/**
 * @author Christian Burger (christian@krikkel.de)
 */

#include "kNCurses/PtyWindow.hpp"
#include "Debug.hpp"

#include <cstdio>
#include <unistd.h>
#include <sys/select.h>
#include <gsl/gsl>
#include <cctype>
#include <termios.h>
#include <fcntl.h>
#include <exception>
#include <cerrno>

namespace krikkel::NCurses
{
    using gsl::narrow;
    using std::scoped_lock;
    using std::recursive_mutex;
    using std::system_error;
    using std::system_category;
    using std::string;

    PtyWindow::PtyWindow(recursive_mutex *ncursesMutex, int lines, int columns, int y, int x)
            : Window(lines, columns, y, x), ncursesMutex(ncursesMutex)
    {
        // to get the original terminal we need to shutdown ncurses for a moment
        /// @todo maybe try `reset_prog_mode()` and `reset_shell_mode()` instead
        ::endwin();
        tcgetattr(STDIN_FILENO, &terminalParameters);
        ::refresh();

        winsize windowSize =
        {
            /*.ws_row =*/ narrow<short unsigned int>(this->height())
          , /*.ws_col =*/ narrow<short unsigned int>(this->width())
          , /*.y =*/ 0
          , /*.x =*/ 0
        };
        openpty(&fdPtyHost, &fdPtyClient, NULL, &terminalParameters, &windowSize);

        pseudoTerminal = vterm_new(windowSize.ws_row, windowSize.ws_col);
        vterm_set_utf8(pseudoTerminal, true);
        pseudoTerminalScreen = vterm_obtain_screen(pseudoTerminal);
        vterm_screen_reset(pseudoTerminalScreen, true);
        vterm_screen_set_callbacks(pseudoTerminalScreen, &screenCallbacks, this);
        vterm_output_set_callback(pseudoTerminal, &staticHandlerOutput, this);
        vterm_screen_enable_altscreen(pseudoTerminalScreen, true);

        //raw();         // — cbreak might suffice
        //noecho();      // — already set by NCursesWindow
        keypad(true);    /// — already set by NCursesWindow
        //meta(true);    // — already set by NCursesWindow
        //nodelay(true); // — @todo would need some programming, not sure if useful
        nonl();

        /// @todo block all signals, this thread does not handle any
        readPtyClientThread =
                std::thread(&PtyWindow::readFromPtyClientThreadMethod, this);
    }

    PtyWindow::~PtyWindow()
    {
        close(fdPtyHost);
        close(fdPtyClient);
        vterm_free(pseudoTerminal);
    }

    int PtyWindow::getFdPtyClient() const
    {
        return fdPtyClient;
    }

    void PtyWindow::writeToPtyClient(const char *output, size_t length)
    {
        size_t bytesWritten = write(fdPtyHost, output, length);
        /// @todo this is a bit too simple; partial write is possible
        if(bytesWritten != length)
        {
            string basicError("Could not write to PTY client (i. e. the shell).");
            throw system_error(errno, system_category(), basicError);
        }
        //__debug_log("written to PTY client: '" + __debug_make_bytes_printable(std::string(output, length)) + '\'');
    }

    void PtyWindow::writeUnicodeCharToClient(wint_t character)
    {
        scoped_lock lock(ptyMutex);
        vterm_keyboard_unichar(pseudoTerminal, character, VTERM_MOD_NONE);
    }

    void PtyWindow::writeFunctionKeyToClient(VTermKey key)
    {
        scoped_lock lock(ptyMutex);
        //__debug_log("writing key: " + std::to_string(key));
        vterm_keyboard_key(pseudoTerminal, key, VTERM_MOD_NONE);
    }

    void PtyWindow::readFromPtyClientThreadMethod()
    {
        /// @todo in theory, there is no need for a timeout or select …
        ///       file descriptor is blocking
        while(1)
        {
            readFromPtyClient();
            struct timeval timeout = { /*.tv_sec =*/ 0, /*.tv_usec =*/ 200000 };
            fd_set readFds;

            FD_ZERO(&readFds);
            FD_SET(fdPtyHost, &readFds);
            if(select(fdPtyHost + 1, &readFds, NULL, NULL, &timeout) < 0)
                break;
        }
    }

    void PtyWindow::readFromPtyClient()
    {
        size_t bytesRead = read(fdPtyHost, ptyClientOutputBuffer, PTY_CLIENT_OUTPUT_BUFFER_SIZE);
        if(bytesRead != (size_t) -1 && bytesRead != 0)
        {
            scoped_lock lock(ptyMutex, *ncursesMutex);
            vterm_input_write(pseudoTerminal, ptyClientOutputBuffer, bytesRead);
        }
        //__debug_log("read from PTY client: '" + __debug_make_bytes_printable(std::string(ptyClientOutputBuffer, bytesRead)) + '\'');
    }

    VTermScreenCallbacks PtyWindow::screenCallbacks =
    {
          /*.damage =*/ staticHandlerDamage
        , /*.moverect =*/ staticHandlerMoveRect
        , /*.movecursor =*/ staticHandlerMoveCursor
        , /*.settermprop =*/ staticHandlerSetTermProp
        , /*.bell =*/ staticHandlerBell
        , /*.resize =*/ staticHandlerResize
        , /*.sb_pushline =*/ staticHandlerPushLine
        , /*.sb_popline =*/ staticHandlerPopLine
    };

    int PtyWindow::handlerDamage(VTermRect rect)
    {
        scoped_lock lock(ptyMutex, *ncursesMutex);

        for(int x = rect.start_col; x < rect.end_col; ++x)
            for(int y = rect.start_row; y < rect.end_row; ++y)
                copyPtyCellToNCursesWindow(x, y);

        refresh();

        return 0;
    }

    int PtyWindow::handlerMoveRect(VTermRect dest, VTermRect src)
    {
        (void) dest;
        (void) src;

        __debug_log("(unimplemented) move content in rectangle from ("
              + std::to_string(src.start_col) + ", "
              + std::to_string(src.start_row) + ", "
              + std::to_string(src.end_col) + ", "
              + std::to_string(src.end_row) + ") "
              + "size: " + std::to_string((src.start_col - src.end_col) * (src.start_row - src.end_row))
              + " to ("
              + std::to_string(dest.start_col) + ", "
              + std::to_string(dest.start_row) + ", "
              + std::to_string(dest.end_col) + ", "
              + std::to_string(dest.end_row) + ") "
              + "size: " + std::to_string((dest.start_col - dest.end_col) * (dest.start_row - dest.end_row)));
        return 0;
    }

    int PtyWindow::handlerMoveCursor(VTermPos pos, VTermPos oldpos, int visible)
    {
        (void) oldpos;
        (void) visible;

        scoped_lock lock(*ncursesMutex);
        cursorX = pos.col;
        cursorY = pos.row;
        refresh();
        return 0;
    }

    int PtyWindow::handlerSetTermProp(VTermProp prop, VTermValue *val)
    {
        (void) prop;
        (void) val;

        /// @todo maybe use "vterm_get_prop_type() —> bool, number, string"?
        __debug_stringify_switch_begin(handlerSetTermProp, prop, val);
            __debug_stringify_switch_case(VTERM_PROP_CURSORVISIBLE);
            __debug_stringify_switch_case(VTERM_PROP_CURSORBLINK);
            __debug_stringify_switch_case(VTERM_PROP_ALTSCREEN);
                __debug_stringify_switch_last_case_bool(VTERM_PROP_REVERSE, val->boolean);
            __debug_stringify_switch_case(VTERM_PROP_TITLE);
                __debug_stringify_switch_last_case_string(VTERM_PROP_ICONNAME, val->string);
            __debug_stringify_switch_case(VTERM_PROP_CURSORSHAPE);
                __debug_stringify_switch_last_case_number(VTERM_PROP_MOUSE, val->number);
        __debug_stringify_switch_end(prop);

        __debug_log(std::string("unimplemented handler called: ")
                  + __debug_stringify_get_string(handlerSetTermProp)
                   );
        return 0;
    }

    int PtyWindow::handlerBell()
    {
        beep();
        return 0;
    }

    int PtyWindow::handlerResize(int rows, int cols)
    {
        (void) rows;
        (void) cols;

        __debug_log("unimplemented handler called");
        return 0;
    }

    int PtyWindow::handlerPushLine(int cols, const VTermScreenCell *cells)
    {
        (void) cols;
        (void) cells;

        __debug_log("(unimplemented) push line with " + std::to_string(cols) + " columns");
        return 0;
    }

    int PtyWindow::handlerPopLine(int cols, VTermScreenCell *cells)
    {
        (void) cols;
        (void) cells;

        __debug_log("unimplemented handler called");
        return 0;
    }

    attr_t PtyWindow::extractAttributesFromVTermCell(VTermScreenCell vTermCell)
    {
        (void) vTermCell;

        attr_t result = A_NORMAL;
        //__debug_log("unimplemented method called");
        return result;
    }

    short PtyWindow::extractColorFromVTermCell(VTermScreenCell vTermCell)
    {
        (void) vTermCell;

        //__debug_log("unimplemented method called");
        return 0;
    }

    void PtyWindow::copyPtyCellToNCursesWindow(int x, int y)
    {
        VTermPos cellPosition = {y, x};
        VTermScreenCell vTermCell;
        cchar_t converted;
        attr_t formatting;
        short colorPair;
        wchar_t character;

        vterm_screen_get_cell(pseudoTerminalScreen, cellPosition, &vTermCell);
        formatting = extractAttributesFromVTermCell(vTermCell);
        colorPair = extractColorFromVTermCell(vTermCell);

        if(vTermCell.chars[0] == 0)
            character = ' ';
        else
            character = *vTermCell.chars;

        //__debug_log(std::string("written '") + (char) character + std::string("' ") + std::to_string(x) + ", " + std::to_string(y));
        setcchar(&converted, &character, formatting, colorPair, NULL);
        {
            move(cellPosition.row, cellPosition.col);
            chgat(1, formatting, colorPair, NULL);
            add_wch(&converted);
        }
    }

    int PtyWindow::refresh()
    {
        //__debug_log("refreshing");
        scoped_lock lock(*ncursesMutex);
        move(cursorY, cursorX);
        return Window::refresh();
    }

    /// @todo potential racing condition where drawing into terminal while
    ///       resizing?
    int PtyWindow::resize(int rows, int cols)
    {
        scoped_lock lock(ptyMutex, *ncursesMutex);

        winsize windowSize =
        {
            /*.ws_row =*/ narrow<unsigned short>(rows)
          , /*.ws_col =*/ narrow<unsigned short>(cols)
          , 0
          , 0
        };
        ioctl(fdPtyHost, TIOCSWINSZ, &windowSize);
        vterm_set_size(pseudoTerminal, rows, cols);

        return Window::resize(rows, cols);
    }

    int PtyWindow::staticHandlerDamage(VTermRect rect, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerDamage(rect);
    }

    int PtyWindow::staticHandlerMoveRect(VTermRect dest, VTermRect src, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerMoveRect(dest, src);
    }

    int PtyWindow::staticHandlerMoveCursor(VTermPos pos, VTermPos oldpos, int visible, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerMoveCursor(pos, oldpos, visible);
    }

    int PtyWindow::staticHandlerSetTermProp(VTermProp prop, VTermValue *val, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerSetTermProp(prop, val);
    }

    int PtyWindow::staticHandlerBell(void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerBell();
    }

    int PtyWindow::staticHandlerResize(int rows, int cols, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerResize(rows, cols);
    }

    int PtyWindow::staticHandlerPushLine(int cols, const VTermScreenCell *cells, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerPushLine(cols, cells);
    }

    int PtyWindow::staticHandlerPopLine(int cols, VTermScreenCell *cells, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        return instance->handlerPopLine(cols, cells);
    }

    void PtyWindow::staticHandlerOutput(const char *s, size_t len, void *user)
    {
        PtyWindow *instance = static_cast<PtyWindow *>(user);
        instance->writeToPtyClient(s, len);
   }
}