/* This file is term.c.  It's written in C and uses Tk. */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tk.h>

Tcl_Interp *interp;
Tk_Window mainWindow;
const int height = 24;
const int width = 80;

void term_construct(void)
{
	static int n = 0;	/* how many terminals have been constructed */
	const char background = ' ';
	char buffer[12];

	interp = Tcl_CreateInterp();
	mainWindow = Tk_CreateMainWindow(interp, getenv("DISPLAY"), "game", "Game");

	if (mainWindow == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(1);
	}

	sprintf(buffer, "%d", n++);
	if (Tcl_SetVar(interp, "n", buffer, TCL_LEAVE_ERR_MSG) == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(2);
	}

	sprintf(buffer, "%d", height);
	if (Tcl_SetVar(interp, "height", buffer, TCL_LEAVE_ERR_MSG) == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(3);
	}

	sprintf(buffer, "%d", width);
	if (Tcl_SetVar(interp, "width", buffer, TCL_LEAVE_ERR_MSG) == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(4);
	}

	sprintf(buffer, "%c", background);
	if (Tcl_SetVar(interp, "background", buffer, TCL_LEAVE_ERR_MSG) == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(5);
	}

	if (Tcl_Eval(interp,
		"toplevel .toplevel$n\n"

		"text .toplevel$n.text"
		" -height $height"
		" -width $width"
		" -background White"
		" -foreground Black"
		" -font -adobe-courier-medium-r-normal--12-*-*-m-*-*-*\n"

		"#Must fill the text widget with lines of characters."
		"set line \"\"\n"
		"for {set i 0} {$i < $width} {incr i} {"
			"append line $background"
		"}\n"
		"append line \"\n\"\n"
		"for {set i 1} {$i <= $height} {incr i} {"
			".toplevel$n.text insert $i.0 $line"
		"}\n"

		"#queue of keystrokes, used by term_key\n"
		"set queue \"\"\n"
		"bind .toplevel$n.text <Any-KeyPress> {append queue \"\%K\"}\n"

		"focus .toplevel$n.text\n"
		"wm title .toplevel$n \"game\"\n"
		"wm withdraw .\n"
		"pack .toplevel$n.text\n"
		"update\n"
		) != TCL_OK) {

		fprintf(stderr, "%s\n", interp->result);
		exit(6);
	}
}

void term_destruct(void)
{
	/* If the user has not already destroyed the main window by clicking
	on its go-away box, */

	if (tk_NumMainWindows == 1) {
		if (Tcl_Eval(interp, "destroy .toplevel$n.text .toplevel$n\n") != TCL_OK) {
			fprintf(stderr, "%s\n", interp->result);
			exit(7);
		}
		Tk_DestroyWindow(mainWindow);
	}
	Tcl_DeleteInterp(interp);
}

unsigned term_xmax(void) {return width;}
unsigned term_ymax(void) {return height;}

int term_get(unsigned x, unsigned y)
{
	char buffer[256];

	/* The line numbers in a text widget are 1-based.
	The character on each line are 0-based. */

	sprintf(buffer, ".toplevel$n.text get %d.%d\n", y + 1, x);
	if (Tcl_Eval(interp, buffer) != TCL_OK) {
		fprintf(stderr, "%s\n", interp->result);
		exit(8);
	}

	return interp->result[0];
}

void term_put(unsigned x, unsigned y, char c)
{
	char buffer[256];

	if (x < 0 || x > term_xmax() ||
	    y < 0 || y > term_ymax()) {
		fprintf(stderr, "out of bounds (%d, %d)\n", x, y);
		exit(9);
	}

	/* The line numbers in a text widget are 1-based.
	The character on each line are 0-based. */

	sprintf(buffer,
		".toplevel$n.text delete %d.%d\n"
		".toplevel$n.text insert %d.%d \"%s%c\"\n"
		"update\n",
		y + 1, x,
		y + 1, x, c == '"' ? "\\" : "", c);

	if (Tcl_Eval(interp, buffer) != TCL_OK) {
		fprintf(stderr, "%s\n", interp->result);
		exit(10);
	}
}

/* Wrap around, if necessary. */

void term_puts(unsigned x, unsigned y, const char *s)
{
	const int number_of_rows    = term_xmax();
	const int number_of_columns = term_ymax();
	const int len = strlen(s);

	int i;
	for (i = 0; i < len; ++i) {
		const int zero_based_x = x + i;
		const int j = zero_based_x / number_of_columns;
		const int zero_based_y = y + j;

		term_put(
			zero_based_x % number_of_columns,
			zero_based_y % number_of_rows, s[i]);
	}
}

int term_key(void)
{
	char *p;
	char c;

	/* Process all outstanding events, including keystrokes. */
	while (Tk_DoOneEvent(TK_ALL_EVENTS | TK_DONT_WAIT) != 0) {
		if (tk_NumMainWindows != 1) {
			return EOF;
		}
	}

	/* Remove and return the first character in the value of queue. */
	if ((p = Tcl_GetVar(interp, "queue", 0)) == NULL) {
		fprintf(stderr, "the variable queue doesn't exist");
		exit(12);
	}

	if ((c = p[0]) != '\0' &&
		Tcl_SetVar(interp, "queue", p + 1, TCL_LEAVE_ERR_MSG) == NULL) {
		fprintf(stderr, "%s\n", interp->result);
		exit(13);
	}

	return c;
}

void term_wait(int milliseconds)
{
	Tk_Sleep(milliseconds);
}

void term_beep(void)
{
	if (Tcl_Eval(interp, "puts stderr \\a\n") != TCL_OK) {
		fprintf(stderr, "%s\n", interp->result);
		exit(14);
	}
}