#include "../../include/mgl/graphics/font.h"
#include "../../include/mgl/system/fileutils.h"
#include <stdio.h>

#define STB_RECT_PACK_IMPLEMENTATION
#include "../../external/stb_rect_pack.h"

#define STB_TRUETYPE_IMPLEMENTATION
#include "../../external/stb_truetype.h"

/* TODO: Test and fix .tcc files */

static unsigned int to_div2_ceil(unsigned int value) {
    const uint32_t v = value;
    return v + (v & 1);
}

int mgl_font_load_from_file(mgl_font *self, const char *filepath, unsigned int character_size) {
    self->texture.id = 0;

    self->font_atlas.atlas = NULL;
    self->font_atlas.width = 0;
    self->font_atlas.height = 0;

    self->character_size = character_size;
    self->packed_chars = NULL;
    self->num_packed_chars = 0;

    mgl_memory_mapped_file mapped_file;
    if(mgl_mapped_file_load(filepath, &mapped_file, &(mgl_memory_mapped_file_load_options){ .readable = true, .writable = false }) != 0) {
        fprintf(stderr, "Error: failed to load font %s, error: mgl_load_file failed\n", filepath);
        return -1;
    }

    stbtt_fontinfo font;
    if(!stbtt_InitFont(&font, mapped_file.data, stbtt_GetFontOffsetForIndex(mapped_file.data, 0))) {
        fprintf(stderr, "Error: failed to load font %s, error: stbtt_InitFont failed\n", filepath);
        mgl_mapped_file_unload(&mapped_file);
        return -1;
    }

    self->num_packed_chars = 256;
    self->packed_chars = malloc(self->num_packed_chars * sizeof(stbtt_packedchar));
    if(!self->packed_chars) {
        fprintf(stderr, "Error: failed to load font %s, error: out of memory\n", filepath);
        goto error;
    }

    bool atlas_created = false;
    /* TODO: Optimize */
    /* Find optimal size for atlas, starting from small to large */
    for(int i = 0; i < 4; ++i) {
        /*
            This to_div2_ceil is needed because otherwise for character sizes such as 33 which are not divisable by 2
            causes the font texture to be skewed. I dont know why this happens. Maybe a bug in stbtt?
            TODO: Figure out why it happens.
        */
        self->font_atlas.width = (14 + (8 * i)) * to_div2_ceil(self->character_size);
        self->font_atlas.height = (14 + (8 * i)) * to_div2_ceil(self->character_size);
        unsigned char *new_atlas = realloc(self->font_atlas.atlas, self->font_atlas.width * self->font_atlas.height);
        if(!new_atlas) {
            fprintf(stderr, "Error: failed to load font %s, error: out of memory\n", filepath);
            goto error;
        }
        self->font_atlas.atlas = new_atlas;

        stbtt_pack_context pc;

        if(!stbtt_PackBegin(&pc, self->font_atlas.atlas, self->font_atlas.width, self->font_atlas.height, self->font_atlas.width, 1, NULL)) {
            fprintf(stderr, "Error: failed to load font %s, error: stbtt_PackBegin failed\n", filepath);
            goto error;
        }

        stbtt_PackSetOversampling(&pc, 2, 2);

        if(!stbtt_PackFontRange(&pc, mapped_file.data, 0, self->character_size, 0, self->num_packed_chars, self->packed_chars)) {
            stbtt_PackEnd(&pc);
            continue;
        }

        /*if(!stbtt_PackFontRange(&pc, mapped_file.data, 0, self->character_size, 0x00004E00, self->num_packed_chars, self->packed_chars)) {
            stbtt_PackEnd(&pc);
            continue;
        }*/

        stbtt_PackEnd(&pc);
        atlas_created = true;
        break;
    }

    if(!atlas_created) {
        fprintf(stderr, "Error: failed to load font %s, error: failed to create atlas\n", filepath);
        goto error;
    }

    if(mgl_texture_load_from_memory(&self->texture, self->font_atlas.atlas, self->font_atlas.width, self->font_atlas.height, MGL_IMAGE_FORMAT_ALPHA, NULL) != 0) {
        fprintf(stderr, "Error: failed to load font %s, error: mgl_texture_load_from_memory failed\n", filepath);
        goto error;
    }

    /* TODO: Use stbtt_GetCodepointSDF */
    
    mgl_mapped_file_unload(&mapped_file);
    return 0;

    error:
    mgl_mapped_file_unload(&mapped_file);
    mgl_font_unload(self);
    return -1;
}

void mgl_font_unload(mgl_font *self) {
    mgl_texture_unload(&self->texture);

    free(self->font_atlas.atlas);
    self->font_atlas.atlas = NULL;
    self->font_atlas.width = 0;
    self->font_atlas.height = 0;

    free(self->packed_chars);
    self->packed_chars = NULL;
    self->num_packed_chars = 0;
}

int mgl_font_get_glyph(const mgl_font *self, uint32_t codepoint, mgl_font_glyph *glyph) {
    stbtt_packedchar *packed_chars = self->packed_chars;
    if(codepoint < 0 || codepoint >= 0 + self->num_packed_chars)
        return -1;

    float x = 0.0f;
    float y = 0.0f;
    stbtt_aligned_quad quad;
    stbtt_GetPackedQuad(packed_chars, self->font_atlas.width, self->font_atlas.height, codepoint, &x, &y, &quad, 0);

    glyph->position         = (mgl_vec2f){ quad.x0, quad.y0 };
    glyph->size             = (mgl_vec2f){ quad.x1 - quad.x0, quad.y1 - quad.y0 };
    glyph->texture_position = (mgl_vec2f){ quad.s0, quad.t0 };
    glyph->texture_size     = (mgl_vec2f){ quad.s1 - quad.s0, quad.t1 - quad.t0 };
    glyph->advance = x;
    return 0;
}