/* Copyright (C) 2001-2023 Artifex Software, Inc.
   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied,
   modified or distributed except as expressly authorized under the terms
   of the license contained in the file LICENSE in this distribution.

   Refer to licensing information at http://www.artifex.com or contact
   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,
   CA 94129, USA, for further information.
*/


/* XPS interpreter - general font functions */

#include "ghostxps.h"

static void xps_load_sfnt_cmap(xps_font_t *font);

/*
 * Big-endian memory accessor functions
 */

static inline int s16(byte *p)
{
    return (signed short)( (p[0] << 8) | p[1] );
}

static inline int u16(byte *p)
{
    return (p[0] << 8) | p[1];
}

static inline int u24(byte *p)
{
    return (p[0] << 16) | (p[1] << 8) | p[2];
}

static inline int u32(byte *p)
{
    return (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
}

xps_font_t *
xps_new_font(xps_context_t *ctx, byte *buf, int buflen, int index)
{
    xps_font_t *font;
    int code;

    font = xps_alloc(ctx, sizeof(xps_font_t));
    if (!font)
    {
        gs_throw(gs_error_VMerror, "out of memory");
        return NULL;
    }

    font->data = buf;
    font->length = buflen;
    font->font = NULL;

    font->subfontid = index;
    font->cmaptable = 0;
    font->cmapsubcount = 0;
    font->cmapsubtable = 0;
    font->usepua = 0;

    font->cffdata = 0;
    font->cffend = 0;
    font->gsubrs = 0;
    font->subrs = 0;
    font->charstrings = 0;

    if (memcmp(font->data, "OTTO", 4) == 0)
        code = xps_init_postscript_font(ctx, font);
    else if (memcmp(font->data, "\0\1\0\0", 4) == 0)
        code = xps_init_truetype_font(ctx, font);
    else if (memcmp(font->data, "true", 4) == 0)
        code = xps_init_truetype_font(ctx, font);
    else if (memcmp(font->data, "ttcf", 4) == 0)
        code = xps_init_truetype_font(ctx, font);
    else
    {
        xps_free_font(ctx, font);
        gs_throw(-1, "not an opentype font");
        return NULL;
    }

    if (code < 0)
    {
        xps_free_font(ctx, font);
        gs_rethrow(-1, "cannot init font");
        return NULL;
    }

    xps_load_sfnt_cmap(font);

    return font;
}

void
xps_free_font(xps_context_t *ctx, xps_font_t *font)
{
    if (font == NULL)
        return;
    if (font->font)
    {
        gs_font_finalize(ctx->memory, font->font);
        gs_free_object(ctx->memory, font->font, "font object");
    }
    xps_free(ctx, font->data);
    xps_free(ctx, font);
}

/*
 * Find the offset and length of an SFNT table.
 * Return -1 if no table by the specified name is found.
 */

int
xps_find_sfnt_table(xps_font_t *font, const char *name, int *lengthp)
{
    int offset;
    int ntables;
    int i;

    if (font->length < 12)
        return -1;

    if (!memcmp(font->data, "ttcf", 4))
    {
        int nfonts = u32(font->data + 8);

        /* check if the buffer contains enough data to contain nfonts subfonts */
        int min_len = 12 + nfonts * 4;
        if (min_len < 0 || font->length < min_len)
        {
            gs_warn("font data length too small");
            return -1;
        }

        if (font->subfontid < 0 || font->subfontid >= nfonts)
        {
            gs_warn("Invalid subfont ID");
            return -1;
        }
        offset = u32(font->data + 12 + font->subfontid * 4);
        if (offset < 0)
        {
            gs_warn("subfont table offset negative");
            return -1;
        }
    }
    else
    {
        offset = 0;
    }

    if (font->length < offset + 6)
    {
        gs_warn("subfont length insufficient for ntables read");
        return -1;

    }
    ntables = u16(font->data + offset + 4);
    if (font->length < offset + 12 + ntables * 16)
    {
        gs_warn("subfont length insufficient for entry reads");
        return -1;
    }
    for (i = 0; i < ntables; i++)
    {
        byte *entry = font->data + offset + 12 + i * 16;
        if (!memcmp(entry, name, 4))
        {
            if (lengthp)
                *lengthp = u32(entry + 12);
            return u32(entry + 8);
        }
    }

    return -1;
}

/*
 * Get the windows truetype font file name - position 4 in the name table.
 */
void
xps_load_sfnt_name(xps_font_t *font, char *namep, const int buflen)
{
    byte *namedata;
    int offset, length;
    /*int format;*/
    int count, stringoffset;
    int found;
    int i, k;

    found = 0;
    strcpy(namep, "Unknown");

    offset = xps_find_sfnt_table(font, "name", &length);
    if (offset < 0 || length < 6)
    {
        gs_warn("cannot find name table");
        return;
    }

    /* validate the offset, and the data for the two
     * values we're about to read
     */
    if (offset + 6 > font->length)
    {
        gs_warn("name table byte offset invalid");
        return;
    }
    namedata = font->data + offset;

    /*format = u16(namedata + 0);*/
    count = u16(namedata + 2);
    stringoffset = u16(namedata + 4);

    if (stringoffset + offset > font->length
        || offset + 6 + count * 12 > font->length)
    {
        gs_warn("name table invalid");
        return;
    }

    if (length < 6 + (count * 12))
    {
        gs_warn("name table too short");
        return;
    }

    for (i = 0; i < count; i++)
    {
        byte *record = namedata + 6 + i * 12;
        int pid = u16(record + 0);
        int eid = u16(record + 2);
        int langid = u16(record + 4);
        int nameid = u16(record + 6);
        length = u16(record + 8);
        offset = u16(record + 10);

        length = length > buflen - 1 ? buflen - 1: length;
        if (namedata + stringoffset + offset >= font->data + font->length)
            continue;

        if (namedata + stringoffset + offset + length >= font->data +  font->length)
            length = (font->data +  font->length) - (namedata + stringoffset + offset);

        /* Full font name or postscript name */
        if (nameid == 4 || nameid == 6)
        {
            if (pid == 1 && eid == 0 && langid == 0) /* mac roman, english */
            {
                if (found < 3)
                {
                    memcpy(namep, namedata + stringoffset + offset, length);
                    namep[length] = 0;
                    found = 3;
                }
            }

            if (pid == 3 && eid == 1 && langid == 0x409) /* windows unicode ucs-2, US */
            {
                if (found < 2)
                {
                    unsigned char *s = namedata + stringoffset + offset;
                    int n = length / 2;
                    for (k = 0; k < n; k ++)
                    {
                        int c = u16(s + k * 2);
                        namep[k] = isprint(c) ? c : '?';
                    }
                    namep[k] = 0;
                    found = 2;
                }
            }

            if (pid == 3 && eid == 10 && langid == 0x409) /* windows unicode ucs-4, US */
            {
                if (found < 1)
                {
                    unsigned char *s = namedata + stringoffset + offset;
                    int n = length / 4;
                    for (k = 0; k < n; k ++)
                    {
                        int c = u32(s + k * 4);
                        namep[k] = isprint(c) ? c : '?';
                    }
                    namep[k] = 0;
                    found = 1;
                }
            }
        }
    }
}

/*
 * Locate the 'cmap' table and count the number of subtables.
 */

static void
xps_load_sfnt_cmap(xps_font_t *font)
{
    byte *cmapdata;
    int offset, length;
    int nsubtables;

    offset = xps_find_sfnt_table(font, "cmap", &length);
    if (offset < 0 || length < 4)
    {
        gs_warn("cannot find cmap table");
        return;
    }

    cmapdata = font->data + offset;
    if (cmapdata + 4 < font->data + font->length)
    {
        nsubtables = u16(cmapdata + 2);
        if (nsubtables < 0 || length < 4 + nsubtables * 8)
        {
            gs_warn("cannot find cmap sub-tables");
            return;
        }

        font->cmaptable = offset;
        font->cmapsubcount = nsubtables;
        font->cmapsubtable = 0;
    }
}

/*
 * Return the number of cmap subtables.
 */

int
xps_count_font_encodings(xps_font_t *font)
{
    return font->cmapsubcount;
}

/*
 * Extract PlatformID and EncodingID for a cmap subtable.
 */

void
xps_identify_font_encoding(xps_font_t *font, int idx, int *pid, int *eid)
{
    byte *cmapdata, *entry;
    if (idx < 0 || idx >= font->cmapsubcount)
        return;
    cmapdata = font->data + font->cmaptable;
    entry = cmapdata + 4 + idx * 8;
    *pid = u16(entry + 0);
    *eid = u16(entry + 2);
}

/*
 * Select a cmap subtable for use with encoding functions.
 */

int
xps_select_font_encoding(xps_font_t *font, int idx)
{
    byte *cmapdata, *entry;
    int pid, eid;
    if (idx < 0 || idx >= font->cmapsubcount)
        return 0;
    cmapdata = font->data + font->cmaptable;
    entry = cmapdata + 4 + idx * 8;
    pid = u16(entry + 0);
    eid = u16(entry + 2);
    font->cmapsubtable = font->cmaptable + u32(entry + 4);
    if (font->cmapsubtable >= font->length) {
        font->cmapsubtable = 0;
        return 0;
    }
    font->usepua = (pid == 3 && eid == 0);
    return 1;
}

/*
 * Encode a character using the selected cmap subtable.
 * TODO: extend this to cover more cmap formats.
 */

static int
xps_encode_font_char_imp(xps_font_t *font, int code)
{
    byte *table;

    /* no cmap selected: return identity */
    if (font->cmapsubtable <= 0)
        return code;

    table = font->data + font->cmapsubtable;

    switch (u16(table))
    {
    case 0: /* Apple standard 1-to-1 mapping. */
        return table[code + 6];

    case 4: /* Microsoft/Adobe segmented mapping. */
        {
            int segCount2 = u16(table + 6);
            byte *endCount = table + 14;
            byte *startCount = endCount + segCount2 + 2;
            byte *idDelta = startCount + segCount2;
            byte *idRangeOffset = idDelta + segCount2;
            byte *giddata;
            int i2;

            if (segCount2 < 3 || segCount2 > 65535 ||
               idRangeOffset > font->data + font->length)
               return gs_error_invalidfont;

           for (i2 = 0; i2 < segCount2 - 3; i2 += 2)
            {
                int delta, roff;
                int start = u16(startCount + i2);
                int glyph;

                if ( code < start )
                    return 0;
                if ( code > u16(endCount + i2) )
                    continue;
                delta = s16(idDelta + i2);
                roff = u16(idRangeOffset + i2);
                if ( roff == 0 )
                {
                    return ( code + delta ) & 0xffff; /* mod 65536 */
                }
                if ((giddata = (idRangeOffset + i2 + roff + ((code - start) << 1))) >
                    font->data + font->length) {
                    return code;
                }
                glyph = u16(giddata);
                return (glyph == 0 ? 0 : glyph + delta);
            }

            /*
             * The TrueType documentation says that the last range is
             * always supposed to end with 0xffff, so this shouldn't
             * happen; however, in some real fonts, it does.
             */
            return 0;
        }

    case 6: /* Single interval lookup. */
        {
            int firstCode = u16(table + 6);
            int entryCount = u16(table + 8);
            if ( code < firstCode || code >= firstCode + entryCount )
                return 0;
            return u16(table + 10 + ((code - firstCode) << 1));
        }

    case 10: /* Trimmed array (like 6) */
        {
            int startCharCode = u32(table + 12);
            int numChars = u32(table + 16);
            if ( code < startCharCode || code >= startCharCode + numChars )
                return 0;
            return u32(table + 20 + (code - startCharCode) * 4);
        }

    case 12: /* Segmented coverage. (like 4) */
        {
            int nGroups = u32(table + 12);
            byte *group = table + 16;
            int i;

            for (i = 0; i < nGroups; i++)
            {
                int startCharCode = u32(group + 0);
                int endCharCode = u32(group + 4);
                int startGlyphID = u32(group + 8);
                if ( code < startCharCode )
                    return 0;
                if ( code <= endCharCode )
                    return startGlyphID + (code - startCharCode);
                group += 12;
            }

            return 0;
        }

    case 2: /* High-byte mapping through table. */
    case 8: /* Mixed 16-bit and 32-bit coverage (like 2) */
    default:
        gs_warn1("unknown cmap format: %d\n", u16(table));
        return 0;
    }

    return 0;
}

/*
 * Given a GID, reverse the CMAP subtable lookup to turn it back into a character code
 * We need a Unicode return value, so we might need to do some fixed tables for
 * certain kinds of CMAP subtables (ie non-Unicode ones). That would be a future enhancement
 * if we ever encounter such a beast.
 */
static int
xps_decode_font_char_imp(xps_font_t *font, int code)
{
    byte *table, *t;

    /* no cmap selected: return identity */
    if (font->cmapsubtable <= 0)
        return code;

    table = font->data + font->cmapsubtable;
    if (table >= font->data + font->length)
        return code;

    switch (u16(table))
    {
        case 0: /* Apple standard 1-to-1 mapping. */
            {
                int i, length = u16(&table[2]) - 6;

                if (length < 0 || length > 256)
                    return gs_error_invalidfont;

                for (i=0;i<length;i++) {
                    if (table[6 + i] == code)
                        return i;
                }
            }
            return 0;
        case 4: /* Microsoft/Adobe segmented mapping. */
            {
                int segCount2 = u16(table + 6);
                byte *endCount = table + 14;
                byte *startCount = endCount + segCount2 + 2;
                byte *idDelta = startCount + segCount2;
                byte *idRangeOffset = idDelta + segCount2;
                byte *giddata;
                int i2;

                if (segCount2 < 3 || segCount2 > 65535 ||
                    idRangeOffset > font->data + font->length)
                    return gs_error_invalidfont;

                for (i2 = 0; i2 < segCount2 - 3; i2 += 2)
                {
                    int delta = s16(idDelta + i2), roff = u16(idRangeOffset + i2);
                    int start = u16(startCount + i2);
                    int end = u16(endCount + i2);
                    int glyph, i;

                    if (end < start)
                        return gs_error_invalidfont;

                    for (i=start;i<=end;i++) {
                        if (roff == 0) {
                            glyph = (i + delta) & 0xffff;
                        } else {
                            if ((giddata = (idRangeOffset + i2 + roff + ((i - start) << 1))) >
                                 font->data + font->length) {
                                return_error(gs_error_invalidfont);
                            }
                            glyph = u16(giddata);
                        }
                        if (glyph == code) {
                            return i;
                        }
                    }
                }
            }
            return 0;
        case 6: /* Single interval lookup. */
            {
                int ch, i, length = u16(&table[8]);
                int firstCode = u16(&table[6]);

                if (length < 0 || length > 65535)
                    return gs_error_invalidfont;

                for (i=0;i<length;i++) {
                    t = &table[10 + (i * 2)];
                    if (t + 2 > font->data + font->length)
                        return gs_error_invalidfont;
                    ch = u16(t);
                    if (ch == code)
                        return (firstCode + i);
                }
            }
            return 0;
        case 10: /* Trimmed array (like 6) */
            {
                unsigned int ch, i, length = u32(&table[20]);
                int firstCode = u32(&table[16]);
                for (i=0;i<length;i++) {
                    t = &table[10 + (i * 2)];
                    if (t + 2 > font->data + font->length)
                        return gs_error_invalidfont;
                    ch = u16(t);
                    if (ch == code)
                        return (firstCode + i);
                }
            }
            return 0;
        case 12: /* Segmented coverage. (like 4) */
            {
                unsigned int nGroups = u32(&table[12]);
                int Group;

                for (Group=0;Group<nGroups;Group++)
                {
                    int startCharCode = u32(&table[16 + (Group * 12)]);
                    int endCharCode = u32(&table[16 + (Group * 12) + 4]);
                    int startGlyphCode = u32(&table[16 + (Group * 12) + 8]);

                    if (code >= startGlyphCode && code <= (startGlyphCode + (endCharCode - startCharCode))) {
                        return startGlyphCode + (code - startCharCode);
                    }
                }
            }
            return 0;
        case 2: /* High-byte mapping through table. */
        case 8: /* Mixed 16-bit and 32-bit coverage (like 2) */
        default:
            gs_warn1("unknown cmap format: %d\n", u16(table));
            return 0;
    }
    return 0;
}

int
xps_decode_font_char(xps_font_t *font, int code)
{
    int gid = xps_decode_font_char_imp(font, code);
    if (gid == 0)
        return code;
    return gid;
}

int
xps_encode_font_char(xps_font_t *font, int code)
{
    int gid = xps_encode_font_char_imp(font, code);
    if (gid == 0 && font->usepua)
        gid = xps_encode_font_char_imp(font, 0xF000 | code);
    return gid;
}

/*
 * Get glyph metrics by parsing TTF tables manually.
 * XPS needs more and different metrics than postscript/ghostscript
 * use so the native ghostscript functions are not adequate.
 */

void
xps_measure_font_glyph(xps_context_t *ctx, xps_font_t *font, int gid, xps_glyph_metrics_t *mtx)
{

    int head, format, loca, glyf;
    int ofs, len;
    int idx, i, n;
    int hadv, vadv, vorg;
    int vtop, ymax, desc;
    int scale;

    /* some insane defaults */

    scale = 1000; /* units-per-em */
    hadv = 500;
    vadv = -1000;
    vorg = 1000;

    /*
     * Horizontal metrics are easy.
     */

    ofs = xps_find_sfnt_table(font, "hhea", &len);
    if (ofs < 0 || len < 2 * 18)
    {
        gs_warn("hhea table is too short");
        return;
    }

    vorg = s16(font->data + ofs + 4); /* ascender is default vorg */
    desc = s16(font->data + ofs + 6); /* descender */
    if (desc < 0)
        desc = -desc;
    n = u16(font->data + ofs + 17 * 2);

    ofs = xps_find_sfnt_table(font, "hmtx", &len);
    if (ofs < 0)
    {
        gs_warn("cannot find hmtx table");
        return;
    }

    idx = gid;
    if (idx > n - 1)
        idx = n - 1;

    hadv = u16(font->data + ofs + idx * 4);
    vadv = 0;

    /*
     * Vertical metrics are hairy (with missing tables).
     */

    head = xps_find_sfnt_table(font, "head", &len);
    if (head > 0)
    {
        scale = u16(font->data + head + 18); /* units per em */
    }

    ofs = xps_find_sfnt_table(font, "OS/2", &len);
    if (ofs > 0 && len > 70)
    {
        vorg = s16(font->data + ofs + 68); /* sTypoAscender */
        desc = s16(font->data + ofs + 70); /* sTypoDescender */
        if (desc < 0)
            desc = -desc;
    }

    ofs = xps_find_sfnt_table(font, "vhea", &len);
    if (ofs > 0 && len >= 2 * 18)
    {
        n = u16(font->data + ofs + 17 * 2);

        ofs = xps_find_sfnt_table(font, "vmtx", &len);
        if (ofs < 0)
        {
            gs_warn("cannot find vmtx table");
            return;
        }

        idx = gid;
        if (idx > n - 1)
            idx = n - 1;

        vadv = u16(font->data + ofs + idx * 4);
        vtop = u16(font->data + ofs + idx * 4 + 2);

        glyf = xps_find_sfnt_table(font, "glyf", &len);
        loca = xps_find_sfnt_table(font, "loca", &len);
        if (head > 0 && glyf > 0 && loca > 0)
        {
            format = u16(font->data + head + 50); /* indexToLocaFormat */

            if (format == 0)
                ofs = u16(font->data + loca + gid * 2) * 2;
            else
                ofs = u32(font->data + loca + gid * 4);

            ymax = u16(font->data + glyf + ofs + 8); /* yMax */

            vorg = ymax + vtop;
        }
    }

    ofs = xps_find_sfnt_table(font, "VORG", &len);
    if (ofs > 0)
    {
        vorg = u16(font->data + ofs + 6);
        n = u16(font->data + ofs + 6);
        for (i = 0; i < n; i++)
        {
            if (u16(font->data + ofs + 8 + 4 * i) == gid)
            {
                vorg = s16(font->data + ofs + 8 + 4 * i + 2);
                break;
            }
        }
    }

    if (vadv == 0)
        vadv = vorg + desc;

    mtx->hadv = hadv / (float) scale;
    mtx->vadv = vadv / (float) scale;
    mtx->vorg = vorg / (float) scale;
}