Shell: Switch to using Core::EventLoop

This commit refactors Shell to a Core::Object and switches its looping
to Core::EventLoop.

Shell/Shell.h

@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2020, The SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Job.h"
+#include "Parser.h"
+#include <AK/CircularQueue.h>
+#include <AK/HashMap.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <AK/Types.h>
+#include <AK/Vector.h>
+#include <LibCore/Notifier.h>
+#include <LibCore/Object.h>
+#include <LibLine/Editor.h>
+#include <termios.h>
+
+struct ExitCodeOrContinuationRequest {
+    enum ContinuationRequest {
+        Nothing,
+        Pipe,
+        DoubleQuotedString,
+        SingleQuotedString,
+    };
+
+    ExitCodeOrContinuationRequest(ContinuationRequest continuation)
+        : continuation(continuation)
+    {
+    }
+
+    ExitCodeOrContinuationRequest(int exit)
+        : exit_code(exit)
+    {
+    }
+
+    bool has_value() const { return exit_code.has_value(); }
+    int value() const
+    {
+        ASSERT(has_value());
+        return exit_code.value();
+    }
+
+    Optional<int> exit_code;
+    ContinuationRequest continuation { Nothing };
+};
+
+using ContinuationRequest = ExitCodeOrContinuationRequest::ContinuationRequest;
+
+#define ENUMERATE_SHELL_BUILTINS()     \
+    __ENUMERATE_SHELL_BUILTIN(cd)      \
+    __ENUMERATE_SHELL_BUILTIN(cdh)     \
+    __ENUMERATE_SHELL_BUILTIN(pwd)     \
+    __ENUMERATE_SHELL_BUILTIN(exit)    \
+    __ENUMERATE_SHELL_BUILTIN(export)  \
+    __ENUMERATE_SHELL_BUILTIN(unset)   \
+    __ENUMERATE_SHELL_BUILTIN(history) \
+    __ENUMERATE_SHELL_BUILTIN(umask)   \
+    __ENUMERATE_SHELL_BUILTIN(dirs)    \
+    __ENUMERATE_SHELL_BUILTIN(pushd)   \
+    __ENUMERATE_SHELL_BUILTIN(popd)    \
+    __ENUMERATE_SHELL_BUILTIN(time)    \
+    __ENUMERATE_SHELL_BUILTIN(jobs)    \
+    __ENUMERATE_SHELL_BUILTIN(fg)      \
+    __ENUMERATE_SHELL_BUILTIN(bg)
+
+class Shell;
+
+class Shell : public Core::Object {
+    C_OBJECT(Shell);
+
+public:
+    ExitCodeOrContinuationRequest run_command(const StringView&);
+    bool run_builtin(int argc, const char** argv, int& retval);
+    String prompt() const;
+
+    static String expand_tilde(const String&);
+    static Vector<String> expand_globs(const StringView& path, const StringView& base);
+    Vector<String> expand_parameters(const StringView&) const;
+
+    static String escape_token(const String& token);
+    static String unescape_token(const String& token);
+
+    static bool is_glob(const StringView&);
+    static Vector<StringView> split_path(const StringView&);
+
+    Vector<String> process_arguments(const Vector<Token>&);
+
+    static ContinuationRequest is_complete(const Vector<Command>&);
+
+    void highlight(Line::Editor&) const;
+    Vector<Line::CompletionSuggestion> complete_first(const String&);
+    Vector<Line::CompletionSuggestion> complete_other(const String&);
+
+    String get_history_path();
+    void load_history();
+    void save_history();
+    void print_path(const String& path);
+
+    bool should_read_more() const { return m_should_continue != ContinuationRequest::Nothing; }
+    void finish_command() { m_should_break_current_command = true; }
+
+    void read_single_line();
+
+    struct termios termios;
+    struct termios default_termios;
+    bool was_interrupted { false };
+    bool was_resized { false };
+
+    String cwd;
+    String username;
+    String home;
+
+    constexpr static auto TTYNameSize = 32;
+    constexpr static auto HostNameSize = 64;
+
+    char ttyname[TTYNameSize];
+    char hostname[HostNameSize];
+
+    uid_t uid;
+    int last_return_code { 0 };
+    Vector<String> directory_stack;
+    CircularQueue<String, 8> cd_history; // FIXME: have a configurable cd history length
+    HashMap<u64, OwnPtr<Job>> jobs;
+    Vector<String, 256> cached_path;
+
+    enum ShellEventType {
+        ReadLine,
+        ChildExited,
+    };
+
+private:
+    Shell();
+    virtual ~Shell() override;
+
+    struct SpawnedProcess {
+        String name;
+        pid_t pid;
+    };
+
+    void cache_path();
+
+    IterationDecision wait_for_pid(const SpawnedProcess&, bool is_first_command_in_chain, int& return_value);
+
+    virtual void custom_event(Core::CustomEvent&) override;
+
+#define __ENUMERATE_SHELL_BUILTIN(builtin) \
+    int builtin_##builtin(int argc, const char** argv);
+
+    ENUMERATE_SHELL_BUILTINS();
+
+#undef __ENUMERATE_SHELL_BUILTIN
+
+    ExitCodeOrContinuationRequest::ContinuationRequest m_should_continue { ExitCodeOrContinuationRequest::Nothing };
+    StringBuilder m_complete_line_builder;
+    bool m_should_break_current_command { false };
+};
+
+static constexpr bool is_word_character(char c)
+{
+    return c == '_' || (c <= 'Z' && c >= 'A') || (c <= 'z' && c >= 'a');
+}