#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <ft2build.h>
#include <stdio.h>
#include FT_FREETYPE_H
#include <string.h>
#include <strings.h>
#include <ctype.h>

#define N_CHARS 128

#define round_up_26_6(val) (((val) + 63) >> 6u)

int max_advance;
int max_top = -9999;
int min_bottom = 9999;
int line_height;
int baseline_offset;

typedef struct {
    int width;
    int height;
    int top;
    int left;
    uint8_t * bitmap;
} char_info_t;

static char_info_t char_infos[N_CHARS];

static void load_char(FT_Face face, int char_code)
{
    if (FT_Load_Char(face, char_code, FT_LOAD_RENDER) != 0)
    {
        return;
    }
    int advance = round_up_26_6(face->glyph->advance.x);
    if (advance > max_advance)
    {
        max_advance = advance;
    }
    if ((face->glyph->bitmap.width == 0) ||
            (face->glyph->bitmap.rows == 0))
    {
        return;
    }
    char_infos[char_code].width = face->glyph->bitmap.width;
    char_infos[char_code].height = face->glyph->bitmap.rows;
    char_infos[char_code].top = face->glyph->bitmap_top;
    if (char_infos[char_code].top > max_top)
    {
        max_top = char_infos[char_code].top;
    }
    int bottom = char_infos[char_code].top - char_infos[char_code].height;
    if (bottom < min_bottom)
    {
        min_bottom = bottom;
    }
    char_infos[char_code].left = face->glyph->bitmap_left;
    char_infos[char_code].bitmap = malloc(char_infos[char_code].width * char_infos[char_code].height);
    memcpy(char_infos[char_code].bitmap,
            face->glyph->bitmap.buffer,
            char_infos[char_code].width * char_infos[char_code].height);
}

static void generate_bytes(FILE * file, const uint8_t * bytes, int count)
{
    for (int i = 0; i < count; i++)
    {
        if (i % 8 == 0)
        {
            fprintf(file, "                ");
        }
        fprintf(file, "0x%02xu,", bytes[i]);
        if ((i + 1) % 8 == 0)
        {
            fprintf(file, "\n");
        }
        else if (i < (count - 1))
        {
            fprintf(file, " ");
        }
    }
    if (count % 8 != 0)
    {
        fprintf(file, "\n");
    }
}

static bool generate(const char * d_file_name)
{
    FILE * fh = fopen(d_file_name, "wb");
    fprintf(fh, "module hulk.kfont;\n");
    fprintf(fh, "struct CharInfo {\n");
    fprintf(fh, "    /** Glyph bitmap width. */\n");
    fprintf(fh, "    ubyte width;\n");
    fprintf(fh, "    /** Glyph bitmap height. */\n");
    fprintf(fh, "    ubyte height;\n");
    fprintf(fh, "    /** Glyph bitmap top offset (descent from top of text row). */\n");
    fprintf(fh, "    ubyte top;\n");
    fprintf(fh, "    /** Glyph bitmap left offset. */\n");
    fprintf(fh, "    ubyte left;\n");
    fprintf(fh, "    /** Glyph bitmap. */\n");
    fprintf(fh, "    const ubyte[] bitmap;\n");
    fprintf(fh, "};\n");
    fprintf(fh, "struct FontInfo {\n");
    fprintf(fh, "    /** Font line height. */\n");
    fprintf(fh, "    ubyte line_height;\n");
    fprintf(fh, "    /** Font advance. */\n");
    fprintf(fh, "    ubyte advance;\n");
    fprintf(fh, "    /** Characters. */\n");
    fprintf(fh, "    const CharInfo[] chars;\n");
    fprintf(fh, "};\n");
    fprintf(fh, "/** Kernel font data. */\n");
    fprintf(fh, "__gshared const FontInfo Kfont = {\n");
    fprintf(fh, "    %du,\n", line_height);
    fprintf(fh, "    %du,\n", max_advance);
    fprintf(fh, "    [\n");
    for (int i = 0; i < N_CHARS; i++)
    {
        fprintf(fh, "        /* %d */", i);
        fprintf(fh, "        CharInfo(\n");
        fprintf(fh, "            %du /* width */,\n", char_infos[i].width);
        fprintf(fh, "            %du /* height */,\n", char_infos[i].height);
        fprintf(fh, "            %du /* top */,\n", char_infos[i].top);
        fprintf(fh, "            %du /* left */,\n", char_infos[i].left);
        if (char_infos[i].width > 0)
        {
            fprintf(fh, "            [\n");
            generate_bytes(fh, char_infos[i].bitmap, char_infos[i].width * char_infos[i].height);
            fprintf(fh, "            ]\n");
        }
        else
        {
            fprintf(fh, "            []\n");
        }
        fprintf(fh, "        ),\n");
    }
    fprintf(fh, "    ],\n");
    fprintf(fh, "};\n");
    fclose(fh);
    return true;
}

int main(int argc, char * argv[])
{
    /* Expect: font file, size, out file */
    if (argc != 4)
    {
        fprintf(stderr, "Incorrect arguments\n");
        return 1;
    }
    const char * font_file = argv[1];
    int size = atoi(argv[2]);
    const char * out_file = argv[3];

    FT_Library ft_library;
    if (FT_Init_FreeType(&ft_library) != 0)
    {
        fprintf(stderr, "Could not initialize freetype\n");
        return 2;
    }

    FT_Face face;
    if (FT_New_Face(ft_library, font_file, 0, &face) != 0)
    {
        fprintf(stderr, "Could not open %s\n", font_file);
        return 3;
    }

    FT_Set_Pixel_Sizes(face, 0, size);

    for (int i = 0; i < N_CHARS; i++)
    {
        load_char(face, i);
    }
    line_height = round_up_26_6(face->size->metrics.height);
    baseline_offset = (line_height - (max_top - min_bottom)) / 2 - min_bottom;

    if ((line_height < 1) || (line_height > 0xFF))
    {
        fprintf(stderr, "Error: invalid line_height %d\n", line_height);
        return false;
    }
    if ((max_advance < 1) || (max_advance > 0xFF))
    {
        fprintf(stderr, "Error: invalid max_advance %d\n", max_advance);
        return false;
    }

    for (int i = 0; i < N_CHARS; i++)
    {
        if ((char_infos[i].width < 0) || (char_infos[i].width > max_advance))
        {
            fprintf(stderr, "Error: invalid character %d width: %d\n", i, char_infos[i].width);
            return false;
        }
        if ((char_infos[i].height < 0) || (char_infos[i].height > line_height))
        {
            fprintf(stderr, "Error: invalid character %d height: %d\n", i, char_infos[i].height);
            return false;
        }
        if ((char_infos[i].left < 0) || (char_infos[i].left >= max_advance))
        {
            fprintf(stderr, "Error: invalid character %d left: %d\n", i, char_infos[i].left);
            return false;
        }
        /* Adjust character top to be index downward from top of font box. */
        char_infos[i].top = line_height - baseline_offset - char_infos[i].top;
        if ((char_infos[i].top < 0) || (char_infos[i].top >= line_height))
        {
            fprintf(stderr, "Error: invalid character %d top: %d\n", i, char_infos[i].top);
            return false;
        }
        if ((char_infos[i].left + char_infos[i].width) > max_advance)
        {
            fprintf(stderr, "Error: character %d left (%d) + width (%d) > advance (%d)\n",
                    i, char_infos[i].left, char_infos[i].width, max_advance);
            return false;
        }
        if ((char_infos[i].top + char_infos[i].height) > line_height)
        {
            fprintf(stderr, "Error: character %d top (%d) + height (%d) > line height (%d)\n",
                    i, char_infos[i].top, char_infos[i].height, line_height);
            return false;
        }
    }

    if (!generate(out_file))
    {
        return 1;
    }

    return 0;
}