#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <memory.h>

#define WMAX 512
#define HMAX 256
#define CHARH 12
#define RL32(arr, ofs) (arr[ofs] + (arr[ofs+1] << 8) + (arr[ofs+2] << 16) + (arr[ofs+3] << 24))
#define LINEL 12

static int S(int x) {
    //this function computes the offset of the glyph for symbol x from
    //the start of the font, shifted right two bits (to fit in 8 bits)
    int hi = x / 21;
    int lo = (x % 21) * 12;
    return hi | lo;
}

int main(int argc, char **argv) {
    uint8_t header[54], image[HMAX][WMAX];
    int x, y, w, h, bpp, c, x2, y2, nlines = 0, nglyphs = 0;
    FILE *f;
    char lines[256][LINEL+1] = {{0}};
    int counts[256] = {0};
    int symbols[256];
    char font[256][CHARH][8];
    unsigned char glyphdata[256];   //bytes to be stuffed into the font
    int i;

    /* read 8-bit images as they are, RGB images as grayscale */
    if (!(f = fopen(argv[1], "rb"))) {
        fprintf(stderr, "failed to open %s\n" , argv[1]);
        return 1;
    }

    fread(header, 54, 1, f);

    w = RL32(header, 18);
    h = RL32(header, 22);
    bpp = header[28] + (header[29] << 8);
    fseek(f, RL32(header, 10), SEEK_SET);

    fprintf(stderr, "%ix%i %i bpp\n", w, h, bpp);

    if (w > WMAX || h > HMAX) {
        fprintf(stderr, "image too large\n");
        return -1;
    }

    for (x = 0; x < 256; x++)
        strcpy(lines[x], "            ");

    for (y = h-1; y >= 0; y--) {
        switch(bpp) {
        case 8:
            fread(image[y], w, 1, f);
            break;
        case 24:
        case 32:
            for (x = 0; x < w; x++) {
                int temp = getc(f) + getc(f) + getc(f);
                if (bpp == 32) getc(f);
                image[y][x] = temp / 3;
            }
            break;
        default:
            fprintf(stderr, "can't handle %i-bit BMPs\n", bpp);
        }

        /* align */
        if (w*(bpp/8) & 3)
            fseek(f, 4 - (w*(bpp/8) & 3), SEEK_CUR);
    }

    fclose(f);

    for (i = 0; i < 66; i++) {
        c = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890!?.,abcdefghijklmnopqrstuvwxyz"[i];
        for (y = 0; y < CHARH; y++) {
            font[c][y][7] = 0;
            for (x = 0; x < 7; x++)
                font[c][y][x] = image[y][i*7+x] > 128;
        }
    }

    for (x = 0;;) {
        if ((c = getc(stdin)) < 0)
            break;

        if (c == '\n') {
            x = 0;
            nlines++;
            continue;
        }

        lines[nlines][x++] = c;
        counts[c]++;
    }

    printf("    MAC FONT\n");
    printf("Font");

    i = 0;  //offset
    for (x = 0; x < 256; x++)
        if (counts[x]) {
            symbols[x] = nglyphs++;

            printf("\n    ;'%c'\n", x);
            for (y = CHARH-1; y >= 0; y--) {
                printf("    byte %%%i%i%i%i%i%i%i%i\n",
                        font[x][y][0], font[x][y][1],
                        font[x][y][2], font[x][y][3],
                        font[x][y][4], font[x][y][5],
                        font[x][y][6], font[x][y][7]);
            }

            if (i % 21 == 20) {
                printf("\n    ;padding to next page\n");
                printf("    word $FFFF,$FFFF\n");
            }

            i++;
        }

    printf("    ENDM\n");

    printf("    MAC TEXT_DATA\n");
    printf("Lines\n");
    for (x = 0; x < nlines; x++) {
        printf ("    byte ");
        for (y = 0; y < 12; y += 4) {
            if (y > 0)
                printf(",");

            //lower six bits = glyph index
            //concat top two bits of all three bytes to form fourth glyph index
            //like so:
            //glyphs: Aaaaaa, Bbbbbb, Cccccc, Dddddd
            //byte 0: DdAaaaaa
            //byte 1: ddBbbbbb
            //byte 2: ddCccccc
            //TODO: pack the other way around? whichever is faster to decode
            /*printf("$%02X,$%02X,$%02X",
                    symbols[lines[x][y+0]] | ((symbols[lines[x][y+3]] << 6) & 192),
                    symbols[lines[x][y+1]] | ((symbols[lines[x][y+3]] << 4) & 192),
                    symbols[lines[x][y+2]] | ((symbols[lines[x][y+3]] << 2) & 192));*/
            printf("$%02X,$%02X,$%02X,$%02X",
                    S(symbols[lines[x][y+0]]), S(symbols[lines[x][y+1]]),
                    S(symbols[lines[x][y+2]]), S(symbols[lines[x][y+3]]));
        }

        printf(" ;%i: '%s'\n", x, lines[x]);
    }

    printf("    ENDM\n");
    printf("CHARH  equ %i\n", CHARH);
    printf("NSYM   equ %i\n", nglyphs);
    printf("NLINES equ %i\n", nlines);

    x = nglyphs * CHARH;
    y = nlines * 9;
    printf(";font size:  %i\n", CHARH*nglyphs);
    printf(";total size: %i + %i = %i B\n", x, y, x+y);

    return 0;
}