#include "term.h"

#include <X11/Xft/Xft.h>
#include <harfbuzz/hb-ft.h>

#define FEATURE(c1,c2,c3,c4) { .tag = HB_TAG(c1,c2,c3,c4), .value = 1, .start = HB_FEATURE_GLOBAL_START, .end = HB_FEATURE_GLOBAL_END }

hb_font_t *hbfindfont(XftFont *match);
void hbtransformsegment(XftFont *xfont, const Letter *glyph, rune *codepoints, int start, int end);

typedef struct 
{
    XftFont *match;
    hb_font_t *font;
} HbFontMatch;

static int hbfontslen = 0;
static HbFontMatch *hbfontcache = nil;

/* 
 * Replace 0 with a list of font features, wrapped in FEATURE macro, e.g. 
 * FEATURE('c', 'a', 'l', 't'), FEATURE('d', 'l', 'i', 'g')
 */
hb_feature_t features[] = { 0 };

void
hbunloadfonts()
{
    int i;
    for(i = 0; i < hbfontslen; i++) {
        hb_font_destroy(hbfontcache[i].font);
        XftUnlockFace(hbfontcache[i].match);
    }

    if(hbfontcache != nil) {
        free(hbfontcache);
        hbfontcache = nil;
    }

    hbfontslen = 0;
}

hb_font_t *
hbfindfont(XftFont *match)
{
    int i;
    for (i = 0; i < hbfontslen; i++) {
        if (hbfontcache[i].match == match)
            return hbfontcache[i].font;
    }

    /* Font not found in cache, caching it now. */
    hbfontcache = realloc(hbfontcache, sizeof(HbFontMatch) * (hbfontslen + 1));
    FT_Face face = XftLockFace(match);
    hb_font_t *font = hb_ft_font_create(face, NULL);
    if(!font)
        fatal("failed to load Harfbuzz font.");

    hbfontcache[hbfontslen].match = match;
    hbfontcache[hbfontslen].font = font;
    hbfontslen += 1;

    return font;
}

void
hbtransform(XftGlyphFontSpec *specs, const Letter *glyphs, size_t len, int x, int y)
{
	int idx, specidx, start = 0, length = 1, gstart = 0;
	rune *runes = calloc((unsigned int)len, sizeof(hb_codepoint_t));

    for(idx = 1, specidx = 1; idx < len; idx++) {
        if(glyphs[idx].mode & Gwdummy) {
            length += 1;
            continue;
        }

        if(specs[specidx].font != specs[start].font
       || GLYPHCMP(glyphs[gstart], glyphs[idx])
       || selected(x + idx, y) != selected(x + gstart, y)
        ) {
            hbtransformsegment(specs[start].font, glyphs, runes, gstart, length);
            /* reset the sequence. */
            length = 1;
            start = specidx;
            gstart = idx;
        } else {
            length += 1;
        }

        specidx++;
    }

    /* eol */
    hbtransformsegment(specs[start].font, glyphs, runes, gstart, length);

    /* apply the transformation to glyph specs. */
    for(idx = 0, specidx = 0; idx < len; idx++) {
        if(glyphs[idx].mode & Gwdummy)
            continue;

        if(runes[idx] != specs[specidx].glyph)
            ((Letter *)glyphs)[idx].mode |= Gliga;

        specs[specidx++].glyph = runes[idx];
    }

	free(runes);
}

void
hbtransformsegment(XftFont *xfont, const Letter *glyph, rune *codepoints, int start, int len)
{
    hb_font_t *font = hbfindfont(xfont);
    if(!font)
        return;

    int i;
    rune r;
    ushort mode = USHRT_MAX;
    hb_buffer_t *buffer = hb_buffer_create();
    hb_buffer_set_direction(buffer, HB_DIRECTION_LTR);

    /* Fill buffer with codepoints. */
    for(i=start; i < (start+len); i++) {
        r = glyph[i].u;
        mode = glyph[i].mode;
        if(mode & Gwdummy)
            r = 0x0020;
        hb_buffer_add_codepoints(buffer, &r, 1, 0, 1);
    }

    /* Shape the segment. */
    hb_shape(font, buffer, features, sizeof(features));

    /* Get new glyph info. */
    hb_glyph_info_t *info = hb_buffer_get_glyph_infos(buffer, NULL);

    /* Write new codepoints. */
    for(i = 0; i < len; i++) {
        r = info[i].codepoint;
        codepoints[start+i] = r;
    }

    /* Cleanup. */
    hb_buffer_destroy(buffer);
}