#include <errno.h>
#include <luna/String.h>
#include <luna/Vector.h>
#include <os/ArgumentParser.h>
#include <os/File.h>
#include <os/FileSystem.h>
#include <os/Process.h>
#include <pwd.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/utsname.h>
#include <unistd.h>

using os::File;

static Result<Vector<String>> split_command_into_args(StringView cmd)
{
    return cmd.split(" \n"_sv);
}

static Result<void> execute_command(StringView command)
{
    if (strcspn(command.chars(), " #") == 0) return {};

    auto args = TRY(split_command_into_args(command));
    if (args.size() < 1) exit(0);

    return os::Process::exec(args[0].view(), args.slice());
}

struct utsname g_sysinfo;

const char* hostname = "";
const char* username = "";
char prompt_end = '$';

Result<int> luna_main(int argc, char** argv)
{
    StringView path;
    StringView command;
    bool interactive { false };

    SharedPtr<File> input_file;

    os::ArgumentParser parser;
    parser.add_description("The Luna system's command shell."_sv);
    parser.add_system_program_info("sh"_sv);
    parser.add_positional_argument(path, "path"_sv, "-"_sv);
    parser.add_value_argument(command, 'c', "command"_sv, true, "execute a single command and then exit"_sv);
    parser.parse(argc, argv);

    if (!command.is_empty()) TRY(execute_command(command));

    if (path == "-")
    {
        input_file = File::standard_input();
        interactive = true;
    }
    else
    {
        input_file = TRY(File::open(path, File::ReadOnly));
        input_file->set_close_on_exec();
    }

    if (interactive)
    {
        // Set up everything to form a prompt.
        uname(&g_sysinfo);
        hostname = g_sysinfo.nodename;

        if (getuid() == 0) prompt_end = '#';

        struct passwd* pw = getpwuid(getuid());
        if (pw) { username = pw->pw_name; }
        else { username = getenv("USER"); }
        endpwent();
    }

    while (1)
    {
        if (interactive)
        {
            auto cwd = TRY(os::FileSystem::working_directory());
            os::print("%s@%s:%s%c ", username, hostname, cwd.chars(), prompt_end);
        }

        auto cmd = TRY(input_file->read_line());
        if (cmd.is_empty())
        {
            if (interactive) puts("exit");
            break;
        }

        if (strspn(cmd.chars(), " \n") == cmd.length()) continue;

        if (strcspn(cmd.chars(), " #") == 0) continue;

        if (!strncmp(cmd.chars(), "cd", 2))
        {
            auto args = TRY(split_command_into_args(cmd.view()));
            check(args[0].view() == "cd");

            if (args.size() == 1)
            {
                auto home = TRY(os::FileSystem::home_directory());
                TRY(os::FileSystem::change_directory(home.view()));
                continue;
            }

            TRY(os::FileSystem::change_directory(args[1].view()));
            continue;
        }

        pid_t child = TRY(os::Process::fork());

        if (child == 0) { TRY(execute_command(cmd.view())); }

        TRY(os::Process::wait(child, nullptr));
    }

    return 0;
}