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cdp: refacto message JSON read
This commit is contained in:
Pierre Tachoire
214
src/cdp/msg.zig
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214
src/cdp/msg.zig
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// Copyright (C) 2023-2024 Lightpanda (Selecy SAS)
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//
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// Francis Bouvier <francis@lightpanda.io>
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// Pierre Tachoire <pierre@lightpanda.io>
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as
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// published by the Free Software Foundation, either version 3 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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const std = @import("std");
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// Parse incoming protocol message in json format.
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pub const IncomingMessage = struct {
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scanner: std.json.Scanner,
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json: []const u8,
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obj_begin: bool = false,
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obj_end: bool = false,
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id: ?u16 = null,
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scan_sessionId: bool = false,
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sessionId: ?[]const u8 = null,
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method: ?[]const u8 = null,
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params_skip: bool = false,
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pub fn init(alloc: std.mem.Allocator, json: []const u8) IncomingMessage {
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return .{
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.json = json,
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.scanner = std.json.Scanner.initCompleteInput(alloc, json),
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};
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}
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pub fn deinit(self: *IncomingMessage) void {
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self.scanner.deinit();
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}
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fn scanUntil(self: *IncomingMessage, key: []const u8) !void {
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while (true) {
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switch (try self.scanner.next()) {
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.end_of_document => return error.EndOfDocument,
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.object_begin => {
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if (self.obj_begin) return error.InvalidObjectBegin;
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self.obj_begin = true;
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},
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.object_end => {
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if (!self.obj_begin) return error.InvalidObjectEnd;
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if (self.obj_end) return error.InvalidObjectEnd;
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self.obj_end = true;
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},
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.string => |s| {
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// is the key what we expects?
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if (std.mem.eql(u8, s, key)) return;
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// save other known keys
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if (std.mem.eql(u8, s, "id")) try self.scanId();
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if (std.mem.eql(u8, s, "sessionId")) try self.scanSessionId();
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if (std.mem.eql(u8, s, "method")) try self.scanMethod();
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if (std.mem.eql(u8, s, "params")) try self.scanParams();
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// TODO should we skip unknown key?
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},
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else => return error.InvalidToken,
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}
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}
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}
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fn scanId(self: *IncomingMessage) !void {
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const t = try self.scanner.next();
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if (t != .number) return error.InvalidId;
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self.id = try std.fmt.parseUnsigned(u16, t.number, 10);
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}
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fn getId(self: *IncomingMessage) !u16 {
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if (self.id != null) return self.id.?;
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try self.scanUntil("id");
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try self.scanId();
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return self.id.?;
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}
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fn scanSessionId(self: *IncomingMessage) !void {
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switch (try self.scanner.next()) {
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// session id can be null.
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.null => return,
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.string => |s| self.sessionId = s,
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else => return error.InvalidSessionId,
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}
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self.scan_sessionId = true;
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}
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fn getSessionId(self: *IncomingMessage) !?[]const u8 {
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if (self.scan_sessionId) return self.sessionId;
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self.scanUntil("sessionId") catch |err| {
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if (err != error.EndOfDocument) return err;
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// if the document doesn't contains any session id key, we must
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// return null value.
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self.scan_sessionId = true;
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return null;
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};
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try self.scanSessionId();
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return self.sessionId;
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}
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fn scanMethod(self: *IncomingMessage) !void {
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const t = try self.scanner.next();
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if (t != .string) return error.InvalidMethod;
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self.method = t.string;
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}
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pub fn getMethod(self: *IncomingMessage) ![]const u8 {
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if (self.method != null) return self.method.?;
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try self.scanUntil("method");
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try self.scanMethod();
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return self.method.?;
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}
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// scanParams skip found parameters b/c if we encounter params *before*
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// asking for getParams, we don't know how to parse them.
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fn scanParams(self: *IncomingMessage) !void {
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const tt = try self.scanner.peekNextTokenType();
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if (tt != .object_begin) return error.InvalidParams;
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try self.scanner.skipValue();
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self.params_skip = true;
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}
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// getParams restart the JSON parsing
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fn getParams(self: *IncomingMessage, alloc: std.mem.Allocator, T: type) !T {
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if (T == void) return void{};
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if (self.params_skip) {
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// TODO if the params have been skipped, we have to retart the
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// parsing from start.
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return error.SkippedParams;
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}
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try self.scanUntil("params");
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// parse "params"
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const options = std.json.ParseOptions{
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.max_value_len = self.scanner.input.len,
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.allocate = .alloc_if_needed,
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};
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return try std.json.innerParse(T, alloc, &self.scanner, options);
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}
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pub fn getInput(self: *IncomingMessage, alloc: std.mem.Allocator, T: type) !struct { id: u16, sessionId: ?[]const u8, params: T } {
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return .{
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.params = try self.getParams(alloc, T),
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.id = try self.getId(),
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.sessionId = try self.getSessionId(),
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};
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}
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};
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test "read incoming message" {
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const inputs = [_][]const u8{
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\\{"id":1,"method":"foo","sessionId":"bar","params":{"bar":"baz"}}
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,
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\\{"params":{"bar":"baz"},"id":1,"method":"foo","sessionId":"bar"}
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,
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\\{"sessionId":"bar","params":{"bar":"baz"},"id":1,"method":"foo"}
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,
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\\{"method":"foo","sessionId":"bar","params":{"bar":"baz"},"id":1}
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,
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};
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for (inputs) |input| {
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var msg = IncomingMessage.init(std.testing.allocator, input);
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defer msg.deinit();
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try std.testing.expectEqual(1, try msg.getId());
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try std.testing.expectEqualSlices(u8, "foo", try msg.getMethod());
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try std.testing.expectEqualSlices(u8, "bar", (try msg.getSessionId()).?);
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const T = struct { bar: []const u8 };
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const in = msg.getInput(std.testing.allocator, T) catch |err| {
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if (err != error.SkippedParams) return err;
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// TODO remove this check when params in the beginning is handled.
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continue;
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};
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try std.testing.expectEqualSlices(u8, "baz", in.params.bar);
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}
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}
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test "read incoming message with null session id" {
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const inputs = [_][]const u8{
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\\{"id":1}
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,
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\\{"params":{"bar":"baz"},"id":1,"method":"foo"}
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,
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\\{"sessionId":null,"params":{"bar":"baz"},"id":1,"method":"foo"}
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,
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};
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for (inputs) |input| {
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var msg = IncomingMessage.init(std.testing.allocator, input);
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defer msg.deinit();
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try std.testing.expect(try msg.getSessionId() == null);
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try std.testing.expectEqual(1, try msg.getId());
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}
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}
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