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// Copyright 2009-2012 Joubin Houshyar
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package redis

import (
"errors"
"fmt"
"log"
)

// ----------------------------------------------------------------------------
// ERRORS
// ----------------------------------------------------------------------------

// redis.Errors can be either user or system category.
//
// REDIS_ERR are sent by the Redis server in response to user commands. (For example
// "operation against key holding the wrong value). If a call to the client method
// has a non nil error with this cateogry, it means you did something wrong. If you
// want to know the details, see Error.GetMessage() which returns the precise error
// sent from Redis.
//
// If error is of category SYSTEM_ERR, it either means there were errors during exeuction
// (which may be due to your system environment, networking, memory, etc.) OR, there is
// a bug in the package. Unlike REDIS_ERR cateogry, SYSTEM_ERR category errors may have
// and underlying cause (os.Error) which can be obtained by Error.Cause() method.

type ErrorCategory uint8

const (
_ ErrorCategory = iota
REDIS_ERR
SYSTEM_ERR
)

func (ec ErrorCategory) String() (s string) {
switch ec {
case SYSTEM_ERR:
s = "SYSTEM_ERROR"
case REDIS_ERR:
s = "REDIS_ERROR"
}
return
}

// Defines the interfce to get details of an Error.
//
type Error interface {
// underlying error that caused this error - or nil
Cause() error

// support std. Go Error interface
Error() string

// category of error -- never nil
Category() ErrorCategory

// the error message - if a Redis error these are exactly
// as provided by the server e.g. "ERR - invalid password"
// possibly "" if SYSTEM-ERR
Message() string

// conv to String
String() string

// check if error is a Redis error e.g. "ERR - invalid password"
// a convenience method
IsRedisError() bool
}
type redisError struct {
msg string
category ErrorCategory
cause error
}

func (e redisError) IsRedisError() bool { return e.category == REDIS_ERR}
func (e redisError) Cause() error { return e.cause }
func (e redisError) Error() string { return e.String() }
func (e redisError) Category() ErrorCategory { return e.category }
func (e redisError) Message() string { return e.msg }
func (e redisError) String() string {
var errCat string
var causeDetails string = ""
switch e.category {
case REDIS_ERR:
errCat = "REDIS-ERROR"
case SYSTEM_ERR:
errCat = "SYSTEM-ERROR"
if e.Cause() != nil {
causeDetails = fmt.Sprintf(" [cause: %s]", e.Cause())
}
}
return fmt.Sprintf("[go-redis|%d|%s]: %s %s", e.category, errCat, e.msg, causeDetails)
}

func _newRedisError(cat ErrorCategory, msg string) redisError {
var e redisError
e.msg = msg
e.category = cat
return e
}

// Creates an Error of REDIS_ERR category with the message.
//
func NewRedisError(msg string) Error {
return _newRedisError(REDIS_ERR, msg)
}

// Creates an Error of REDIS_ERR category with the message.
//
func NewSystemError(msg string) Error {
return _newRedisError(SYSTEM_ERR, msg)
}

// Creates an Error of specified category with the message.
//
func NewError(cat ErrorCategory, msg string) Error {
return _newRedisError(cat, msg)
}

// Creates an Error of specified category with the message and cause.
//
func NewErrorWithCause(cat ErrorCategory, msg string, cause error) Error {
e := _newRedisError(cat, msg)
e.cause = cause
return e
}


// utility function emits log if _debug flag /debug() is true
// Error is returned.
// usage:
// foo, e := FooBar()
// if e != nil {
// return withError(e)
// }
func withError(e Error) Error {
if debug() {
log.Println(e)
}
return e
}

// creates a new generic (Go) error
// and emits log if _debug flag /debug() is true
// Error is returned.
// usage:
// v := FooBar()
// if v != expected {
// return withNewError("value v is unexpected")
// }
func withNewError(m string) error {
e := errors.New(m)
if debug() {
log.Println(e)
}
return e
}

// creates a new redis.Error of category SYSTEM_ERR
// and emits log if _debug flag /debug() is true
// Error is returned.
// usage:
// _, e := SomeLibraryOrGoCall()
// if e != nil {
// return withNewError("value v is unexpected", e)
// }
func withOsError(m string, cause error) error {
return withNewError(fmt.Sprintf("%s [cause: %s]", m, cause))
}
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