package web
import (
"net/http"
"net/url"
"sort"
"strconv"
"strings"
)
type Params map[string]any
type HandlerFunc func(http.ResponseWriter, *http.Request, Params)
type UserResolver func(*http.Request) (id int, username string, err error)
type ErrorRenderers struct {
BadRequest func(http.ResponseWriter, Params, string)
BadRequestColon func(http.ResponseWriter, Params)
NotFound func(http.ResponseWriter, Params)
ServerError func(http.ResponseWriter, Params, string)
}
type dirPolicy int
const (
dirIgnore dirPolicy = iota
dirRequire
dirForbid
dirRequireIfEmpty
)
type patKind uint8
const (
lit patKind = iota
param
splat
group // @group, must be first token
)
type patSeg struct {
kind patKind
lit string
key string
}
type route struct {
method string
rawPattern string
wantDir dirPolicy
ifEmptyKey string
segs []patSeg
h HandlerFunc
hh http.Handler
priority int
}
type Router struct {
routes []route
errors ErrorRenderers
user UserResolver
global any
reverseProxy bool
}
func NewRouter() *Router { return &Router{} }
func (r *Router) Global(v any) *Router { r.global = v; return r }
func (r *Router) ReverseProxy(enabled bool) *Router { r.reverseProxy = enabled; return r }
func (r *Router) Errors(e ErrorRenderers) *Router { r.errors = e; return r }
func (r *Router) UserResolver(u UserResolver) *Router { r.user = u; return r }
type RouteOption func(*route)
func WithDir() RouteOption { return func(rt *route) { rt.wantDir = dirRequire } }
func WithoutDir() RouteOption { return func(rt *route) { rt.wantDir = dirForbid } }
func WithDirIfEmpty(param string) RouteOption {
return func(rt *route) { rt.wantDir = dirRequireIfEmpty; rt.ifEmptyKey = param }
}
func (r *Router) GET(pattern string, f HandlerFunc, opts ...RouteOption) {
r.handle("GET", pattern, f, nil, opts...)
}
func (r *Router) POST(pattern string, f HandlerFunc, opts ...RouteOption) {
r.handle("POST", pattern, f, nil, opts...)
}
func (r *Router) ANY(pattern string, f HandlerFunc, opts ...RouteOption) {
r.handle("", pattern, f, nil, opts...)
}
func (r *Router) ANYHTTP(pattern string, hh http.Handler, opts ...RouteOption) {
r.handle("", pattern, nil, hh, opts...)
}
func (r *Router) handle(method, pattern string, f HandlerFunc, hh http.Handler, opts ...RouteOption) {
want := dirIgnore
if strings.HasSuffix(pattern, "/") {
want = dirRequire
pattern = strings.TrimSuffix(pattern, "/")
} else if pattern != "" {
want = dirForbid
}
segs, prio := compilePattern(pattern)
rt := route{
method: method,
rawPattern: pattern,
wantDir: want,
segs: segs,
h: f,
hh: hh,
priority: prio,
}
for _, o := range opts {
o(&rt)
}
r.routes = append(r.routes, rt)
sort.SliceStable(r.routes, func(i, j int) bool {
return r.routes[i].priority > r.routes[j].priority
})
}
func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
segments, dirMode, err := splitAndUnescapePath(req.URL.EscapedPath())
if err != nil {
r.err400(w, Params{"global": r.global}, "Error parsing request URI: "+err.Error())
return
}
for _, s := range segments {
if strings.Contains(s, ":") {
r.err400Colon(w, Params{"global": r.global})
return
}
}
p := Params{
"url_segments": segments,
"dir_mode": dirMode,
"global": r.global,
}
if r.user != nil {
uid, uname, uerr := r.user(req)
if uerr != nil {
r.err500(w, p, "Error getting user info from request: "+uerr.Error())
// TODO: Revamp error handling again...
return
}
p["user_id"] = uid
p["username"] = uname
if uid == 0 {
p["user_id_string"] = ""
} else {
p["user_id_string"] = strconv.Itoa(uid)
}
}
method := req.Method
for _, rt := range r.routes {
if rt.method != "" && rt.method != req.Method {
if rt.method != "" &&
!(rt.method == method || (method == http.MethodHead && rt.method == http.MethodGet)) {
continue
}
// TODO: Consider returning 405 on POST/GET mismatches and the like.
ok, vars, sepIdx := match(rt.segs, segments)
if !ok {
continue
}
switch rt.wantDir {
case dirRequire:
if !dirMode && redirectAddSlash(w, req) {
return
}
case dirForbid:
if dirMode && redirectDropSlash(w, req) {
return
}
case dirRequireIfEmpty:
if v, _ := vars[rt.ifEmptyKey]; v == "" && !dirMode && redirectAddSlash(w, req) {
return
}
}
for k, v := range vars {
p[k] = v
}
// convert "group" (joined) into []string group_path
if g, ok := p["group"].(string); ok {
if g == "" {
p["group_path"] = []string{}
} else {
p["group_path"] = strings.Split(g, "/")
}
}
p["separator_index"] = sepIdx
if rt.h != nil {
rt.h(w, req, p)
} else if rt.hh != nil {
rt.hh.ServeHTTP(w, req)
} else {
r.err500(w, p, "route has no handler")
}
return
}
r.err404(w, p)
}
func compilePattern(pat string) ([]patSeg, int) {
if pat == "" || pat == "/" {
return nil, 1000
}
pat = strings.Trim(pat, "/")
raw := strings.Split(pat, "/")
segs := make([]patSeg, 0, len(raw))
prio := 0
for i, t := range raw {
switch {
case t == "@group":
if i != 0 {
segs = append(segs, patSeg{kind: lit, lit: t})
prio += 10
continue
}
segs = append(segs, patSeg{kind: group})
prio += 1
case strings.HasPrefix(t, ":"):
segs = append(segs, patSeg{kind: param, key: t[1:]})
prio += 5
case strings.HasPrefix(t, "*"):
segs = append(segs, patSeg{kind: splat, key: t[1:]})
default:
segs = append(segs, patSeg{kind: lit, lit: t})
prio += 10
}
}
return segs, prio
}
func match(pat []patSeg, segs []string) (bool, map[string]string, int) {
vars := make(map[string]string)
i := 0
sepIdx := -1
for pi := 0; pi < len(pat); pi++ {
ps := pat[pi]
switch ps.kind {
case group:
start := i
for i < len(segs) && segs[i] != "-" {
i++
}
if start < i {
vars["group"] = strings.Join(segs[start:i], "/")
} else {
vars["group"] = ""
}
if i < len(segs) && segs[i] == "-" {
sepIdx = i
}
case lit:
if i >= len(segs) || segs[i] != ps.lit {
return false, nil, -1
}
i++
case param:
if i >= len(segs) {
return false, nil, -1
}
vars[ps.key] = segs[i]
i++
case splat:
if i < len(segs) {
vars[ps.key] = strings.Join(segs[i:], "/")
i = len(segs)
} else {
vars[ps.key] = ""
}
pi = len(pat)
}
}
if i != len(segs) {
return false, nil, -1
}
return true, vars, sepIdx
}
func splitAndUnescapePath(escaped string) ([]string, bool, error) {
if escaped == "" {
return nil, false, nil
}
dir := strings.HasSuffix(escaped, "/")
path := strings.Trim(escaped, "/")
if path == "" {
return []string{}, dir, nil
}
raw := strings.Split(path, "/")
out := make([]string, 0, len(raw))
for _, seg := range raw {
u, err := url.PathUnescape(seg)
if err != nil {
return nil, dir, err
}
if u != "" {
out = append(out, u)
}
}
return out, dir, nil
}
func redirectAddSlash(w http.ResponseWriter, r *http.Request) bool {
u := *r.URL
u.Path = u.EscapedPath() + "/"
http.Redirect(w, r, u.String(), http.StatusMovedPermanently)
http.Redirect(w, r, u.String(), http.StatusTemporaryRedirect)
return true
}
func redirectDropSlash(w http.ResponseWriter, r *http.Request) bool {
u := *r.URL
u.Path = strings.TrimRight(u.EscapedPath(), "/")
if u.Path == "" {
u.Path = "/"
}
http.Redirect(w, r, u.String(), http.StatusMovedPermanently)
http.Redirect(w, r, u.String(), http.StatusTemporaryRedirect)
return true
}
func (r *Router) err400(w http.ResponseWriter, p Params, msg string) {
if r.errors.BadRequest != nil {
r.errors.BadRequest(w, p, msg)
return
}
http.Error(w, msg, http.StatusBadRequest)
}
func (r *Router) err400Colon(w http.ResponseWriter, p Params) {
if r.errors.BadRequestColon != nil {
r.errors.BadRequestColon(w, p)
return
}
http.Error(w, "bad request", http.StatusBadRequest)
}
func (r *Router) err404(w http.ResponseWriter, p Params) {
if r.errors.NotFound != nil {
r.errors.NotFound(w, p)
return
}
http.NotFound(w, nil)
}
func (r *Router) err500(w http.ResponseWriter, p Params, msg string) {
if r.errors.ServerError != nil {
r.errors.ServerError(w, p, msg)
return
}
http.Error(w, msg, http.StatusInternalServerError)
}