/*
 * Copyright (c) 2020, the SerenityOS developers.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include "Job.h"
#include "Parser.h"
#include <AK/CircularQueue.h>
#include <AK/HashMap.h>
#include <AK/NonnullOwnPtrVector.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>

#define ENUMERATE_SHELL_BUILTINS()     \
    __ENUMERATE_SHELL_BUILTIN(alias)   \
    __ENUMERATE_SHELL_BUILTIN(cd)      \
    __ENUMERATE_SHELL_BUILTIN(cdh)     \
    __ENUMERATE_SHELL_BUILTIN(pwd)     \
    __ENUMERATE_SHELL_BUILTIN(type)    \
    __ENUMERATE_SHELL_BUILTIN(exec)    \
    __ENUMERATE_SHELL_BUILTIN(exit)    \
    __ENUMERATE_SHELL_BUILTIN(export)  \
    __ENUMERATE_SHELL_BUILTIN(glob)    \
    __ENUMERATE_SHELL_BUILTIN(unset)   \
    __ENUMERATE_SHELL_BUILTIN(history) \
    __ENUMERATE_SHELL_BUILTIN(umask)   \
    __ENUMERATE_SHELL_BUILTIN(not )    \
    __ENUMERATE_SHELL_BUILTIN(dirs)    \
    __ENUMERATE_SHELL_BUILTIN(pushd)   \
    __ENUMERATE_SHELL_BUILTIN(popd)    \
    __ENUMERATE_SHELL_BUILTIN(setopt)  \
    __ENUMERATE_SHELL_BUILTIN(shift)   \
    __ENUMERATE_SHELL_BUILTIN(source)  \
    __ENUMERATE_SHELL_BUILTIN(time)    \
    __ENUMERATE_SHELL_BUILTIN(jobs)    \
    __ENUMERATE_SHELL_BUILTIN(disown)  \
    __ENUMERATE_SHELL_BUILTIN(fg)      \
    __ENUMERATE_SHELL_BUILTIN(bg)      \
    __ENUMERATE_SHELL_BUILTIN(wait)    \
    __ENUMERATE_SHELL_BUILTIN(dump)    \
    __ENUMERATE_SHELL_BUILTIN(kill)

#define ENUMERATE_SHELL_OPTIONS()                                                                                    \
    __ENUMERATE_SHELL_OPTION(inline_exec_keep_empty_segments, false, "Keep empty segments in inline execute $(...)") \
    __ENUMERATE_SHELL_OPTION(verbose, false, "Announce every command that is about to be executed")

#define ENUMERATE_SHELL_IMMEDIATE_FUNCTIONS()           \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(concat_lists)  \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(length)        \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(length_across) \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(remove_suffix) \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(remove_prefix) \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(regex_replace) \
    __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(split)

namespace Shell {

class Shell;

class Shell : public Core::Object {
    C_OBJECT(Shell);

public:
    constexpr static auto local_init_file_path = "~/.shellrc";
    constexpr static auto global_init_file_path = "/etc/shellrc";

    bool should_format_live() const { return m_should_format_live; }
    void set_live_formatting(bool value) { m_should_format_live = value; }

    void setup_signals();

    struct SourcePosition {
        String source_file;
        String literal_source_text;
        Optional<AST::Position> position;
    };

    int run_command(const StringView&, Optional<SourcePosition> = {});
    bool is_runnable(const StringView&);
    RefPtr<Job> run_command(const AST::Command&);
    NonnullRefPtrVector<Job> run_commands(Vector<AST::Command>&);
    bool run_file(const String&, bool explicitly_invoked = true);
    bool run_builtin(const AST::Command&, const NonnullRefPtrVector<AST::Rewiring>&, int& retval);
    bool has_builtin(const StringView&) const;
    RefPtr<AST::Node> run_immediate_function(StringView name, AST::ImmediateExpression& invoking_node, const NonnullRefPtrVector<AST::Node>&);
    static bool has_immediate_function(const StringView&);
    void block_on_job(RefPtr<Job>);
    void block_on_pipeline(RefPtr<AST::Pipeline>);
    String prompt() const;

    static String expand_tilde(const String&);
    static Vector<String> expand_globs(const StringView& path, StringView base);
    static Vector<String> expand_globs(Vector<StringView> path_segments, const StringView& base);
    Vector<AST::Command> expand_aliases(Vector<AST::Command>);
    String resolve_path(String) const;
    String resolve_alias(const String&) const;

    static String find_in_path(const StringView& program_name);

    static bool has_history_event(StringView);

    RefPtr<AST::Value> get_argument(size_t);
    RefPtr<AST::Value> lookup_local_variable(const String&);
    String local_variable_or(const String&, const String&);
    void set_local_variable(const String&, RefPtr<AST::Value>, bool only_in_current_frame = false);
    void unset_local_variable(const String&, bool only_in_current_frame = false);

    void define_function(String name, Vector<String> argnames, RefPtr<AST::Node> body);
    bool has_function(const String&);
    bool invoke_function(const AST::Command&, int& retval);

    String format(const StringView&, ssize_t& cursor) const;

    RefPtr<Line::Editor> editor() const { return m_editor; }

    struct LocalFrame {
        LocalFrame(String name, HashMap<String, RefPtr<AST::Value>> variables)
            : name(move(name))
            , local_variables(move(variables))
        {
        }

        String name;
        HashMap<String, RefPtr<AST::Value>> local_variables;
    };

    struct Frame {
        Frame(NonnullOwnPtrVector<LocalFrame>& frames, const LocalFrame& frame)
            : frames(frames)
            , frame(frame)
        {
        }
        ~Frame();

        void leak_frame() { should_destroy_frame = false; }

    private:
        NonnullOwnPtrVector<LocalFrame>& frames;
        const LocalFrame& frame;
        bool should_destroy_frame { true };
    };

    [[nodiscard]] Frame push_frame(String name);
    void pop_frame();

    static String escape_token_for_double_quotes(const String& token);
    static String escape_token_for_single_quotes(const String& token);
    static String escape_token(const String& token);
    static String unescape_token(const String& token);
    static bool is_special(char c);

    static bool is_glob(const StringView&);
    static Vector<StringView> split_path(const StringView&);

    enum class ExecutableOnly {
        Yes,
        No
    };

    void highlight(Line::Editor&) const;
    Vector<Line::CompletionSuggestion> complete();
    Vector<Line::CompletionSuggestion> complete_path(const String& base, const String&, size_t offset, ExecutableOnly executable_only);
    Vector<Line::CompletionSuggestion> complete_program_name(const String&, size_t offset);
    Vector<Line::CompletionSuggestion> complete_variable(const String&, size_t offset);
    Vector<Line::CompletionSuggestion> complete_user(const String&, size_t offset);
    Vector<Line::CompletionSuggestion> complete_option(const String&, const String&, size_t offset);
    Vector<Line::CompletionSuggestion> complete_immediate_function_name(const String&, size_t offset);

    void restore_ios();

    u64 find_last_job_id() const;
    const Job* find_job(u64 id, bool is_pid = false);
    const Job* current_job() const { return m_current_job; }
    void kill_job(const Job*, int sig);

    String get_history_path();
    void print_path(const String& path);

    bool read_single_line();

    void notify_child_event();

    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, NonnullRefPtr<Job>> jobs;
    Vector<String, 256> cached_path;

    String current_script;

    enum ShellEventType {
        ReadLine,
    };

    enum class ShellError {
        None,
        InternalControlFlowBreak,
        InternalControlFlowContinue,
        EvaluatedSyntaxError,
        NonExhaustiveMatchRules,
        InvalidGlobError,
        InvalidSliceContentsError,
        OpenFailure,
    };

    void raise_error(ShellError kind, String description, Optional<AST::Position> position = {})
    {
        m_error = kind;
        m_error_description = move(description);
        if (m_source_position.has_value() && position.has_value())
            m_source_position.value().position = position.release_value();
    }
    bool has_error(ShellError err) const { return m_error == err; }
    const String& error_description() const { return m_error_description; }
    ShellError take_error()
    {
        auto err = m_error;
        m_error = ShellError::None;
        m_error_description = {};
        return err;
    }
    void possibly_print_error() const;
    static bool is_control_flow(ShellError error)
    {
        switch (error) {
        case ShellError::InternalControlFlowBreak:
        case ShellError::InternalControlFlowContinue:
            return true;
        default:
            return false;
        }
    }

#define __ENUMERATE_SHELL_OPTION(name, default_, description) \
    bool name { default_ };

    struct Options {
        ENUMERATE_SHELL_OPTIONS();
    } options;

#undef __ENUMERATE_SHELL_OPTION

private:
    Shell(Line::Editor&, bool attempt_interactive);
    Shell();
    virtual ~Shell() override;

    // FIXME: Port to Core::Property
    void save_to(JsonObject&);
    void bring_cursor_to_beginning_of_a_line() const;

    Optional<int> resolve_job_spec(const String&);
    void cache_path();
    void add_entry_to_cache(const String&);
    void stop_all_jobs();
    const Job* m_current_job { nullptr };
    LocalFrame* find_frame_containing_local_variable(const String& name);

    void run_tail(RefPtr<Job>);
    void run_tail(const AST::Command&, const AST::NodeWithAction&, int head_exit_code);

    [[noreturn]] void execute_process(Vector<const char*>&& argv);

    virtual void custom_event(Core::CustomEvent&) override;

#define __ENUMERATE_SHELL_IMMEDIATE_FUNCTION(name) \
    RefPtr<AST::Node> immediate_##name(AST::ImmediateExpression& invoking_node, const NonnullRefPtrVector<AST::Node>&);

    ENUMERATE_SHELL_IMMEDIATE_FUNCTIONS();

#undef __ENUMERATE_SHELL_IMMEDIATE_FUNCTION

    RefPtr<AST::Node> immediate_length_impl(AST::ImmediateExpression& invoking_node, const NonnullRefPtrVector<AST::Node>&, bool across);

#define __ENUMERATE_SHELL_BUILTIN(builtin) \
    int builtin_##builtin(int argc, const char** argv);

    ENUMERATE_SHELL_BUILTINS();

#undef __ENUMERATE_SHELL_BUILTIN

    constexpr static const char* builtin_names[] = {
#define __ENUMERATE_SHELL_BUILTIN(builtin) #builtin,

        ENUMERATE_SHELL_BUILTINS()

#undef __ENUMERATE_SHELL_BUILTIN
    };

    bool m_should_ignore_jobs_on_next_exit { false };
    pid_t m_pid { 0 };

    struct ShellFunction {
        String name;
        Vector<String> arguments;
        RefPtr<AST::Node> body;
    };

    HashMap<String, ShellFunction> m_functions;
    NonnullOwnPtrVector<LocalFrame> m_local_frames;
    NonnullRefPtrVector<AST::Redirection> m_global_redirections;

    HashMap<String, String> m_aliases;
    bool m_is_interactive { true };
    bool m_is_subshell { false };
    bool m_should_reinstall_signal_handlers { true };

    ShellError m_error { ShellError::None };
    String m_error_description;
    Optional<SourcePosition> m_source_position;

    bool m_should_format_live { false };

    RefPtr<Line::Editor> m_editor;

    bool m_default_constructed { false };

    mutable bool m_last_continuation_state { false }; // false == not needed.
};

[[maybe_unused]] static constexpr bool is_word_character(char c)
{
    return c == '_' || (c <= 'Z' && c >= 'A') || (c <= 'z' && c >= 'a') || (c <= '9' && c >= '0');
}

inline size_t find_offset_into_node(const String& unescaped_text, size_t escaped_offset)
{
    size_t unescaped_offset = 0;
    size_t offset = 0;
    for (auto& c : unescaped_text) {
        if (offset == escaped_offset)
            return unescaped_offset;

        if (Shell::is_special(c))
            ++offset;
        ++offset;
        ++unescaped_offset;
    }

    return unescaped_offset;
}

}