Merge pull request #11 from runreveal/rpc

Experimental RPC Framework

Author: abraithwaite

loader/loader.go

@@ -42,7 +42,8 @@ type Registry[T any] struct {
 }
 
 var registry = struct {
-	// map[type]registry[T] where T is variadic
+	// map[typeString]registry[T] where T is variadic and typeString is:
+	// reflect.TypeOf(T).String()
 	m map[string]any
 	sync.RWMutex
 }{

rpc/README.md

@@ -0,0 +1,8 @@
+
+RPC is a framework for easily creating HTTP APIs in Go.
+
+It handles serialization, validation, documentation and client generation.
+
+It has escape hatches to access the standard Go HTTP request and response
+objects.
+

rpc/context.go

@@ -0,0 +1,29 @@
+package rpc
+
+import (
+	"context"
+	"net/http"
+)
+
+type contextKey struct{ name string }
+
+var (
+	reqContextKey  = contextKey{name: "requestKey"}
+	respContextKey = contextKey{name: "responseKey"}
+)
+
+func Request(ctx context.Context) *http.Request {
+	v, ok := ctx.Value(reqContextKey).(*http.Request)
+	if !ok {
+		panic("request not set on context. ensure handler is wrapped")
+	}
+	return v
+}
+
+func ResponseWriter(ctx context.Context) http.ResponseWriter {
+	v, ok := ctx.Value(respContextKey).(*responseWrapper)
+	if !ok {
+		panic("response not set on context. ensure handler is wrapped")
+	}
+	return v
+}

rpc/errors.go

@@ -0,0 +1,202 @@
+package rpc
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"runtime"
+	"time"
+)
+
+type CustomError interface {
+	error
+	Status() int
+	Format(context.Context) any
+}
+
+var (
+	errorRegistry = []CustomError{}
+)
+
+func RegisterErrorHandler(ce CustomError) {
+	fmt.Printf("registering error handler: %p, %I, %v\n", &ce, ce, ce)
+	errorRegistry = append(errorRegistry, ce)
+}
+
+// HandleErr is equivlant to errResp but using more flexible error types
+func handleErr(ctx context.Context, w *responseWrapper, err error) {
+	errorHelper("error: %v\n", err)
+
+	if w.status != 0 {
+		slog.Error("response sent before error was handled")
+		return
+	}
+
+	e := json.NewEncoder(w)
+	// Custom errors take precedence over default errors
+	for _, ce := range errorRegistry {
+		if errors.As(err, &ce) {
+			w.WriteHeader(ce.Status())
+			encErr := e.Encode(ce.Format(ctx))
+			if encErr != nil {
+				errorHelper("error encountered encoding error response: %v", encErr)
+			}
+			return
+		}
+	}
+
+	var (
+		ue     UserError
+		ae     AuthError
+		le     LimitError
+		encErr error
+	)
+	switch {
+	case errors.As(err, &ae):
+		w.WriteHeader(http.StatusUnauthorized)
+		encErr = e.Encode(RPCResponse{Error: ae.AuthError()})
+
+	case errors.As(err, &ue):
+		w.WriteHeader(http.StatusBadRequest)
+		encErr = e.Encode(RPCResponse{Error: ue.UserError()})
+
+	case errors.Is(err, context.Canceled):
+		w.WriteHeader(http.StatusServiceUnavailable)
+		encErr = e.Encode(RPCResponse{Error: "context canceled"})
+
+	case errors.Is(err, sql.ErrNoRows):
+		w.WriteHeader(http.StatusBadRequest)
+		encErr = e.Encode(RPCResponse{Error: "no record could be found"})
+
+	case errors.As(err, &le):
+		w.WriteHeader(http.StatusUpgradeRequired)
+		encErr = e.Encode(RPCResponse{Error: le.LimitError()})
+
+	default:
+		w.WriteHeader(http.StatusInternalServerError)
+		encErr = e.Encode(RPCResponse{Error: "unknown error"})
+	}
+	if encErr != nil {
+		errorHelper("error encountered encoding error response: %v", encErr)
+	}
+}
+
+type UserError interface {
+	UserError() string
+}
+
+type userErr struct {
+	err error
+}
+
+func UserErr(err error) error {
+	if err == nil {
+		return nil
+	}
+	return userErr{
+		err: err,
+	}
+}
+
+func (ue userErr) UserError() string {
+	return ue.err.Error()
+}
+
+func (ue userErr) Error() string {
+	return ue.err.Error()
+}
+
+//////////////////////
+
+type AuthError interface {
+	AuthError() string
+}
+
+type authErr struct {
+	err error
+}
+
+func AuthErr(err error) error {
+	if err == nil {
+		return nil
+	}
+	return authErr{
+		err: err,
+	}
+}
+
+func (ae authErr) AuthError() string {
+	return ae.err.Error()
+}
+
+func (ae authErr) Error() string {
+	return ae.err.Error()
+}
+
+//////////////////
+
+type LimitError interface {
+	LimitError() string
+}
+
+type limitErr struct {
+	err error
+}
+
+func LimitErr(err error) error {
+	if err == nil {
+		return nil
+	}
+	return limitErr{
+		err: err,
+	}
+}
+
+func (le limitErr) Error() string {
+	return le.err.Error()
+}
+
+func (le limitErr) LimitError() string {
+	return le.err.Error()
+}
+
+var (
+	ErrLimitReached = AuthErr(errors.New("limit reached"))
+)
+
+type ErrVersionMismatch struct {
+	Err           error
+	ClientVersion string
+	ServerVersion string
+}
+
+func (e ErrVersionMismatch) Error() string {
+	// Don't mask the wrapped error if it's rewrapped
+	return e.Err.Error()
+}
+
+func (e ErrVersionMismatch) Warning() string {
+	return fmt.Sprintf("client/server version mismatch (c: %s s: %s).", e.ClientVersion, e.ServerVersion)
+}
+
+func (e ErrVersionMismatch) Unwrap() error {
+	return e.Err
+}
+
+// errorHelper is a helper function to log errors to the default logger and
+// include the file and line number of the function calling HandleErr
+// we may want to inject the logger in the future
+func errorHelper(format string, args ...any) {
+	l := slog.Default()
+	if !l.Enabled(context.Background(), slog.LevelInfo) {
+		return
+	}
+	var pcs [1]uintptr
+	runtime.Callers(3, pcs[:]) // skip [Callers, errorHelper, HandleErr]
+	r := slog.NewRecord(time.Now(), slog.LevelError, fmt.Sprintf(format, args...), pcs[0])
+	_ = l.Handler().Handle(context.Background(), r)
+}