Initial Commit

packages/networking/drive/drive-webrtc/src/client/offer-answer/offer-answer.ts

@@ -0,0 +1,113 @@
+/**
+ * SDP offer / answer primitives.
+ *
+ * Pure async wrappers over the spec-standard
+ * `pc.createOffer() → pc.setLocalDescription()` pattern (and inverse).
+ * Every failure mode is translated into `DriveWebRtcError(PEER_HANDSHAKE_FAILED)`
+ * with the original DOMException attached as `cause` so callers never see
+ * raw browser errors leak past the package boundary.
+ */
+
+import {
+    DRIVE_WEBRTC_CODES,
+    DriveWebRtcError,
+} from "../../error-codes/error-codes.js";
+
+function throwIfAborted(signal: AbortSignal | undefined, where: string): void {
+    if (signal?.aborted === true) {
+        throw new DriveWebRtcError(
+            DRIVE_WEBRTC_CODES.PEER_HANDSHAKE_FAILED,
+            `${where} aborted`
+        );
+    }
+}
+
+function wrap(cause: unknown, message: string): DriveWebRtcError {
+    return new DriveWebRtcError(
+        DRIVE_WEBRTC_CODES.PEER_HANDSHAKE_FAILED,
+        message,
+        { cause: cause as Error }
+    );
+}
+
+/**
+ * Create an SDP offer on `pc`, apply it as local description, and return it.
+ */
+export async function createOffer(
+    pc: RTCPeerConnection,
+    signal?: AbortSignal
+): Promise<RTCSessionDescriptionInit> {
+    throwIfAborted(signal, "createOffer");
+    let offer: RTCSessionDescriptionInit;
+    try {
+        offer = await pc.createOffer();
+    } catch (cause) {
+        throw wrap(cause, "RTCPeerConnection.createOffer failed");
+    }
+    throwIfAborted(signal, "createOffer");
+    try {
+        await pc.setLocalDescription(offer);
+    } catch (cause) {
+        throw wrap(
+            cause,
+            "RTCPeerConnection.setLocalDescription(offer) failed"
+        );
+    }
+    return offer;
+}
+
+/**
+ * Apply a remote offer to `pc`, create an answer, apply it as local
+ * description, and return the answer.
+ */
+export async function handleOffer(
+    pc: RTCPeerConnection,
+    offer: RTCSessionDescriptionInit,
+    signal?: AbortSignal
+): Promise<RTCSessionDescriptionInit> {
+    throwIfAborted(signal, "handleOffer");
+    try {
+        await pc.setRemoteDescription(offer);
+    } catch (cause) {
+        throw wrap(
+            cause,
+            "RTCPeerConnection.setRemoteDescription(offer) failed"
+        );
+    }
+    throwIfAborted(signal, "handleOffer");
+    let answer: RTCSessionDescriptionInit;
+    try {
+        answer = await pc.createAnswer();
+    } catch (cause) {
+        throw wrap(cause, "RTCPeerConnection.createAnswer failed");
+    }
+    throwIfAborted(signal, "handleOffer");
+    try {
+        await pc.setLocalDescription(answer);
+    } catch (cause) {
+        throw wrap(
+            cause,
+            "RTCPeerConnection.setLocalDescription(answer) failed"
+        );
+    }
+    return answer;
+}
+
+/**
+ * Apply a remote answer to an outbound offer we already sent.
+ */
+export async function handleAnswer(
+    pc: RTCPeerConnection,
+    answer: RTCSessionDescriptionInit,
+    signal?: AbortSignal
+): Promise<void> {
+    throwIfAborted(signal, "handleAnswer");
+    try {
+        await pc.setRemoteDescription(answer);
+    } catch (cause) {
+        throw wrap(
+            cause,
+            "RTCPeerConnection.setRemoteDescription(answer) failed"
+        );
+    }
+}