| // Copyright 2013 Joshua Tacoma. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package uritemplates is a level 3 implementation of RFC 6570 (URI |
| // Template, http://tools.ietf.org/html/rfc6570). |
| // uritemplates does not support composite values (in Go: slices or maps) |
| // and so does not qualify as a level 4 implementation. |
| package uritemplates |
| |
| import ( |
| "bytes" |
| "errors" |
| "regexp" |
| "strconv" |
| "strings" |
| ) |
| |
| var ( |
| unreserved = regexp.MustCompile("[^A-Za-z0-9\\-._~]") |
| reserved = regexp.MustCompile("[^A-Za-z0-9\\-._~:/?#[\\]@!$&'()*+,;=]") |
| validname = regexp.MustCompile("^([A-Za-z0-9_\\.]|%[0-9A-Fa-f][0-9A-Fa-f])+$") |
| hex = []byte("0123456789ABCDEF") |
| ) |
| |
| func pctEncode(src []byte) []byte { |
| dst := make([]byte, len(src)*3) |
| for i, b := range src { |
| buf := dst[i*3 : i*3+3] |
| buf[0] = 0x25 |
| buf[1] = hex[b/16] |
| buf[2] = hex[b%16] |
| } |
| return dst |
| } |
| |
| // pairWriter is a convenience struct which allows escaped and unescaped |
| // versions of the template to be written in parallel. |
| type pairWriter struct { |
| escaped, unescaped bytes.Buffer |
| } |
| |
| // Write writes the provided string directly without any escaping. |
| func (w *pairWriter) Write(s string) { |
| w.escaped.WriteString(s) |
| w.unescaped.WriteString(s) |
| } |
| |
| // Escape writes the provided string, escaping the string for the |
| // escaped output. |
| func (w *pairWriter) Escape(s string, allowReserved bool) { |
| w.unescaped.WriteString(s) |
| if allowReserved { |
| w.escaped.Write(reserved.ReplaceAllFunc([]byte(s), pctEncode)) |
| } else { |
| w.escaped.Write(unreserved.ReplaceAllFunc([]byte(s), pctEncode)) |
| } |
| } |
| |
| // Escaped returns the escaped string. |
| func (w *pairWriter) Escaped() string { |
| return w.escaped.String() |
| } |
| |
| // Unescaped returns the unescaped string. |
| func (w *pairWriter) Unescaped() string { |
| return w.unescaped.String() |
| } |
| |
| // A uriTemplate is a parsed representation of a URI template. |
| type uriTemplate struct { |
| raw string |
| parts []templatePart |
| } |
| |
| // parse parses a URI template string into a uriTemplate object. |
| func parse(rawTemplate string) (*uriTemplate, error) { |
| split := strings.Split(rawTemplate, "{") |
| parts := make([]templatePart, len(split)*2-1) |
| for i, s := range split { |
| if i == 0 { |
| if strings.Contains(s, "}") { |
| return nil, errors.New("unexpected }") |
| } |
| parts[i].raw = s |
| continue |
| } |
| subsplit := strings.Split(s, "}") |
| if len(subsplit) != 2 { |
| return nil, errors.New("malformed template") |
| } |
| expression := subsplit[0] |
| var err error |
| parts[i*2-1], err = parseExpression(expression) |
| if err != nil { |
| return nil, err |
| } |
| parts[i*2].raw = subsplit[1] |
| } |
| return &uriTemplate{ |
| raw: rawTemplate, |
| parts: parts, |
| }, nil |
| } |
| |
| type templatePart struct { |
| raw string |
| terms []templateTerm |
| first string |
| sep string |
| named bool |
| ifemp string |
| allowReserved bool |
| } |
| |
| type templateTerm struct { |
| name string |
| explode bool |
| truncate int |
| } |
| |
| func parseExpression(expression string) (result templatePart, err error) { |
| switch expression[0] { |
| case '+': |
| result.sep = "," |
| result.allowReserved = true |
| expression = expression[1:] |
| case '.': |
| result.first = "." |
| result.sep = "." |
| expression = expression[1:] |
| case '/': |
| result.first = "/" |
| result.sep = "/" |
| expression = expression[1:] |
| case ';': |
| result.first = ";" |
| result.sep = ";" |
| result.named = true |
| expression = expression[1:] |
| case '?': |
| result.first = "?" |
| result.sep = "&" |
| result.named = true |
| result.ifemp = "=" |
| expression = expression[1:] |
| case '&': |
| result.first = "&" |
| result.sep = "&" |
| result.named = true |
| result.ifemp = "=" |
| expression = expression[1:] |
| case '#': |
| result.first = "#" |
| result.sep = "," |
| result.allowReserved = true |
| expression = expression[1:] |
| default: |
| result.sep = "," |
| } |
| rawterms := strings.Split(expression, ",") |
| result.terms = make([]templateTerm, len(rawterms)) |
| for i, raw := range rawterms { |
| result.terms[i], err = parseTerm(raw) |
| if err != nil { |
| break |
| } |
| } |
| return result, err |
| } |
| |
| func parseTerm(term string) (result templateTerm, err error) { |
| // TODO(djd): Remove "*" suffix parsing once we check that no APIs have |
| // mistakenly used that attribute. |
| if strings.HasSuffix(term, "*") { |
| result.explode = true |
| term = term[:len(term)-1] |
| } |
| split := strings.Split(term, ":") |
| if len(split) == 1 { |
| result.name = term |
| } else if len(split) == 2 { |
| result.name = split[0] |
| var parsed int64 |
| parsed, err = strconv.ParseInt(split[1], 10, 0) |
| result.truncate = int(parsed) |
| } else { |
| err = errors.New("multiple colons in same term") |
| } |
| if !validname.MatchString(result.name) { |
| err = errors.New("not a valid name: " + result.name) |
| } |
| if result.explode && result.truncate > 0 { |
| err = errors.New("both explode and prefix modifiers on same term") |
| } |
| return result, err |
| } |
| |
| // Expand expands a URI template with a set of values to produce the |
| // resultant URI. Two forms of the result are returned: one with all the |
| // elements escaped, and one with the elements unescaped. |
| func (t *uriTemplate) Expand(values map[string]string) (escaped, unescaped string) { |
| var w pairWriter |
| for _, p := range t.parts { |
| p.expand(&w, values) |
| } |
| return w.Escaped(), w.Unescaped() |
| } |
| |
| func (tp *templatePart) expand(w *pairWriter, values map[string]string) { |
| if len(tp.raw) > 0 { |
| w.Write(tp.raw) |
| return |
| } |
| var first = true |
| for _, term := range tp.terms { |
| value, exists := values[term.name] |
| if !exists { |
| continue |
| } |
| if first { |
| w.Write(tp.first) |
| first = false |
| } else { |
| w.Write(tp.sep) |
| } |
| tp.expandString(w, term, value) |
| } |
| } |
| |
| func (tp *templatePart) expandName(w *pairWriter, name string, empty bool) { |
| if tp.named { |
| w.Write(name) |
| if empty { |
| w.Write(tp.ifemp) |
| } else { |
| w.Write("=") |
| } |
| } |
| } |
| |
| func (tp *templatePart) expandString(w *pairWriter, t templateTerm, s string) { |
| if len(s) > t.truncate && t.truncate > 0 { |
| s = s[:t.truncate] |
| } |
| tp.expandName(w, t.name, len(s) == 0) |
| w.Escape(s, tp.allowReserved) |
| } |