Dialectic.Backend/internal/httpapi/routes.go

package httpapi

import (
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	chimw "github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/cors"
	"github.com/jmoiron/sqlx"

	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/auth"
	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/config"
	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/httpapi/handlers"
	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/store"
)

// Mount returns the root router with all v2 endpoints wired. Owners of
// individual middleware chains:
//
//   - /api/healthz             : public (no auth)
//   - /api/topics              : mixed — list/get optional auth (anon
//     sees public only); create requires CallerAgent or CallerUser
//   - /api/topics/{id}/signups : agent-only (CallerAgent)
//
// Browser-side OIDC and agent-side bearer middlewares co-exist on the
// same route by being "optional auth" — if either succeeds, Caller is
// attached; otherwise the handler sees anonymous and decides whether
// to 401 or fall through to public behavior.
func Mount(cfg *config.Config, db *sqlx.DB, version string) http.Handler {
	r := chi.NewRouter()

	// Boilerplate middleware — these run on every request.
	r.Use(chimw.RealIP)
	r.Use(chimw.RequestID)
	r.Use(chimw.Logger)
	r.Use(chimw.Recoverer)
	r.Use(chimw.Timeout(30 * time.Second))
	r.Use(cors.Handler(cors.Options{
		AllowedOrigins:   cfg.CORSAllowOrigins,
		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "x-dev-bypass"},
		ExposedHeaders:   []string{},
		AllowCredentials: true,
		MaxAge:           300,
	}))

	// Auth middlewares — composed as "try agent, then user, else pass anonymous".
	optionalAuth := optionalAuthChain(db, cfg)
	requireAgent := auth.AgentAPIKey(db, cfg.AgentAPIKeyPepper) // strict bearer
	requireAnyAuth := requireAnyAuthChain(db, cfg)

	// Handler instances.
	topicStore := store.NewTopicStore(db)
	signupStore := store.NewSignupStore(db)
	health := handlers.NewHealthHandler(db, version)
	topicsH := handlers.NewTopicsHandler(topicStore)
	signupsH := handlers.NewSignupsHandler(topicStore, signupStore)

	// Routes.
	r.Route("/api", func(r chi.Router) {
		r.Get("/healthz", health.Healthz)

		// Topics: list+get optional-auth (visibility-gated by handler);
		// create+visibility-flip require any auth.
		r.Group(func(r chi.Router) {
			r.Use(optionalAuth)
			r.Get("/topics", topicsH.List)
			r.Get("/topics/{id}", topicsH.Get)
		})
		r.Group(func(r chi.Router) {
			r.Use(requireAnyAuth)
			r.Post("/topics", topicsH.Create)
			r.Put("/topics/{id}/visibility", topicsH.SetVisibility)
		})

		// Signups: agent-only.
		r.Group(func(r chi.Router) {
			r.Use(requireAgent)
			r.Post("/topics/{id}/signups", signupsH.Create)
		})
		// List signups: any authenticated caller.
		r.Group(func(r chi.Router) {
			r.Use(requireAnyAuth)
			r.Get("/topics/{id}/signups", signupsH.List)
		})
	})

	return r
}

// optionalAuthChain: if either auth method succeeds, attach Caller;
// otherwise let the request through anonymous. Handlers decide what
// to do with anonymous (typically: serve public subset, hide private).
func optionalAuthChain(db *sqlx.DB, cfg *config.Config) func(http.Handler) http.Handler {
	agent := auth.AgentAPIKey(db, cfg.AgentAPIKeyPepper)
	oidc := auth.OIDCBrowser(cfg.IsDev(), cfg.OIDCDevBypassToken)
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			// Bearer present → try agent path; on success it ServeHTTPs next.
			// On failure it 401s, which we want to demote to "anonymous" for
			// optional auth. The pattern is: capture the response; if it's
			// 401, fall through to OIDC; if OIDC also 401s, finally fall
			// through to next (anonymous).
			if r.Header.Get("authorization") != "" {
				rw := &captureWriter{ResponseWriter: w}
				agent(next).ServeHTTP(rw, r)
				if rw.status != http.StatusUnauthorized {
					return
				}
				// reset captured state and try anon path (since OIDC
				// won't apply if there's no cookie / bypass header)
			}
			if r.Header.Get("x-dev-bypass") != "" {
				rw := &captureWriter{ResponseWriter: w}
				oidc(next).ServeHTTP(rw, r)
				if rw.status != http.StatusUnauthorized {
					return
				}
			}
			// Anonymous — call next with no Caller attached.
			next.ServeHTTP(w, r)
		})
	}
}

// requireAnyAuthChain: 401 if neither agent nor user auth succeeds.
func requireAnyAuthChain(db *sqlx.DB, cfg *config.Config) func(http.Handler) http.Handler {
	agent := auth.AgentAPIKey(db, cfg.AgentAPIKeyPepper)
	oidc := auth.OIDCBrowser(cfg.IsDev(), cfg.OIDCDevBypassToken)
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			if r.Header.Get("authorization") != "" {
				rw := &captureWriter{ResponseWriter: w}
				agent(next).ServeHTTP(rw, r)
				if rw.status != http.StatusUnauthorized {
					return
				}
			}
			oidc(next).ServeHTTP(w, r)
		})
	}
}

// captureWriter records the status so the optional-auth chain can
// distinguish "401 from inner middleware (try next)" from "actual
// response from handler (deliver)". Body bytes are passed through
// when status != 401.
type captureWriter struct {
	http.ResponseWriter
	status      int
	wroteHeader bool
	suppressing bool
}

func (c *captureWriter) WriteHeader(s int) {
	c.status = s
	c.wroteHeader = true
	if s == http.StatusUnauthorized {
		// don't actually write — we may fall through
		c.suppressing = true
		return
	}
	c.ResponseWriter.WriteHeader(s)
}

func (c *captureWriter) Write(b []byte) (int, error) {
	if c.suppressing {
		// swallow; caller will fall through to next chain step
		return len(b), nil
	}
	if !c.wroteHeader {
		c.ResponseWriter.WriteHeader(http.StatusOK)
		c.wroteHeader = true
	}
	return c.ResponseWriter.Write(b)
}