/* vscreen.c - screen half of the vim editor for the C64 (Power C)
 *
 * Draws the text window, the status line and the cursor straight into
 * the screen matrix at $0400 and colour RAM at $d800. Kept in its own
 * file because Power C overflows its compiler when the whole editor is
 * one source.
 *
 * This module owns no program state: draw() receives everything it
 * needs from vim.c as arguments. Sharing variables between Power C
 * object files proved unreliable, so only functions cross the boundary.
 */

static char stat[40];           /* status line build buffer */
static int  slen;

/* ---------- status line text ---------- */

static sclr()
{
    slen = 0;
    stat[0] = 0;
}

static sadd(c)
char c;
{
    if (slen < 39) {
        stat[slen] = c;
        slen = slen + 1;
        stat[slen] = 0;
    }
}

static sstr(s)
char *s;
{
    while (*s) {
        sadd(*s);
        s = s + 1;
    }
}

static snum(n)
int n;
{
    char b[6];
    int i;

    if (n < 0) {
        sadd('-');
        n = -n;
    }
    if (n == 0) {
        sadd('0');
        return;
    }
    i = 0;
    while (n > 0) {
        b[i] = '0' + (n % 10);
        i = i + 1;
        n = n / 10;
    }
    while (i > 0) {
        i = i - 1;
        sadd(b[i]);
    }
}

/* ---------- PETSCII byte -> screen code ---------- */

static sccode(c)
int c;
{
    if (c >= 193 && c <= 218) return c - 192;   /* shifted letters $C1-$DA */
    if (c >= 96 && c <= 127)  return c - 32;
    if (c >= 64 && c <= 95)   return c - 64;
    /* the C-only characters have no glyph of their own in the ROM */
    if (c == 219) return 91;        /* {  -> [ */
    if (c == 221) return 93;        /* }  -> ] */
    if (c == 223) return 94;        /* |  -> up arrow */
    if (c == 175) return 126;       /* ~  -> its graphics glyph */
    if (c == 164) return 95;        /* _  -> left arrow */
    return c;
}

/* ---------- screen output ---------- */

clrscr()
{
    char *s;
    char *m;
    int i;

    s = (char *) 1024;
    m = (char *) 55296;
    for (i = 0; i < 1000; i++) {
        s[i] = 32;
        m[i] = 1;
    }
}

static putchr(x, y, ch, c)
int x;
int y;
int ch;
int c;
{
    char *s;
    char *m;
    int o;

    if (x < 0) return;
    if (x > 39) return;
    if (y < 0) return;
    if (y > 24) return;
    o = y * 40 + x;
    s = (char *) 1024;
    m = (char *) 55296;
    s[o] = ch;
    m[o] = c;
}

static putstr(x, y, s, c)
int x;
int y;
char *s;
int c;
{
    while (*s && x < 40) {
        putchr(x, y, sccode(*s), c);
        x = x + 1;
        s = s + 1;
    }
}

static revchr(o)                /* reverse the character in a cell */
int o;
{
    char *s;

    s = (char *) 1024;
    if (s[o] < 128) s[o] = s[o] + 128;
}

/* ---------- buffer scans over the caller's text ---------- */

static lstartx(tp, len, n)      /* offset of the first byte of line n */
char *tp;
int len;
int n;
{
    int i;
    int c;

    if (n <= 0) return 0;
    c = 0;
    i = 0;
    while (i < len) {
        if (tp[i] == 13) {
            c = c + 1;
            if (c == n) return i + 1;
        }
        i = i + 1;
    }
    return len;
}

static lnofx(tp, cur)           /* line holding the cursor */
char *tp;
int cur;
{
    int i;
    int c;

    c = 0;
    for (i = 0; i < cur; i++)
        if (tp[i] == 13) c = c + 1;
    return c;
}

/* ---------- full redraw ---------- */

draw(tp, len, cur, md, name, cp, cl, mc)
char *tp;
int len;
int cur;
int md;
char *name;
char *cp;
int cl;
int mc;
{
    int ln;
    int top;
    int r;
    int i;
    int to;
    int c;
    int cs;
    int cr;

    ln = lnofx(tp, cur);
    top = ln - 11;
    if (top < 0) top = 0;

    clrscr();

    to = lstartx(tp, len, top);
    for (r = 0; r < 23; r++) {
        i = 0;
        while (to < len && i < 40) {
            c = tp[to];
            if (c == 13) break;
            putchr(i, r, sccode(c), 1);
            i = i + 1;
            to = to + 1;
        }
        while (to < len && tp[to] != 13) to = to + 1;
        if (to < len) to = to + 1;
    }

    for (i = 0; i < 40; i++) putchr(i, 24, 32, 11);

    sclr();
    if (md == 1) sstr("INSERT");
    else if (md == 2) sstr(": ");
    else sstr("COMMAND");
    sstr("  line ");
    snum(ln + 1);
    sstr("  ");
    sstr(name);
    if (mc == 1) sstr("  full");
    else if (mc == 2) sstr("  save err");
    else if (mc == 3) sstr("  saved");
    else if (mc == 4) sstr("  ?cmd");
    putstr(0, 24, stat, 11);

    if (md == 2) {
        putchr(0, 23, sccode(':'), 1);
        for (i = 0; i < cl; i++) putchr(i + 1, 23, sccode(cp[i]), 1);
    }

    cs = cur - lstartx(tp, len, ln);
    if (cs > 39) cs = 39;
    if (cs < 0) cs = 0;
    cr = ln - top;
    if (cr >= 0 && cr < 23) revchr(cr * 40 + cs);
}