authorization enforced on webpages

README.md

@@ -17,6 +17,7 @@
 ## Nice to haves
 
 - [ ] Drop in a good logger
+- [ ] log all errors caught by the http server
 
 ## Constraints
 

internal/consts/errors.go

@@ -3,6 +3,6 @@ package consts
 import "errors"
 
 var (
-	// TODO: use throught the database methods and the site template parsing to treat it as a 404 (not a redirect)
 	ErrNotFound = errors.New("not found")
+	ErrConflict = errors.New("conflict")
 )

internal/domains/accounts/accounts.go

@@ -25,6 +25,10 @@ type (
 		ID     int64
 		Email  string
 	}
+
+	OAuthUser struct {
+		UserID string
+	}
 )
 
 func NewStore(db *pgxpool.Pool) *Store {
@@ -52,6 +56,7 @@ func (db *Store) CreateAccount(ctx context.Context, userID, email string) (Accou
 				@user_id,
 				@email
 			)
+			ON CONFLICT DO NOTHING
 			RETURNING
 				account_id
 		`,
@@ -67,7 +72,7 @@ func (db *Store) CreateAccount(ctx context.Context, userID, email string) (Accou
 	acctID, err := pgx.CollectExactlyOneRow(rows, pgx.RowTo[int64])
 	if err != nil {
 		if errors.Is(err, pgx.ErrNoRows) {
-			return Account{}, consts.ErrNotFound
+			return Account{}, fmt.Errorf("account already exists: %w", consts.ErrConflict)
 		}
 		return Account{}, fmt.Errorf("failed to scan row: %w", err)
 	}
@@ -171,6 +176,55 @@ func (db *Store) GetAccountByEmail(ctx context.Context, email string) (Account,
 	}, nil
 }
 
+func (db *Store) GetUserAndAccountByAccessToken(ctx context.Context, accessToken string) (OAuthUser, *Account, error) {
+	rows, err := db.db.Query(
+		ctx,
+		`
+			SELECT
+				u.user_id,
+				a.account_id,
+				a.email
+			FROM oauth_users u
+			LEFT JOIN oauth_tokens t
+				ON u.user_id = id_token_subject
+			LEFT JOIN accounts a
+				USING (user_id)
+			WHERE access_token = @access_token
+		`,
+		pgx.NamedArgs{
+			"access_token": accessToken,
+		},
+	)
+	if err != nil {
+		return OAuthUser{}, nil, fmt.Errorf("failed to perform query: %w", err)
+	}
+
+	type Row struct {
+		User_ID    string
+		Account_ID *int64
+		Email      *string
+	}
+
+	r, err := pgx.CollectExactlyOneRow(rows, pgx.RowToStructByNameLax[Row])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return OAuthUser{}, nil, consts.ErrNotFound
+		}
+		return OAuthUser{}, nil, fmt.Errorf("failed to scan row: %w", err)
+	}
+
+	var acct *Account
+	if r.Account_ID != nil {
+		acct = &Account{
+			UserID: r.User_ID,
+			ID:     *r.Account_ID,
+			Email:  *r.Email,
+		}
+	}
+
+	return OAuthUser{UserID: r.User_ID}, acct, nil
+}
+
 func (db *StoreWithContext) CreateAccount(userID, email string) (Account, error) {
 	return db.db.CreateAccount(db.ctx, userID, email)
 }

internal/domains/authentication/auth.go

@@ -100,22 +100,16 @@ func (a *Authenticator) Exchange(ctx context.Context, state, code string) (acces
 		return "", time.Time{}, fmt.Errorf("failed to exchange an authorization code for a token: %w", err)
 	}
 
-	fmt.Println("TOKEN:", token)
-
 	idToken, err := a.VerifyIDToken(ctx, token)
 	if err != nil {
 		return "", time.Time{}, fmt.Errorf("failed to verify ID Token: %w", err)
 	}
 
-	fmt.Println("ID TOKEN:", idToken)
-
 	var claims map[string]any
 	if err := idToken.Claims(&claims); err != nil {
 		return "", time.Time{}, fmt.Errorf("Failed to obtain id token claims: %w", err)
 	}
 
-	fmt.Println("CUSTOM CLAIMS / PROFILE:", claims)
-
 	claimsJSON, _ := json.Marshal(claims)
 
 	// store the token, and the potentially new user

internal/site/accounts.go

@@ -1,9 +1,11 @@
 package site
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 
+	"ruben/inventory2/internal/consts"
 	"ruben/inventory2/internal/site/response"
 )
 
@@ -15,10 +17,14 @@ func (s *Server) createAccount(r *http.Request) (response.Response, error) {
 		return nil, response.BadRequest().Msg("no email provided")
 	}
 
-	userID := getAccessTokenClaims(ctx).Subject
+	userID := getIdentity(ctx).User.UserID
 
 	acct, err := s.accts.CreateAccount(ctx, userID, email)
 	if err != nil {
+		if errors.Is(err, consts.ErrConflict) {
+			return nil, response.Conflict().
+				Msg("user already has an account")
+		}
 		return nil, response.Errorf("failed to create account: %w", err)
 	}
 

internal/site/auth.go

@@ -5,24 +5,82 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"strconv"
+	"strings"
 	"time"
 
 	"ruben/inventory2/internal/consts"
+	"ruben/inventory2/internal/domains/accounts"
 	"ruben/inventory2/internal/domains/authentication"
 	"ruben/inventory2/internal/site/response"
 )
 
 // just keep this around long enough for testing auth middleware..
 func (s *Server) testAuthEndpoint(r *http.Request) (response.Response, error) {
-	fmt.Println("AUTH TEST SUCCESS:", getAccessTokenClaims(r.Context()))
+	fmt.Println("AUTH TEST SUCCESS:", getIdentity(r.Context()))
 
 	return response.TemporaryRedirect("/"), nil
 }
 
-type customClaimsKey struct{}
+type identity struct {
+	AccessToken string
+	Claims      authentication.AccessTokenClaims
+	User        accounts.OAuthUser
+	Account     *accounts.Account
+}
+
+func (s *Server) addIdentity(fn response.HandlerFunc) response.HandlerFunc {
+	return func(r *http.Request) (response.Response, error) {
+		r, err := s.addIdentityToRequest(r)
+		if err != nil {
+			return nil, err
+		}
+
+		return fn(r)
+	}
+}
+
+func (s *Server) addIdentityToRequest(r *http.Request) (*http.Request, error) {
+	ck, err := r.Cookie("access_token")
+	if err != nil {
+		return r, nil
+	}
+
+	ctx := r.Context()
+
+	accessToken := ck.Value
+
+	claims, expiration, err := s.auth.GetAccessTokenClaimsAndExpiration(ctx, accessToken)
+	if err != nil {
+		if errors.Is(err, consts.ErrNotFound) {
+			return r, nil
+		}
+
+		return r, response.Errorf("failed to load authentication details: %w", err)
+	}
+
+	if expiration.Before(time.Now()) {
+		return r, nil
+	}
+
+	user, acct, err := s.accts.GetUserAndAccountByAccessToken(ctx, accessToken)
+	if err != nil {
+		return r, response.Errorf("failed to load user and account defails: %w", err)
+	}
+
+	return r.WithContext(setIdentity(ctx, identity{
+		AccessToken: accessToken,
+		Claims:      claims,
+		User:        user,
+		Account:     acct,
+	})), nil
+}
+
+// TODO: after getting auth, consider making http handler functions take 'claims', etc, as function arguments
+//	- then consider doing the same with authorizationAssertions
 
 // auth middleware to verify access_token cookie and set custom claims in the request context
-func (s *Server) authenticate(f response.HandlerFunc) response.HandlerFunc {
+func (s *Server) authenticateAndAddIdentity(f response.HandlerFunc, assertions ...authorizationAssertions) response.HandlerFunc {
 	return func(r *http.Request) (response.Response, error) {
 		ck, err := r.Cookie("access_token")
 		if err != nil {
@@ -31,7 +89,9 @@ func (s *Server) authenticate(f response.HandlerFunc) response.HandlerFunc {
 
 		ctx := r.Context()
 
-		claims, expiration, err := s.auth.GetAccessTokenClaimsAndExpiration(ctx, ck.Value)
+		accessToken := ck.Value
+
+		claims, expiration, err := s.auth.GetAccessTokenClaimsAndExpiration(ctx, accessToken)
 		if err != nil {
 			if errors.Is(err, consts.ErrNotFound) {
 				return response.TemporaryRedirect("/"), nil
@@ -44,7 +104,32 @@ func (s *Server) authenticate(f response.HandlerFunc) response.HandlerFunc {
 			return response.TemporaryRedirect("/").Cookie(getExpiredCookie("access_token")), nil
 		}
 
-		return f(r.WithContext(setAccessTokenClaims(ctx, claims)))
+		user, acct, err := s.accts.GetUserAndAccountByAccessToken(ctx, accessToken)
+		if err != nil {
+			return nil, response.Errorf("failed to authorize: %w", err)
+		}
+
+		for _, as := range assertions {
+			if res, err := as(r); res != nil || err != nil {
+				return res, err
+			}
+		}
+
+		return f(r.WithContext(setIdentity(ctx, identity{
+			AccessToken: accessToken,
+			Claims:      claims,
+			User:        user,
+			Account:     acct,
+		})))
+	}
+}
+
+type authorizationAssertions = response.HandlerFunc
+
+// TODO: test this!
+func authorizeByMatchingAccountID_tmp(acctIDPathPosition int) authorizationAssertions {
+	return func(r *http.Request) (response.Response, error) {
+		return nil, authorizeByMatchingAccountID(r, acctIDPathPosition)
 	}
 }
 
@@ -67,13 +152,37 @@ func (s *Server) getAccessTokenClaims(r *http.Request) (authentication.AccessTok
 	return claims, true
 }
 
-// stores custom claims in request context
+type identityKey struct{}
-func setAccessTokenClaims(ctx context.Context, claims authentication.AccessTokenClaims) context.Context {
+
-	return context.WithValue(ctx, customClaimsKey{}, claims)
+// stores identity in request context
+func setIdentity(ctx context.Context, id identity) context.Context {
+	return context.WithValue(ctx, identityKey{}, id)
 }
 
-// get custom claims from request context
+// get identity from request context
-func getAccessTokenClaims(ctx context.Context) authentication.AccessTokenClaims {
+func getIdentity(ctx context.Context) identity {
-	c, _ := ctx.Value(customClaimsKey{}).(authentication.AccessTokenClaims)
+	id, _ := ctx.Value(identityKey{}).(identity)
-	return c
+	return id
+}
+
+func authorizeByMatchingAccountID(r *http.Request, acctIDPathPosition int) error {
+	pathParts := strings.Split(strings.TrimSuffix(strings.TrimPrefix(r.URL.Path, "/"), "/"), "/")
+	if len(pathParts) < acctIDPathPosition {
+		return fmt.Errorf("authorization failed due to unexpected path: %s", r.URL.Path)
+	}
+
+	part := pathParts[acctIDPathPosition-1]
+	acctID, err := strconv.ParseInt(part, 10, 64)
+	if err != nil {
+		return response.NotFound().
+			Msgf("account does not exist: %s", part)
+	}
+
+	id := getIdentity(r.Context())
+	if id.Account == nil || id.Account.ID != acctID {
+		return response.Unauthorized().
+			Msgf("user does not have access to account %d", acctID)
+	}
+
+	return nil
 }

internal/site/response/body.go

@@ -0,0 +1,84 @@
+package response
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"ruben/inventory2/internal/site/redirect"
+)
+
+type (
+	bodyRes struct {
+		body io.ReadCloser
+		res  Response
+	}
+)
+
+var _ Response = bodyRes{}
+
+func Body(body io.ReadCloser) Response {
+	return bodyRes{
+		body: body,
+	}
+}
+
+func (b bodyRes) String() string {
+	if b.res != nil {
+		return fmt.Sprintf(`{"body": %q, "nested": %s}`, b.body, b.res)
+	}
+	return fmt.Sprintf(`{"body": %q}`, b.body)
+}
+
+func (b bodyRes) wrap(res Response) Response {
+	b.res = res
+	return b
+}
+
+func (b bodyRes) Status(code int) Response {
+	return Status(code).wrap(b)
+}
+
+func (b bodyRes) Redirect(code redirect.Code, to string) Response {
+	return Redirect(code, to).wrap(b)
+}
+
+func (b bodyRes) JSON(body any) Response {
+	return JSON(body).wrap(b)
+}
+
+func (b bodyRes) Body(body io.ReadCloser) Response {
+	b.body = body
+	return b
+}
+
+func (b bodyRes) Cookie(ck http.Cookie) Response {
+	return Cookie(ck).wrap(b)
+}
+
+func (b bodyRes) getStatus() (int, bool) {
+	if b.res == nil {
+		return 0, false
+	}
+
+	return b.res.getStatus()
+}
+
+func (b bodyRes) getRedirect() (code redirect.Code, to string, ok bool) {
+	if b.res == nil {
+		return 0, "", false
+	}
+
+	return b.res.getRedirect()
+}
+
+func (b bodyRes) getBody() (body io.ReadCloser, ok bool, err error) {
+	return b.body, true, nil
+}
+
+func (b bodyRes) getCookies() []http.Cookie {
+	if b.res != nil {
+		return b.res.getCookies()
+	}
+
+	return nil
+}

internal/site/response/cookie.go

@@ -24,9 +24,9 @@ func Cookie(c http.Cookie) Response {
 
 func (c cookieRes) String() string {
 	if c.res != nil {
-		return fmt.Sprintf(`{"cookie": %q, "nested": %s}`, c.cookie, c.res)
+		return fmt.Sprintf(`{"cookie": %q, "nested": %s}`, &c.cookie, c.res)
 	}
-	return fmt.Sprintf(`{"cookie": %q}`, c.cookie)
+	return fmt.Sprintf(`{"cookie": %q}`, &c.cookie)
 }
 
 func (c cookieRes) wrap(res Response) Response {
@@ -46,6 +46,10 @@ func (c cookieRes) JSON(body any) Response {
 	return JSON(body).wrap(c)
 }
 
+func (c cookieRes) Body(body io.ReadCloser) Response {
+	return Body(body).wrap(c)
+}
+
 func (c cookieRes) Cookie(ck http.Cookie) Response {
 	return Cookie(ck).wrap(c)
 }

internal/site/response/error.go

@@ -48,6 +48,12 @@ func Forbidden() ErrorResponse {
 	}
 }
 
+func Conflict() ErrorResponse {
+	return ErrorResponse{
+		status: http.StatusConflict,
+	}
+}
+
 // builder pattern implementation
 
 func (e ErrorResponse) Msg(msg string) ErrorResponse {
@@ -55,6 +61,11 @@ func (e ErrorResponse) Msg(msg string) ErrorResponse {
 	return e
 }
 
+func (e ErrorResponse) Msgf(format string, args ...any) ErrorResponse {
+	e.msg = fmt.Sprintf(format, args...)
+	return e
+}
+
 func (e ErrorResponse) Status(status int) ErrorResponse {
 	e.status = status
 	return e
@@ -92,33 +103,33 @@ func (e ErrorResponse) Unwrap() error {
 
 // nested response value resolution
 
-func (e ErrorResponse) getStatus() (int, bool) {
+func (e ErrorResponse) GetStatus() (int, bool) {
 	if e.status != 0 {
 		return e.status, true
 	}
 
-	ce, ok := getError(e.err)
+	ce, ok := GetError(e.err)
 	if ok {
-		return ce.getStatus()
+		return ce.GetStatus()
 	}
 
 	return 0, false
 }
 
-func (e ErrorResponse) getMsg() (string, bool) {
+func (e ErrorResponse) GetMsg() (string, bool) {
 	if e.msg != "" {
 		return e.msg, true
 	}
 
-	ce, ok := getError(e.err)
+	ce, ok := GetError(e.err)
 	if ok {
-		return ce.getMsg()
+		return ce.GetMsg()
 	}
 
 	return "", false
 }
 
-func getError(err error) (e ErrorResponse, ok bool) {
+func GetError(err error) (e ErrorResponse, ok bool) {
 	ok = errors.As(err, &e)
 	return e, ok
 }

internal/site/response/json.go

@@ -49,6 +49,10 @@ func (j jsonRes) JSON(body any) Response {
 	return j
 }
 
+func (j jsonRes) Body(body io.ReadCloser) Response {
+	return Body(body).wrap(j)
+}
+
 func (j jsonRes) Cookie(ck http.Cookie) Response {
 	return Cookie(ck).wrap(j)
 }

internal/site/response/redirect.go

@@ -87,6 +87,10 @@ func (r redirectRes) JSON(body any) Response {
 	return JSON(body).wrap(r)
 }
 
+func (r redirectRes) Body(body io.ReadCloser) Response {
+	return Body(body).wrap(r)
+}
+
 func (r redirectRes) Cookie(ck http.Cookie) Response {
 	return Cookie(ck).wrap(r)
 }

internal/site/response/response.go

@@ -11,6 +11,7 @@ type (
 	Response interface {
 		Status(int) Response
 		Redirect(code redirect.Code, to string) Response
+		Body(io.ReadCloser) Response
 		JSON(any) Response
 		Cookie(http.Cookie) Response
 

internal/site/response/status.go

@@ -48,6 +48,10 @@ func (s statusRes) JSON(body any) Response {
 	return JSON(body).wrap(s)
 }
 
+func (s statusRes) Body(body io.ReadCloser) Response {
+	return Body(body).wrap(s)
+}
+
 func (s statusRes) Cookie(ck http.Cookie) Response {
 	return Cookie(ck).wrap(s)
 }

internal/site/response/write.go

@@ -46,8 +46,8 @@ func Write(w http.ResponseWriter, r *http.Request, res Response) {
 func WriteError(w http.ResponseWriter, err error) {
 	var status int
 
-	if e, ok := getError(err); ok {
+	if e, ok := GetError(err); ok {
-		if status, ok = e.getStatus(); !ok {
+		if status, ok = e.GetStatus(); !ok {
 			status = http.StatusInternalServerError
 		}
 	}

internal/site/site.go

@@ -19,7 +19,7 @@ import (
 )
 
 type Server struct {
-	mux        *http.ServeMux
+	http.Handler
 	contentDir string
 	templater  *templater.Templater
 	rawEvents  *raw_events.Store
@@ -35,8 +35,9 @@ func NewServer(
 	etsy *etsy_platform.Platform,
 	auth *authentication.Authenticator,
 ) *Server {
+	mux := http.NewServeMux()
+
 	s := &Server{
-		mux:        http.NewServeMux(),
 		contentDir: contentDir,
 		templater: templater.NewTemplater(
 			contentDir+"/templates",
@@ -91,36 +92,32 @@ func NewServer(
 
 	// api routes
 
-	s.mux.HandleFunc("GET /login", response.Handler(s.loginPage))
+	mux.Handle("GET /login", response.Handler(s.loginPage))
-	s.mux.HandleFunc("GET /login/callback", response.Handler(s.loginCallback))
+	mux.Handle("GET /login/callback", response.Handler(s.loginCallback))
-	s.mux.HandleFunc("GET /logout", response.Handler(s.logoutPage))
+	mux.Handle("GET /logout", response.Handler(s.logoutPage))
-	s.mux.Handle("POST /accounts", response.Handler(s.authenticate(s.createAccount)))
+	mux.Handle("POST /accounts", response.Handler(s.authenticateAndAddIdentity(s.createAccount)))
 
 	// TODO: eliminate once no longer used.
-	s.mux.HandleFunc("POST /login", response.Handler(s.login))
+	mux.HandleFunc("POST /login", response.Handler(s.login))
 
 	// TODO: get rid of this, once we're confident this isn't needed...
-	s.mux.Handle("GET /test-auth", response.Handler(s.authenticate(s.testAuthEndpoint)))
+	mux.Handle("GET /test-auth", response.Handler(s.authenticateAndAddIdentity(s.testAuthEndpoint)))
 
 	// webpage content
 
 	scfs := http.FileServer(http.Dir(contentDir + "/scripts"))
-	s.mux.Handle("GET /scripts/", http.StripPrefix("/scripts", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	mux.Handle("GET /scripts/", http.StripPrefix("/scripts", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/javascript")
 		if path.Ext(r.URL.Path) == ".gz" {
 			w.Header().Set("Content-Encoding", "gzip")
 		}
 		scfs.ServeHTTP(w, r)
 	})))
-	s.mux.Handle("GET /styles/", http.StripPrefix("/styles", http.FileServer(http.Dir(contentDir+"/styles"))))
+	mux.Handle("GET /styles/", http.StripPrefix("/styles", http.FileServer(http.Dir(contentDir+"/styles"))))
 
-	// TODO: put auth on individual templates, somehow...
+	mux.HandleFunc("GET /", response.Handler(s.addIdentity(s.serveTemplates)))
-	s.mux.HandleFunc("GET /", s.serveTemplates)
+
+	s.Handler = mux
 
 	return s
 }
-
-// http.Handler implementation
-func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	s.mux.ServeHTTP(w, r)
-}

internal/site/templates.go

@@ -1,38 +1,28 @@
 package site
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
 	"os"
 	"path"
 	"path/filepath"
+	"ruben/inventory2/internal/site/response"
 	"strings"
-
-	"ruben/inventory2/internal/domains/accounts"
 )
 
 // GET /
-func (s *Server) serveTemplates(w http.ResponseWriter, r *http.Request) {
+func (s *Server) serveTemplates(r *http.Request) (response.Response, error) {
 	ctx := r.Context()
 	name, pathParams := getPageTemplateNameForURL(r.URL)
 
-	var (
+	templateArgs := []any{
-		acct   accounts.Account
-		userID string
-	)
-	claims, ok := s.getAccessTokenClaims(r)
-	if ok {
-		userID = claims.Subject
-		acct, _ = s.accts.GetAccountByUserID(ctx, userID)
-	}
-
-	b, err := s.templater.ExecutePage(
-		name,
 		"Request",
 		r,
-		// add services here
+		// add services and data here
 		"RawEvents",
 		s.rawEvents.WithContext(ctx),
 		"URLCalc",
@@ -44,37 +34,26 @@ func (s *Server) serveTemplates(w http.ResponseWriter, r *http.Request) {
 		"Etsy",
 		s.etsy.WithContext(ctx),
 
-		// claims
+		// TODO: apply auth to all templates needed!
-		"Claims",
+		// auth tooling
-		claims,
+		/*
-		"UserID",
+			AccessToken string
-		userID,
+			Claims      authentication.AccessTokenClaims
-		"Account",
+			User        accounts.OAuthUser
-		acct,
+			Account     *accounts.Account
-	)
+		*/
+		"Identity",
+		getIdentity(r.Context()),
+		"Auth",
+		newTemplateAuthenticator(r),
+	}
+
+	b, err := s.templater.ExecutePage(name, templateArgs...)
 	if err != nil {
-		// TODO: handle 401
+		return s.handleTemplateError(err, templateArgs...)
-
-		// TODO: handle 403
-
-		// TODO: handle 404
-		if isFileNotFoundError(err) {
 	}
 
-		// TODO: handle 'not found' as a 404?
+	return response.Body(io.NopCloser(bytes.NewBuffer(b))), nil
-		fmt.Println("[ERROR]: failed to load or parse layout template:", err)
-		http.Redirect(w, r, "/", http.StatusTemporaryRedirect)
-		return
-	}
-
-	w.Write(b)
-}
-
-func isFileNotFoundError(err error) bool {
-	var pe *os.PathError
-	isPathErr := errors.As(err, &pe)
-
-	return isPathErr && pe.Err != nil && pe.Err.Error() == "no such file or directory"
 }
 
 // TODO: clean this up...
@@ -142,6 +121,63 @@ func getMatchingGlobPatternsCapturingFilepathIncludingParametrizedFilepaths(file
 	}
 }
 
+func (s *Server) handleTemplateError(err error, templateArgs ...any) (response.Response, error) {
+	code := getHTTPStatusCode(err)
+
+	if code == http.StatusNotFound ||
+		code == http.StatusForbidden ||
+		code == http.StatusUnauthorized ||
+		isFileNotFoundError(err) {
+
+		b, err := s.templater.ExecutePage("not-found", templateArgs...)
+		if err != nil {
+			fmt.Println("failed to render not found page:", err)
+			return nil, response.NotFound().
+				Wrap(err).
+				Msg("resource not found")
+		}
+
+		return response.Body(io.NopCloser(bytes.NewBuffer(b))), nil
+	}
+
+	if code == http.StatusConflict {
+		b, err := s.templater.ExecutePage("conflict", templateArgs...)
+		if err != nil {
+			fmt.Println("failed to render conflict page:", err)
+			return nil, response.Conflict().
+				Wrap(err).
+				Msg("conflict")
+		}
+
+		return response.Body(io.NopCloser(bytes.NewBuffer(b))), nil
+	}
+
+	return nil, fmt.Errorf("failed to render page: %w", err)
+}
+
+func isFileNotFoundError(err error) bool {
+	var pe *os.PathError
+	isPathErr := errors.As(err, &pe)
+
+	return isPathErr && pe.Err != nil && pe.Err.Error() == "no such file or directory"
+}
+
+func getHTTPStatusCode(err error) int {
+	rerr, ok := response.GetError(err)
+	if !ok {
+		return http.StatusInternalServerError
+	}
+
+	code, ok := rerr.GetStatus()
+	if !ok {
+		return http.StatusInternalServerError
+	}
+
+	return code
+}
+
+// template tooling
+
 type URLCalculator struct {
 	url *url.URL
 }
@@ -161,3 +197,22 @@ func (c URLCalculator) SetQueryParam(k string, v any) string {
 
 	return u.String()
 }
+
+// template authenticator
+
+type templateAuthenticator struct {
+	req *http.Request
+}
+
+func newTemplateAuthenticator(req *http.Request) *templateAuthenticator {
+	return &templateAuthenticator{
+		req: req,
+	}
+}
+
+// templateAuthorizationFunc these shouild always return an empty string
+type templateAuthorizationFunc = func() (string, error)
+
+func (a *templateAuthenticator) ByMatchingAccountID(acctIDPathPosition int) (string, error) {
+	return "", authorizeByMatchingAccountID(a.req, acctIDPathPosition)
+}

internal/site/templates/component_bodies/nav_bar.html.tmpl

@@ -2,7 +2,19 @@
 
 {{/* "dot" . */}}
 
-<nav>
+<nav
+	style="
+		margin: 0;
+		padding: 1em;
+		background-color: #bdf;
+
+		font-size: 1.25em;
+
+		display: flex;
+		flex-direction: column;
+		align-items: center;
+	"
+>
 	<ul>
 		<li>
 			<a href="/">
@@ -10,22 +22,38 @@
 			</a>
 		</li>
 
-	{{- if .dot.UserID }}
+	{{/* */}}
+	{{- $userID := .dot.Identity.User.UserID }}
+	{{- $acct := .dot.Identity.Account }}
+	{{- $acctID := 0 }}
+	{{- if $acct }}
+		{{- $acctID = $acct.ID }}
+	{{- end }}
+
+	{{- if not $userID }}
 
 		<li>
-			<a href="/accounts/{{.dot.Account.ID}}">
+			<a href="/login">
+				Log In / Sign Up
+			</a>
+		</li>
+
+	{{- else if $acctID }}
+
+		<li>
+			<a href="/accounts/{{$acctID}}">
 				Account
 			</a>
 		</li>
 
 		<li>
-			<a href="/accounts/{{.dot.Account.ID}}/reports">
+			<a href="/accounts/{{$acctID}}/reports">
 				Reports
 			</a>
 		</li>
 
 		<li>
-			<a href="/accounts/{{.dot.Account.ID}}/inventory">
+			<a href="/accounts/{{$acctID}}/inventory">
 				Inventory
 			</a>
 		</li>
@@ -36,14 +64,6 @@
 			</a>
 		</li>
 
-	{{- else }}
-
-		<li>
-			<a href="/login">
-				Log In / Sign Up
-			</a>
-		</li>
-
 	{{- end }}
 	</ul>
 </nav>

internal/site/templates/layout.html.tmpl

@@ -38,22 +38,38 @@
 						</a>
 					</li>
 
-				{{- if .UserID }}
+				{{/* */}}
+				{{- $userID := .Identity.User.UserID }}
+				{{- $acct := .Identity.Account }}
+				{{- $acctID := 0 }}
+				{{- if $acct }}
+					{{- $acctID = $acct.ID }}
+				{{- end }}
+
+				{{- if not $userID }}
 
 					<li>
-						<a href="/accounts/{{.Account.ID}}">
+						<a href="/login">
+							Log In / Sign Up
+						</a>
+					</li>
+
+				{{- else if $acctID }}
+
+					<li>
+						<a href="/accounts/{{$acctID}}">
 							Account
 						</a>
 					</li>
 
 					<li>
-						<a href="/accounts/{{.Account.ID}}/reports">
+						<a href="/accounts/{{$acctID}}/reports">
 							Reports
 						</a>
 					</li>
 
 					<li>
-						<a href="/accounts/{{.Account.ID}}/inventory">
+						<a href="/accounts/{{$acctID}}/inventory">
 							Inventory
 						</a>
 					</li>
@@ -64,14 +80,6 @@
 						</a>
 					</li>
 
-				{{- else }}
-
-					<li>
-						<a href="/login">
-							Log In / Sign Up
-						</a>
-					</li>
-
 				{{- end }}
 				</ul>
 			</nav>

internal/site/templates/page_bodies/accounts/{acctID}/index.html.tmpl

@@ -1,16 +1,20 @@
+{{- .Auth.ByMatchingAccountID 2 }}
+
 {{- define "title" }} Inventory++ Account {{ end }}
 
-<h1>Account: {{ .Account.Email }}</h1>
+{{- $acctID := .Identity.Account }}
 
-{{- $etsyUser := .Etsy.GetUserPointerByAccountID .Account.ID }}
+<h1>Account: {{ $acctID.Email }}</h1>
+
+{{- $etsyUser := .Etsy.GetUserPointerByAccountID $acctID.ID }}
 {{- if $etsyUser }}
 	<h3>Etsy User: {{ $etsyUser.UserID }}; Shop ID: {{ $etsyUser.ShopID }}</h3>
 {{- else }}
 	<h3>
 		{{/* TODO: create this link dynamically, not EVERYTIME THE PAGE IS LOADED */}}
-		<a href="{{ .Etsy.GenerateConnectionURLForNewAccount .Account.ID }}">
+		<a href="{{ .Etsy.GenerateConnectionURLForNewAccount $acctID.ID }}">
 			Link Your Etsy Store!
 		</a>
 	</h3>
 {{- end }}
-<h2><a href="/accounts/{{.Account.ID}}/reports">View Reports</a></h2>
+<h2><a href="/accounts/{{$acctID.ID}}/reports">View Reports</a></h2>

internal/site/templates/page_bodies/accounts/{acctID}/inventory.html.tmpl

@@ -1,3 +1,5 @@
+{{- .Auth.ByMatchingAccountID 2 }}
+
 {{- define "title" }} Inventory++ {{ end }}
 
 <h1>Inventory management page: WIP</h1>

internal/site/templates/page_bodies/accounts/{acctID}/reports.html.tmpl

@@ -1,3 +1,5 @@
+{{- .Auth.ByMatchingAccountID 2 }}
+
 {{- define "title" }} Inventory++ Reports {{ end }}
 
 {{ $storeID := .Request.URL.Query.Get "store-id" }}

internal/site/templates/page_bodies/conflict.html.tmpl

@@ -0,0 +1,11 @@
+{{- define "title" }} Inventory++ Invalid Link {{ end }}
+
+
+<section>
+	Invalid Link: {{ .Request.URL.Path }}
+</section>
+
+
+<section>
+	<a href="/">Return Home</a>
+</section>

internal/site/templates/page_bodies/index.html.tmpl

@@ -1,6 +1,6 @@
 <h1>Home</h1>
 
-{{- if and .UserID (not .Account.ID) }}
+{{- if and .Identity.User.UserID (not .Identity.Account) }}
 	<h2><a href="/account-creation">New Account</a></h2>
 {{- end }}
 

internal/site/templates/page_bodies/not-found.html.tmpl

@@ -0,0 +1,11 @@
+{{- define "title" }} Inventory++ Page Not Found {{ end }}
+
+
+<section>
+	Page Not Found: {{ .Request.URL.Path }}
+</section>
+
+
+<section>
+	<a href="/">Return Home</a>
+</section>