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handler.go
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handler.go
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package restli
import (
"context"
"fmt"
"io"
"log"
"net/http"
"runtime/debug"
"strconv"
"strings"
"github.com/PapaCharlie/go-restli/restli/batchkeyset"
"github.com/PapaCharlie/go-restli/restlicodec"
"github.com/PapaCharlie/go-restli/restlidata"
)
type handler func(
ctx *RequestContext,
segments []restlicodec.Reader,
body []byte,
) (responseBody restlicodec.Marshaler, err error)
type rootNode struct {
*pathNode
prefix string
filters []Filter
}
type pathNode struct {
ResourcePathSegment
rootNode *rootNode
methods map[Method]handler
finders map[string]handler
actions map[string]handler
subNodes map[string]*pathNode
}
func copyMap[K comparable, V any](m map[K]V) map[K]V {
mCopy := make(map[K]V, len(m))
for k, v := range m {
mCopy[k] = v
}
return mCopy
}
func copyCloneableMap[K comparable, V interface{ clone() V }](m map[K]V) map[K]V {
mCopy := make(map[K]V, len(m))
for k, v := range m {
mCopy[k] = v.clone()
}
return mCopy
}
func (p *pathNode) clone() *pathNode {
return &pathNode{
ResourcePathSegment: p.ResourcePathSegment,
rootNode: p.rootNode,
methods: copyMap(p.methods),
finders: copyMap(p.finders),
actions: copyMap(p.actions),
subNodes: copyCloneableMap(p.subNodes),
}
}
func (r *rootNode) Handler() http.Handler {
deepCopy := &rootNode{
prefix: r.prefix,
filters: append([]Filter(nil), r.filters...),
}
p := new(pathNode)
*p = *r.pathNode
p.rootNode = deepCopy
deepCopy.pathNode = p.clone()
return deepCopy
}
func (r *rootNode) ServeHTTP(res http.ResponseWriter, req *http.Request) {
path := req.URL.RawPath
if path == "" {
path = req.URL.Path
}
if !strings.HasPrefix(path, r.prefix) {
http.NotFound(res, req)
return
}
path = strings.TrimPrefix(path, r.prefix)
segments := strings.Split(path, "/")
if len(segments) == 0 || r.subNodes[segments[0]] == nil {
http.NotFound(res, req)
return
}
sub := r.subNodes[segments[0]]
ctx := &RequestContext{
Request: req,
ResponseHeaders: res.Header(),
ResponseStatus: http.StatusOK,
}
res.Header().Set(ProtocolVersionHeader, ProtocolVersion)
responseBody, err := sub.receive(ctx, nil, nil, segments)
if err == nil {
for i := len(r.filters) - 1; i >= 0; i-- {
err = r.filters[i].PostRequest(ctx.Request.Context(), res.Header())
if err != nil {
break
}
}
}
if errRes, ok := err.(*restlidata.ErrorResponse); ok {
res.Header().Set(ErrorResponseHeader, "true")
responseBody = errRes
if errRes.Status != nil {
ctx.ResponseStatus = int(*errRes.Status)
} else {
ctx.ResponseStatus = http.StatusInternalServerError
}
if errRes.Message == nil {
errRes.Message = StringPointer(http.StatusText(int(*errRes.Status)))
}
} else if err != nil {
http.Error(res, err.Error(), http.StatusInternalServerError)
return
}
if responseBody != nil {
w := restlicodec.NewCompactJsonWriter()
err = responseBody.MarshalRestLi(w)
if err != nil {
http.Error(res, err.Error(), http.StatusInternalServerError)
return
} else {
data := []byte(w.Finalize())
res.Header().Set("Content-Type", "application/json")
res.Header().Set("Content-Length", strconv.Itoa(len(data)))
res.WriteHeader(ctx.ResponseStatus)
// not much we can do about this error
_, _ = res.Write(data)
}
} else {
res.WriteHeader(ctx.ResponseStatus)
}
}
func (p *pathNode) receive(
ctx *RequestContext,
pathSegments []ResourcePathSegment,
entitySegments []restlicodec.Reader,
remainingSegments []string,
) (responseBody restlicodec.Marshaler, err error) {
pathSegments = append(pathSegments, p.ResourcePathSegment)
hasEntity := false
if len(remainingSegments) >= 1 {
if p.isCollection && len(remainingSegments) > 1 {
var r restlicodec.Reader
r, err = restlicodec.NewRor2Reader(remainingSegments[1])
if err != nil {
return newErrorResponsef(err, http.StatusNotFound, "Invalid path segment %q: %s", remainingSegments[1])
}
hasEntity = true
entitySegments = append(entitySegments, r)
remainingSegments = remainingSegments[2:]
} else {
remainingSegments = remainingSegments[1:]
}
if len(remainingSegments) != 0 {
subResource := remainingSegments[0]
if sub, ok := p.subNodes[subResource]; ok {
return sub.receive(ctx, pathSegments, entitySegments, remainingSegments)
} else {
return newErrorResponsef(nil, http.StatusNotFound, "Unknown sub resource: %q", subResource)
}
}
}
restLiMethod := MethodNameMapping[ctx.Request.Header.Get(MethodHeader)]
httpMethod := ctx.Request.Method
params, err := restlicodec.ParseQueryParams(ctx.Request.URL.RawQuery)
if err != nil {
return nil, err
}
var finder string
if q, ok := params["q"]; ok {
finder = q.String()
}
var action string
if a, ok := params["action"]; ok {
action = a.String()
}
if p.isCollection {
// For whatever reason rest.li makes the method header optional, because it supposedly can be inferred from the
// method itself and query params. The documentation (https://linkedin.github.io/rest.li/spec/protocol#message-headers)
// implies this procedure is unambiguous so the following assumes "q", "action" and "ids" are reserved query
// parameter names for their corresponding HTTP method to make the routing simpler. In practice, this isn't
// actually true since the Java implementation lets you define query parameters named "q" or "action" for
// methods like GET, but until this bites, this is how this logic will be implemented.
if restLiMethod == Method_Unknown {
hasIds := params[batchkeyset.EntityIDsField] != nil
switch httpMethod {
case http.MethodGet:
switch {
// Only the GET method can specify an entity, so skip checking the query params
case hasEntity:
restLiMethod = Method_get
case finder != "":
restLiMethod = Method_finder
case hasIds:
restLiMethod = Method_batch_get
default:
restLiMethod = Method_get_all
}
case http.MethodPost:
return newErrorResponsef(nil, http.StatusBadRequest,
"Header %q is required for POST requests", MethodHeader)
case http.MethodDelete:
if hasIds {
restLiMethod = Method_batch_delete
} else {
restLiMethod = Method_delete
}
case http.MethodPut:
if hasIds {
restLiMethod = Method_batch_update
} else {
restLiMethod = Method_update
}
}
}
switch restLiMethod {
case Method_get, Method_delete, Method_update, Method_partial_update:
if !hasEntity {
return newErrorResponsef(nil, http.StatusBadRequest, "No entity provided for %q method", restLiMethod)
}
case Method_finder, Method_create, Method_batch_get, Method_batch_create, Method_batch_delete,
Method_batch_update, Method_batch_partial_update, Method_get_all:
if hasEntity {
return newErrorResponsef(nil, http.StatusBadRequest, "Cannot provide an entity for %q", restLiMethod)
}
}
} else {
switch httpMethod {
case http.MethodGet:
restLiMethod = Method_get
case http.MethodPut:
restLiMethod = Method_update
case http.MethodDelete:
restLiMethod = Method_delete
case http.MethodPost:
if action != "" {
restLiMethod = Method_action
} else {
restLiMethod = Method_partial_update
}
}
if hasEntity {
return newErrorResponsef(nil, http.StatusBadRequest, "Cannot provide an entity for simple resources")
}
}
newCtx := context.WithValue(ctx.Request.Context(), methodCtxKey, restLiMethod)
newCtx = context.WithValue(newCtx, resourcePathSegmentsCtxKey, pathSegments)
newCtx = context.WithValue(newCtx, entitySegmentsCtxKey, entitySegments)
var h handler
if restLiMethod == Method_finder {
h = p.finders[finder]
if h == nil {
return newErrorResponsef(nil, http.StatusBadRequest, "Finder %q not defined on %q", finder, p.name)
}
newCtx = context.WithValue(newCtx, finderNameCtxKey, finder)
} else if restLiMethod == Method_action {
h = p.actions[action]
if h == nil {
return newErrorResponsef(nil, http.StatusBadRequest, "Action %q not defined on %q", action, p.name)
}
newCtx = context.WithValue(newCtx, actionNameCtxKey, action)
} else {
h = p.methods[restLiMethod]
if h == nil {
return newErrorResponsef(nil, http.StatusBadRequest, "%q not defined on %q", restLiMethod, p.name)
}
}
defer func() {
if r := recover(); r != nil {
stack := string(debug.Stack())
log.Printf("Failed to handle %q (%s)\n%s", ctx.Request.URL, r, stack)
err = &restlidata.ErrorResponse{
Status: Int32Pointer(http.StatusInternalServerError),
Message: StringPointer(fmt.Sprint(r)),
StackTrace: &stack,
}
}
}()
body, err := io.ReadAll(ctx.Request.Body)
if err != nil {
return nil, err
}
ctx.Request = ctx.Request.WithContext(newCtx)
for _, f := range p.rootNode.filters {
newCtx, err = f.PreRequest(ctx.Request)
if err != nil {
return nil, err
}
if newCtx != nil {
ctx.Request = ctx.Request.WithContext(newCtx)
}
}
return h(ctx, entitySegments, body)
}
func GetMethodFromContext(ctx context.Context) Method {
return ctx.Value(methodCtxKey).(Method)
}
func GetResourcePathSegmentsFromContext(ctx context.Context) []ResourcePathSegment {
return ctx.Value(resourcePathSegmentsCtxKey).([]ResourcePathSegment)
}
func GetEntitySegmentsFromContext(ctx context.Context) []restlicodec.Reader {
segments := ctx.Value(entitySegmentsCtxKey).([]restlicodec.Reader)
clonedSegments := make([]restlicodec.Reader, len(segments))
for i, r := range segments {
clonedSegments[i] = r.Clone()
}
return clonedSegments
}
func GetFinderNameFromContext(ctx context.Context) string {
return ctx.Value(finderNameCtxKey).(string)
}
func GetActionNameFromContext(ctx context.Context) string {
return ctx.Value(actionNameCtxKey).(string)
}
func newErrorResponsef(cause error, status int, format string, a ...any) (restlicodec.Marshaler, error) {
if e, ok := cause.(*restlidata.ErrorResponse); ok {
return nil, e
}
if cause != nil {
a = append(a, cause)
}
return nil, &restlidata.ErrorResponse{
Status: Int32Pointer(int32(status)),
Message: StringPointerf(format, a...),
}
}
type Server interface {
// AddToMux adds a http.Handler for each root resource registered against this Server. Note that resources
// registered to this Server after AddToMux is called will not be reflected.
AddToMux(mux *http.ServeMux)
// Handler returns a raw http.Handler backed by a copy of this sever. Note that resources registered to this Server
// after Handler will not be reflected. This is not meant to be used in conjunction with a http.ServeMux, but
// instead with methods like http.ListenAndServe or http.ListenAndServeTLS
Handler() http.Handler
subNode(segments []ResourcePathSegment) *pathNode
}
func (p *pathNode) newSubNode(segment ResourcePathSegment) *pathNode {
return &pathNode{
ResourcePathSegment: segment,
rootNode: p.rootNode,
methods: map[Method]handler{},
finders: map[string]handler{},
actions: map[string]handler{},
subNodes: map[string]*pathNode{},
}
}
// Filter implementations can enrich the request as it comes in by adding values to the context. They also receive a
// callback to add any response headers, if necessary. Filters' PreRequest methods will ve called in the order in which
// they were passed to NewServer, and PostRequest methods in the inverse order.
type Filter interface {
// PreRequest is called after the request is parsed and the corresponding method is found. It is not called on any
// invalid requests. The request's context will have corresponding values for the method, resource segments, entity
// segments, finder name (only set if the method is Method_finder) and action name (only set if the method is
// Method_action). Use the corresponding FromContext methods to get the values. If the returned context is non-nil,
// it will replace the context passed to the actual resource implementation.
PreRequest(req *http.Request) (context.Context, error)
// PostRequest is called with the original request context and the response header map right before the response
// header is written.
PostRequest(ctx context.Context, responseHeaders http.Header) error
}
func NewPrefixedServer(prefix string, filters ...Filter) Server {
if prefix == "" {
prefix = "/"
}
if !strings.HasSuffix(prefix, "/") {
prefix += "/"
}
r := &rootNode{
pathNode: &pathNode{
ResourcePathSegment: ResourcePathSegment{},
methods: map[Method]handler{},
finders: map[string]handler{},
actions: map[string]handler{},
subNodes: map[string]*pathNode{},
},
prefix: "/",
filters: filters,
}
r.rootNode = r
return r
}
func NewServer(filters ...Filter) Server {
return NewPrefixedServer("/", filters...)
}
type ResourcePathSegment struct {
name string
isCollection bool
}
func NewResourcePathSegment(name string, isCollection bool) ResourcePathSegment {
return ResourcePathSegment{
name: name,
isCollection: isCollection,
}
}
func (p *pathNode) subNode(segments []ResourcePathSegment) *pathNode {
subNode := p
for _, s := range segments {
if subNode.subNodes == nil {
subNode.subNodes = make(map[string]*pathNode)
}
if subNode.subNodes[s.name] == nil {
subNode.subNodes[s.name] = subNode.newSubNode(s)
}
subNode = subNode.subNodes[s.name]
if subNode.isCollection != s.isCollection {
log.Panicf("go-restli: Inconsistent isCollection value for %v", segments)
}
}
return subNode
}
func (r *rootNode) AddToMux(mux *http.ServeMux) {
h := r.Handler()
for rootResource := range r.subNodes {
mux.Handle(r.prefix+rootResource, h)
}
}
func registerMethod[RP ResourcePathUnmarshaler[RP], QP restlicodec.QueryParamsDecoder[QP]](
s Server,
segments []ResourcePathSegment,
method Method,
h func(
ctx *RequestContext,
rp RP,
qp QP,
body []byte,
) (responseBody restlicodec.Marshaler, err error),
) {
p := s.subNode(segments)
if _, ok := p.methods[method]; ok {
log.Panicf("go-restli: Cannot register method %q twice for %v", method, segments)
}
p.methods[method] = func(
ctx *RequestContext,
segments []restlicodec.Reader,
body []byte,
) (responseBody restlicodec.Marshaler, err error) {
rp, err := UnmarshalResourcePath[RP](segments)
if err != nil {
return newErrorResponsef(err, http.StatusBadRequest, "Invalid path for %q: %s", method)
}
var queryParams QP
if !restlidata.IsEmptyRecord(queryParams) {
queryParams, err = restlicodec.UnmarshalQueryParamsDecoder[QP](ctx.Request.URL.RawQuery)
if err != nil {
return newErrorResponsef(err, http.StatusBadRequest, "Invalid query params for %q: %s", method)
}
}
responseBody, err = h(ctx, rp, queryParams, body)
if _, ok := err.(*restlidata.ErrorResponse); err != nil && !ok {
return newErrorResponsef(err, http.StatusInternalServerError, "%q failed: %s", method)
} else {
return responseBody, err
}
}
}
func registerMethodWithNoBody[RP ResourcePathUnmarshaler[RP], QP restlicodec.QueryParamsDecoder[QP]](
s Server,
segments []ResourcePathSegment,
method Method,
h func(
ctx *RequestContext,
rp RP,
qp QP,
) (responseBody restlicodec.Marshaler, err error),
) {
registerMethod(s, segments, method,
func(ctx *RequestContext, rp RP, qp QP, body []byte) (responseBody restlicodec.Marshaler, err error) {
if len(body) != 0 {
return newErrorResponsef(nil, http.StatusBadRequest, "%q does not take a body", method)
}
return h(ctx, rp, qp)
})
}
func registerMethodWithBody[RP ResourcePathUnmarshaler[RP], QP restlicodec.QueryParamsDecoder[QP], V any](
s Server,
segments []ResourcePathSegment,
method Method,
excludedFields restlicodec.PathSpec,
leadingScopeToIgnore int,
unmarshaler restlicodec.GenericUnmarshaler[V],
h func(
ctx *RequestContext,
rp RP,
v V,
qp QP,
) (responseBody restlicodec.Marshaler, err error),
) {
registerMethod(s, segments, method,
func(ctx *RequestContext, rp RP, qp QP, body []byte) (responseBody restlicodec.Marshaler, err error) {
var v V
r, err := restlicodec.NewJsonReaderWithExcludedFields(body, excludedFields, leadingScopeToIgnore)
if err == nil {
v, err = unmarshaler(r)
}
if err != nil {
return newErrorResponsef(err, http.StatusBadRequest, "Invalid request body for %q: %s", method)
}
return h(ctx, rp, v, qp)
})
}
type RequestContext struct {
Request *http.Request
ResponseHeaders http.Header
ResponseStatus int
}
func SetLocation[K any](ctx *RequestContext, c *restlidata.CreatedEntity[K]) error {
c.Location = new(string)
w := restlicodec.NewRor2PathWriter()
err := restlicodec.MarshalRestLi[K](c.Id, w)
if err != nil {
return err
}
*c.Location = strings.TrimSuffix(ctx.Request.RequestURI, "/") + "/" + w.Finalize()
return nil
}