if !slices.Contains(wrapper.Context, addToContext) {
			wrapper.Context = append(wrapper.Context, addToContext)
		}
	}

	w.Header().Set("Content-Type", "application/did+ld+json")
	json.NewEncoder(w).Encode(wrapper)
}

// handleCreatePLC handles the POST /{did} endpoint.
func (s *Server) handleCreatePLC(w http.ResponseWriter, r *http.Request, did string) {
	var op didplc.OpEnum
	if err := json.NewDecoder(r.Body).Decode(&op); err != nil {
		sendErrorResponse(w, http.StatusBadRequest, "Invalid operation")
		return
	}

	if s.node == nil {
		// Validate only
		// Marshal the operation to JSON bytes for validation
		opBytes, err := json.Marshal(op)
		if err != nil {
			sendErrorResponse(w, http.StatusBadRequest, "Invalid operation")
			return
		}

		if err := s.plc.ValidateOperation(r.Context(), s.txFactory.ReadCommitted(), did, opBytes); err != nil {
			sendErrorResponse(w, http.StatusBadRequest, "Invalid operation")
			return
		}
		w.WriteHeader(http.StatusOK)
		return
	}

	uuid, err := uuid.NewRandom()
	if handlePLCError(w, err, "") {
		return
	}

	tx := abciapp.Transaction[abciapp.CreatePlcOpArguments]{
		Action: abciapp.TransactionActionCreatePlcOp,
		Arguments: abciapp.CreatePlcOpArguments{
			DID:       did,
			Operation: &op,
		},
	}

	txBytes, err := cbornode.DumpObject(tx)
	if handlePLCError(w, err, "") {
		return
	}

	// broadcastTxCommit will wait for inclusion, up until the TimeoutBroadcastTxCommit configured for the node, or until the context deadline expires
	// in practice we expect operations to be included in about one second
	result, err := broadcastTxCommit(r.Context(), s.node, uuid.String(), txBytes)
	// TODO more robust error handling
	if handlePLCError(w, err, "") {
		return
	}

	if result.CheckTx.Code != 0 {
		sendErrorResponse(w, http.StatusBadRequest, "Invalid operation")
		return
	}

	if result.TxResult.Code != 0 {
		sendErrorResponse(w, http.StatusBadRequest, "Invalid operation")
		return
	}

	w.WriteHeader(http.StatusOK)
}

// handleGetPLCLog handles the GET /{did}/log endpoint.
func (s *Server) handleGetPLCLog(w http.ResponseWriter, r *http.Request, did string) {
	ops, err := s.plc.OperationLog(r.Context(), s.txFactory.ReadCommitted(), did)
	if handlePLCError(w, err, did) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(ops)
}

// handleGetPLCAuditLog handles the GET /{did}/log/audit endpoint.
func (s *Server) handleGetPLCAuditLog(w http.ResponseWriter, r *http.Request, did string) {
	entries, err := s.plc.AuditLog(r.Context(), s.txFactory.ReadCommitted(), did)
	if handlePLCError(w, err, did) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(entries)
}

// handleGetLastOp handles the GET /{did}/log/last endpoint.
func (s *Server) handleGetLastOp(w http.ResponseWriter, r *http.Request, did string) {
	op, err := s.plc.LastOperation(r.Context(), s.txFactory.ReadCommitted(), did)
	if handlePLCError(w, err, did) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(op)
}

// handleGetPLCData handles the GET /{did}/data endpoint.
func (s *Server) handleGetPLCData(w http.ResponseWriter, r *http.Request, did string) {
	data, err := s.plc.Data(r.Context(), s.txFactory.ReadCommitted(), did)
	if handlePLCError(w, err, did) {
		return
	}

	resp := struct {
		DID                 string                      `json:"did"`
		RotationKeys        []string                    `json:"rotationKeys"`
		VerificationMethods map[string]string           `json:"verificationMethods"`
		AlsoKnownAs         []string                    `json:"alsoKnownAs"`
		Services            map[string]didplc.OpService `json:"services"`
	}{
		DID:                 did,
		RotationKeys:        data.RotationKeys,
		VerificationMethods: data.VerificationMethods,
		AlsoKnownAs:         data.AlsoKnownAs,
		Services:            data.Services,
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}

// handleExport handles the GET /export endpoint.
func (s *Server) handleExport(w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query()
	count := 1000 // The OpenAPI spec says the default is 10, but in practice the official server defaults to 1000
	if c := query.Get("count"); c != "" {
		if _, err := fmt.Sscanf(c, "%d", &count); err != nil {
			sendErrorResponse(w, http.StatusBadRequest, "Invalid count parameter")
			return
		}

		if count > 1000 {
			sendErrorResponse(w, http.StatusBadRequest, "Invalid count parameter")
			return
		}
	}

	afterStr := query.Get("after")
	after := uint64(0)
	var err error
	if afterStr != "" {
		after, err = strconv.ParseUint(afterStr, 10, 64)
		if err != nil {
			sendErrorResponse(w, http.StatusBadRequest, "Only sequence-based pagination is supported")
			return
		}
	}

	entries, err := s.plc.Export(r.Context(), s.txFactory.ReadCommitted(), after, count)
	if handlePLCError(w, err, "") {
		return
	}

	w.Header().Set("Content-Type", "application/jsonlines")

	type jsonEntry struct {
		Seq  uint64 `json:"seq"`
		Type string `json:"type"`
		*didplc.LogEntry
	}
	for _, entry := range entries {
		json.NewEncoder(w).Encode(jsonEntry{
			Seq:      entry.Seq,
			Type:     "sequenced_op",
			LogEntry: lo.ToPtr(entry.ToDIDPLCLogEntry()),
		})
	}
}

// handlePLCError handles errors from the PLC interface and sends the appropriate HTTP response.
func handlePLCError(w http.ResponseWriter, err error, did string) bool {
	if err == nil {
		return false
	}
	switch {
	case errors.Is(err, plc.ErrDIDNotFound):
		sendErrorResponse(w, http.StatusNotFound, fmt.Sprintf("DID not registered: %s", did))
	case errors.Is(err, plc.ErrDIDGone):
		sendErrorResponse(w, http.StatusGone, fmt.Sprintf("DID not available: %s", did))
	default:
		sendErrorResponse(w, http.StatusInternalServerError, "Internal server error")
	}
	return true
}

// sendErrorResponse sends an error response with the specified status code and message.
func sendErrorResponse(w http.ResponseWriter, statusCode int, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(statusCode)
	json.NewEncoder(w).Encode(map[string]string{"message": message})
}