cdp: introduce current page

avoid page struct copy

src/browser/browser.zig

@@ -82,6 +82,12 @@ pub const Browser = struct {
         self.session.deinit();
         try Session.init(&self.session, alloc, loop, uri);
     }
+
+    pub fn currentPage(self: *Browser) ?*Page {
+        if (self.session.page == null) return null;
+
+        return &self.session.page.?;
+    }
 };
 
 // Session is like a browser's tab.

src/cdp/dom.zig

@@ -112,16 +112,10 @@ fn getDocument(
     std.debug.assert(input.sessionId != null);
     log.debug("Req > id {d}, method {s}", .{ input.id, "DOM.getDocument" });
 
-    if (ctx.browser.session.page == null) {
-        return error.NoPage;
-    }
-
     // retrieve the root node
-    const page = ctx.browser.session.page.?;
+    const page = ctx.browser.currentPage() orelse return error.NoPage;
 
-    if (page.doc == null) {
-        return error.NoDocument;
-    }
+    if (page.doc == null) return error.NoDocument;
 
     const root = try parser.documentGetDocumentElement(page.doc.?) orelse {
         return error.NoRoot;

src/cdp/page.zig

@@ -333,7 +333,7 @@ fn navigate(
 
     // Launch navigate, the page must have been created by a
     // target.createTarget.
-    var p = ctx.browser.session.page orelse return error.NoPage;
+    var p = ctx.browser.currentPage() orelse return error.NoPage;
     ctx.state.executionContextId += 1;
     const auxData = try std.fmt.allocPrint(
         alloc,

src/cdp/target.zig

@@ -353,7 +353,7 @@ fn createTarget(
     }
 
     // TODO stop the previous page instead?
-    if (ctx.browser.session.page != null) return error.pageAlreadyExists;
+    if (ctx.browser.currentPage() != null) return error.pageAlreadyExists;
 
     // create the page
     const p = try ctx.browser.session.createPage();
@@ -464,7 +464,7 @@ fn closeTarget(
         null,
     );
 
-    if (ctx.browser.session.page != null) ctx.browser.session.page.?.end();
+    if (ctx.browser.currentPage()) |page| page.end();
 
     return "";
 }