package api

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"

	kithttp "github.com/go-kit/kit/transport/http"
	"github.com/go-zoo/bone"
	"github.com/mainflux/mainflux"
	"github.com/mainflux/mainflux/internal/apiutil"
	"github.com/mainflux/mainflux/logger"
	"github.com/mainflux/mainflux/pkg/errors"
	"github.com/mainflux/mainflux/provision"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

const (
	contentType = "application/json"
)

// MakeHandler returns a HTTP handler for API endpoints.
func MakeHandler(svc provision.Service, logger logger.Logger, instanceID string) http.Handler {
	opts := []kithttp.ServerOption{
		kithttp.ServerErrorEncoder(apiutil.LoggingErrorEncoder(logger, encodeError)),
	}

	r := bone.New()

	r.Post("/mapping", kithttp.NewServer(
		doProvision(svc),
		decodeProvisionRequest,
		encodeResponse,
		opts...,
	))

	r.Get("/mapping", kithttp.NewServer(
		getMapping(svc),
		decodeMappingRequest,
		encodeResponse,
		opts...,
	))

	r.Handle("/metrics", promhttp.Handler())
	r.GetFunc("/health", mainflux.Health("provision", instanceID))

	return r
}

func encodeResponse(_ context.Context, w http.ResponseWriter, response interface{}) error {
	w.Header().Set("Content-Type", contentType)

	if ar, ok := response.(mainflux.Response); ok {
		for k, v := range ar.Headers() {
			w.Header().Set(k, v)
		}

		w.WriteHeader(ar.Code())

		if ar.Empty() {
			return nil
		}
	}

	return json.NewEncoder(w).Encode(response)
}

func decodeProvisionRequest(_ context.Context, r *http.Request) (interface{}, error) {
	if r.Header.Get("Content-Type") != contentType {
		return nil, errors.Wrap(apiutil.ErrValidation, apiutil.ErrUnsupportedContentType)
	}

	req := provisionReq{token: apiutil.ExtractBearerToken(r)}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		return nil, errors.Wrap(apiutil.ErrValidation, err)
	}

	return req, nil
}

func decodeMappingRequest(_ context.Context, r *http.Request) (interface{}, error) {
	if r.Header.Get("Content-Type") != contentType {
		return nil, errors.Wrap(apiutil.ErrValidation, apiutil.ErrUnsupportedContentType)
	}

	req := mappingReq{token: apiutil.ExtractBearerToken(r)}

	return req, nil
}

func encodeError(_ context.Context, err error, w http.ResponseWriter) {
	var wrapper error
	if errors.Contains(err, apiutil.ErrValidation) {
		wrapper, err = errors.Unwrap(err)
	}

	switch {
	case errors.Contains(err, errors.ErrAuthentication),
		errors.Contains(err, apiutil.ErrBearerToken):
		w.WriteHeader(http.StatusUnauthorized)
	case errors.Contains(err, apiutil.ErrUnsupportedContentType):
		w.WriteHeader(http.StatusUnsupportedMediaType)
	case errors.Contains(err, errors.ErrMalformedEntity),
		errors.Contains(err, apiutil.ErrMissingID),
		errors.Contains(err, apiutil.ErrBearerKey):
		w.WriteHeader(http.StatusBadRequest)
	case errors.Contains(err, errors.ErrConflict):
		w.WriteHeader(http.StatusConflict)
	default:
		w.WriteHeader(http.StatusInternalServerError)
	}

	if wrapper != nil {
		err = errors.Wrap(wrapper, err)
	}

	if errorVal, ok := err.(errors.Error); ok {
		w.Header().Set("Content-Type", contentType)

		errMsg := errorVal.Msg()
		if errorVal.Err() != nil {
			errMsg = fmt.Sprintf("%s : %s", errMsg, errorVal.Err().Msg())
		}

		if err := json.NewEncoder(w).Encode(apiutil.ErrorRes{Err: errMsg}); err != nil {
			w.WriteHeader(http.StatusInternalServerError)
		}
	}
}