From 4a282ffe96735645173adf860880f3b048bb9750 Mon Sep 17 00:00:00 2001
From: Felipe Martinez <pipernene@gmail.com>
Date: Thu, 21 Jan 2021 14:12:35 +0100
Subject: [PATCH] Add errors package and handling

---
 client/client.go     |  4 ++++
 errors/error.go      | 51 ++++++++++++++++++++++++++++++++++++++++++++
 errors/errors.go     | 21 ++++++++++++++++++
 transport/message.go | 35 +++++++++++++++++++++++++++++-
 4 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 errors/error.go
 create mode 100644 errors/errors.go

diff --git a/client/client.go b/client/client.go
index e3c52fe..0543f2c 100644
--- a/client/client.go
+++ b/client/client.go
@@ -104,6 +104,10 @@ func (c *client) Call(service string, path string, reqval interface{}, respval i
 		return fmt.Errorf("decode response: %w", err)
 	}
 
+	if err, ok := respmsg.GetError(); ok {
+		return err
+	}
+
 	return nil
 }
 
diff --git a/errors/error.go b/errors/error.go
new file mode 100644
index 0000000..9fad7c5
--- /dev/null
+++ b/errors/error.go
@@ -0,0 +1,51 @@
+package errors
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/gob"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+type Error struct {
+	StatusCode int16
+	Detail     string
+}
+
+func NewError(code int16, format string, a ...interface{}) error {
+	return &Error{
+		StatusCode: code,
+		Detail:     fmt.Sprintf(format, a...),
+	}
+}
+
+// Encode transforms the error instance into a base64-encoded blob
+func (e *Error) Encode() (string, error) {
+	var b bytes.Buffer
+	enc := gob.NewEncoder(&b)
+
+	if err := enc.Encode(e); err != nil {
+		return "", err
+	}
+
+	return base64.StdEncoding.EncodeToString(b.Bytes()), nil
+}
+
+// Decode tries to decode en error from a base64-encoded string
+func Decode(str string) (*Error, error) {
+	b := strings.NewReader(str)
+	dec := gob.NewDecoder(b)
+
+	var merr Error
+	if err := dec.Decode(&merr); err != nil {
+		return nil, err
+	}
+
+	return &merr, nil
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%s: %s", http.StatusText(int(e.StatusCode)), e.Detail)
+}
diff --git a/errors/errors.go b/errors/errors.go
new file mode 100644
index 0000000..e90a654
--- /dev/null
+++ b/errors/errors.go
@@ -0,0 +1,21 @@
+package errors
+
+func BadRequest(format string, a ...string) error {
+	return NewError(400, format, a)
+}
+
+func Unauthorized(format string, a ...string) error {
+	return NewError(401, format, a)
+}
+
+func Forbidden(format string, a ...string) error {
+	return NewError(403, format, a)
+}
+
+func NotFound(format string, a ...string) error {
+	return NewError(404, format, a)
+}
+
+func InternalServerError(format string, a ...string) error {
+	return NewError(404, format, a)
+}
diff --git a/transport/message.go b/transport/message.go
index 8aa1760..96c2b44 100644
--- a/transport/message.go
+++ b/transport/message.go
@@ -1,5 +1,11 @@
 package transport
 
+import (
+	goerrors "errors"
+
+	"github.com/MouseHatGames/mice/errors"
+)
+
 type Message struct {
 	Headers map[string]string
 	Data    []byte
@@ -12,5 +18,32 @@ func NewMessage() *Message {
 }
 
 func (m *Message) SetError(err error) {
-	m.Headers[HeaderError] = err.Error()
+	var value string
+
+	if merr, ok := err.(*errors.Error); ok {
+		enc, err := merr.Encode()
+
+		if err != nil {
+			value = err.Error()
+		} else {
+			value = enc
+		}
+	} else {
+		value = err.Error()
+	}
+
+	m.Headers[HeaderError] = value
+}
+
+func (m *Message) GetError() (err error, hasError bool) {
+	value, ok := m.Headers[HeaderError]
+	if !ok {
+		return nil, false
+	}
+
+	if merr, err := errors.Decode(value); err != nil {
+		return merr, true
+	}
+
+	return goerrors.New(value), true
 }