1// Copyright 2012 Gary Burd
2//
3// Licensed under the Apache License, Version 2.0 (the "License"): you may
4// not use this file except in compliance with the License. You may obtain
5// a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12// License for the specific language governing permissions and limitations
13// under the License.
14
15package redis
16
17import (
18	"crypto/sha1"
19	"encoding/hex"
20	"io"
21	"strings"
22)
23
24// Script encapsulates the source, hash and key count for a Lua script. See
25// http://redis.io/commands/eval for information on scripts in Redis.
26type Script struct {
27	keyCount int
28	src      string
29	hash     string
30}
31
32// NewScript returns a new script object. If keyCount is greater than or equal
33// to zero, then the count is automatically inserted in the EVAL command
34// argument list. If keyCount is less than zero, then the application supplies
35// the count as the first value in the keysAndArgs argument to the Do, Send and
36// SendHash methods.
37func NewScript(keyCount int, src string) *Script {
38	h := sha1.New()
39	io.WriteString(h, src)
40	return &Script{keyCount, src, hex.EncodeToString(h.Sum(nil))}
41}
42
43func (s *Script) args(spec string, keysAndArgs []interface{}) []interface{} {
44	var args []interface{}
45	if s.keyCount < 0 {
46		args = make([]interface{}, 1+len(keysAndArgs))
47		args[0] = spec
48		copy(args[1:], keysAndArgs)
49	} else {
50		args = make([]interface{}, 2+len(keysAndArgs))
51		args[0] = spec
52		args[1] = s.keyCount
53		copy(args[2:], keysAndArgs)
54	}
55	return args
56}
57
58// Do evaluates the script. Under the covers, Do optimistically evaluates the
59// script using the EVALSHA command. If the command fails because the script is
60// not loaded, then Do evaluates the script using the EVAL command (thus
61// causing the script to load).
62func (s *Script) Do(c Conn, keysAndArgs ...interface{}) (interface{}, error) {
63	v, err := c.Do("EVALSHA", s.args(s.hash, keysAndArgs)...)
64	if e, ok := err.(Error); ok && strings.HasPrefix(string(e), "NOSCRIPT ") {
65		v, err = c.Do("EVAL", s.args(s.src, keysAndArgs)...)
66	}
67	return v, err
68}
69
70// SendHash evaluates the script without waiting for the reply. The script is
71// evaluated with the EVALSHA command. The application must ensure that the
72// script is loaded by a previous call to Send, Do or Load methods.
73func (s *Script) SendHash(c Conn, keysAndArgs ...interface{}) error {
74	return c.Send("EVALSHA", s.args(s.hash, keysAndArgs)...)
75}
76
77// Send evaluates the script without waiting for the reply.
78func (s *Script) Send(c Conn, keysAndArgs ...interface{}) error {
79	return c.Send("EVAL", s.args(s.src, keysAndArgs)...)
80}
81
82// Load loads the script without evaluating it.
83func (s *Script) Load(c Conn) error {
84	_, err := c.Do("SCRIPT", "LOAD", s.src)
85	return err
86}
87