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// Copyright 2012 The Gorilla Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package mux
import (
"bytes"
"fmt"
"net/http"
"net/url"
"regexp"
"strconv"
"strings"
)
// newRouteRegexp parses a route template and returns a routeRegexp,
// used to match a host, a path or a query string.
//
// It will extract named variables, assemble a regexp to be matched, create
// a "reverse" template to build URLs and compile regexps to validate variable
// values used in URL building.
//
// Previously we accepted only Python-like identifiers for variable
// names ([a-zA-Z_][a-zA-Z0-9_]*), but currently the only restriction is that
// name and pattern can't be empty, and names can't contain a colon.
func newRouteRegexp(tpl string, matchHost, matchPrefix, matchQuery, strictSlash, useEncodedPath bool) (*routeRegexp, error) {
// Check if it is well-formed.
idxs, errBraces := braceIndices(tpl)
if errBraces != nil {
return nil, errBraces
}
// Backup the original.
template := tpl
// Now let's parse it.
defaultPattern := "[^/]+"
if matchQuery {
defaultPattern = "[^?&]*"
} else if matchHost {
defaultPattern = "[^.]+"
matchPrefix = false
}
// Only match strict slash if not matching
if matchPrefix || matchHost || matchQuery {
strictSlash = false
}
// Set a flag for strictSlash.
endSlash := false
if strictSlash && strings.HasSuffix(tpl, "/") {
tpl = tpl[:len(tpl)-1]
endSlash = true
}
varsN := make([]string, len(idxs)/2)
varsR := make([]*regexp.Regexp, len(idxs)/2)
pattern := bytes.NewBufferString("")
pattern.WriteByte('^')
reverse := bytes.NewBufferString("")
var end int
var err error
for i := 0; i < len(idxs); i += 2 {
// Set all values we are interested in.
raw := tpl[end:idxs[i]]
end = idxs[i+1]
parts := strings.SplitN(tpl[idxs[i]+1:end-1], ":", 2)
name := parts[0]
patt := defaultPattern
if len(parts) == 2 {
patt = parts[1]
}
// Name or pattern can't be empty.
if name == "" || patt == "" {
return nil, fmt.Errorf("mux: missing name or pattern in %q",
tpl[idxs[i]:end])
}
// Build the regexp pattern.
fmt.Fprintf(pattern, "%s(?P<%s>%s)", regexp.QuoteMeta(raw), varGroupName(i/2), patt)
// Build the reverse template.
fmt.Fprintf(reverse, "%s%%s", raw)
// Append variable name and compiled pattern.
varsN[i/2] = name
varsR[i/2], err = regexp.Compile(fmt.Sprintf("^%s$", patt))
if err != nil {
return nil, err
}
}
// Add the remaining.
raw := tpl[end:]
pattern.WriteString(regexp.QuoteMeta(raw))
if strictSlash {
pattern.WriteString("[/]?")
}
if matchQuery {
// Add the default pattern if the query value is empty
if queryVal := strings.SplitN(template, "=", 2)[1]; queryVal == "" {
pattern.WriteString(defaultPattern)
}
}
if !matchPrefix {
pattern.WriteByte('$')
}
reverse.WriteString(raw)
if endSlash {
reverse.WriteByte('/')
}
// Compile full regexp.
reg, errCompile := regexp.Compile(pattern.String())
if errCompile != nil {
return nil, errCompile
}
// Check for capturing groups which used to work in older versions
if reg.NumSubexp() != len(idxs)/2 {
panic(fmt.Sprintf("route %s contains capture groups in its regexp. ", template) +
"Only non-capturing groups are accepted: e.g. (?:pattern) instead of (pattern)")
}
// Done!
return &routeRegexp{
template: template,
matchHost: matchHost,
matchQuery: matchQuery,
strictSlash: strictSlash,
useEncodedPath: useEncodedPath,
regexp: reg,
reverse: reverse.String(),
varsN: varsN,
varsR: varsR,
}, nil
}
// routeRegexp stores a regexp to match a host or path and information to
// collect and validate route variables.
type routeRegexp struct {
// The unmodified template.
template string
// True for host match, false for path or query string match.
matchHost bool
// True for query string match, false for path and host match.
matchQuery bool
// The strictSlash value defined on the route, but disabled if PathPrefix was used.
strictSlash bool
// Determines whether to use encoded path from getPath function or unencoded
// req.URL.Path for path matching
useEncodedPath bool
// Expanded regexp.
regexp *regexp.Regexp
// Reverse template.
reverse string
// Variable names.
varsN []string
// Variable regexps (validators).
varsR []*regexp.Regexp
}
// Match matches the regexp against the URL host or path.
func (r *routeRegexp) Match(req *http.Request, match *RouteMatch) bool {
if !r.matchHost {
if r.matchQuery {
return r.matchQueryString(req)
}
path := req.URL.Path
if r.useEncodedPath {
path = getPath(req)
}
return r.regexp.MatchString(path)
}
return r.regexp.MatchString(getHost(req))
}
// url builds a URL part using the given values.
func (r *routeRegexp) url(values map[string]string) (string, error) {
urlValues := make([]interface{}, len(r.varsN))
for k, v := range r.varsN {
value, ok := values[v]
if !ok {
return "", fmt.Errorf("mux: missing route variable %q", v)
}
urlValues[k] = value
}
rv := fmt.Sprintf(r.reverse, urlValues...)
if !r.regexp.MatchString(rv) {
// The URL is checked against the full regexp, instead of checking
// individual variables. This is faster but to provide a good error
// message, we check individual regexps if the URL doesn't match.
for k, v := range r.varsN {
if !r.varsR[k].MatchString(values[v]) {
return "", fmt.Errorf(
"mux: variable %q doesn't match, expected %q", values[v],
r.varsR[k].String())
}
}
}
return rv, nil
}
// getURLQuery returns a single query parameter from a request URL.
// For a URL with foo=bar&baz=ding, we return only the relevant key
// value pair for the routeRegexp.
func (r *routeRegexp) getURLQuery(req *http.Request) string {
if !r.matchQuery {
return ""
}
templateKey := strings.SplitN(r.template, "=", 2)[0]
for key, vals := range req.URL.Query() {
if key == templateKey && len(vals) > 0 {
return key + "=" + vals[0]
}
}
return ""
}
func (r *routeRegexp) matchQueryString(req *http.Request) bool {
return r.regexp.MatchString(r.getURLQuery(req))
}
// braceIndices returns the first level curly brace indices from a string.
// It returns an error in case of unbalanced braces.
func braceIndices(s string) ([]int, error) {
var level, idx int
var idxs []int
for i := 0; i < len(s); i++ {
switch s[i] {
case '{':
if level++; level == 1 {
idx = i
}
case '}':
if level--; level == 0 {
idxs = append(idxs, idx, i+1)
} else if level < 0 {
return nil, fmt.Errorf("mux: unbalanced braces in %q", s)
}
}
}
if level != 0 {
return nil, fmt.Errorf("mux: unbalanced braces in %q", s)
}
return idxs, nil
}
// varGroupName builds a capturing group name for the indexed variable.
func varGroupName(idx int) string {
return "v" + strconv.Itoa(idx)
}
// ----------------------------------------------------------------------------
// routeRegexpGroup
// ----------------------------------------------------------------------------
// routeRegexpGroup groups the route matchers that carry variables.
type routeRegexpGroup struct {
host *routeRegexp
path *routeRegexp
queries []*routeRegexp
}
// setMatch extracts the variables from the URL once a route matches.
func (v *routeRegexpGroup) setMatch(req *http.Request, m *RouteMatch, r *Route) {
// Store host variables.
if v.host != nil {
host := getHost(req)
matches := v.host.regexp.FindStringSubmatchIndex(host)
if len(matches) > 0 {
extractVars(host, matches, v.host.varsN, m.Vars)
}
}
path := req.URL.Path
if r.useEncodedPath {
path = getPath(req)
}
// Store path variables.
if v.path != nil {
matches := v.path.regexp.FindStringSubmatchIndex(path)
if len(matches) > 0 {
extractVars(path, matches, v.path.varsN, m.Vars)
// Check if we should redirect.
if v.path.strictSlash {
p1 := strings.HasSuffix(path, "/")
p2 := strings.HasSuffix(v.path.template, "/")
if p1 != p2 {
u, _ := url.Parse(req.URL.String())
if p1 {
u.Path = u.Path[:len(u.Path)-1]
} else {
u.Path += "/"
}
m.Handler = http.RedirectHandler(u.String(), 301)
}
}
}
}
// Store query string variables.
for _, q := range v.queries {
queryURL := q.getURLQuery(req)
matches := q.regexp.FindStringSubmatchIndex(queryURL)
if len(matches) > 0 {
extractVars(queryURL, matches, q.varsN, m.Vars)
}
}
}
// getHost tries its best to return the request host.
func getHost(r *http.Request) string {
if r.URL.IsAbs() {
return r.URL.Host
}
host := r.Host
// Slice off any port information.
if i := strings.Index(host, ":"); i != -1 {
host = host[:i]
}
return host
}
func extractVars(input string, matches []int, names []string, output map[string]string) {
for i, name := range names {
output[name] = input[matches[2*i+2]:matches[2*i+3]]
}
}