/*
Copyright 2019 Benji Dial

Permission to use, copy, modify, and/or distribute this
software for any purpose with or without fee is hereby
granted, provided that the above copyright notice and this
permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS
ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.
*/

#include "vga.h"
#include "files.h"
#include "mem.h"
#include "proc.h"
#include <stdbool.h>

extern uint32_t info_pointer;

enum tag_type {
  BOOT_COMMAND     =  1,
  LOADER_NAME      =  2,
  BOOT_MODULES     =  3,
  MEMORY_INFO      =  4,
  BOOT_DEVICE      =  5,
  MEMORY_MAP       =  6,
  VBE_INFO         =  7,
  FBUF_INFO        =  8,
  ELF_SYMBOLS      =  9,
  APM_TABLE        = 10,
  EFI_I386_TABLE   = 11,
  EFI_AMD64_TABLE  = 12,
  SMBIOS_TABLE     = 13,
  RSDP_ACPI1       = 14,
  RSDP_ACPI2       = 15,
  NETWORK_INFO     = 16,
  EFI_MEMORY_MAP   = 17,
  EFI_SERVICES     = 18,
  EFI_I386_HANDLE  = 19,
  EFI_AMD64_HANDLE = 20,
  IMAGE_BASE_ADDR  = 21
};

struct tag_start {
  uint32_t type;
  uint32_t size;
  uint8_t rest;
} __attribute__ ((__packed__));

struct boot_device_tag {
  uint32_t bios_device;
  uint32_t partition;
  uint32_t subpartition;
} __attribute__ ((__packed__));

enum mem_type {
  AVAILABLE = 1,
  ACPI      = 3,
  PRESERVE  = 4,
  DEFECTIVE = 5
};

struct mmap_tag_entry {
  uint64_t base;
  uint64_t length;
  uint32_t type;
} __attribute__ ((__packed__));

struct boot_device_tag boot_device;
bool have_boot_device = false;
bool have_mmap = false;

enum error_codes {
  NO_BOOT_DEVICE = 000000000000,
  NO_MMAP        = 000000000001,
  INSUFF_MEMORY  = 000000000002
};

uint32_t main(void) {
  for (uint32_t *i = (uint32_t *)VGA_BUFFER; i < (uint32_t *)0x000b8fa0; ++i)
    *i = 0x70207020;

  put_sz("Starting...\n");

  uint32_t info_size = *(uint32_t *)info_pointer;
  struct tag_start *tag_pointer = (struct tag_start *)(info_pointer + 2);

  while (tag_pointer->type) {
    switch (tag_pointer->type) {

    case BOOT_DEVICE:
      boot_device = *(struct boot_device_tag *)&tag_pointer->rest;
      have_boot_device = true;
      put_sz("Boot device: 0x");
      put_32_hex(boot_device.bios_device);
      if (boot_device.partition != 0xffffffff) {
        put_sz(", 0x");
        put_32_hex(boot_device.partition);
        if (boot_device.subpartition != 0xffffffff) {
          put_sz(", 0x");
          put_32_hex(boot_device.subpartition);
        }
      }
      put_char('\n');
      break;

    case MEMORY_MAP:
    {
      struct mmap_tag_entry *tag = (struct mmap_tag_entry *)((uint32_t)&tag_pointer->rest + 8);
      uint32_t size = *(uint32_t *)&tag_pointer->rest;
      struct mmap_entry *entry = (struct mmap_entry *)tag;
      struct mmap_entry **last_next = &mmap_start;
      uint32_t usable = 0;
      while (tag) {
        if (!(tag->base & 0xffffffff00000000)) {
          entry->base = (uint32_t)tag->base;
          entry->length = (tag->base + tag->length - 1) & 0xffffffff00000000 ?
            1 + ~(uint32_t)tag->base : (uint32_t)tag->length;
          put_sz("Memory: 0x");
          put_32_hex(entry->base);
          put_sz(" - 0x");
          put_32_hex(entry->base + entry->length - 1);
          switch (tag->type) {
          case AVAILABLE:
            put_sz(": usable\n");
            entry->whose = FREE;
            usable += entry->length;
            break;
          case ACPI:
            put_sz(": ACPI info\n");
            entry->whose = HARDWARE;
            break;
          case PRESERVE:
            put_sz(": hardware use\n");
            entry->whose = HARDWARE;
            break;
          case DEFECTIVE:
            put_sz(": defective\n");
            entry->whose = HARDWARE;
            break;
          default:
            put_sz(": unrecognized type, assuming hardware use\n");
            entry->whose = HARDWARE;
            break;
          }
          *last_next = entry;
          last_next = &entry->next;
          ++entry;
        }
        tag = (struct mmap_tag_entry *)((uint32_t)tag + size);
      }

      put_sz("Total usable memory: 0x");
      put_32_hex(usable);
      put_char('\n');

      bool clean;
      do {
        clean = true;
        for (struct mmap_entry *current = mmap_start; current; current = current->next)
          for (struct mmap_entry *against = mmap_start; against; against = against->next)
            if ((current->base + current->length == against->base) &&
                (current->whose == against->whose)) {
              current->length += against->length;
              if (against == mmap_start)
                mmap_start = against->next;
              else {
                for (current = mmap_start; current->next != against; current = current->next)
                  ;
                current->next = against->next;
              }
              clean = false;
            }
      } while (clean);

      have_mmap = true;
      break;
    }
    default:
      put_sz("Ignoring multiboot tag 0x");
      put_32_hex(tag_pointer->type);
      put_char('\n');

    }
    tag_pointer = (struct tag_start *)((uint32_t)tag_pointer + tag_pointer->size);
  };

  if (!have_boot_device)
    return NO_BOOT_DEVICE;
  if (!have_mmap)
    return NO_MMAP;

  if (!((proc_table = allocate_block(sizeof(struct proc_info) * 65536, KERNEL)) &&
        (file_table = allocate_block(sizeof(struct file_info) * 65536, KERNEL))))
    return INSUFF_MEMORY;

  put_sz("Welcome to Portland version 0.0.9!\n");
  while (1)
    put_sz("|\b/\b-\b\\\b");
}