/*
 * mykernel/kernel.c
 *
 * Copyright (C) 2017 - 2020 bzt (bztsrc@gitlab)
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * This file is part of the BOOTBOOT Protocol package.
 * @brief A sample BOOTBOOT compatible kernel
 *
 */

/* function to display a string, see below */
void puts(char *s);

/* we don't assume stdint.h exists */
typedef short int           int16_t;
typedef unsigned char       uint8_t;
typedef unsigned short int  uint16_t;
typedef unsigned int        uint32_t;
typedef unsigned long int   uint64_t;

#include <bootboot.h>

/* imported virtual addresses, see linker script */
extern BOOTBOOT bootboot;               // see bootboot.h
extern unsigned char environment[4096]; // configuration, UTF-8 text key=value pairs
extern uint8_t fb;                      // linear framebuffer mapped

/******************************************
 * Entry point, called by BOOTBOOT Loader *
 ******************************************/
void _start()
{
    /*** NOTE: this code runs on all cores in parallel ***/
    int x, y, s=bootboot.fb_scanline, w=bootboot.fb_width, h=bootboot.fb_height;

    // cross-hair to see screen dimension detected correctly
    for(y=0;y<h;y++) { *((uint32_t*)(&fb + s*y + (w*2)))=0x00FFFFFF; }
    for(x=0;x<w;x++) { *((uint32_t*)(&fb + s*(h/2)+x*4))=0x00FFFFFF; }

    // red, green, blue boxes in order
    for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+20)*4))=0x00FF0000; } }
    for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+50)*4))=0x0000FF00; } }
    for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+80)*4))=0x000000FF; } }

    // say hello
    puts("Hello from a simple BOOTBOOT kernel");

    // hang for now
    while(1);
}

/**************************
 * Display text on screen *
 **************************/
typedef struct {
    uint32_t magic;
    uint32_t version;
    uint32_t headersize;
    uint32_t flags;
    uint32_t numglyph;
    uint32_t bytesperglyph;
    uint32_t height;
    uint32_t width;
    uint8_t glyphs;
} __attribute__((packed)) psf2_t;
extern volatile unsigned char _binary_font_psf_start;

void puts(char *s)
{
    psf2_t *font = (psf2_t*)&_binary_font_psf_start;
    int x,y,kx=0,line,mask,offs;
    int bpl=(font->width+7)/8;
    while(*s) {
        unsigned char *glyph = (unsigned char*)&_binary_font_psf_start + font->headersize +
            (*s>0&&*s<font->numglyph?*s:0)*font->bytesperglyph;
        offs = (kx * (font->width+1) * 4);
        for(y=0;y<font->height;y++) {
            line=offs; mask=1<<(font->width-1);
            for(x=0;x<font->width;x++) {
                *((uint32_t*)((uint64_t)&fb+line))=((int)*glyph) & (mask)?0xFFFFFF:0;
                mask>>=1; line+=4;
            }
            *((uint32_t*)((uint64_t)&fb+line))=0; glyph+=bpl; offs+=bootboot.fb_scanline;
        }
        s++; kx++;
    }
}