#include <stdio.h>
#include <string.h>
#include "terminal.h"

#ifndef _WIN32
#include <termios.h>
#include <unistd.h>

static struct termios terminal_orig_termios;
static int terminal_raw_mode_active = 0;
#endif

/* terminal device */
#define TERMINAL_INPUT 0x0
#define TERMINAL_OUTPUT 0x1
#define TERMINAL_ON_KEYPRESS 0x2
#define TERMINAL_ON_ARGUMENT 0x4

#define TERMINAL_POLL_INTERVAL_MS 100
#define TERMINAL_ERROR_NOT_A_TTY 0x11

//// Platform-specific non-blocking key input

#ifdef _WIN32
#include <conio.h>
#include <windows.h>
static int getch_timeout(int timeout_ms)
{
    HANDLE h = GetStdHandle(STD_INPUT_HANDLE);
    if (WaitForSingleObject(h, timeout_ms) == WAIT_OBJECT_0 && _kbhit())
        return _getch();
    return 0;
}
#else
static int getch_timeout(int timeout_ms)
{
    (void)timeout_ms; // bounded by VMIN=0/VTIME in terminal_setup()
    int c = getchar();
    return (c == EOF) ? 0 : c;
}
#endif

//// Argument feeding state

static int arg_index = 1;
static int arg_char_pos = 0;
static int exec_args_pos = 0;

//// Generic save/restore

void terminal_save(xyw_byte *data, xyw_byte *state)
{
    (void)data;
    memcpy(&state[0], &arg_index, sizeof(arg_index));
    memcpy(&state[4], &arg_char_pos, sizeof(arg_char_pos));
    memcpy(&state[8], &exec_args_pos, sizeof(exec_args_pos));
}

void terminal_restore(xyw_byte *data, const xyw_byte *state)
{
    (void)data;
    memcpy(&arg_index, &state[0], sizeof(arg_index));
    memcpy(&arg_char_pos, &state[4], sizeof(arg_char_pos));
    memcpy(&exec_args_pos, &state[8], sizeof(exec_args_pos));
}

//// Poll: argument feeding and keypress handling

int terminal_poll(xyw_byte *data)
{
    // Feed command line arguments
    xyw_word on_arg_handler = XYW_PEEKW(&data[TERMINAL_ON_ARGUMENT]);
    if (!xyw_argv_processed && on_arg_handler)
    {
        if (xyw_exec_args_active)
        {
            char c = xyw_exec_args[exec_args_pos];
            if (c == ' ')
            {
                data[TERMINAL_INPUT] = XYW_ARGUMENT_SEPARATOR;
                exec_args_pos++;
            }
            else if (c != '\0')
            {
                data[TERMINAL_INPUT] = (xyw_byte)c;
                exec_args_pos++;
            }
            else
            {
                data[TERMINAL_INPUT] = XYW_END_OF_ARGUMENTS;
                xyw_argv_processed = 1;
                xyw_exec_args_active = 0;
            }
        }
        else if (arg_index < xyw_argc)
        {
            char c = xyw_argv[arg_index][arg_char_pos];
            if (c != '\0')
            {
                data[TERMINAL_INPUT] = (xyw_byte)c;
                arg_char_pos++;
            }
            else if (arg_index < xyw_argc - 1)
            {
                data[TERMINAL_INPUT] = XYW_ARGUMENT_SEPARATOR;
                arg_index++;
                arg_char_pos = 0;
            }
            else
            {
                data[TERMINAL_INPUT] = XYW_END_OF_ARGUMENTS;
                xyw_argv_processed = 1;
            }
        }
        else
        {
            data[TERMINAL_INPUT] = XYW_END_OF_ARGUMENTS;
            xyw_argv_processed = 1;
        }
        xyw_vm_set_running(1);
        xyw_vm_push_frame(XYW_DEVICE_AREA_START);
        *pc = on_arg_handler;
        return 1;
    }

    // Keypress handling
    xyw_word on_keypress_handler = XYW_PEEKW(&data[TERMINAL_ON_KEYPRESS]);
    if (on_keypress_handler)
    {
        int c = getch_timeout(TERMINAL_POLL_INTERVAL_MS);
        if (c > 0)
        {
            if (c == 3 || c == 4)
            {
                xyw_vm_set_waiting(0);
                return 0;
            }
            data[TERMINAL_INPUT] = (xyw_byte)c;
            xyw_vm_set_running(1);
            xyw_vm_push_frame(XYW_DEVICE_AREA_START);
            *pc = on_keypress_handler;
            return 1;
        }
        return -1; // active handler, no event yet (keep polling)
    }

    return 0;
}

//// Device init/teardown/IO

void terminal_setup(xyw_byte *data, xyw_byte *error)
{
    (void)data;
    (void)error;
    // Reset arg feeding state for fresh image
    arg_index = 1;
    arg_char_pos = 0;
    exec_args_pos = 0;
#ifndef _WIN32
    struct termios raw;

    if (!isatty(STDIN_FILENO))
    {
        *error = TERMINAL_ERROR_NOT_A_TTY;
        return;
    }

    if (tcgetattr(STDIN_FILENO, &terminal_orig_termios) != 0)
    {
        XYW_DBG("terminal: tcgetattr failed, raw mode not enabled\n");
        *error = TERMINAL_ERROR_NOT_A_TTY;
        return;
    }

    raw = terminal_orig_termios;
    raw.c_lflag &= ~(ICANON | ECHO | ISIG);
    raw.c_cc[VMIN] = 0;
    raw.c_cc[VTIME] = 1;

    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) != 0)
    {
        XYW_DBG("terminal: tcsetattr failed, raw mode not enabled\n");
        *error = TERMINAL_ERROR_NOT_A_TTY;
        return;
    }

    terminal_raw_mode_active = 1;
#endif
}

void terminal_teardown(xyw_byte *data)
{
    (void)data;
#ifndef _WIN32
    if (terminal_raw_mode_active)
    {
        tcsetattr(STDIN_FILENO, TCSAFLUSH, &terminal_orig_termios);
        terminal_raw_mode_active = 0;
    }
#endif
}

void terminal_output(xyw_byte *data, xyw_byte addr, xyw_byte *error)
{
    (void)error;
    if (addr == TERMINAL_OUTPUT) {
        fputc(data[addr], stdout);
        fflush(stdout);
    }
}

xyw_byte terminal_input(xyw_byte *data, xyw_byte addr, xyw_byte *error)
{
    (void)error;
    return data[addr];
}