/* vim.c - a small modal editor for the commodore 64, written for power c.
 *
 * Increment 2 edits: it reads a petscii SEQ file into one buffer, keeps a line
 * index, shows 24 lines plus a status row, and supports
 *   move   h j k l / arrows, 0 $ gg G
 *   insert i a A I o O   (RUN/STOP leaves insert mode, DEL backspaces)
 *   change x dd p
 *   colon  :w  :w name  :wq  :x  :q  :q!
 *
 * The buffer holds the file exactly as it sits on disk: petscii bytes with $0d
 * between lines. Keys are compared as numbers, never as character constants,
 * so nothing depends on how the compiler treats literals. (Unshifted letters
 * arrive as $41-$5a, so h = 72; shifted ones as $c1-$da, so G = 199.)
 */

char *malloc();
char *bfr;                          /* file text, $0d separated */
unsigned blen;                      /* bytes used */
unsigned lptr[600];                 /* offset of each line start */
int nlines;
int cy, cx;                         /* cursor line and column */
int top;                            /* first line on screen */
int leftcol;                        /* horizontal scroll */
char fname[24];
int mode;                           /* 0 normal, 1 insert */
int dirty;                          /* buffer changed since the last save */
int pend;                           /* first key of a two key command: d or g */
char *note;                         /* one-shot message for the status row */
char ybuf[160];                     /* the yanked line */
int ylen, yok;
int redraw;                         /* 1 cursor row, 2 whole screen */

/* screen rows are 0..23, the status row is 24 */

/* shorten fname to what fits */
shortn(n)
int n;
{
    int i;

    i = 0;
    while (fname[i] && i < n) i++;
    fname[i] = 0;
    return 0;
}

/* a message that waits for a key */
msg(s)
char *s;
{
    sclr(24, 0, 40);
    sps(24, 0, s);
    skey();
    return 0;
}

/* read a line of lowercase petscii into s, echoed from column c of row 24 */
getln(c, s, max)
int c, max;
char *s;
{
    int n, k;

    n = 0;
    s[0] = 0;
    for (;;) {
        k = skey();
        if (k == 13) break;
        if (k == 3) {
            n = 0;
            s[0] = 0;
            break;
        }
        if (k == 20) {
            if (n > 0) {
                n--;
                s[n] = 0;
            }
        } else {
            if (k >= 0xc1 && k <= 0xda) k = k - 0x80;
            if (k >= 32 && k != 127 && n < max) {
                s[n] = k;
                n++;
                s[n] = 0;
            }
        }
        sclr(24, c, max);
        sps(24, c, s);
    }
    return n;
}

/* a yes/no question on the status row: 1 for y, 0 for n or run/stop */
askyn(q)
char *q;
{
    int k;

    sclr(24, 0, 40);
    sps(24, 0, q);
    for (;;) {
        k = skey();
        if (k == 89) return 1;                  /* y */
        if (k == 217) return 1;                 /* Y */
        if (k == 78) return 0;                  /* n */
        if (k == 206) return 0;                 /* N */
        if (k == 3) return 0;
    }
}

/* ask which file to open */
askname()
{
    sclr(24, 0, 40);
    sps(24, 0, "file: ");
    if (getln(6, fname, 20) == 0) fname[0] = 0;
    return 0;
}

/* the drive's error channel (already open as file 15): the two digit code of
   the last command. 0-19 are fine ("00, ok"), 62 is file not found. open() of
   a missing file succeeds on a cbm drive - only the error channel tells.
   do not close 15 while another file is open: closing the command channel
   closes every file on the drive. */
dosst()
{
    int ch, n, d;

    n = 0;
    d = 0;
    for (;;) {
        ch = getc(15);
        if (ch < 0) break;
        if (ch == 13) break;
        if (d < 2) {
            if (ch >= 48 && ch <= 57) {
                n = n * 10 + ch - 48;
                d++;
            }
        }
    }
    if (d < 2) return 99;
    return n;
}

int split;                                      /* a long line was split on load */

/* read fname into bfr. 1 on success, 0 if the file is not there.
   lines longer than 80 are split - the editor's line limit */
loadf()
{
    int f, ch, prev, c, col;
    char on[28];
    int i;

    if (fname[0] == 0) return 1;
    i = 0;
    while (fname[i] && i < 20) {
        on[i] = fname[i];
        i++;
    }
    on[i++] = 44;                               /* , */
    on[i++] = 83;                               /* S  (petscii, not ascii) */
    on[i++] = 44;                               /* , */
    on[i++] = 82;                               /* R */
    on[i] = 0;

    if (open(15, 8, 15, "") == 0) return 0;   /* status channel first */
    f = open(5, 8, 2, on);
    if (f == 0) {
        close(15);
        return 0;
    }
    if (dosst() >= 20) {
        close(5);
        close(15);
        return 0;
    }
    blen = 0;
    prev = 0;
    col = 0;
    split = 0;
    for (;;) {
        ch = getc(5);
        if (ch < 0) break;                      /* end of file */
        if (ch == 26) break;
        if (ch == 10 && prev == 13) {           /* crlf seen as two bytes */
            prev = ch;
            continue;
        }
        if (ch == 13) c = 13;
        else if (ch == 10) c = 13;
        else c = ch;
        if (c != 13 && col >= 80) {             /* 80 columns at most */
            if (blen < 18999) bfr[blen++] = 13;
            col = 0;
            split = 1;
        }
        if (blen < 18999) bfr[blen++] = c;
        if (c == 13) col = 0;
        else col++;
        prev = ch;
    }
    close(5);
    close(15);                                  /* last: it closes everything */
    return 1;
}

/* find the start of every line */
buildidx()
{
    unsigned i;

    nlines = 1;
    lptr[0] = 0;
    for (i = 0; i < blen; i++) {
        if (bfr[i] == 13) {
            if (nlines < 599) {
                lptr[nlines] = i + 1;
                nlines++;
            }
        }
    }
    return 0;
}

/* the ":" command line. returns 1 when the editor should quit */
doscmd()
{
    int n, p, ok, qf;
    char cmd[24];

    sclr(24, 0, 40);
    spc(24, 0, 58);                             /* : */
    n = getln(1, cmd, 20);
    sclr(24, 0, 40);
    if (n == 0) return 0;

    if (cmd[0] == 81) {                         /* q, q! */
        if (cmd[1] == 33) return 1;
        if (dirty) {
            note = "unsaved - :q! quits";
            return 0;
        }
        return 1;
    }

    ok = 0;
    qf = 0;
    p = 1;
    if (cmd[0] == 87) ok = 1;                   /* w, wq, w name */
    if (cmd[0] == 88) {                         /* x */
        ok = 1;
        qf = 1;
    }
    if (ok == 0) {
        note = "unknown command";
        return 0;
    }
    if (cmd[0] == 87 && cmd[1] == 81) {
        qf = 1;
        p = 2;
    }
    while (cmd[p] == 32) p++;
    if (cmd[p]) {
        n = 0;
        while (cmd[p] && n < 20) fname[n++] = cmd[p++];
        fname[n] = 0;
    }
    if (fname[0] == 0) {
        note = "no file name";
        return 0;
    }
    if (savef()) {
        dirty = 0;
        note = "written";
        return qf;
    }
    note = "cannot write";
    return 0;
}

main()
{
    int k, ok, p;

    sinit();
    mlinit();                                   /* ML helpers to $c000: before malloc */
    bfr = malloc(19000);
    if (bfr == 0) {
        sps(0, 0, "out of memory");
        skey();
        return;
    }

    blen = 0;
    nlines = 1;
    lptr[0] = 0;
    cy = 0;
    cx = 0;
    top = 0;
    leftcol = 0;
    fname[0] = 0;
    mode = 0;
    dirty = 0;
    pend = 0;
    note = 0;
    ylen = 0;
    yok = 0;
    split = 0;
    redraw = 2;

    for (;;) {                                  /* a file to edit */
        askname();
        shortn(20);
        if (fname[0] == 0) {                    /* no name: an empty buffer */
            ok = 1;
            break;
        }
        ok = loadf();
        if (ok) break;
        if (askyn("not found - create it? (y/n) ")) break;
    }
    buildidx();
    if (ok == 0) {                              /* keep the name: :w creates it */
        nlines = 1;
        blen = 0;
        note = "new file";
    }
    if (split) note = "long lines split at 80";

    for (;;) {
        scroll();
        dall();
        k = skey();
        note = 0;

        if (mode) {                             /* ---- insert mode */
            if (k == 3) {                       /* RUN/STOP = Esc */
                mode = 0;
                if (cx > 0) cx--;
            } else if (k == 13) {
                newline();
            } else if (k == 20) {
                bkspace();
            } else if (arrow(k)) {
                cx = cx;
            } else if (k >= 32 && k < 128) {
                inschar(k);
            } else if (k >= 161) {
                inschar(k);
            }
            continue;
        }

        if (pend) {                             /* ---- second key of dd / gg */
            p = pend;
            pend = 0;
            if (p == 68 && k == 68) delline();
            if (p == 71 && k == 71) {
                cy = 0;
                cx = 0;
            }
            clampx();
            continue;
        }

        if (arrow(k)) {
            cx = cx;
        } else if (k == 72) {                   /* h */
            if (cx > 0) cx--;
        } else if (k == 76) {                   /* l */
            cx++;
            clampx();
        } else if (k == 74) {                   /* j */
            arrow(17);
        } else if (k == 75) {                   /* k */
            arrow(145);
        } else if (k == 48) {                   /* 0 */
            cx = 0;
        } else if (k == 36) {                   /* $ */
            cx = linend(cy) - lptr[cy];
        } else if (k == 199) {                  /* G */
            cy = nlines - 1;
            cx = 0;
        } else if (k == 68) {                   /* d.. */
            pend = 68;
        } else if (k == 71) {                   /* g.. */
            pend = 71;
        } else if (k == 88) {                   /* x */
            delchar();
            clampx();
        } else if (k == 80) {                   /* p */
            paste();
        } else if (k == 73) {                   /* i */
            mode = 1;
        } else if (k == 65) {                   /* a */
            cx++;
            clampx();
            mode = 1;
        } else if (k == 193) {                  /* A */
            cx = linend(cy) - lptr[cy];
            mode = 1;
        } else if (k == 201) {                  /* I */
            cx = 0;
            mode = 1;
        } else if (k == 79) {                   /* o */
            cx = linend(cy) - lptr[cy];
            newline();
            mode = 1;
        } else if (k == 207) {                  /* O */
            cx = 0;
            newline();
            cy--;
            mode = 1;
        } else if (k == 58) {                   /* : */
            if (doscmd() == 1) {
                sdone();
                return;
            }
        }
    }
}