blob: 648b38cb6546db2778bb1f1ed161b04d305e2c13 [file] [log] [blame]
Matthias Andreas Benkard832a54e2019-01-29 09:27:38 +01001/*
2HTTP Content-Type Autonegotiation.
3
4The functions in this package implement the behaviour specified in
5http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
6
7Copyright (c) 2011, Open Knowledge Foundation Ltd.
8All rights reserved.
9
10Redistribution and use in source and binary forms, with or without
11modification, are permitted provided that the following conditions are
12met:
13
14 Redistributions of source code must retain the above copyright
15 notice, this list of conditions and the following disclaimer.
16
17 Redistributions in binary form must reproduce the above copyright
18 notice, this list of conditions and the following disclaimer in
19 the documentation and/or other materials provided with the
20 distribution.
21
22 Neither the name of the Open Knowledge Foundation Ltd. nor the
23 names of its contributors may be used to endorse or promote
24 products derived from this software without specific prior written
25 permission.
26
27THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
32SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
33LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
37OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38
39
40*/
41package goautoneg
42
43import (
44 "sort"
45 "strconv"
46 "strings"
47)
48
49// Structure to represent a clause in an HTTP Accept Header
50type Accept struct {
51 Type, SubType string
52 Q float64
53 Params map[string]string
54}
55
56// For internal use, so that we can use the sort interface
57type accept_slice []Accept
58
59func (accept accept_slice) Len() int {
60 slice := []Accept(accept)
61 return len(slice)
62}
63
64func (accept accept_slice) Less(i, j int) bool {
65 slice := []Accept(accept)
66 ai, aj := slice[i], slice[j]
67 if ai.Q > aj.Q {
68 return true
69 }
70 if ai.Type != "*" && aj.Type == "*" {
71 return true
72 }
73 if ai.SubType != "*" && aj.SubType == "*" {
74 return true
75 }
76 return false
77}
78
79func (accept accept_slice) Swap(i, j int) {
80 slice := []Accept(accept)
81 slice[i], slice[j] = slice[j], slice[i]
82}
83
84// Parse an Accept Header string returning a sorted list
85// of clauses
86func ParseAccept(header string) (accept []Accept) {
87 parts := strings.Split(header, ",")
88 accept = make([]Accept, 0, len(parts))
89 for _, part := range parts {
90 part := strings.Trim(part, " ")
91
92 a := Accept{}
93 a.Params = make(map[string]string)
94 a.Q = 1.0
95
96 mrp := strings.Split(part, ";")
97
98 media_range := mrp[0]
99 sp := strings.Split(media_range, "/")
100 a.Type = strings.Trim(sp[0], " ")
101
102 switch {
103 case len(sp) == 1 && a.Type == "*":
104 a.SubType = "*"
105 case len(sp) == 2:
106 a.SubType = strings.Trim(sp[1], " ")
107 default:
108 continue
109 }
110
111 if len(mrp) == 1 {
112 accept = append(accept, a)
113 continue
114 }
115
116 for _, param := range mrp[1:] {
117 sp := strings.SplitN(param, "=", 2)
118 if len(sp) != 2 {
119 continue
120 }
121 token := strings.Trim(sp[0], " ")
122 if token == "q" {
123 a.Q, _ = strconv.ParseFloat(sp[1], 32)
124 } else {
125 a.Params[token] = strings.Trim(sp[1], " ")
126 }
127 }
128
129 accept = append(accept, a)
130 }
131
132 slice := accept_slice(accept)
133 sort.Sort(slice)
134
135 return
136}
137
138// Negotiate the most appropriate content_type given the accept header
139// and a list of alternatives.
140func Negotiate(header string, alternatives []string) (content_type string) {
141 asp := make([][]string, 0, len(alternatives))
142 for _, ctype := range alternatives {
143 asp = append(asp, strings.SplitN(ctype, "/", 2))
144 }
145 for _, clause := range ParseAccept(header) {
146 for i, ctsp := range asp {
147 if clause.Type == ctsp[0] && clause.SubType == ctsp[1] {
148 content_type = alternatives[i]
149 return
150 }
151 if clause.Type == ctsp[0] && clause.SubType == "*" {
152 content_type = alternatives[i]
153 return
154 }
155 if clause.Type == "*" && clause.SubType == "*" {
156 content_type = alternatives[i]
157 return
158 }
159 }
160 }
161 return
162}