errors.go

package gotham

import (
	"fmt"
	"strings"
)

// ErrorType is an unsigned 64-bit error code as defined in the gotham spec.
type ErrorType uint64

const (
	// ErrorTypePrivate indicates a private error.
	ErrorTypePrivate ErrorType = 1 << 0
	// ErrorTypePublic indicates a public error.
	ErrorTypePublic ErrorType = 1 << 1
	// ErrorTypeAny indicates any other error.
	ErrorTypeAny ErrorType = 1<<64 - 1
)

// Error represents a error's specification.
type Error struct {
	Err  error
	Type ErrorType
	Meta interface{}
}

type errorMsgs []*Error

var _ error = &Error{}

// SetType sets the error's type.
func (msg *Error) SetType(flags ErrorType) *Error {
	msg.Type = flags
	return msg
}

// SetMeta sets the error's meta data.
func (msg *Error) SetMeta(data interface{}) *Error {
	msg.Meta = data
	return msg
}

// Error implements the error interface.
func (msg Error) Error() string {
	return msg.Err.Error()
}

// IsType judges one error.
func (msg *Error) IsType(flags ErrorType) bool {
	return (msg.Type & flags) > 0
}

// ByType returns a readonly copy filtered the byte.
// ie ByType(gotham.ErrorTypePublic) returns a slice of errors with type=ErrorTypePublic.
func (a errorMsgs) ByType(typ ErrorType) errorMsgs {
	if len(a) == 0 {
		return nil
	}
	if typ == ErrorTypeAny {
		return a
	}
	var result errorMsgs
	for _, msg := range a {
		if msg.IsType(typ) {
			result = append(result, msg)
		}
	}
	return result
}

// Last returns the last error in the slice. It returns nil if the array is empty.
// Shortcut for errors[len(errors)-1].
func (a errorMsgs) Last() *Error {
	if length := len(a); length > 0 {
		return a[length-1]
	}
	return nil
}

// Errors returns an array will all the error messages.
// Example:
// 		c.Error(errors.New("first"))
// 		c.Error(errors.New("second"))
// 		c.Error(errors.New("third"))
// 		c.Errors.Errors() // == []string{"first", "second", "third"}
func (a errorMsgs) Errors() []string {
	if len(a) == 0 {
		return nil
	}
	errorStrings := make([]string, len(a))
	for i, err := range a {
		errorStrings[i] = err.Error()
	}
	return errorStrings
}

func (a errorMsgs) String() string {
	if len(a) == 0 {
		return ""
	}
	var buffer strings.Builder
	for i, msg := range a {
		fmt.Fprintf(&buffer, "Error #%02d: %s\n", i+1, msg.Err)
		if msg.Meta != nil {
			fmt.Fprintf(&buffer, "Meta: %v\n", msg.Meta)
		}
	}
	return buffer.String()
}