#include "multiboot.h"
#include "interrupts.h"
#include "gdt.h"
#include "common.h"
#include "scheduler.h"
#include "vfs.h"
#include "elf.h"
#include "gdt.h"

#include <lib/print.h>
#include <lib/stream.h>
#include <lib/memory.h>

#include <memory/mm.h>

#include <drivers/iso/iso.h>
#include <drivers/ide/ide.h>
#include <drivers/pic/pic.h>
#include <drivers/ps2/ps2.h>
#include <drivers/pit/pit.h>
#include <drivers/vga/vga.h>
#include <drivers/cpio/cpio.h>

#include <stddef.h>
#include <stdint.h>

extern char __kernel_start;
extern char __kernel_end;

extern uint32_t page_directory[1024];
void* kernel_cr3 = page_directory;

void parse_multiboot_modules(uint32_t mbi_vaddr) {
  // find where grub put the boot module containing initrd
  multiboot_info* mbi = (multiboot_info*)mbi_vaddr;

  uint32_t mod_count = mbi->mods_count;
  multiboot_module_t* mod = (multiboot_module_t*)((uint32_t)mbi->mods_addr + 0xC0000000);

  kprintf("found %d mods starting @ [v]0x%x\n", mod_count, (uint32_t)mod);

  for (uint32_t i = 0; i < mod_count; i++) {
    uint32_t start = mod[i].mod_start;
    uint32_t end = mod[i].mod_end;
    uint32_t cmdline = mod[i].cmdline;

    multiboot_module_info_table[i].mod_start = start + 0xC0000000;
    multiboot_module_info_table[i].mod_end = end + 0xC0000000;
    multiboot_module_info_table[i].cmdline = cmdline + 0xC0000000;
  }
}

vfs_node_t* load_initrd() {
  multiboot_module_t* initrd_module = &multiboot_module_info_table[0];
  kprintf("initrd found @ [v] 0x%x\n", initrd_module->mod_start);
  return cpio_read_fs(initrd_module->mod_start);
}

void load_root_program(const char* path) {
  lock_scheduler();
  uint32_t kernel_cr3 = fetch_cr3();
  void* cr3 = create_task_pd();
  
  load_pd(cr3);
  flush_tlb();

  int fd = open(path, 0);
  if (fd == -1) {
    kprintf("failed to open program: %s\n", path);
    return;;
  }
  elf_header_t* e_hdr = kalloc(sizeof(elf_header_t));
  memset((void*)e_hdr, 0, sizeof(elf_header_t));

  uint32_t bytes_rd = read(fd, e_hdr, sizeof(elf_header_t));
  if (bytes_rd <= 0) {
    kprintf("failed to read program data for %s\n", path);
    return;
  }

  uint32_t ph_table_ptr = e_hdr->e_phoff;
  elf_program_header_t* ph = kalloc(sizeof(elf_program_header_t));
  uint32_t heap_start = 0;

  for (uint32_t i = 0; i < e_hdr->e_phnum; i++) {
    fseek(fd, ph_table_ptr);
    memset((void*)ph, 0, sizeof(elf_program_header_t));
    read(fd, ph, sizeof(elf_program_header_t));

    if (ph->p_type == PT_LOAD) {
      uint32_t vstart = ph->p_vaddr;
      uint32_t vend = vstart + ph->p_memsz;

      if (vend > heap_start) {
        heap_start = vend;
      }

      uint32_t page_start = vstart & ~(PAGE_SIZE - 1);
      uint32_t page_end = (vend + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);

      for (uint32_t v = page_start; v < page_end; v += PAGE_SIZE) {
          void* phys_frame = p_alloc_frame();
          map_page(v, (uint32_t)phys_frame, PAGE_PRESENT | PAGE_WRITABLE | PAGE_USER);
      }

      uint32_t data_ptr = ph->p_offset;
      fseek(fd, data_ptr);
      read(fd, (void*)vstart, ph->p_filesz);

      // 0 out bss
      if (ph->p_memsz > ph->p_filesz) {
        size_t bss_size = ph->p_memsz - ph->p_filesz;
        memset((void*)(vstart + ph->p_filesz), 0, bss_size);
      }
    }

    ph_table_ptr += sizeof(elf_program_header_t);
  }

  uint32_t stack_sz = PAGE_SIZE * 16;
  uint32_t stack_top = 0xBFFF0000;
  uint32_t stack_bottom = stack_top - stack_sz;
  for (uint32_t vaddr = stack_bottom; vaddr < stack_top; vaddr += PAGE_SIZE) {
    void* phys_frame = p_alloc_frame();
    map_page(vaddr, (uint32_t)phys_frame, PAGE_PRESENT | PAGE_WRITABLE | PAGE_USER);
  }

  uint32_t* u_esp = (uint32_t*)stack_top;
  *(--u_esp) = 0;          // envp = NULL
  *(--u_esp) = 0;          // argv = NULL
  *(--u_esp) = 0;          // argc = 0

  process_t* process = kalloc(sizeof(process_t));
  init_task(process, e_hdr->e_entry, (uint32_t)cr3, 1, (uint32_t)u_esp);
  add_task(process);

  unlock_scheduler();
  
  load_pd((void*)kernel_cr3);
  flush_tlb();  
}

void kmain(uint32_t magic, multiboot_info* mbi)  {
  disable_interrupts();
  if (!(mbi->flags & (1 << 6))) {
    return;
  } 

  vga_init();

  uint32_t mmap_virtual_addr = mbi->mmap_addr + 0xC0000000;
  init_pmm((void*)mmap_virtual_addr, mbi->mmap_length);
  kprintf("memory detection complete. total free memory: %dMB\n", total_free_memory() / 1024 / 1024);

  init_gdt();
  init_idt();
  init_pic();
  init_pit();
  
  init_page_tables();

  parse_multiboot_modules((uint32_t)mbi);
  
  kprintf("basic initializations complete\n");

  vfs_node_t* vfs_root = vfs_create_root();

  vfs_node_t* initrd_root = load_initrd();
  if (!initrd_root) {
    kprintf("failed to load initrd\n");
  }

  mount(vfs_root, initrd_root);
  kprintf("initrd read, mounted @ /\n");

  disable_interrupts();
  init_scheduler();
  enable_interrupts();

  kprintf("loading test program\n");
  load_root_program("/test.elf");

  kprintf("kernel going to sleep...\n");
}