cdp: add Target.sendMessageToTarget support

see https://chromedevtools.github.io/devtools-protocol/tot/Target/#method-sendMessageToTarget

src/cdp/cdp.zig

@@ -31,6 +31,7 @@ const emulation = @import("emulation.zig").emulation;
 const fetch = @import("fetch.zig").fetch;
 const performance = @import("performance.zig").performance;
 const IncomingMessage = @import("msg.zig").IncomingMessage;
+const Input = @import("msg.zig").Input;
 
 const log_cdp = std.log.scoped(.cdp);
 
@@ -69,12 +70,20 @@ pub fn do(
     alloc: std.mem.Allocator,
     s: []const u8,
     ctx: *Ctx,
-) ![]const u8 {
+) anyerror![]const u8 {
 
     // incoming message parser
     var msg = IncomingMessage.init(alloc, s);
     defer msg.deinit();
 
+    return dispatch(alloc, &msg, ctx);
+}
+
+pub fn dispatch(
+    alloc: std.mem.Allocator,
+    msg: *IncomingMessage,
+    ctx: *Ctx,
+) anyerror![]const u8 {
     const method = try msg.getMethod();
 
     // retrieve domain from method
@@ -85,15 +94,15 @@ pub fn do(
     // select corresponding domain
     const action = iter.next() orelse return error.BadMethod;
     return switch (domain) {
-        .Browser => browser(alloc, &msg, action, ctx),
-        .Target => target(alloc, &msg, action, ctx),
-        .Page => page(alloc, &msg, action, ctx),
-        .Log => log(alloc, &msg, action, ctx),
-        .Runtime => runtime(alloc, &msg, action, ctx),
-        .Network => network(alloc, &msg, action, ctx),
-        .Emulation => emulation(alloc, &msg, action, ctx),
-        .Fetch => fetch(alloc, &msg, action, ctx),
-        .Performance => performance(alloc, &msg, action, ctx),
+        .Browser => browser(alloc, msg, action, ctx),
+        .Target => target(alloc, msg, action, ctx),
+        .Page => page(alloc, msg, action, ctx),
+        .Log => log(alloc, msg, action, ctx),
+        .Runtime => runtime(alloc, msg, action, ctx),
+        .Network => network(alloc, msg, action, ctx),
+        .Emulation => emulation(alloc, msg, action, ctx),
+        .Fetch => fetch(alloc, msg, action, ctx),
+        .Performance => performance(alloc, msg, action, ctx),
     };
 }
 

src/cdp/msg.zig

@@ -130,7 +130,8 @@ pub const IncomingMessage = struct {
     // asking for getParams, we don't know how to parse them.
     fn scanParams(self: *IncomingMessage) !void {
         const tt = try self.scanner.peekNextTokenType();
-        if (tt != .object_begin) return error.InvalidParams;
+        // accept object begin or null JSON value.
+        if (tt != .object_begin and tt != .null) return error.InvalidParams;
         try self.scanner.skipValue();
         self.params_skip = true;
     }

src/cdp/target.zig

@@ -38,6 +38,7 @@ const Methods = enum {
     disposeBrowserContext,
     createTarget,
     closeTarget,
+    sendMessageToTarget,
 };
 
 pub fn target(
@@ -58,6 +59,7 @@ pub fn target(
         .disposeBrowserContext => disposeBrowserContext(alloc, msg, ctx),
         .createTarget => createTarget(alloc, msg, ctx),
         .closeTarget => closeTarget(alloc, msg, ctx),
+        .sendMessageToTarget => sendMessageToTarget(alloc, msg, ctx),
     };
 }
 
@@ -438,3 +440,44 @@ fn closeTarget(
 
     return "";
 }
+
+// noop
+fn sendMessageToTarget(
+    alloc: std.mem.Allocator,
+    msg: *IncomingMessage,
+    ctx: *Ctx,
+) ![]const u8 {
+    // input
+    const Params = struct {
+        message: []const u8,
+        sessionId: []const u8,
+    };
+    const input = try Input(Params).get(alloc, msg);
+    defer input.deinit();
+    log.debug("Req > id {d}, method {s}", .{ input.id, "target.sendMessageToTarget" });
+
+    // get the wrapped message.
+    var wmsg = IncomingMessage.init(alloc, input.params.message);
+    defer wmsg.deinit();
+
+    const res = try cdp.dispatch(alloc, &wmsg, ctx);
+
+    // receivedMessageFromTarget event
+    const ReceivedMessageFromTarget = struct {
+        sessionId: []const u8,
+        message: []const u8,
+    };
+    try cdp.sendEvent(
+        alloc,
+        ctx,
+        "Target.receivedMessageFromTarget",
+        ReceivedMessageFromTarget,
+        .{
+            .sessionId = input.params.sessionId,
+            .message = res,
+        },
+        input.params.sessionId,
+    );
+
+    return "";
+}