LibIMAP: Add a new IMAP client and support NOOP

A large commit, but sets up the framework for how the IMAP library will
work. Right now only the NOOP command and response is supported.

7 files changed, 643 insertions, 0 deletions

diff --git a/Userland/Libraries/LibIMAP/CMakeLists.txt b/Userland/Libraries/LibIMAP/CMakeLists.txt
new file mode 100644
index 0000000000..95fd92eec1
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/CMakeLists.txt
@@ -0,0 +1,6 @@
+set(SOURCES Objects.cpp Client.cpp  Parser.cpp)
+
+set(GENERATED_SOURCES)
+
+serenity_lib(LibIMAP imap)
+target_link_libraries(LibIMAP LibCore LibTLS)
diff --git a/Userland/Libraries/LibIMAP/Client.cpp b/Userland/Libraries/LibIMAP/Client.cpp
new file mode 100644
index 0000000000..160b51131c
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Client.cpp
@@ -0,0 +1,204 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibIMAP/Client.h>
+
+namespace IMAP {
+Client::Client(StringView host, unsigned int port, bool start_with_tls)
+    : m_host(host)
+    , m_port(port)
+    , m_tls(start_with_tls)
+    , m_parser(Parser())
+{
+    if (start_with_tls) {
+        m_tls_socket = TLS::TLSv12::construct(nullptr);
+        m_tls_socket->set_root_certificates(DefaultRootCACertificates::the().certificates());
+    } else {
+        m_socket = Core::TCPSocket::construct();
+    }
+}
+
+Optional<RefPtr<Promise<Empty>>> Client::connect()
+{
+    bool success;
+    if (m_tls) {
+        success = connect_tls();
+    } else {
+        success = connect_plaintext();
+    }
+    if (!success)
+        return {};
+    m_connect_pending = new Promise<bool> {};
+    return m_connect_pending;
+}
+
+bool Client::connect_tls()
+{
+    m_tls_socket->on_tls_ready_to_read = [&](TLS::TLSv12&) {
+        on_tls_ready_to_receive();
+    };
+    m_tls_socket->on_tls_error = [&](TLS::AlertDescription alert) {
+        dbgln("failed: {}", alert_name(alert));
+    };
+    m_tls_socket->on_tls_connected = [&] {
+        dbgln("connected");
+    };
+    auto success = m_tls_socket->connect(m_host, m_port);
+    dbgln("connecting to {}:{} {}", m_host, m_port, success);
+    return success;
+}
+
+bool Client::connect_plaintext()
+{
+    m_socket->on_ready_to_read = [&] {
+        on_ready_to_receive();
+    };
+    auto success = m_socket->connect(m_host, m_port);
+    dbgln("connecting to {}:{} {}", m_host, m_port, success);
+    return success;
+}
+
+void Client::on_tls_ready_to_receive()
+{
+    if (!m_tls_socket->can_read())
+        return;
+    auto data = m_tls_socket->read();
+    if (!data.has_value())
+        return;
+
+    // Once we get server hello we can start sending
+    if (m_connect_pending) {
+        m_connect_pending->resolve({});
+        m_connect_pending.clear();
+        return;
+    }
+
+    m_buffer += data.value();
+    if (m_buffer[m_buffer.size() - 1] == '\n') {
+        // Don't try parsing until we have a complete line.
+        auto response = m_parser.parse(move(m_buffer), m_expecting_response);
+        handle_parsed_response(move(response));
+        m_buffer.clear();
+    }
+}
+
+void Client::on_ready_to_receive()
+{
+    if (!m_socket->can_read())
+        return;
+    m_buffer += m_socket->read_all();
+
+    // Once we get server hello we can start sending.
+    if (m_connect_pending) {
+        m_connect_pending->resolve({});
+        m_connect_pending.clear();
+        m_buffer.clear();
+        return;
+    }
+
+    if (m_buffer[m_buffer.size() - 1] == '\n') {
+        // Don't try parsing until we have a complete line.
+        auto response = m_parser.parse(move(m_buffer), m_expecting_response);
+        handle_parsed_response(move(response));
+        m_buffer.clear();
+    }
+}
+
+static ReadonlyBytes command_byte_buffer(CommandType command)
+{
+    switch (command) {
+    case CommandType::Noop:
+        return "NOOP"sv.bytes();
+    }
+    VERIFY_NOT_REACHED();
+}
+
+void Client::send_raw(StringView data)
+{
+    if (m_tls) {
+        m_tls_socket->write(data.bytes());
+        m_tls_socket->write("\r\n"sv.bytes());
+    } else {
+        m_socket->write(data.bytes());
+        m_socket->write("\r\n"sv.bytes());
+    }
+}
+
+RefPtr<Promise<Optional<Response>>> Client::send_command(Command&& command)
+{
+    m_command_queue.append(move(command));
+    m_current_command++;
+
+    auto promise = Promise<Optional<Response>>::construct();
+    m_pending_promises.append(promise);
+
+    if (m_pending_promises.size() == 1)
+        send_next_command();
+
+    return promise;
+}
+
+RefPtr<Promise<Optional<Response>>> Client::send_simple_command(CommandType type)
+{
+    auto command = Command { type, m_current_command, {} };
+    return send_command(move(command));
+}
+
+void Client::handle_parsed_response(ParseStatus&& parse_status)
+{
+    if (!m_expecting_response) {
+        if (!parse_status.successful) {
+            dbgln("Parsing failed on unrequested data!");
+        } else if (parse_status.response.has_value()) {
+            unrequested_response_callback(move(parse_status.response.value().get<SolidResponse>().data()));
+        }
+    } else {
+        bool should_send_next = false;
+        if (!parse_status.successful) {
+            m_expecting_response = false;
+            m_pending_promises.first()->resolve({});
+            m_pending_promises.remove(0);
+        }
+        if (parse_status.response.has_value()) {
+            m_expecting_response = false;
+            should_send_next = parse_status.response->has<SolidResponse>();
+            m_pending_promises.first()->resolve(move(parse_status.response));
+            m_pending_promises.remove(0);
+        }
+
+        if (should_send_next && !m_command_queue.is_empty()) {
+            send_next_command();
+        }
+    }
+}
+
+void Client::send_next_command()
+{
+    auto command = m_command_queue.take_first();
+    ByteBuffer buffer;
+    auto tag = AK::String::formatted("A{} ", m_current_command);
+    buffer += tag.to_byte_buffer();
+    auto command_type = command_byte_buffer(command.type);
+    buffer.append(command_type.data(), command_type.size());
+
+    for (auto& arg : command.args) {
+        buffer.append(" ", 1);
+        buffer.append(arg.bytes().data(), arg.length());
+    }
+
+    send_raw(buffer);
+    m_expecting_response = true;
+}
+
+void Client::close()
+{
+    if (m_tls) {
+        m_tls_socket->close();
+    } else {
+        m_socket->close();
+    }
+}
+}
diff --git a/Userland/Libraries/LibIMAP/Client.h b/Userland/Libraries/LibIMAP/Client.h
new file mode 100644
index 0000000000..1481d92eb7
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Client.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <LibIMAP/Parser.h>
+#include <LibTLS/TLSv12.h>
+
+namespace IMAP {
+class Client {
+    friend class Parser;
+
+public:
+    Client(StringView host, unsigned port, bool start_with_tls);
+
+    Optional<RefPtr<Promise<Empty>>> connect();
+    RefPtr<Promise<Optional<Response>>> send_command(Command&&);
+    RefPtr<Promise<Optional<Response>>> send_simple_command(CommandType);
+    void send_raw(StringView data);
+    void close();
+
+    Function<void(ResponseData&&)> unrequested_response_callback;
+
+private:
+    StringView m_host;
+    unsigned m_port;
+    RefPtr<Core::Socket> m_socket;
+    RefPtr<TLS::TLSv12> m_tls_socket;
+
+    void on_ready_to_receive();
+    void on_tls_ready_to_receive();
+
+    bool m_tls;
+    int m_current_command = 1;
+
+    bool connect_tls();
+    bool connect_plaintext();
+
+    // Sent but response not received
+    Vector<RefPtr<Promise<Optional<Response>>>> m_pending_promises;
+    // Not yet sent
+    Vector<Command> m_command_queue {};
+
+    RefPtr<Promise<bool>> m_connect_pending {};
+
+    ByteBuffer m_buffer;
+    Parser m_parser;
+
+    bool m_expecting_response { false };
+    void handle_parsed_response(ParseStatus&& parse_status);
+    void send_next_command();
+};
+}
diff --git a/Userland/Libraries/LibIMAP/Objects.cpp b/Userland/Libraries/LibIMAP/Objects.cpp
new file mode 100644
index 0000000000..11c8222c06
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Objects.cpp
@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibIMAP/Objects.h>
+
+namespace IMAP {
+
+}
diff --git a/Userland/Libraries/LibIMAP/Objects.h b/Userland/Libraries/LibIMAP/Objects.h
new file mode 100644
index 0000000000..037b9387b5
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Objects.h
@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Format.h>
+#include <AK/Function.h>
+#include <AK/Tuple.h>
+#include <AK/Variant.h>
+#include <LibCore/DateTime.h>
+#include <LibCore/EventLoop.h>
+#include <LibCore/Object.h>
+#include <utility>
+
+namespace IMAP {
+enum class CommandType {
+    Noop,
+};
+
+enum class ResponseType : unsigned {
+};
+
+class Parser;
+
+struct Command {
+public:
+    CommandType type;
+    int tag;
+    Vector<String> args;
+};
+
+enum class ResponseStatus {
+    Bad,
+    No,
+    OK,
+};
+
+class ResponseData {
+public:
+    [[nodiscard]] unsigned response_type() const
+    {
+        return m_response_type;
+    }
+
+    ResponseData()
+        : m_response_type(0)
+    {
+    }
+
+    ResponseData(ResponseData&) = delete;
+    ResponseData(ResponseData&&) = default;
+    ResponseData& operator=(const ResponseData&) = delete;
+    ResponseData& operator=(ResponseData&&) = default;
+
+    [[nodiscard]] bool contains_response_type(ResponseType response_type) const
+    {
+        return (static_cast<unsigned>(response_type) & m_response_type) != 0;
+    }
+
+    void add_response_type(ResponseType response_type)
+    {
+        m_response_type = m_response_type | static_cast<unsigned>(response_type);
+    }
+
+private:
+    unsigned m_response_type;
+};
+
+class SolidResponse {
+    // Parser is allowed to set up fields
+    friend class Parser;
+
+public:
+    ResponseStatus status() { return m_status; }
+
+    int tag() const { return m_tag; }
+
+    ResponseData& data() { return m_data; }
+
+    String response_text() { return m_response_text; };
+
+    SolidResponse()
+        : SolidResponse(ResponseStatus::Bad, -1)
+    {
+    }
+
+    SolidResponse(ResponseStatus status, int tag)
+        : m_status(status)
+        , m_tag(tag)
+        , m_data(ResponseData())
+    {
+    }
+
+private:
+    ResponseStatus m_status;
+    String m_response_text;
+    unsigned m_tag;
+
+    ResponseData m_data;
+};
+
+struct ContinueRequest {
+    String data;
+};
+
+template<typename Result>
+class Promise : public Core::Object {
+    C_OBJECT(Promise);
+
+private:
+    Optional<Result> m_pending;
+
+public:
+    Function<void(Result&)> on_resolved;
+
+    void resolve(Result&& result)
+    {
+        m_pending = move(result);
+        if (on_resolved)
+            on_resolved(m_pending.value());
+    }
+
+    bool is_resolved()
+    {
+        return m_pending.has_value();
+    };
+
+    Result await()
+    {
+        while (!is_resolved()) {
+            Core::EventLoop::current().pump();
+        }
+        return m_pending.release_value();
+    }
+
+    // Converts a Promise<A> to a Promise<B> using a function func: A -> B
+    template<typename T>
+    RefPtr<Promise<T>> map(Function<T(Result&)> func)
+    {
+        RefPtr<Promise<T>> new_promise = Promise<T>::construct();
+        on_resolved = [new_promise, func](Result& result) mutable {
+            auto t = func(result);
+            new_promise->resolve(move(t));
+        };
+        return new_promise;
+    }
+};
+using Response = Variant<SolidResponse, ContinueRequest>;
+}
+
+// An RFC 2822 message
+// https://datatracker.ietf.org/doc/html/rfc2822
+struct Message {
+    String data;
+};
diff --git a/Userland/Libraries/LibIMAP/Parser.cpp b/Userland/Libraries/LibIMAP/Parser.cpp
new file mode 100644
index 0000000000..1c872e242a
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Parser.cpp
@@ -0,0 +1,163 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/CharacterTypes.h>
+#include <LibIMAP/Parser.h>
+
+namespace IMAP {
+
+ParseStatus Parser::parse(ByteBuffer&& buffer, bool expecting_tag)
+{
+    if (m_incomplete) {
+        m_buffer += buffer;
+        m_incomplete = false;
+    } else {
+        m_buffer = move(buffer);
+        position = 0;
+        m_response = SolidResponse();
+    }
+
+    if (try_consume("+")) {
+        consume(" ");
+        auto data = parse_while([](u8 x) { return x != '\r'; });
+        consume("\r\n");
+        return { true, { ContinueRequest { data } } };
+    }
+
+    if (expecting_tag) {
+        if (at_end()) {
+            m_incomplete = true;
+            return { true, {} };
+        }
+        parse_response_done();
+    }
+
+    if (m_parsing_failed) {
+        return { false, {} };
+    } else {
+        return { true, { { move(m_response) } } };
+    }
+}
+
+bool Parser::try_consume(StringView x)
+{
+    size_t i = 0;
+    auto previous_position = position;
+    while (i < x.length() && !at_end() && to_ascii_lowercase(x[i]) == to_ascii_lowercase(m_buffer[position])) {
+        i++;
+        position++;
+    }
+    if (i != x.length()) {
+        // We didn't match the full string.
+        position = previous_position;
+        return false;
+    }
+
+    return true;
+}
+
+void Parser::parse_response_done()
+{
+    consume("A");
+    auto tag = parse_number();
+    consume(" ");
+
+    ResponseStatus status = parse_status();
+    consume(" ");
+
+    m_response.m_tag = tag;
+    m_response.m_status = status;
+
+    StringBuilder response_data;
+
+    while (!at_end() && m_buffer[position] != '\r') {
+        response_data.append((char)m_buffer[position]);
+        position += 1;
+    }
+
+    consume("\r\n");
+    m_response.m_response_text = response_data.build();
+}
+
+void Parser::consume(StringView x)
+{
+    if (!try_consume(x)) {
+        dbgln("{} not matched at {}, buffer: {}", x, position, StringView(m_buffer.data(), m_buffer.size()));
+
+        m_parsing_failed = true;
+    }
+}
+
+Optional<unsigned> Parser::try_parse_number()
+{
+    auto number_matched = 0;
+    while (!at_end() && 0 <= m_buffer[position] - '0' && m_buffer[position] - '0' <= 9) {
+        number_matched++;
+        position++;
+    }
+    if (number_matched == 0)
+        return {};
+
+    auto number = StringView(m_buffer.data() + position - number_matched, number_matched);
+
+    return number.to_uint();
+}
+
+unsigned Parser::parse_number()
+{
+    auto number = try_parse_number();
+    if (!number.has_value()) {
+        m_parsing_failed = true;
+        return -1;
+    }
+
+    return number.value();
+}
+
+StringView Parser::parse_atom()
+{
+    auto is_non_atom_char = [](u8 x) {
+        auto non_atom_chars = { '(', ')', '{', ' ', '%', '*', '"', '\\', ']' };
+        return AK::find(non_atom_chars.begin(), non_atom_chars.end(), x) != non_atom_chars.end();
+    };
+
+    auto start = position;
+    auto count = 0;
+    while (!at_end() && !is_ascii_control(m_buffer[position]) && !is_non_atom_char(m_buffer[position])) {
+        count++;
+        position++;
+    }
+
+    return StringView(m_buffer.data() + start, count);
+}
+
+ResponseStatus Parser::parse_status()
+{
+    auto atom = parse_atom();
+
+    if (atom.matches("OK")) {
+        return ResponseStatus::OK;
+    } else if (atom.matches("BAD")) {
+        return ResponseStatus::Bad;
+    } else if (atom.matches("NO")) {
+        return ResponseStatus::No;
+    }
+
+    m_parsing_failed = true;
+    return ResponseStatus::Bad;
+}
+
+StringView Parser::parse_while(Function<bool(u8)> should_consume)
+{
+    int chars = 0;
+    while (!at_end() && should_consume(m_buffer[position])) {
+        position++;
+        chars++;
+    }
+    return StringView(m_buffer.data() + position - chars, chars);
+}
+
+}
diff --git a/Userland/Libraries/LibIMAP/Parser.h b/Userland/Libraries/LibIMAP/Parser.h
new file mode 100644
index 0000000000..9a4ee07e5e
--- /dev/null
+++ b/Userland/Libraries/LibIMAP/Parser.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/Result.h>
+#include <LibIMAP/Objects.h>
+
+namespace IMAP {
+class Client;
+
+struct ParseStatus {
+    bool successful;
+    Optional<Response> response;
+};
+
+class Parser {
+public:
+    ParseStatus parse(ByteBuffer&& buffer, bool expecting_tag);
+
+private:
+    // To retain state if parsing is not finished
+    ByteBuffer m_buffer;
+    SolidResponse m_response;
+    unsigned position { 0 };
+    bool m_incomplete { false };
+    bool m_parsing_failed { false };
+
+    bool try_consume(StringView);
+    bool at_end() { return position >= m_buffer.size(); };
+    void parse_response_done();
+    void consume(StringView x);
+    unsigned parse_number();
+    Optional<unsigned> try_parse_number();
+    void parse_untagged();
+    StringView parse_atom();
+    ResponseStatus parse_status();
+    StringView parse_while(Function<bool(u8)> should_consume);
+};
+}