Handle CDP messages with different order

The 'method' still needs to be the first or the second key
(in this case after the 'id').

Signed-off-by: Francis Bouvier <francis@lightpanda.io>

src/cdp/browser.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 
 const BrowserMethods = enum {
     getVersion,
@@ -15,7 +15,7 @@ const BrowserMethods = enum {
 
 pub fn browser(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
@@ -38,10 +38,12 @@ const JsVersion = "12.4.254.8";
 
 fn browserGetVersion(
     alloc: std.mem.Allocator,
-    id: u64,
-    _: *std.json.Scanner,
+    id: ?u16,
+    scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
+    const msg = try getMsg(alloc, void, scanner);
+
     const Res = struct {
         protocolVersion: []const u8,
         product: []const u8,
@@ -57,12 +59,12 @@ fn browserGetVersion(
         .userAgent = UserAgent,
         .jsVersion = JsVersion,
     };
-    return result(alloc, id, Res, res, null);
+    return result(alloc, id orelse msg.id.?, Res, res, null);
 }
 
 fn browserSetDownloadBehavior(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
@@ -72,15 +74,15 @@ fn browserSetDownloadBehavior(
         downloadPath: ?[]const u8 = null,
         eventsEnabled: ?bool = null,
     };
-    _ = try getParams(alloc, Params, scanner);
-    return result(alloc, id, null, null, null);
+    const msg = try getMsg(alloc, Params, scanner);
+    return result(alloc, id orelse msg.id.?, null, null, null);
 }
 
 const DevToolsWindowID = 1923710101;
 
 fn getWindowForTarget(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
@@ -89,8 +91,8 @@ fn getWindowForTarget(
     const Params = struct {
         targetId: ?[]const u8 = null,
     };
-    const content = try cdp.getContent(alloc, ?Params, scanner);
-    std.debug.assert(content.sessionID != null);
+    const msg = try cdp.getMsg(alloc, ?Params, scanner);
+    std.debug.assert(msg.sessionID != null);
 
     // output
     const Resp = struct {
@@ -103,16 +105,16 @@ fn getWindowForTarget(
             windowState: []const u8 = "normal",
         } = .{},
     };
-    return result(alloc, id, Resp, Resp{}, content.sessionID.?);
+    return result(alloc, id orelse msg.id.?, Resp, Resp{}, msg.sessionID.?);
 }
 
 fn setWindowBounds(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
     // NOTE: noop
-    const content = try cdp.getContent(alloc, void, scanner);
-    return result(alloc, id, null, null, content.sessionID);
+    const msg = try cdp.getMsg(alloc, void, scanner);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }

src/cdp/cdp.zig

@@ -53,26 +53,22 @@ pub fn do(
     // handle 2 possible orders:
     // - id, method <...>
     // - method, id <...>
-    var id_key = (try scanner.next()).string;
-    var id_token = try scanner.next();
     var method_key = (try scanner.next()).string;
-    var method_token = try scanner.next();
+    var method_token: std.json.Token = undefined;
+    var id: ?u16 = null;
     // check swap order
-    if (!std.mem.eql(u8, id_key, "id")) {
-        const swap_key = method_key;
-        const swap_token = method_token;
-        method_key = id_key;
-        method_token = id_token;
-        id_key = swap_key;
-        id_token = swap_token;
+    if (std.mem.eql(u8, method_key, "id")) {
+        id = try getId(&scanner, method_key);
+        method_key = (try scanner.next()).string;
+        method_token = try scanner.next();
+    } else {
+        method_token = try scanner.next();
     }
-    try checkKey(id_key, "id");
     try checkKey(method_key, "method");
 
-    // retrieve id and method
-    const id = try std.fmt.parseUnsigned(u64, id_token.number, 10);
+    // retrieve method
     const method_name = method_token.string;
-    std.log.debug("cmd: id {any}, method {s}", .{ id, method_name });
+    std.log.debug("cmd: method {s}, id {any}", .{ method_name, id });
 
     // retrieve domain from method
     var iter = std.mem.splitScalar(u8, method_name, '.');
@@ -128,7 +124,7 @@ const resultNullSession = "{{\"id\": {d}, \"result\": {{}}, \"sessionId\": \"{s}
 // caller owns the slice returned
 pub fn result(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: u16,
     comptime T: ?type,
     res: anytype,
     sessionID: ?[]const u8,
@@ -142,7 +138,7 @@ pub fn result(
     }
 
     const Resp = struct {
-        id: u64,
+        id: u16,
         result: T.?,
         sessionId: ?[]const u8,
     };
@@ -171,73 +167,18 @@ pub fn sendEvent(
     try server.sendSync(ctx, event_msg);
 }
 
-pub fn getParams(
+fn getParams(
     alloc: std.mem.Allocator,
     comptime T: type,
     scanner: *std.json.Scanner,
+    key: []const u8,
 ) !?T {
 
-    // if next token is the end of the object, there is no "params"
-    const t = try scanner.next();
-    if (t == .object_end) return null;
+    // check key key is "params"
+    if (!std.mem.eql(u8, "params", key)) return null;
 
-    // if next token is not "params" there is no "params"
-    if (!std.mem.eql(u8, "params", t.string)) return null;
-
-    // parse "params"
-    const options = std.json.ParseOptions{
-        .max_value_len = scanner.input.len,
-        .allocate = .alloc_if_needed,
-    };
-    const params = try std.json.innerParse(T, alloc, scanner, options);
-    return params;
-}
-
-pub fn getSessionID(scanner: *std.json.Scanner) !?[]const u8 {
-
-    // if next token is the end of the object, there is no "sessionId"
-    const t = try scanner.next();
-    if (t == .object_end) return null;
-
-    var n = t.string;
-
-    // if next token is "params" ignore them
-    // NOTE: will panic if it's not an empty "params" object
-    // TODO: maybe we should return a custom error here
-    if (std.mem.eql(u8, n, "params")) {
-        // ignore empty params
-        _ = (try scanner.next()).object_begin;
-        _ = (try scanner.next()).object_end;
-        n = (try scanner.next()).string;
-    }
-
-    // if next token is not "sessionId" there is no "sessionId"
-    if (!std.mem.eql(u8, n, "sessionId")) return null;
-
-    // parse "sessionId"
-    return (try scanner.next()).string;
-}
-
-pub fn getContent(
-    alloc: std.mem.Allocator,
-    comptime T: type,
-    scanner: *std.json.Scanner,
-) !struct { params: T, sessionID: ?[]const u8 } {
-
-    // if next token is the end of the object, error
-    const t = try scanner.next();
-    if (t == .object_end) return error.CDPNoContent;
-
-    var params: T = undefined;
-    var sessionID: ?[]const u8 = null;
-
-    var n = t.string;
-
-    // params
-    if (std.mem.eql(u8, n, "params")) {
+    // skip "params" if not requested
     if (T == void) {
-
-            // ignore params
         var finished: usize = 0;
         while (true) {
             switch (try scanner.next()) {
@@ -247,32 +188,73 @@ pub fn getContent(
             }
             if (finished == 0) break;
         }
-            params = void{};
-        } else {
+        return void{};
+    }
 
     // parse "params"
     const options = std.json.ParseOptions{
         .max_value_len = scanner.input.len,
         .allocate = .alloc_if_needed,
     };
-            params = try std.json.innerParse(T, alloc, scanner, options);
+    return try std.json.innerParse(T, alloc, scanner, options);
 }
 
-        // go next
-        n = (try scanner.next()).string;
-    } else {
-        params = switch (@typeInfo(T)) {
-            .Void => void{},
-            .Optional => null,
-            else => return error.CDPNoParams,
-        };
+fn getId(scanner: *std.json.Scanner, key: []const u8) !?u16 {
+
+    // check key is "id"
+    if (!std.mem.eql(u8, "id", key)) return null;
+
+    // parse "id"
+    return try std.fmt.parseUnsigned(u16, (try scanner.next()).number, 10);
 }
 
-    if (std.mem.eql(u8, n, "sessionId")) {
-        sessionID = (try scanner.next()).string;
+fn getSessionId(scanner: *std.json.Scanner, key: []const u8) !?[]const u8 {
+
+    // check key is "sessionId"
+    if (!std.mem.eql(u8, "sessionId", key)) return null;
+
+    // parse "sessionId"
+    return (try scanner.next()).string;
 }
 
-    return .{ .params = params, .sessionID = sessionID };
+pub fn getMsg(
+    alloc: std.mem.Allocator,
+    comptime params_T: type,
+    scanner: *std.json.Scanner,
+) !struct { id: ?u16, params: ?params_T, sessionID: ?[]const u8 } {
+    var id: ?u16 = null;
+    var params: ?params_T = null;
+    var sessionID: ?[]const u8 = null;
+
+    var t: std.json.Token = undefined;
+
+    while (true) {
+        t = try scanner.next();
+        if (t == .object_end) break;
+        if (t != .string) {
+            return error.CDPMsgWrong;
+        }
+        if (id == null) {
+            id = try getId(scanner, t.string);
+            if (id != null) continue;
+        }
+        if (params == null) {
+            params = try getParams(alloc, params_T, scanner, t.string);
+            if (params != null) continue;
+        }
+        if (sessionID == null) {
+            sessionID = try getSessionId(scanner, t.string);
+        }
+    }
+
+    // end
+    std.log.debug(
+        "id {any}, params {any}, sessionID: {any}, token {any}",
+        .{ id, params, sessionID, t },
+    );
+    t = try scanner.next();
+    if (t != .end_of_document) return error.CDPMsgEnd;
+    return .{ .id = id, .params = params, .sessionID = sessionID };
 }
 
 // Common

src/cdp/emulation.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 
 const EmulationMethods = enum {
@@ -15,7 +15,7 @@ const EmulationMethods = enum {
 
 pub fn emulation(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
@@ -36,26 +36,26 @@ const MediaFeature = struct {
 
 fn setEmulatedMedia(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
+
     // input
     const Params = struct {
         media: ?[]const u8 = null,
         features: ?[]MediaFeature = null,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // output
     // TODO: dummy
-    return result(alloc, id, null, null, sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 fn setFocusEmulationEnabled(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
@@ -64,24 +64,23 @@ fn setFocusEmulationEnabled(
     const Params = struct {
         enabled: bool,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // output
     // TODO: dummy
-    return result(alloc, id, null, null, sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 fn setDeviceMetricsOverride(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
 
     // input
-    const content = try cdp.getContent(alloc, void, scanner);
+    const msg = try cdp.getMsg(alloc, void, scanner);
 
     // output
-    return result(alloc, id, null, null, content.sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }

src/cdp/log.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 
 const LogMethods = enum {
@@ -13,24 +13,26 @@ const LogMethods = enum {
 
 pub fn log(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
     const method = std.meta.stringToEnum(LogMethods, action) orelse
         return error.UnknownMethod;
+
     return switch (method) {
-        .enable => enable(alloc, id, scanner, ctx),
+        .enable => logEnable(alloc, id, scanner, ctx),
     };
 }
 
-fn enable(
+fn logEnable(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
-    const sessionID = try cdp.getSessionID(scanner);
-    return result(alloc, id, null, null, sessionID);
+    const msg = try getMsg(alloc, void, scanner);
+
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }

src/cdp/network.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 
 const NetworkMethods = enum {
@@ -13,24 +13,26 @@ const NetworkMethods = enum {
 
 pub fn network(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
     const method = std.meta.stringToEnum(NetworkMethods, action) orelse
         return error.UnknownMethod;
+
     return switch (method) {
-        .enable => enable(alloc, id, scanner, ctx),
+        .enable => networkEnable(alloc, id, scanner, ctx),
     };
 }
 
-fn enable(
+fn networkEnable(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
-    const sessionID = try cdp.getSessionID(scanner);
-    return result(alloc, id, null, null, sessionID);
+    const msg = try getMsg(alloc, void, scanner);
+
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }

src/cdp/page.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 const sendEvent = cdp.sendEvent;
 
@@ -21,7 +21,7 @@ const PageMethods = enum {
 
 pub fn page(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
@@ -40,12 +40,12 @@ pub fn page(
 
 fn enable(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
-    const sessionID = try cdp.getSessionID(scanner);
-    return result(alloc, id, null, null, sessionID);
+    const msg = try getMsg(alloc, void, scanner);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 const Frame = struct {
@@ -65,11 +65,12 @@ const Frame = struct {
 
 fn getFrameTree(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try cdp.getMsg(alloc, void, scanner);
+
     const FrameTree = struct {
         frameTree: struct {
             frame: Frame,
@@ -87,12 +88,12 @@ fn getFrameTree(
             },
         },
     };
-    return result(alloc, id, FrameTree, frameTree, sessionID);
+    return result(alloc, id orelse msg.id.?, FrameTree, frameTree, msg.sessionID);
 }
 
 fn setLifecycleEventsEnabled(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
@@ -101,13 +102,12 @@ fn setLifecycleEventsEnabled(
     const Params = struct {
         enabled: bool,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     ctx.state.page_life_cycle_events = true;
 
     // output
-    return result(alloc, id, null, null, sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 const LifecycleEvent = struct {
@@ -119,7 +119,7 @@ const LifecycleEvent = struct {
 
 fn addScriptToEvaluateOnNewDocument(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
@@ -131,37 +131,34 @@ fn addScriptToEvaluateOnNewDocument(
         includeCommandLineAPI: bool = false,
         runImmediately: bool = false,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // output
     const Res = struct {
         identifier: []const u8 = "1",
     };
-    return result(alloc, id, Res, Res{}, sessionID);
+    return result(alloc, id orelse msg.id.?, Res, Res{}, msg.sessionID);
 }
 
 fn createIsolatedWorld(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
-
-    // input
-    const content = try cdp.getContent(alloc, void, scanner);
+    const msg = try getMsg(alloc, void, scanner);
 
     // output
     const Resp = struct {
         executionContextId: u8 = 2,
     };
 
-    return result(alloc, id, Resp, .{}, content.sessionID);
+    return result(alloc, id orelse msg.id.?, Resp, .{}, msg.sessionID);
 }
 
 fn navigate(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
@@ -174,12 +171,12 @@ fn navigate(
         frameId: ?[]const u8 = null,
         referrerPolicy: ?[]const u8 = null, // TODO: enum
     };
-    const input = try cdp.getContent(alloc, Params, scanner);
-    const sessionID = input.sessionID;
-    std.debug.assert(sessionID != null);
+    const msg = try getMsg(alloc, Params, scanner);
+    std.debug.assert(msg.sessionID != null);
+    const params = msg.params.?;
 
     // change state
-    ctx.state.url = input.params.url;
+    ctx.state.url = params.url;
     ctx.state.loaderID = "AF8667A203C5392DBE9AC290044AA4C2";
 
     var life_event = LifecycleEvent{
@@ -193,11 +190,25 @@ fn navigate(
         frameId: []const u8,
     };
     const frame_started_loading = FrameStartedLoading{ .frameId = ctx.state.frameID };
-    try sendEvent(alloc, ctx, "Page.frameStartedLoading", FrameStartedLoading, frame_started_loading, sessionID);
+    try sendEvent(
+        alloc,
+        ctx,
+        "Page.frameStartedLoading",
+        FrameStartedLoading,
+        frame_started_loading,
+        msg.sessionID,
+    );
     if (ctx.state.page_life_cycle_events) {
         life_event.name = "init";
         life_event.timestamp = 343721.796037;
-        try sendEvent(alloc, ctx, "Page.lifecycleEvent", LifecycleEvent, life_event, sessionID);
+        try sendEvent(
+            alloc,
+            ctx,
+            "Page.lifecycleEvent",
+            LifecycleEvent,
+            life_event,
+            msg.sessionID,
+        );
     }
 
     // output
@@ -210,16 +221,16 @@ fn navigate(
         .frameId = ctx.state.frameID,
         .loaderId = ctx.state.loaderID,
     };
-    const res = try result(alloc, id, Resp, resp, sessionID);
+    const res = try result(alloc, id orelse msg.id.?, Resp, resp, msg.sessionID);
     std.log.debug("res {s}", .{res});
     try server.sendSync(ctx, res);
 
     // Runtime.executionContextsCleared event
-    try sendEvent(alloc, ctx, "Runtime.executionContextsCleared", void, {}, sessionID);
+    try sendEvent(alloc, ctx, "Runtime.executionContextsCleared", void, {}, msg.sessionID);
 
     // launch navigate
     var p = try ctx.browser.currentSession().createPage();
-    _ = try p.navigate(input.params.url);
+    _ = try p.navigate(params.url);
 
     // frameNavigated event
     const FrameNavigated = struct {
@@ -235,11 +246,25 @@ fn navigate(
             .loaderId = ctx.state.loaderID,
         },
     };
-    try sendEvent(alloc, ctx, "Page.frameNavigated", FrameNavigated, frame_navigated, sessionID);
+    try sendEvent(
+        alloc,
+        ctx,
+        "Page.frameNavigated",
+        FrameNavigated,
+        frame_navigated,
+        msg.sessionID,
+    );
     if (ctx.state.page_life_cycle_events) {
         life_event.name = "load";
         life_event.timestamp = 343721.824655;
-        try sendEvent(alloc, ctx, "Page.lifecycleEvent", LifecycleEvent, life_event, sessionID);
+        try sendEvent(
+            alloc,
+            ctx,
+            "Page.lifecycleEvent",
+            LifecycleEvent,
+            life_event,
+            msg.sessionID,
+        );
     }
 
     try Runtime.executionContextCreated(
@@ -250,7 +275,7 @@ fn navigate(
         "",
         "7102379147004877974.3265385113993241162",
         .{ .frameId = ctx.state.frameID },
-        sessionID,
+        msg.sessionID,
     );
 
     try Runtime.executionContextCreated(
@@ -261,30 +286,65 @@ fn navigate(
         "__playwright_utility_world__",
         "-4572718120346458707.6016875269626438350",
         .{ .isDefault = false, .type = "isolated", .frameId = ctx.state.frameID },
-        sessionID,
+        msg.sessionID,
     );
 
     // domContentEventFired event
     ts_event = .{ .timestamp = 343721.803338 };
-    try sendEvent(alloc, ctx, "Page.domContentEventFired", cdp.TimestampEvent, ts_event, sessionID);
+    try sendEvent(
+        alloc,
+        ctx,
+        "Page.domContentEventFired",
+        cdp.TimestampEvent,
+        ts_event,
+        msg.sessionID,
+    );
     if (ctx.state.page_life_cycle_events) {
         life_event.name = "DOMContentLoaded";
         life_event.timestamp = 343721.803338;
-        try sendEvent(alloc, ctx, "Page.lifecycleEvent", LifecycleEvent, life_event, sessionID);
+        try sendEvent(
+            alloc,
+            ctx,
+            "Page.lifecycleEvent",
+            LifecycleEvent,
+            life_event,
+            msg.sessionID,
+        );
     }
 
     // loadEventFired event
     ts_event = .{ .timestamp = 343721.824655 };
-    try sendEvent(alloc, ctx, "Page.loadEventFired", cdp.TimestampEvent, ts_event, sessionID);
+    try sendEvent(
+        alloc,
+        ctx,
+        "Page.loadEventFired",
+        cdp.TimestampEvent,
+        ts_event,
+        msg.sessionID,
+    );
     if (ctx.state.page_life_cycle_events) {
         life_event.name = "load";
         life_event.timestamp = 343721.824655;
-        try sendEvent(alloc, ctx, "Page.lifecycleEvent", LifecycleEvent, life_event, sessionID);
+        try sendEvent(
+            alloc,
+            ctx,
+            "Page.lifecycleEvent",
+            LifecycleEvent,
+            life_event,
+            msg.sessionID,
+        );
     }
 
     // frameStoppedLoading
     const FrameStoppedLoading = struct { frameId: []const u8 };
-    try sendEvent(alloc, ctx, "Page.frameStoppedLoading", FrameStoppedLoading, .{ .frameId = ctx.state.frameID }, sessionID);
+    try sendEvent(
+        alloc,
+        ctx,
+        "Page.frameStoppedLoading",
+        FrameStoppedLoading,
+        .{ .frameId = ctx.state.frameID },
+        msg.sessionID,
+    );
 
     return "";
 }

src/cdp/runtime.zig

@@ -6,7 +6,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 
 const RuntimeMethods = enum {
@@ -17,7 +17,7 @@ const RuntimeMethods = enum {
 
 pub fn runtime(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
@@ -33,14 +33,13 @@ pub fn runtime(
 
 fn enable(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
-    ctx: *Ctx,
+    _: *Ctx,
 ) ![]const u8 {
-    _ = ctx;
 
     // input
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, void, scanner);
 
     // output
     // const uniqueID = "1367118932354479079.-1471398151593995849";
@@ -56,7 +55,7 @@ fn enable(
     // std.log.debug("res {s}", .{mainCtx});
     // try server.sendAsync(ctx, mainCtx);
 
-    return result(alloc, id, null, null, sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 pub const AuxData = struct {
@@ -76,7 +75,7 @@ const ExecutionContextDescription = struct {
 pub fn executionContextCreated(
     alloc: std.mem.Allocator,
     ctx: *Ctx,
-    id: u64,
+    id: u16,
     origin: []const u8,
     name: []const u8,
     uniqueID: []const u8,
@@ -100,17 +99,18 @@ pub fn executionContextCreated(
 
 fn runIfWaitingForDebugger(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
-    const sessionID = try cdp.getSessionID(scanner);
-    return result(alloc, id, null, null, sessionID);
+    const msg = try getMsg(alloc, void, scanner);
+
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 fn evaluate(
     alloc: std.mem.Allocator,
-    id: u64,
+    _id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
@@ -124,20 +124,21 @@ fn evaluate(
         contextId: ?u8,
     };
 
-    const input = try cdp.getContent(alloc, Params, scanner);
-    const sessionID = input.sessionID;
-    std.debug.assert(sessionID != null);
+    const msg = try getMsg(alloc, Params, scanner);
+    std.debug.assert(msg.sessionID != null);
+    const params = msg.params.?;
+    const id = _id orelse msg.id.?;
 
     // save script in file at debug mode
-    std.log.debug("script {d} length: {d}", .{ id, input.params.expression.len });
+    std.log.debug("script {d} length: {d}", .{ id, params.expression.len });
     if (std.log.defaultLogEnabled(.debug)) {
         const name = try std.fmt.allocPrint(alloc, "id_{d}.js", .{id});
         defer alloc.free(name);
         const dir = try std.fs.cwd().makeOpenPath("zig-cache/tmp", .{});
         const f = try dir.createFile(name, .{});
         defer f.close();
-        const nb = try f.write(input.params.expression);
-        std.debug.assert(nb == input.params.expression.len);
+        const nb = try f.write(params.expression);
+        std.debug.assert(nb == params.expression.len);
         const p = try dir.realpathAlloc(alloc, name);
         defer alloc.free(p);
         std.log.debug("Script {d} saved at {s}", .{ id, p });
@@ -149,7 +150,7 @@ fn evaluate(
     // const page_alloc = ctx.browser.currentSession().page.?.arena.allocator();
     const session_alloc = ctx.browser.currentSession().alloc;
     var res = jsruntime.JSResult{};
-    try ctx.browser.currentSession().env.run(session_alloc, input.params.expression, "cdp", &res, null);
+    try ctx.browser.currentSession().env.run(session_alloc, params.expression, "cdp", &res, null);
     defer res.deinit(session_alloc);
 
     if (!res.success) {
@@ -168,5 +169,5 @@ fn evaluate(
         description: []const u8 = "UtilityScript",
         objectId: []const u8 = "7481631759780215274.3.2",
     };
-    return result(alloc, id, Resp, Resp{}, sessionID);
+    return result(alloc, id, Resp, Resp{}, msg.sessionID);
 }

src/cdp/target.zig

@@ -4,7 +4,7 @@ const server = @import("../server.zig");
 const Ctx = server.Cmd;
 const cdp = @import("cdp.zig");
 const result = cdp.result;
-const getParams = cdp.getParams;
+const getMsg = cdp.getMsg;
 const stringify = cdp.stringify;
 
 const TargetMethods = enum {
@@ -16,7 +16,7 @@ const TargetMethods = enum {
 
 pub fn target(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     action: []const u8,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
@@ -56,7 +56,7 @@ const TargetFilter = struct {
 
 fn tagetSetAutoAttach(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
@@ -66,12 +66,10 @@ fn tagetSetAutoAttach(
         flatten: bool = true,
         filter: ?[]TargetFilter = null,
     };
-    const params = try getParams(alloc, Params, scanner);
-    std.log.debug("params {any}", .{params});
+    const msg = try getMsg(alloc, Params, scanner);
+    std.log.debug("params {any}", .{msg.params});
 
-    const sessionID = try cdp.getSessionID(scanner);
-
-    if (sessionID == null) {
+    if (msg.sessionID == null) {
         const attached = AttachToTarget{
             .sessionId = cdp.SessionID,
             .targetInfo = .{
@@ -84,12 +82,12 @@ fn tagetSetAutoAttach(
         try cdp.sendEvent(alloc, ctx, "Target.attachedToTarget", AttachToTarget, attached, null);
     }
 
-    return result(alloc, id, null, null, sessionID);
+    return result(alloc, id orelse msg.id.?, null, null, msg.sessionID);
 }
 
 fn tagetGetTargetInfo(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     _: *Ctx,
 ) ![]const u8 {
@@ -98,7 +96,7 @@ fn tagetGetTargetInfo(
     const Params = struct {
         targetId: ?[]const u8 = null,
     };
-    _ = try getParams(alloc, Params, scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // output
     const TargetInfo = struct {
@@ -117,7 +115,7 @@ fn tagetGetTargetInfo(
         .targetId = BrowserTargetID,
         .type = "browser",
     };
-    return result(alloc, id, TargetInfo, targetInfo, null);
+    return result(alloc, id orelse msg.id.?, TargetInfo, targetInfo, null);
 }
 
 const ContextID = "22648B09EDCCDD11109E2D4FEFBE4F89";
@@ -125,9 +123,9 @@ const ContextSessionID = "4FDC2CB760A23A220497A05C95417CF4";
 
 fn createBrowserContext(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
-    _: *Ctx,
+    ctx: *Ctx,
 ) ![]const u8 {
 
     // input
@@ -137,21 +135,20 @@ fn createBrowserContext(
         proxyBypassList: ?[]const u8 = null,
         originsWithUniversalNetworkAccess: ?[][]const u8 = null,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // output
     const Resp = struct {
         browserContextId: []const u8 = ContextID,
     };
-    return result(alloc, id, Resp, Resp{}, sessionID);
+    return result(alloc, id orelse msg.id.?, Resp, Resp{}, msg.sessionID);
 }
 
 const TargetID = "57356548460A8F29706A2ADF14316298";
 
 fn createTarget(
     alloc: std.mem.Allocator,
-    id: u64,
+    id: ?u16,
     scanner: *std.json.Scanner,
     ctx: *Ctx,
 ) ![]const u8 {
@@ -167,8 +164,7 @@ fn createTarget(
         background: bool = false,
         forTab: ?bool = null,
     };
-    _ = try getParams(alloc, Params, scanner);
-    const sessionID = try cdp.getSessionID(scanner);
+    const msg = try getMsg(alloc, Params, scanner);
 
     // change CDP state
     ctx.state.frameID = TargetID;
@@ -188,11 +184,11 @@ fn createTarget(
         },
         .waitingForDebugger = true,
     };
-    try cdp.sendEvent(alloc, ctx, "Target.attachedToTarget", AttachToTarget, attached, sessionID);
+    try cdp.sendEvent(alloc, ctx, "Target.attachedToTarget", AttachToTarget, attached, msg.sessionID);
 
     // output
     const Resp = struct {
         targetId: []const u8 = TargetID,
     };
-    return result(alloc, id, Resp, Resp{}, sessionID);
+    return result(alloc, id orelse msg.id.?, Resp, Resp{}, msg.sessionID);
 }