feat: make corehttp a reusable component

core/corehttp/gateway.go

@@ -1,18 +1,20 @@
 package corehttp
 
 import (
+	"context"
 	"fmt"
 	"net"
 	"net/http"
 	"sort"
 
+	coreiface "github.com/ipfs/interface-go-ipfs-core"
+	options "github.com/ipfs/interface-go-ipfs-core/options"
+	path "github.com/ipfs/interface-go-ipfs-core/path"
 	version "github.com/ipfs/kubo"
 	core "github.com/ipfs/kubo/core"
 	coreapi "github.com/ipfs/kubo/core/coreapi"
-	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
-
-	options "github.com/ipfs/interface-go-ipfs-core/options"
 	id "github.com/libp2p/go-libp2p/p2p/protocol/identify"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 )
 
 type GatewayConfig struct {
@@ -22,6 +24,21 @@ type GatewayConfig struct {
 	FastDirIndexThreshold int
 }
 
+// NodeAPI defines the minimal set of API services required by a gateway handler
+type NodeAPI interface {
+	// Unixfs returns an implementation of Unixfs API
+	Unixfs() coreiface.UnixfsAPI
+
+	// Block returns an implementation of Block API
+	Block() coreiface.BlockAPI
+
+	// Dag returns an implementation of Dag API
+	Dag() coreiface.APIDagService
+
+	// ResolvePath resolves the path using Unixfs resolver
+	ResolvePath(context.Context, path.Path) (path.Resolved, error)
+}
+
 // A helper function to clean up a set of headers:
 // 1. Canonicalizes.
 // 2. Deduplicates.
@@ -59,49 +76,19 @@ func GatewayOption(writable bool, paths ...string) ServeOption {
 			headers[http.CanonicalHeaderKey(h)] = v
 		}
 
-		// Hard-coded headers.
-		const ACAHeadersName = "Access-Control-Allow-Headers"
-		const ACEHeadersName = "Access-Control-Expose-Headers"
-		const ACAOriginName = "Access-Control-Allow-Origin"
-		const ACAMethodsName = "Access-Control-Allow-Methods"
+		AddAccessControlHeaders(headers)
 
-		if _, ok := headers[ACAOriginName]; !ok {
-			// Default to *all*
-			headers[ACAOriginName] = []string{"*"}
-		}
-		if _, ok := headers[ACAMethodsName]; !ok {
-			// Default to GET
-			headers[ACAMethodsName] = []string{http.MethodGet}
+		offlineApi, err := api.WithOptions(options.Api.Offline(true))
+		if err != nil {
+			return nil, err
 		}
 
-		headers[ACAHeadersName] = cleanHeaderSet(
-			append([]string{
-				"Content-Type",
-				"User-Agent",
-				"Range",
-				"X-Requested-With",
-			}, headers[ACAHeadersName]...))
-
-		headers[ACEHeadersName] = cleanHeaderSet(
-			append([]string{
-				"Content-Length",
-				"Content-Range",
-				"X-Chunked-Output",
-				"X-Stream-Output",
-				"X-Ipfs-Path",
-				"X-Ipfs-Roots",
-			}, headers[ACEHeadersName]...))
-
-		var gateway http.Handler
-		gateway, err = newGatewayHandler(GatewayConfig{
+		gateway := NewGatewayHandler(GatewayConfig{
 			Headers:               headers,
 			Writable:              writable,
 			PathPrefixes:          cfg.Gateway.PathPrefixes,
 			FastDirIndexThreshold: int(cfg.Gateway.FastDirIndexThreshold.WithDefault(100)),
-		}, api)
-		if err != nil {
-			return nil, err
-		}
+		}, api, offlineApi)
 
 		gateway = otelhttp.NewHandler(gateway, "Gateway.Request")
 
@@ -112,6 +99,50 @@ func GatewayOption(writable bool, paths ...string) ServeOption {
 	}
 }
 
+// AddAccessControlHeaders adds default headers used for controlling
+// cross-origin requests. This function adds several values to the
+// Access-Control-Allow-Headers and Access-Control-Expose-Headers entries.
+// If the Access-Control-Allow-Origin entry is missing a value of '*' is
+// added, indicating that browsers should allow requesting code from any
+// origin to access the resource.
+// If the Access-Control-Allow-Methods entry is missing a value of 'GET' is
+// added, indicating that browsers may use the GET method when issuing cross
+// origin requests.
+func AddAccessControlHeaders(headers map[string][]string) {
+	// Hard-coded headers.
+	const ACAHeadersName = "Access-Control-Allow-Headers"
+	const ACEHeadersName = "Access-Control-Expose-Headers"
+	const ACAOriginName = "Access-Control-Allow-Origin"
+	const ACAMethodsName = "Access-Control-Allow-Methods"
+
+	if _, ok := headers[ACAOriginName]; !ok {
+		// Default to *all*
+		headers[ACAOriginName] = []string{"*"}
+	}
+	if _, ok := headers[ACAMethodsName]; !ok {
+		// Default to GET
+		headers[ACAMethodsName] = []string{http.MethodGet}
+	}
+
+	headers[ACAHeadersName] = cleanHeaderSet(
+		append([]string{
+			"Content-Type",
+			"User-Agent",
+			"Range",
+			"X-Requested-With",
+		}, headers[ACAHeadersName]...))
+
+	headers[ACEHeadersName] = cleanHeaderSet(
+		append([]string{
+			"Content-Length",
+			"Content-Range",
+			"X-Chunked-Output",
+			"X-Stream-Output",
+			"X-Ipfs-Path",
+			"X-Ipfs-Roots",
+		}, headers[ACEHeadersName]...))
+}
+
 func VersionOption() ServeOption {
 	return func(_ *core.IpfsNode, _ net.Listener, mux *http.ServeMux) (*http.ServeMux, error) {
 		mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {

core/corehttp/gateway_handler.go

@@ -24,7 +24,6 @@ import (
 	path "github.com/ipfs/go-path"
 	"github.com/ipfs/go-path/resolver"
 	coreiface "github.com/ipfs/interface-go-ipfs-core"
-	options "github.com/ipfs/interface-go-ipfs-core/options"
 	ipath "github.com/ipfs/interface-go-ipfs-core/path"
 	routing "github.com/libp2p/go-libp2p-core/routing"
 	prometheus "github.com/prometheus/client_golang/prometheus"
@@ -68,8 +67,8 @@ type redirectTemplateData struct {
 // (it serves requests like GET /ipfs/QmVRzPKPzNtSrEzBFm2UZfxmPAgnaLke4DMcerbsGGSaFe/link)
 type gatewayHandler struct {
 	config     GatewayConfig
-	api        coreiface.CoreAPI
-	offlineApi coreiface.CoreAPI
+	api        NodeAPI
+	offlineApi NodeAPI
 
 	// generic metrics
 	firstContentBlockGetMetric *prometheus.HistogramVec
@@ -213,11 +212,13 @@ func newGatewayHistogramMetric(name string, help string) *prometheus.HistogramVe
 	return histogramMetric
 }
 
-func newGatewayHandler(c GatewayConfig, api coreiface.CoreAPI) (*gatewayHandler, error) {
-	offlineApi, err := api.WithOptions(options.Api.Offline(true))
-	if err != nil {
-		return nil, err
-	}
+// NewGatewayHandler returns an http.Handler that can act as a gateway to IPFS content
+// offlineApi is a version of the API that should not make network requests for missing data
+func NewGatewayHandler(c GatewayConfig, api NodeAPI, offlineApi NodeAPI) http.Handler {
+	return newGatewayHandler(c, api, offlineApi)
+}
+
+func newGatewayHandler(c GatewayConfig, api NodeAPI, offlineApi NodeAPI) *gatewayHandler {
 	i := &gatewayHandler{
 		config:     c,
 		api:        api,
@@ -262,7 +263,7 @@ func newGatewayHandler(c GatewayConfig, api coreiface.CoreAPI) (*gatewayHandler,
 			"The time to receive the first UnixFS node on a GET from the gateway.",
 		),
 	}
-	return i, nil
+	return i
 }
 
 func parseIpfsPath(p string) (cid.Cid, string, error) {