/*
    See license.txt in the root of this project.
*/

# include "luametatex.h"

# define SERIAL_METATABLE "serial"

# ifdef _WIN32

    /* see: https://ds.opdenbrouw.nl/micprg/pdf/serial-win.pdf */
    /* see: https://learn.microsoft.com/en-us/previous-versions/ff802693(v=msdn.10)?redirectedfrom=MSDN */

    /* COM6 */

    typedef struct serial_data {
        HANDLE   handle;
        int      closed;
    } serial_data;

    static serial_data *seriallib_aux_open(lua_State *L, serial_data *existing)
    {
        int           success  = 0;
        HANDLE        handle   = NULL;
        const char   *portname = lua_type(L, 1) == LUA_TSTRING ? lua_tostring(L, 1) : NULL;
        lua_Integer   baudrate = lua_type(L, 2) == LUA_TNUMBER ? lua_tointeger(L, 2) : CBR_19200;
        DCB           dcb      = { 0 };
        COMMTIMEOUTS  timeouts = { 0 };
        /* */
        if (! portname || strlen(portname) == 0) {
            goto DONE;
        }
        handle = CreateFile(
            portname,
            GENERIC_WRITE,      
            0, /* Sharing doesn't work for serial devices. */
            NULL,               
            OPEN_EXISTING,      
            0,                  
            NULL                
        );
        if (handle == INVALID_HANDLE_VALUE) {
            goto DONE;
        } 
        /* */
        dcb.DCBlength = sizeof(dcb);
        if (! GetCommState(handle, &dcb)) {
            goto DONE;
        }
        dcb.BaudRate = (DWORD) (baudrate ? dcb.BaudRate : CBR_19200);
        dcb.ByteSize = 8;
        dcb.StopBits = ONESTOPBIT;
        dcb.Parity   = NOPARITY;
        if (! SetCommState(handle, &dcb)) {
            goto DONE;
        }
        /* */
        timeouts.ReadIntervalTimeout = 50;
        timeouts.ReadTotalTimeoutConstant = 50;
        timeouts.ReadTotalTimeoutMultiplier = 10;
        timeouts.WriteTotalTimeoutConstant = 50;
        timeouts.WriteTotalTimeoutMultiplier = 10;
        if (SetCommTimeouts(handle, &timeouts) == FALSE) {
            goto DONE;
        }
        /* */    
        success = 1;
      DONE:   
        if (success) { 
            serial_data *serial = existing ? existing : (serial_data *) lua_newuserdatauv(L, sizeof(serial_data), 1);
            serial->handle = handle;
            serial->closed = 0;
            if (! existing) {
                lua_pushstring(L, portname);
                lua_setiuservalue(L, -2, 1);
            }
            return serial;
        } else { 
            if (handle) {
                CloseHandle(handle);
            }
            return NULL;
        }
    }

    static void seriallib_aux_close(serial_data *serial)
    {
        CloseHandle(serial->handle);
    }

    static int seriallib_aux_send(serial_data *serial, const char *sequence, size_t length)
    {
        DWORD written = 0;
        return WriteFile(serial->handle, sequence, length, &written, NULL) ? 1 : 0;
    }

    /*tex For old times sake, no temporary user data. */

    static int seriallib_write(lua_State *L)
    { 
        serial_data serial = { 
            .handle = NULL, 
            .closed = 0 
        };
        int success = seriallib_aux_open(L, &serial) && serial.handle;
        if (success) {
            size_t      length   = 0;
            const char *sequence = lua_tolstring(L, 3, &length);
            if (length) {
                DWORD written  = 0;
                success = WriteFile(serial.handle, sequence, length, &written, NULL) ? 1 : 0;
            }
            CloseHandle(serial.handle);
        }
        lua_pushboolean(L, success);
        return 1;
    }

# else 

    #include <stdio.h>
    #include <fcntl.h>
    #include <termios.h>
    #include <unistd.h>
    #include <errno.h>

	/* /dev/ttyUSBx /dev/ttySx /dev/ttyACM0 */

    typedef struct serial_data {
        int handle;
        int closed;
    } serial_data;

    static serial_data *seriallib_aux_open(lua_State *L, serial_data *existing)
    {
        int            success  = 0;
        int            handle   = 0;
        const char    *portname = lua_type(L, 1) == LUA_TSTRING ? lua_tostring(L, 1) : NULL;
        lua_Integer    baudrate = lua_type(L, 2) == LUA_TNUMBER ? lua_tointeger(L, 2) : B19200;
		struct termios settings;	
	    /* */
        if (! portname || strlen(portname) == 0) {
            goto DONE;
        }
	    /* */
        handle = open(
            portname,
            O_WRONLY | O_NOCTTY | O_NDELAY
        );
        if (handle == -1) {
            goto DONE;
        }
	    /* */	
		tcgetattr(handle, &settings);
        cfsetispeed(&settings, baudrate ? baudrate : B19200);
        cfsetospeed(&settings, baudrate ? baudrate : B19200);
        settings.c_cflag &= ~PARENB;
        settings.c_cflag &= ~CSTOPB;
        settings.c_cflag &= ~CSIZE;
        settings.c_cflag |=  CS8;
        settings.c_cflag &= ~CRTSCTS;
        settings.c_cflag |=  (CREAD | CLOCAL);
        settings.c_iflag &= ~(IXON | IXOFF | IXANY);
        settings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);
        settings.c_oflag &= ~OPOST;

        // ASYNC_LOW_LATENCY

     // settings.c_cc[VMIN]  = 0; // don't block 
     // settings.c_cc[VTIME] = 2; // timeout in 1/10 sec 

     // settings.c_lflag  = 0; /* no echo etc */
     // settings.c_oflag  = 0;

     // cfmakeraw(&settings);

        if (tcsetattr(handle, TCSANOW, &settings) != 0) {
            goto DONE;
        }
        /* */
        success = 1;
      DONE:		
        if (success) { 
            serial_data *serial = existing ? existing : (serial_data *) lua_newuserdatauv(L, sizeof(serial_data), 1);
            if (! existing) {
                lua_pushstring(L, portname);
                lua_setiuservalue(L, -2, 1);
            }
            serial->handle = handle;
            serial->closed = 0;
            return serial;
        } else { 
            return NULL;
        }
    }

    static void seriallib_aux_close(serial_data *serial)
    {
        close(serial->handle);
    }

    static int seriallib_aux_send(serial_data *serial, const char *sequence, size_t length)
    {
        return write(serial->handle, sequence, length) ? 1 : 0;

    }

    /*tex For old times sake, no temporary user data. */

    static int seriallib_write(lua_State *L)
    { 
        serial_data serial = { 
            .handle = -1, 
            .closed = 0 
        };
        int success = seriallib_aux_open(L, &serial) && serial.handle >= 0;
        if (success) {
            size_t      length   = 0;
            const char *sequence = lua_tolstring(L, 3, &length);
            if (length) {
                success = write(serial.handle, sequence, length) ? 1 : 0;
            }
            close(serial.handle);
        }
        lua_pushboolean(L, success);
        return 1;
    }


# endif 

static int seriallib_open(lua_State *L)
{
    serial_data *serial = seriallib_aux_open(L, NULL);
    if (serial) { 
        luaL_getmetatable(L, SERIAL_METATABLE);
        lua_setmetatable(L, -2);
    } else { 
        lua_pushnil(L);
    }
    return 1;
}

static int seriallib_send(lua_State *L)
{
    serial_data *serial = (serial_data *) luaL_checkudata(L, 1, SERIAL_METATABLE);
    int success = 0;
    if (serial && ! serial->closed) {
        size_t      length   = 0;
        const char *sequence = lua_tolstring(L, 2, &length);
        if (seriallib_aux_send(serial, sequence, length)) { 
            success = 1;
        }
    }
    lua_pushboolean(L, success);
    return 1;
}

static int seriallib_close(lua_State *L) /* maybe use the onclose method */
{
    serial_data *serial = (serial_data *) luaL_checkudata(L, 1, SERIAL_METATABLE);
    if (serial && ! serial->closed) {
        serial->closed = 1;
        seriallib_aux_close(serial);
    }
    return 0;
}

static int seriallib_tostring(lua_State *L) {
    serial_data *serial = (serial_data *) luaL_checkudata(L, 1, SERIAL_METATABLE);
    if (serial && ! serial->closed) {
        const char *port;
        lua_getiuservalue(L, 1, 1);
        port = lua_tostring(L, -1);
        lua_pop(L, -1);
        lua_pushfstring(L, "<serial %s>", port); 
        return 1;
    } else {
        return 0;
    }
}

static const luaL_Reg seriallib_function_list[] =
{
    /* management */
    { "open",         seriallib_open      },
    { "close",        seriallib_close     },
    { "send",         seriallib_send      },
    { "write",        seriallib_write     },
    /* */
    { "tostring",     seriallib_tostring  },
    /* */
    { "__gc",         seriallib_close     },
    /* */
    { NULL,           NULL                },
};

int luaopen_serial(lua_State *L)
{
    luaL_newmetatable(L, SERIAL_METATABLE);
    luaL_setfuncs(L, seriallib_function_list, 0);
    lua_pushliteral(L, "__index");
    lua_pushvalue(L, -2);
    lua_settable(L, -3);
    lua_pushliteral(L, "__tostring");
    lua_pushliteral(L, "tostring");
    lua_gettable(L, -3);
    lua_settable(L, -3);
    lua_pushliteral(L, "__name");
    lua_pushliteral(L, "serial");
    lua_settable(L, -3);
    return 1;
}