#include "m.h"
#include <errno.h>
#include <ctype.h>

#include <stdarg.h>	/* ANSI */

int line_number = 1;

#define MAXBUF 600
#define MAXLEN 128

static char buf[MAXBUF][MAXLEN];
static char *p = NULL;
static int n = -1;
static int savedef = -1;

#define inc(n) if( ++n > MAXBUF-1) n = 0
#define dec(n) if( --n < 0) n = MAXBUF - 1

static void h_error( void)
{
    char *q = p+1;

    --line_number;
    dec(n);
    p = NULL;
    error( "event not found: ", q);
}

static void recall( void)
{
    int len, k = n;
    char *q;

    if( p[1] == '!') {

	dec(k);

    } else if( isdigit(p[1]) || p[1] == '-') {

	errno = 0;
	k = strtol( p+1, &q, 10);
	if( errno) {
	    perror("strtol");
	    h_error();
	}

	if( k == 0) {

	    h_error();

	} else if( k < 0) {

	    if( abs(k) > MAXBUF-1)
		h_error();
	    k += n;
	    if( k < 0)
		k += MAXBUF;

	} else {	/* k > 0 */

	    if( k >= line_number || k <= line_number - MAXBUF)
		h_error();
	    k += n + 1 - line_number;
	    if( k < 0)
		k += MAXBUF;
	}

    } else { /* recall by string */

	len = strlen(p+1) - 1;
	dec(k);

	while( buf[k][0] && k != n)
	    if( strncmp( buf[k], p+1, len) == 0)
		break;
	    else
		dec(k);

	if( k == n)
	    h_error();
    }

    if( !buf[k][0])
	h_error();

    (void) strcpy( buf[n], buf[k]);
}

void history( int nlines, FILE *fout)
{
    int start, num;

    if( nlines > MAXBUF)
	nlines = MAXBUF;

    start = n - nlines + 1;

    if( !buf[MAXBUF-1][0]) {
	if( start < 0)
	    start = 0;
	num = n - start + 1;
    } else {
	num = n - start + 1;
	if( start < 0)
	    start += MAXBUF;
    }

    while( num) {
	if( fout == stdout)
	    printf( "%6d  ", line_number - num);
	fputs( buf[start], fout);
	inc(start);
	--num;
    }
}

int m_getc( void)
{
    if( !p || !*p) {

	inc(n);
	p = buf[n];

	if( (p = fgets( p, MAXLEN, fin)) == NULL) {
	    dec(n);
	    return EOF;
	}

	++line_number;

    loop:

	if( (echo && fin != stdin) || (batch && fin == stdin) ) 
	    dprint( "%s", p);
	else if( diary && fin == stdin &&
		fprintf( fdiary, "m:%d> %s", line_number - 1, p) < 0)
	    perror("fprintf");

	if( *p == '$') {
	    *(p + strlen(p) - 1) = '\0';	/* kill \n */
	    if( system( p+1) == -1)
	      yyerror("system() failed");
	    *(p + strlen(p) - 1) = '\n';	/* put \n back */
	    m_gets();
	    if( !batch) prompt();
	    return m_getc();
	} else if( *p == '!') {
	    recall();
	    dprint( "%s", p);
	    goto loop;
	}
    }
#ifdef YYDEBUG
    if( yydebug)
	(void) printf("m_getc: returning %c\n", *p);
#endif

    if( *p == '\\' && *(p+1) == '\n') {
	p += 2;
	return m_getc();
    }

    return *p++;
}

void m_ungetc( int c)
{
    if( --p < buf[n]) {
	dec(n);
	p = buf[n] + strlen(buf[n]) - 1;
    }
#ifdef YYDEBUG
    if( yydebug)
	(void) printf("m_ungetc: %c\n", c);
#endif
    *p = c;
}

int m_scanf( double *x)
{
    char *q;

#ifdef YYDEBUG
    if( yydebug)
	(void) printf("m_scanf: %s", p);
#endif
    errno = 0;
    *x = strtod( p, &q);

    if( errno)
	perror("m_scanf");

    if( errno || q == p)
	return 0;
    else {
	p = q;
	return 1;
    }
}

void m_gets( void)	/* advance pointer to end of buffer */
{
#ifdef YYDEBUG
    if( yydebug)
	(void) printf("m_gets: skipping %s", p);
#endif
    p = buf[n] + strlen(buf[n]);
}

void fn_start( void)
{
    savedef = n;
}

char *defn( void)
{
    int i, len;
    char *f;

    if( savedef < 0)
	return NULL;

    i = savedef;
    len = strlen(buf[i]);
    while( i != n) {
	inc(i);
	len += strlen(buf[i]);
    }

    if( (f = (char *) malloc( len+1)) == NULL) {
	yyerror("malloc() failed in defn()");
	return NULL;
    }

    i = savedef;
    strcpy( f, buf[i]);
    while( i != n) {
	inc(i);
	strcat( f, buf[i]);
    }

    return f;
}

void dprint( char *fmt, ...)
{
    va_list args;

    va_start( args, fmt);

	if( vprintf( fmt, args) < 0)
	    perror("vprintf");
	if( diary)
	    if( vfprintf( fdiary, fmt, args) < 0)
		perror("vfprintf");

    va_end( args);
}

void dputchar( int c)
{
    if( fputc( c, stdout) < 0)
	perror("fputc()");
    if( diary && fputc( c, fdiary) < 0)
	perror("fputc()");
}

void derror( void)
{
    int i = -1, k = p - buf[n] - 1;

    dprint( "%s", buf[n]);
    while( ++i < k)
	dputchar( buf[n][i] == '\t' ? '\t' : ' ');
    dputchar( '^');
    dputchar( '\n');
}