feat: add rfc8908 basic api endpoint implementation

rfc8908/handler.go

@@ -0,0 +1,72 @@
+package rfc8908
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/pkg/errors"
+)
+
+type IsCaptiveFunc func(*http.Request) (bool, error)
+
+// RFC8098
+// See https://tools.ietf.org/html/rfc8908 - "5.  API State Structure"
+type Response struct {
+	Captive          bool   `json:"captive"`
+	UserPortalURL    string `json:"user-portal-url,omitempty"`
+	VenueInfoURL     string `json:"venue-info-url,omitempty"`
+	CanExtendSession *bool  `json:"can-extend-session,omitempty"`
+	SecondsRemaining *int   `json:"seconds-remaining,omitempty"`
+	BytesRemaining   *int   `json:"bytes-remaining,omitempty"`
+}
+
+// Handler returns a basic implementation of a Captive Portal API endpoint
+// as described in the IETF 8908 RFC (https://tools.ietf.org/html/rfc8908)
+func Handler(isCaptive IsCaptiveFunc, opts ...OptionsFunc) http.HandlerFunc {
+	options := DefaultOptions()
+
+	for _, o := range opts {
+		o(options)
+	}
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		isCaptive, err := isCaptive(r)
+		if err != nil {
+			panic(errors.Wrap(err, "could not retrieve client id"))
+		}
+
+		ctx := r.Context()
+
+		var bytesRemaining *int
+		if options.BytesRemaining != nil {
+			bytesRemaining, err = options.BytesRemaining(ctx)
+			if err != nil {
+				panic(errors.Wrap(err, "could not retrieve client remaining bytes"))
+			}
+		}
+
+		var secondsRemaining *int
+		if options.SecondsRemaining != nil {
+			secondsRemaining, err = options.SecondsRemaining(ctx)
+			if err != nil {
+				panic(errors.Wrap(err, "could not retrieve client remaining seconds"))
+			}
+		}
+
+		w.Header().Add("Content-Type", "application/captive+json")
+
+		encoder := json.NewEncoder(w)
+		res := &Response{
+			Captive:          isCaptive,
+			VenueInfoURL:     options.VenueInfoURL,
+			UserPortalURL:    options.UserPortalURL,
+			CanExtendSession: options.CanExtendSession,
+			SecondsRemaining: secondsRemaining,
+			BytesRemaining:   bytesRemaining,
+		}
+
+		if err := encoder.Encode(res); err != nil {
+			panic(errors.WithStack(err))
+		}
+	}
+}

rfc8908/option.go

@@ -0,0 +1,51 @@
+package rfc8908
+
+import "context"
+
+type Options struct {
+	UserPortalURL    string
+	VenueInfoURL     string
+	CanExtendSession *bool
+	SecondsRemaining SecondsRemainingFunc
+	BytesRemaining   BytesRemainingFunc
+}
+
+type OptionsFunc func(*Options)
+
+type SecondsRemainingFunc func(context.Context) (*int, error)
+
+type BytesRemainingFunc func(context.Context) (*int, error)
+
+func DefaultOptions() *Options {
+	return &Options{}
+}
+
+func WithUserPortalURL(userPortalURL string) OptionsFunc {
+	return func(o *Options) {
+		o.UserPortalURL = userPortalURL
+	}
+}
+
+func WithVenueInfoURL(venueInfoURL string) OptionsFunc {
+	return func(o *Options) {
+		o.VenueInfoURL = venueInfoURL
+	}
+}
+
+func WithCanExtendSession(canExtend bool) OptionsFunc {
+	return func(o *Options) {
+		o.CanExtendSession = &canExtend
+	}
+}
+
+func WithSecondsRemainingFunc(fn SecondsRemainingFunc) OptionsFunc {
+	return func(o *Options) {
+		o.SecondsRemaining = fn
+	}
+}
+
+func WithBytesRemainingFunc(fn BytesRemainingFunc) OptionsFunc {
+	return func(o *Options) {
+		o.BytesRemaining = fn
+	}
+}