http response tooling written

internal/site/response/error.go

@@ -0,0 +1,124 @@
+package response
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+type (
+	// ErrorResponse is an error
+	ErrorResponse struct {
+		err    error
+		msg    string
+		status int
+	}
+)
+
+// Constructors
+
+func Errorf(format string, args ...any) ErrorResponse {
+	return ErrorResponse{
+		err: fmt.Errorf(format, args...),
+	}
+}
+
+func BadRequest() ErrorResponse {
+	return ErrorResponse{
+		status: http.StatusBadRequest,
+	}
+}
+
+func NotFound() ErrorResponse {
+	return ErrorResponse{
+		status: http.StatusNotFound,
+	}
+}
+
+func Unauthorized() ErrorResponse {
+	return ErrorResponse{
+		status: http.StatusUnauthorized,
+	}
+}
+
+func Forbidden() ErrorResponse {
+	return ErrorResponse{
+		status: http.StatusForbidden,
+	}
+}
+
+// builder pattern implementation
+
+func (e ErrorResponse) Msg(msg string) ErrorResponse {
+	e.msg = msg
+	return e
+}
+
+func (e ErrorResponse) Status(status int) ErrorResponse {
+	e.status = status
+	return e
+}
+
+func (e ErrorResponse) Wrap(err error) ErrorResponse {
+	e.err = err
+	return e
+}
+
+// error implementation
+
+func (e ErrorResponse) Error() string {
+	parts := make([]string, 0, 3)
+
+	if e.msg != "" {
+		parts = append(parts, e.msg)
+	} else if e.status != 0 {
+		parts = append(parts, fmt.Sprintf("status = %d", e.status))
+	}
+	if e.err != nil {
+		parts = append(parts, e.err.Error())
+	}
+
+	if len(parts) == 0 {
+		return "status = 500"
+	}
+
+	return strings.Join(parts, ": ")
+}
+
+func (e ErrorResponse) Unwrap() error {
+	return e.err
+}
+
+// nested response value resolution
+
+func (e ErrorResponse) getStatus() (int, bool) {
+	if e.status != 0 {
+		return e.status, true
+	}
+
+	ce, ok := getError(e.err)
+	if ok {
+		return ce.getStatus()
+	}
+
+	return 0, false
+}
+
+func (e ErrorResponse) getMsg() (string, bool) {
+	if e.msg != "" {
+		return e.msg, true
+	}
+
+	ce, ok := getError(e.err)
+	if ok {
+		return ce.getMsg()
+	}
+
+	return "", false
+}
+
+func getError(err error) (e ErrorResponse, ok bool) {
+	ok = errors.As(err, &e)
+	return e, ok
+}