feat: make it possible to access http response headers (#47)

env.go

@@ -120,6 +120,11 @@ func extismHTTPRequest(request, body extismPointer) extismPointer
 //go:wasmimport extism:host/env http_status_code
 func extismHTTPStatusCode() int32
 
+// extismHTTPHeaders returns the response headers for the last-sent `extism_http_request` call.
+//
+//go:wasmimport extism:host/env http_headers
+func extismHTTPHeaders() extismPointer
+
 // extismLogInfo logs an "info" string to the host from the previously-written UTF-8 string written to `offset`.
 // Note that the memory at `offset` can be immediately freed because it is immediately logged.
 //

extism_pdk.go

@@ -312,8 +312,9 @@ type HTTPRequest struct {
 
 // HTTPResponse represents an HTTP response returned from the host.
 type HTTPResponse struct {
-	memory Memory
-	status uint16
+	memory  Memory
+	status  uint16
+	headers map[string]string
 }
 
 // Memory returns the memory associated with the `HTTPResponse`.
@@ -337,6 +338,11 @@ func (r HTTPResponse) Status() uint16 {
 	return r.status
 }
 
+// Headers returns a map containing the HTTP response headers
+func (r *HTTPResponse) Headers() map[string]string {
+	return r.headers
+}
+
 // HTTPMethod represents an HTTP method.
 type HTTPMethod int32
 
@@ -421,11 +427,22 @@ func (r *HTTPRequest) Send() HTTPResponse {
 	length := extismLengthUnsafe(offset)
 	status := uint16(extismHTTPStatusCode())
 
+	headersOffs := extismHTTPHeaders()
+	headers := map[string]string{}
+
+	if headersOffs != 0 {
+		length := extismLengthUnsafe(headersOffs)
+		mem := Memory{offset: headersOffs, length: length}
+		defer mem.Free()
+		json.Unmarshal(mem.ReadBytes(), &headers)
+	}
+
 	memory := Memory{offset, length}
 
 	return HTTPResponse{
 		memory,
 		status,
+		headers,
 	}
 }