/* vim128.c - a small modal editor for the Commodore 128, built with cc65.
 *
 *   cl65 -t c128 -O -o vim128.prg vim128.c
 *
 * A port of the Power C / C64 editor (vim.c, vscreen.c, vview.c, vedit.c).
 * The Power C version needed hand-written machine code and direct screen
 * pokes; here cc65's conio draws the screen, so the same program works on the
 * 40 column VIC screen and on the 80 column VDC screen (it uses whatever
 * screensize() reports).
 *
 *   move   h j k l / arrows, 0 $ gg G
 *   insert i a A I o O   (RUN/STOP or ESC 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 PETSCII too: unshifted letters arrive as $41-$5a and
 * shifted ones as $c1-$da, which is what KL() and KU() below spell.
 */

#include <conio.h>
#include <cbm.h>
#include <c128.h>
#include <string.h>

#define BUFMAX  19000u                  /* bytes of file text */
#define MAXLN   600                     /* lines */
#define MAXCOL  80                      /* longest line kept */
#define NAMEMAX 20

/* cc65 translates character literals to PETSCII for the c128 target, so 'h'
   is already $48 (what the unshifted key sends) and 'G' is $c7 (shifted). */
#define KL(c)   (c)                     /* unshifted letter, e.g. KL('h') */
#define KU(c)   (c)                     /* shifted letter,   e.g. KU('G') */

#define K_STOP  3
#define K_ESC   27
#define K_DEL   20
#define K_RET   13
#define K_DOWN  17
#define K_UP    145
#define K_RIGHT 29
#define K_LEFT  157

static unsigned char bfr[BUFMAX];       /* file text, $0d separated */
static unsigned blen;                   /* bytes used */
static unsigned lptr[MAXLN];            /* offset of each line start */
static int nlines;
static int cy, cx;                      /* cursor line and column */
static int top, leftcol;                /* first line / column on screen */
static char fname[NAMEMAX + 1];
static int mode;                        /* 0 normal, 1 insert */
static int dirty;                       /* changed since the last save */
static int pend;                        /* first key of dd / gg */
static const char *note;                /* one-shot status message */
static unsigned char ybuf[MAXCOL];      /* the yanked line */
static int ylen, yok;
static int redraw;                      /* 1 cursor row, 2 whole screen */
static int split;                       /* a long line was split on load */
static unsigned char dev;               /* disk device */

static unsigned char sw, sh;            /* screen width, height */
static int rows;                        /* text rows = sh - 1 (last is status) */
static int ltop, lleft, lcy, lcx;

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

static void putstr(int r, int c, const char *s)
{
    gotoxy(c, r);
    while (*s && c < sw) {
        cputc(*s++);
        c++;
    }
}

static char lstat[84];

static void clrstat(int c)
{
    lstat[0] = 0;                               /* status row no longer as drawn */
    /* the very last cell is left alone: writing it can make the screen
       editor wrap */
    gotoxy(c, sh - 1);
    while (c < sw - 1) {
        cputc(' ');
        c++;
    }
}

static void sinit(void)
{
    screensize(&sw, &sh);
    rows = sh - 1;
    cbm_k_bsout(14);                    /* lower/upper case character set */
    cbm_k_bsout(8);                     /* ...and lock it against SHIFT+C= */
    bgcolor(COLOR_BLUE);
    bordercolor(COLOR_BLACK);
    textcolor(COLOR_WHITE);
    cursor(0);
    revers(0);
    clrscr();
    if (sw > 40) fast();                /* 2 MHz: only with the 80 column screen,
                                           the VIC display is blanked in fast mode */
}

static void sdone(void)
{
    slow();
    revers(0);
    bgcolor(COLOR_BLACK);
    bordercolor(COLOR_LIGHTBLUE);
    textcolor(COLOR_LIGHTGREEN);
    clrscr();
    cursor(1);
}

static int skey(void)
{
    return cgetc();
}

/* --------------------------------------------------------------- buffer */

/* end offset (exclusive of the $0d) of line ln */
static unsigned linend(int ln)
{
    if (ln + 1 < nlines) return lptr[ln + 1] - 1;
    return blen;
}

static int linelen(int ln)
{
    return (int) (linend(ln) - lptr[ln]);
}

static void clampx(void)
{
    int len = linelen(cy);
    if (cx > len) cx = len;
    if (cx < 0) cx = 0;
}

static void buildidx(void)
{
    unsigned i;

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

static void adjust(int from, int delta)         /* lptr[from..nlines-1] += delta */
{
    int i;
    for (i = from; i < nlines; i++) lptr[i] += delta;
}

static void bmove(unsigned from, unsigned to, unsigned n)
{
    unsigned char *s, *d;

    if (n == 0 || from == to) return;
    s = bfr + from;
    d = bfr + to;
    if (d < s) {
        while (n--) *d++ = *s++;
    } else {
        s += n;
        d += n;
        while (n--) *--d = *--s;
    }
}

static int bins(unsigned pos, int ch)
{
    if (blen >= BUFMAX - 1) return 0;
    bmove(pos, pos + 1, blen - pos);
    bfr[pos] = ch;
    blen++;
    dirty = 1;
    return 1;
}

static void delrange(unsigned pos, unsigned n)
{
    bmove(pos + n, pos, blen - pos - n);
    blen -= n;
    dirty = 1;
}

static int inschar(int ch)
{
    if (linelen(cy) >= MAXCOL) {
        note = "line full (80)";
        return 0;
    }
    if (!bins(lptr[cy] + cx, ch)) return 0;
    adjust(cy + 1, 1);
    cx++;
    if (redraw < 1) redraw = 1;
    return 1;
}

static int newline(void)
{
    unsigned pos;
    int i;

    if (nlines >= MAXLN - 1) return 0;
    pos = lptr[cy] + cx;
    if (!bins(pos, 13)) return 0;
    for (i = nlines; i > cy + 1; i--) lptr[i] = lptr[i - 1];
    lptr[cy + 1] = pos + 1;
    nlines++;
    adjust(cy + 2, 1);
    redraw = 2;
    cy++;
    cx = 0;
    return 1;
}

static int delchar(void)
{
    if (cx >= linelen(cy)) return 0;
    delrange(lptr[cy] + cx, 1);
    adjust(cy + 1, -1);
    if (redraw < 1) redraw = 1;
    return 1;
}

static void bkspace(void)
{
    int pl, i;

    if (cx > 0) {
        cx--;
        delchar();
        return;
    }
    if (cy == 0) return;
    pl = linelen(cy - 1);
    if (pl + linelen(cy) > MAXCOL) {
        note = "joined line would pass 80";
        return;
    }
    delrange(lptr[cy] - 1, 1);
    for (i = cy; i < nlines - 1; i++) lptr[i] = lptr[i + 1];
    nlines--;
    adjust(cy, -1);
    redraw = 2;
    cy--;
    cx = pl;
}

static void delline(void)
{
    int i;
    unsigned s, e, n;

    s = lptr[cy];
    e = linend(cy);
    ylen = e - s;
    if (ylen > MAXCOL) ylen = MAXCOL;
    for (i = 0; i < ylen; i++) ybuf[i] = bfr[s + i];
    yok = 1;

    if (nlines == 1) {
        blen = 0;
        dirty = 1;
    } else if (cy + 1 < nlines) {
        n = lptr[cy + 1] - s;
        delrange(s, n);
        for (i = cy; i < nlines - 1; i++) lptr[i] = lptr[i + 1];
        nlines--;
        adjust(cy, -(int) n);
    } else {                            /* last line: take its leading $0d */
        delrange(s - 1, blen - s + 1);
        nlines--;
        cy--;
    }
    cx = 0;
    redraw = 2;
}

static void paste(void)
{
    int i;

    if (!yok) return;
    cx = linelen(cy);
    if (!newline()) return;
    for (i = 0; i < ylen; i++) inschar(ybuf[i]);
    cx = 0;
}

/* cursor keys, the same in both modes. 1 if k was one of them */
static int arrow(int k)
{
    if (k == K_DOWN) {
        if (cy + 1 < nlines) { cy++; clampx(); }
        return 1;
    }
    if (k == K_UP) {
        if (cy > 0) { cy--; clampx(); }
        return 1;
    }
    if (k == K_RIGHT) {
        cx++;
        clampx();
        return 1;
    }
    if (k == K_LEFT) {
        if (cx > 0) cx--;
        return 1;
    }
    return 0;
}

/* ------------------------------------------------------------------- view */

static void scroll(void)
{
    if (cy < top) top = cy;
    if (cy > top + rows - 1) top = cy - rows + 1;
    if (top < 0) top = 0;
    if (cx < leftcol) leftcol = cx;
    if (cx > leftcol + sw - 1) leftcol = cx - sw + 1;
    if (leftcol < 0) leftcol = 0;
}

static unsigned char rlen[50];          /* columns drawn on each row last time */

/* the character shown at screen row r, column col (blank past the line) */
static int cellch(int r, int col)
{
    int line = top + r;
    unsigned p;
    int ch = ' ';

    if (line < nlines) {
        p = lptr[line] + leftcol + col;
        if (p < linend(line)) ch = bfr[p];
    }
    if (ch < 32 || (ch >= 128 && ch < 160)) ch = ' ';
    return ch;
}

/* repaint row r from column 'from' to the end of the text, plus whatever old
   text must be blanked. Only the cells that can have changed are written:
   each character costs a real VDC/VIC access. */
static void drawrow(int r, int from)
{
    int line = top + r, vl = 0, col, end;

    if (line < nlines) {
        vl = linelen(line) - leftcol;
        if (vl < 0) vl = 0;
        if (vl > sw) vl = sw;
    }
    end = vl > rlen[r] ? vl : rlen[r];
    if (from < end) {
        gotoxy(from, r);
        for (col = from; col < end; col++) cputc(cellch(r, col));
    }
    rlen[r] = vl;
}

static void drawcell(int r, int col, int rev)
{
    if (r < 0 || r >= rows || col < 0 || col >= sw) return;
    if (rev) revers(1);
    cputcxy(col, r, cellch(r, col));
    if (rev) revers(0);
}

static char *dnum(char *t, int v)
{
    char d[6];
    int n = 0;

    if (v == 0) {
        *t++ = '0';
        return t;
    }
    while (v > 0 && n < 5) {
        d[n++] = '0' + (v % 10);
        v /= 10;
    }
    while (n > 0) *t++ = d[--n];
    return t;
}

static void dstat(void)
{
    char t[84];
    const char *s;
    char *p;
    int i, n, pos;

    if (note) s = note;
    else if (mode) s = "-- insert --";
    else if (fname[0] == 0) s = "[no name]";
    else s = fname;

    n = 0;
    for (i = 0; s[i] && i < sw - 14; i++) t[n++] = s[i];
    pos = sw - 14;                              /* modified flag */
    while (n < pos) t[n++] = ' ';
    t[n++] = dirty ? '+' : ' ';
    t[n++] = ' ';
    p = dnum(t + n, cy + 1);
    *p++ = '/';
    p = dnum(p, nlines);
    while (p < t + sw - 1) *p++ = ' ';
    *p = 0;

    if (strcmp(t, lstat) == 0) return;           /* unchanged: skip the writes */
    strcpy(lstat, t);
    revers(1);
    putstr(sh - 1, 0, t);
    revers(0);
}

static void dall(void)
{
    int crow = cy - top;
    int ccol = cx - leftcol;
    int r, from;

    if (redraw == 2 || top != ltop || leftcol != lleft) {
        for (r = 0; r < rows; r++) drawrow(r, 0);
    } else {
        /* put the old cursor cell back to normal, then repaint what the edit
           touched: the cursor row from the old cursor column on */
        drawcell(lcy - top, lcx - lleft, 0);
        from = lcx - lleft;
        if (ccol < from) from = ccol;
        if (from < 0) from = 0;
        if (redraw == 1) drawrow(crow, from);
    }
    drawcell(crow, ccol, 1);
    if (crow >= 0 && crow < rows && ccol >= rlen[crow] && ccol < sw)
        rlen[crow] = ccol + 1;                  /* a cursor past the text must be blanked later */
    ltop = top;
    lleft = leftcol;
    lcy = cy;
    lcx = cx;
    redraw = 0;
    dstat();
}

/* ------------------------------------------------------------ prompt/disk */

/* read a line of PETSCII into s, echoed from column c of the status row */
static int getln(int c, char *s, int max)
{
    int n = 0, k;

    s[0] = 0;
    for (;;) {
        k = skey();
        if (k == K_RET) break;
        if (k == K_STOP || k == K_ESC) {
            n = 0;
            s[0] = 0;
            break;
        }
        if (k == K_DEL) {
            if (n > 0) s[--n] = 0;
        } else {
            if (k >= 0xc1 && k <= 0xda) k -= 0x80;
            if (k >= 32 && k < 127 && n < max) {
                s[n++] = k;
                s[n] = 0;
            }
        }
        clrstat(c);
        putstr(sh - 1, c, s);
    }
    return n;
}

static int askyn(const char *q)
{
    int k;

    clrstat(0);
    putstr(sh - 1, 0, q);
    for (;;) {
        k = skey();
        if (k == KL('y') || k == KU('Y')) return 1;
        if (k == KL('n') || k == KU('N') || k == K_STOP || k == K_ESC) return 0;
    }
}

static void askname(void)
{
    clrstat(0);
    putstr(sh - 1, 0, "file: ");
    getln(6, fname, NAMEMAX);
}

/* the drive's error channel (open as file 15): the two digit code of the last
   command. 0-19 are fine, 62 is file not found. open of a missing file
   succeeds on a CBM drive - only this channel tells. */
static int dosst(void)
{
    unsigned char ch;
    int n = 0, d = 0;

    for (;;) {
        if (cbm_read(15, &ch, 1) != 1) break;
        if (ch == 13) break;
        if (d < 2 && ch >= '0' && ch <= '9') {
            n = n * 10 + ch - '0';
            d++;
        }
    }
    if (d < 2) return 99;
    return n;
}

/* build "name,s,r" (or "@0:name,s,w") in PETSCII */
static void mkname(char *on, int save)
{
    int i = 0, j = 0;

    if (save) {
        on[i++] = '@';
        on[i++] = '0';
        on[i++] = ':';
    }
    while (fname[j] && j < NAMEMAX) on[i++] = fname[j++];
    on[i++] = ',';
    on[i++] = 0x53;                             /* PETSCII S, not ASCII */
    on[i++] = ',';
    on[i++] = save ? 0x57 : 0x52;               /* W or R */
    on[i] = 0;
}

/* 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 */
static int loadf2(void);
static int loadf(void)
{
    int r;
    slow();
    r = loadf2();
    if (sw > 40) fast();
    return r;
}

static int loadf2(void)
{
    unsigned char tmp[64];
    char on[32];
    int n, i, ch, c, prev = 0, col = 0;

    if (fname[0] == 0) return 1;
    mkname(on, 0);

    if (cbm_open(15, dev, 15, "") != 0) return 0;
    if (cbm_open(5, dev, 2, on) != 0) {
        cbm_close(15);
        return 0;
    }
    if (dosst() >= 20) {
        cbm_close(5);
        cbm_close(15);
        return 0;
    }
    blen = 0;
    split = 0;
    for (;;) {
        n = cbm_read(5, tmp, sizeof tmp);
        if (n <= 0) break;
        for (i = 0; i < n; i++) {
            ch = tmp[i];
            if (ch == 26) goto done;
            if (ch == 10 && prev == 13) {       /* CRLF seen as two bytes */
                prev = ch;
                continue;
            }
            c = (ch == 10) ? 13 : ch;
            if (c != 13 && col >= MAXCOL) {
                if (blen < BUFMAX - 1) bfr[blen++] = 13;
                col = 0;
                split = 1;
            }
            if (blen < BUFMAX - 1) bfr[blen++] = c;
            col = (c == 13) ? 0 : col + 1;
            prev = ch;
        }
    }
done:
    cbm_close(5);
    cbm_close(15);                              /* last: it closes everything */
    return 1;
}

/* write the buffer to fname, replacing any old copy. 1 on success */
static int savef2(void);
static int savef(void)
{
    int r;
    slow();
    r = savef2();
    if (sw > 40) fast();
    return r;
}

static int savef2(void)
{
    char on[32];
    unsigned char cr = 13;
    int ok;

    mkname(on, 1);
    if (cbm_open(15, dev, 15, "") != 0) return 0;
    if (cbm_open(5, dev, 3, on) != 0) {
        cbm_close(15);
        return 0;
    }
    if (blen > 0) cbm_write(5, bfr, blen);
    if (blen > 0 && bfr[blen - 1] != 13) cbm_write(5, &cr, 1);
    ok = (dosst() < 20);
    cbm_close(5);
    cbm_close(15);
    return ok;
}

/* the ":" command line. returns 1 when the editor should quit */
static int doscmd(void)
{
    char cmd[24];
    int n, p = 1, ok = 0, qf = 0;

    clrstat(0);
    putstr(sh - 1, 0, ":");
    n = getln(1, cmd, 20);
    clrstat(0);
    if (n == 0) return 0;

    if (cmd[0] == KL('q')) {
        if (cmd[1] == '!') return 1;
        if (dirty) {
            note = "unsaved - :q! quits";
            return 0;
        }
        return 1;
    }
    if (cmd[0] == KL('w')) ok = 1;
    if (cmd[0] == KL('x')) {
        ok = 1;
        qf = 1;
    }
    if (!ok) {
        note = "unknown command";
        return 0;
    }
    if (cmd[0] == KL('w') && cmd[1] == KL('q')) {
        qf = 1;
        p = 2;
    }
    while (cmd[p] == ' ') p++;
    if (cmd[p]) {
        n = 0;
        while (cmd[p] && n < NAMEMAX) 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 main(void)
{
    int k, ok, p;

    dev = *(unsigned char *) 0x00ba;            /* device we were loaded from */
    if (dev < 8) dev = 8;

    sinit();

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

    for (;;) {                                  /* a file to edit */
        askname();
        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) {                                  /* keep the name: :w creates it */
        nlines = 1;
        blen = 0;
        note = "new file";
    }
    if (split) note = "long lines split at 80";
    clrscr();
    memset(rlen, 0, sizeof rlen);
    lstat[0] = 0;

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

        if (mode) {                             /* ---- insert mode */
            if (k == K_STOP || k == K_ESC) {
                mode = 0;
                if (cx > 0) cx--;
            } else if (k == K_RET) {
                newline();
            } else if (k == K_DEL) {
                bkspace();
            } else if (arrow(k)) {
                ;
            } else if ((k >= 32 && k < 128) || k >= 161) {
                inschar(k);
            }
            continue;
        }

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

        if (arrow(k)) {
            ;
        } else if (k == KL('h')) {
            if (cx > 0) cx--;
        } else if (k == KL('l')) {
            cx++;
            clampx();
        } else if (k == KL('j')) {
            arrow(K_DOWN);
        } else if (k == KL('k')) {
            arrow(K_UP);
        } else if (k == '0') {
            cx = 0;
        } else if (k == '$') {
            cx = linelen(cy);
        } else if (k == KU('G')) {
            cy = nlines - 1;
            cx = 0;
        } else if (k == KL('d')) {
            pend = KL('d');
        } else if (k == KL('g')) {
            pend = KL('g');
        } else if (k == KL('x')) {
            delchar();
            clampx();
        } else if (k == KL('p')) {
            paste();
        } else if (k == KL('i')) {
            mode = 1;
        } else if (k == KL('a')) {
            cx++;
            clampx();
            mode = 1;
        } else if (k == KU('A')) {
            cx = linelen(cy);
            mode = 1;
        } else if (k == KU('I')) {
            cx = 0;
            mode = 1;
        } else if (k == KL('o')) {
            cx = linelen(cy);
            newline();
            mode = 1;
        } else if (k == KU('O')) {
            cx = 0;
            newline();
            cy--;
            mode = 1;
        } else if (k == ':') {
            if (doscmd() == 1) {
                sdone();
                return 0;
            }
        }
    }
}