reply.go

// Copyright 2015 Joel Wu
// Copyright 2012 Gary Burd
//
// 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 (
	"fmt"
	"errors"
	"strconv"
	"reflect"
)

// ErrNil indicates that a reply value is nil.
var ErrNil = errors.New("nil reply")

// Int is a helper that converts a command reply to an integer. If err is not
// equal to nil, then Int returns 0, err. Otherwise, Int converts the
// reply to an int as follows:
//
//  Reply type    Result
//  integer       int(reply), nil
//  bulk string   parsed reply, nil
//  nil           0, ErrNil
//  other         0, error
func Int(reply interface{}, err error) (int, error) {
	if err != nil {
		return 0, err
	}
	switch reply := reply.(type) {
	case int64:
		x := int(reply)
		if int64(x) != reply {
			return 0, strconv.ErrRange
		}
		return x, nil
	case []byte:
		n, err := strconv.ParseInt(string(reply), 10, 0)
		return int(n), err
	case nil:
		return 0, ErrNil
	case redisError:
		return 0, reply
	}
	return 0, fmt.Errorf("unexpected type %T for Int: %v", reply, reply)
}

// Int64 is a helper that converts a command reply to 64 bit integer. If err is
// not equal to nil, then Int returns 0, err. Otherwise, Int64 converts the
// reply to an int64 as follows:
//
//  Reply type    Result
//  integer       reply, nil
//  bulk string   parsed reply, nil
//  nil           0, ErrNil
//  other         0, error
func Int64(reply interface{}, err error) (int64, error) {
	if err != nil {
		return 0, err
	}
	switch reply := reply.(type) {
	case int64:
		return reply, nil
	case []byte:
		n, err := strconv.ParseInt(string(reply), 10, 64)
		return n, err
	case nil:
		return 0, ErrNil
	case redisError:
		return 0, reply
	}
	return 0, fmt.Errorf("unexpected type %T for Int64: %v", reply, reply)
}

// Float64 is a helper that converts a command reply to 64 bit float. If err is
// not equal to nil, then Float64 returns 0, err. Otherwise, Float64 converts
// the reply to an int as follows:
//
//  Reply type    Result
//  bulk string   parsed reply, nil
//  nil           0, ErrNil
//  other         0, error
func Float64(reply interface{}, err error) (float64, error) {
	if err != nil {
		return 0, err
	}
	switch reply := reply.(type) {
	case []byte:
		n, err := strconv.ParseFloat(string(reply), 64)
		return n, err
	case nil:
		return 0, ErrNil
	case redisError:
		return 0, reply
	}
	return 0, fmt.Errorf("unexpected type %T for Float64: %v", reply, reply)
}

// String is a helper that converts a command reply to a string. If err is not
// equal to nil, then String returns "", err. Otherwise String converts the
// reply to a string as follows:
//
//  Reply type      Result
//  bulk string     string(reply), nil
//  simple string   reply, nil
//  nil             "",  ErrNil
//  other           "",  error
func String(reply interface{}, err error) (string, error) {
	if err != nil {
		return "", err
	}
	switch reply := reply.(type) {
	case []byte:
		return string(reply), nil
	case string:
		return reply, nil
	case nil:
		return "", ErrNil
	case redisError:
		return "", reply
	}
	return "", fmt.Errorf("unexpected type[%T] for String: %v", reply, reply)
}

// Bytes is a helper that converts a command reply to a slice of bytes. If err
// is not equal to nil, then Bytes returns nil, err. Otherwise Bytes converts
// the reply to a slice of bytes as follows:
//
//  Reply type      Result
//  bulk string     reply, nil
//  simple string   []byte(reply), nil
//  nil             nil, ErrNil
//  other           nil, error
func Bytes(reply interface{}, err error) ([]byte, error) {
	if err != nil {
		return nil, err
	}
	switch reply := reply.(type) {
	case []byte:
		return reply, nil
	case string:
		return []byte(reply), nil
	case nil:
		return nil, ErrNil
	case redisError:
		return nil, reply
	}
	return nil, fmt.Errorf("unexpected type %T for Bytes: %v", reply, reply)
}

// Bool is a helper that converts a command reply to a boolean. If err is not
// equal to nil, then Bool returns false, err. Otherwise Bool converts the
// reply to boolean as follows:
//
//  Reply type      Result
//  integer         value != 0, nil
//  bulk string     strconv.ParseBool(reply)
//  nil             false, ErrNil
//  other           false, error
func Bool(reply interface{}, err error) (bool, error) {
	if err != nil {
		return false, err
	}
	switch reply := reply.(type) {
	case int64:
		return reply != 0, nil
	case []byte:
		return strconv.ParseBool(string(reply))
	case nil:
		return false, ErrNil
	case redisError:
		return false, reply
	}
	return false, fmt.Errorf("unexpected type %T for Bool: %v", reply, reply)
}

// Values is a helper that converts an array command reply to a []interface{}.
// If err is not equal to nil, then Values returns nil, err. Otherwise, Values
// converts the reply as follows:
//
//  Reply type      Result
//  array           reply, nil
//  nil             nil, ErrNil
//  other           nil, error
func Values(reply interface{}, err error) ([]interface{}, error) {
	if err != nil {
		return nil, err
	}
	switch reply := reply.(type) {
	case []interface{}:
		return reply, nil
	case nil:
		return nil, ErrNil
	case redisError:
		return nil, reply
	}
	return nil, fmt.Errorf("unexpected type %T for Values: %v", reply, reply)
}

// Ints is a helper that converts an array command reply to a []int. 
// If err is not equal to nil, then Ints returns nil, err.
func Ints(reply interface{}, err error) ([]int, error) {
	values, err := Values(reply, err)
	if err != nil {
		return nil, err
	}

	ints := make([]int, len(values))
	slice := make([]interface{}, len(values))
	for i, _ := range ints {
		slice[i] = &ints[i]
	}

	if _, err = Scan(values, slice...); err != nil {
		return nil, err
	}

	return ints, nil
}

// Strings is a helper that converts an array command reply to a []string. If
// err is not equal to nil, then Strings returns nil, err. Nil array items are
// converted to "" in the output slice. Strings returns an error if an array
// item is not a bulk string or nil.
func Strings(reply interface{}, err error) ([]string, error) {
	values, err := Values(reply, err)
	if err != nil {
		return nil, err
	}

	strings := make([]string, len(values))
	slice := make([]interface{}, len(values))
	for i := range strings {
		slice[i] = &strings[i]
	}

	if _, err = Scan(values, slice...); err != nil {
		return nil, err
	}

	return strings, nil
}

// StringMap is a helper that converts an array of strings (alternating key, value)
// into a map[string]string. The HGETALL and CONFIG GET commands return replies in this format.
// Requires an even number of values in result.
func StringMap(result interface{}, err error) (map[string]string, error) {
	values, err := Values(result, err)
	if err != nil {
		return nil, err
	}
	if len(values)%2 != 0 {
		return nil, errors.New("expect even number elements for StringMap")
	}

	m := make(map[string]string, len(values)/2)
	for i := 0; i < len(values); i += 2 {
		key, okKey := values[i].([]byte)
		value, okValue := values[i+1].([]byte)
		if !okKey || !okValue {
			return nil, errors.New("expect bulk string for StringMap")
		}
		m[string(key)] = string(value)
	}

	return m, nil
}

// Scan copies from src to the values pointed at by dest.
//
// The values pointed at by dest must be an integer, float, boolean, string,
// []byte, interface{} or slices of these types. Scan uses the standard strconv
// package to convert bulk strings to numeric and boolean types.
//
// If a dest value is nil, then the corresponding src value is skipped.
//
// If a src element is nil, then the corresponding dest value is not modified.
//
// To enable easy use of Scan in a loop, Scan returns the slice of src
// following the copied values.
func Scan(src []interface{}, dst ...interface{}) ([]interface{}, error) {
	if len(src) < len(dst) {
		return nil, errors.New("mismatch length of source and dest")
	}
	var err error
	for i, d := range dst {
		err = convertAssign(d, src[i])
		if err != nil {
			break
		}
	}
	return src[len(dst):], err
}

func ensureLen(d reflect.Value, n int) {
	if n > d.Cap() {
		d.Set(reflect.MakeSlice(d.Type(), n, n))
	} else {
		d.SetLen(n)
	}
}

func cannotConvert(d reflect.Value, s interface{}) error {
	return fmt.Errorf("redigo: Scan cannot convert from %s to %s",
		reflect.TypeOf(s), d.Type())
}

func convertAssignBytes(d reflect.Value, s []byte) (err error) {
	switch d.Type().Kind() {
	case reflect.Float32, reflect.Float64:
		var x float64
		x, err = strconv.ParseFloat(string(s), d.Type().Bits())
		d.SetFloat(x)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		var x int64
		x, err = strconv.ParseInt(string(s), 10, d.Type().Bits())
		d.SetInt(x)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		var x uint64
		x, err = strconv.ParseUint(string(s), 10, d.Type().Bits())
		d.SetUint(x)
	case reflect.Bool:
		var x bool
		x, err = strconv.ParseBool(string(s))
		d.SetBool(x)
	case reflect.String:
		d.SetString(string(s))
	case reflect.Slice:
		if d.Type().Elem().Kind() != reflect.Uint8 {
			err = cannotConvert(d, s)
		} else {
			d.SetBytes(s)
		}
	default:
		err = cannotConvert(d, s)
	}
	return
}

func convertAssignInt(d reflect.Value, s int64) (err error) {
	switch d.Type().Kind() {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		d.SetInt(s)
		if d.Int() != s {
			err = strconv.ErrRange
			d.SetInt(0)
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		if s < 0 {
			err = strconv.ErrRange
		} else {
			x := uint64(s)
			d.SetUint(x)
			if d.Uint() != x {
				err = strconv.ErrRange
				d.SetUint(0)
			}
		}
	case reflect.Bool:
		d.SetBool(s != 0)
	default:
		err = cannotConvert(d, s)
	}
	return
}

func convertAssignValue(d reflect.Value, s interface{}) (err error) {
	switch s := s.(type) {
	case []byte:
		err = convertAssignBytes(d, s)
	case int64:
		err = convertAssignInt(d, s)
	default:
		err = cannotConvert(d, s)
	}
	return err
}

func convertAssignValues(d reflect.Value, s []interface{}) error {
	if d.Type().Kind() != reflect.Slice {
		return cannotConvert(d, s)
	}
	ensureLen(d, len(s))
	for i := 0; i < len(s); i++ {
		if err := convertAssignValue(d.Index(i), s[i]); err != nil {
			return err
		}
	}
	return nil
}

func convertAssign(d interface{}, s interface{}) (err error) {
	// Handle the most common destination types using type switches and
	// fall back to reflection for all other types.
	switch s := s.(type) {
	case nil:
		// ingore
	case []byte:
		switch d := d.(type) {
		case *string:
			*d = string(s)
		case *int:
			*d, err = strconv.Atoi(string(s))
		case *int64:
			*d, err = strconv.ParseInt(string(s), 10, 64)
		case *bool:
			*d, err = strconv.ParseBool(string(s))
		case *[]byte:
			*d = s
		case *interface{}:
			*d = s
		case nil:
			// skip value
		default:
			if d := reflect.ValueOf(d); d.Type().Kind() != reflect.Ptr {
				err = cannotConvert(d, s)
			} else {
				err = convertAssignBytes(d.Elem(), s)
			}
		}
	case int64:
		switch d := d.(type) {
		case *int:
			x := int(s)
			if int64(x) != s {
				err = strconv.ErrRange
				x = 0
			}
			*d = x
		case *int64:
			*d = s
		case *bool:
			*d = s != 0
		case *interface{}:
			*d = s
		case nil:
			// skip value
		default:
			if d := reflect.ValueOf(d); d.Type().Kind() != reflect.Ptr {
				err = cannotConvert(d, s)
			} else {
				err = convertAssignInt(d.Elem(), s)
			}
		}
	case []interface{}:
		switch d := d.(type) {
		case *[]interface{}:
			*d = s
		case *interface{}:
			*d = s
		case nil:
			// skip value
		default:
			if d := reflect.ValueOf(d); d.Type().Kind() != reflect.Ptr {
				err = cannotConvert(d, s)
			} else {
				err = convertAssignValues(d.Elem(), s)
			}
		}
	case redisError:
		err = s
	default:
		err = cannotConvert(reflect.ValueOf(d), s)
	}
	return
}