Add errors.go

Signed-off-by: Vartan Benohanian <vartanbeno@gmail.com>

errors.go

@@ -0,0 +1,80 @@
+package geddit
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+// RedditError is an error coming from Reddit
+type RedditError struct {
+	Label  string
+	Reason string
+	Field  string
+}
+
+func (e *RedditError) Error() string {
+	return fmt.Sprintf("%s: %s because of field %q", e.Label, e.Reason, e.Field)
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (e *RedditError) UnmarshalJSON(data []byte) error {
+	var info []string
+
+	err := json.Unmarshal(data, &info)
+	if err != nil {
+		return err
+	}
+
+	if len(info) != 3 {
+		return fmt.Errorf("got unexpected Reddit error: %v", info)
+	}
+
+	e.Label = info[0]
+	e.Reason = info[1]
+	e.Field = info[2]
+
+	return nil
+}
+
+// JSONErrorResponse is an error response that sometimes gets returned with a 200 code
+type JSONErrorResponse struct {
+	// HTTP response that caused this error
+	Response *http.Response `json:"-"`
+
+	JSON *struct {
+		Errors []RedditError `json:"errors,omitempty"`
+	} `json:"json,omitempty"`
+}
+
+func (r *JSONErrorResponse) Error() string {
+	var message string
+	if r.JSON != nil && len(r.JSON.Errors) > 0 {
+		for i, err := range r.JSON.Errors {
+			message += err.Error()
+			if i < len(r.JSON.Errors)-1 {
+				message += ";"
+			}
+		}
+	}
+	return fmt.Sprintf(
+		"%v %v: %d %v",
+		r.Response.Request.Method, r.Response.Request.URL, r.Response.StatusCode, message,
+	)
+}
+
+// An ErrorResponse reports the error caused by an API request
+type ErrorResponse struct {
+	// HTTP response that caused this error
+	Response *http.Response `json:"-"`
+
+	// Error message
+	Message string `json:"message"`
+}
+
+func (r *ErrorResponse) Error() string {
+	return fmt.Sprintf(
+		"%v %v: %d %v",
+		r.Response.Request.Method, r.Response.Request.URL, r.Response.StatusCode, r.Message,
+	)
+}