| // 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 4 implementation of RFC 6570 (URI |
| // Template, http://tools.ietf.org/html/rfc6570). |
| // |
| // To use uritemplates, parse a template string and expand it with a value |
| // map: |
| // |
| // template, _ := uritemplates.Parse("https://api.github.com/repos{/user,repo}") |
| // values := make(map[string]interface{}) |
| // values["user"] = "jtacoma" |
| // values["repo"] = "uritemplates" |
| // expanded, _ := template.ExpandString(values) |
| // fmt.Printf(expanded) |
| // |
| package uritemplates |
| |
| import ( |
| "bytes" |
| "errors" |
| "fmt" |
| "reflect" |
| "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 |
| } |
| |
| func escape(s string, allowReserved bool) (escaped string) { |
| if allowReserved { |
| escaped = string(reserved.ReplaceAllFunc([]byte(s), pctEncode)) |
| } else { |
| escaped = string(unreserved.ReplaceAllFunc([]byte(s), pctEncode)) |
| } |
| return escaped |
| } |
| |
| // 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) (template *UriTemplate, err error) { |
| template = new(UriTemplate) |
| template.raw = rawtemplate |
| split := strings.Split(rawtemplate, "{") |
| template.parts = make([]templatePart, len(split)*2-1) |
| for i, s := range split { |
| if i == 0 { |
| if strings.Contains(s, "}") { |
| err = errors.New("unexpected }") |
| break |
| } |
| template.parts[i].raw = s |
| } else { |
| subsplit := strings.Split(s, "}") |
| if len(subsplit) != 2 { |
| err = errors.New("malformed template") |
| break |
| } |
| expression := subsplit[0] |
| template.parts[i*2-1], err = parseExpression(expression) |
| if err != nil { |
| break |
| } |
| template.parts[i*2].raw = subsplit[1] |
| } |
| } |
| if err != nil { |
| template = nil |
| } |
| return template, err |
| } |
| |
| 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) { |
| 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 modifers on same term") |
| } |
| return result, err |
| } |
| |
| // Expand expands a URI template with a set of values to produce a string. |
| func (self *UriTemplate) Expand(value interface{}) (string, error) { |
| values, ismap := value.(map[string]interface{}) |
| if !ismap { |
| if m, ismap := struct2map(value); !ismap { |
| return "", errors.New("expected map[string]interface{}, struct, or pointer to struct.") |
| } else { |
| return self.Expand(m) |
| } |
| } |
| var buf bytes.Buffer |
| for _, p := range self.parts { |
| err := p.expand(&buf, values) |
| if err != nil { |
| return "", err |
| } |
| } |
| return buf.String(), nil |
| } |
| |
| func (self *templatePart) expand(buf *bytes.Buffer, values map[string]interface{}) error { |
| if len(self.raw) > 0 { |
| buf.WriteString(self.raw) |
| return nil |
| } |
| var zeroLen = buf.Len() |
| buf.WriteString(self.first) |
| var firstLen = buf.Len() |
| for _, term := range self.terms { |
| value, exists := values[term.name] |
| if !exists { |
| continue |
| } |
| if buf.Len() != firstLen { |
| buf.WriteString(self.sep) |
| } |
| switch v := value.(type) { |
| case string: |
| self.expandString(buf, term, v) |
| case []interface{}: |
| self.expandArray(buf, term, v) |
| case map[string]interface{}: |
| if term.truncate > 0 { |
| return errors.New("cannot truncate a map expansion") |
| } |
| self.expandMap(buf, term, v) |
| default: |
| if m, ismap := struct2map(value); ismap { |
| if term.truncate > 0 { |
| return errors.New("cannot truncate a map expansion") |
| } |
| self.expandMap(buf, term, m) |
| } else { |
| str := fmt.Sprintf("%v", value) |
| self.expandString(buf, term, str) |
| } |
| } |
| } |
| if buf.Len() == firstLen { |
| original := buf.Bytes()[:zeroLen] |
| buf.Reset() |
| buf.Write(original) |
| } |
| return nil |
| } |
| |
| func (self *templatePart) expandName(buf *bytes.Buffer, name string, empty bool) { |
| if self.named { |
| buf.WriteString(name) |
| if empty { |
| buf.WriteString(self.ifemp) |
| } else { |
| buf.WriteString("=") |
| } |
| } |
| } |
| |
| func (self *templatePart) expandString(buf *bytes.Buffer, t templateTerm, s string) { |
| if len(s) > t.truncate && t.truncate > 0 { |
| s = s[:t.truncate] |
| } |
| self.expandName(buf, t.name, len(s) == 0) |
| buf.WriteString(escape(s, self.allowReserved)) |
| } |
| |
| func (self *templatePart) expandArray(buf *bytes.Buffer, t templateTerm, a []interface{}) { |
| if len(a) == 0 { |
| return |
| } else if !t.explode { |
| self.expandName(buf, t.name, false) |
| } |
| for i, value := range a { |
| if t.explode && i > 0 { |
| buf.WriteString(self.sep) |
| } else if i > 0 { |
| buf.WriteString(",") |
| } |
| var s string |
| switch v := value.(type) { |
| case string: |
| s = v |
| default: |
| s = fmt.Sprintf("%v", v) |
| } |
| if len(s) > t.truncate && t.truncate > 0 { |
| s = s[:t.truncate] |
| } |
| if self.named && t.explode { |
| self.expandName(buf, t.name, len(s) == 0) |
| } |
| buf.WriteString(escape(s, self.allowReserved)) |
| } |
| } |
| |
| func (self *templatePart) expandMap(buf *bytes.Buffer, t templateTerm, m map[string]interface{}) { |
| if len(m) == 0 { |
| return |
| } |
| if !t.explode { |
| self.expandName(buf, t.name, len(m) == 0) |
| } |
| var firstLen = buf.Len() |
| for k, value := range m { |
| if firstLen != buf.Len() { |
| if t.explode { |
| buf.WriteString(self.sep) |
| } else { |
| buf.WriteString(",") |
| } |
| } |
| var s string |
| switch v := value.(type) { |
| case string: |
| s = v |
| default: |
| s = fmt.Sprintf("%v", v) |
| } |
| if t.explode { |
| buf.WriteString(escape(k, self.allowReserved)) |
| buf.WriteRune('=') |
| buf.WriteString(escape(s, self.allowReserved)) |
| } else { |
| buf.WriteString(escape(k, self.allowReserved)) |
| buf.WriteRune(',') |
| buf.WriteString(escape(s, self.allowReserved)) |
| } |
| } |
| } |
| |
| func struct2map(v interface{}) (map[string]interface{}, bool) { |
| value := reflect.ValueOf(v) |
| switch value.Type().Kind() { |
| case reflect.Ptr: |
| return struct2map(value.Elem().Interface()) |
| case reflect.Struct: |
| m := make(map[string]interface{}) |
| for i := 0; i < value.NumField(); i++ { |
| tag := value.Type().Field(i).Tag |
| var name string |
| if strings.Contains(string(tag), ":") { |
| name = tag.Get("uri") |
| } else { |
| name = strings.TrimSpace(string(tag)) |
| } |
| if len(name) == 0 { |
| name = value.Type().Field(i).Name |
| } |
| m[name] = value.Field(i).Interface() |
| } |
| return m, true |
| } |
| return nil, false |
| } |