#include <drivers/ahci.h>
#include <port_io.h>
#include <stdio.h>

#include <drivers/pci.h>

#define PCI_CONFIG_ADDRESS 0xCF8
#define PCI_CONFIG_DATA 0xCFC

/*
  Register 	Offset 	Bits 31-24 	Bits 23-16 	Bits 15-8 	Bits 7-0
  0x0 	        0x0 	Device ID 	                Vendor ID
  0x1 	        0x4 	Status 	                        Command
  0x2 	        0x8 	Class code 	Subclass 	Prog IF 	Revision ID
  0x3 	        0xC 	BIST 	        Header type 	Latency Timer 	Cache Line Size 
*/

uint32_t pci_config_read(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset)
{
  uint32_t address = 0;
  address |= (bus << 16);     /* Bus number (bits 23-16) */
  address |= (device << 11);  /* Device number (bits 15-11) */
  address |= (function << 8); /* Function number (bits 10-8) */
  address |= (offset & 0xFC); /* Register offset (bits 7-0) */
  address |= (1 << 31);       /* Enable configuration access */

  outl(PCI_CONFIG_ADDRESS, address);  /* Write address to PCI config space */
  return inl(PCI_CONFIG_DATA);        /* Read data from PCI config space */
}

void pci_config_write(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset, uint32_t value)
{
  uint32_t address = 0x80000000 | (bus << 16) | (device << 11) | (function << 8) | (offset & 0xFC);
  outl(PCI_CONFIG_ADDRESS, address); /* Send the address to PCI config space */
  outl(PCI_CONFIG_DATA, value);      /* Write data to PCI config space */
}

void pci_config_read_block(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset, void* buffer, size_t size)
{
  uint8_t* buf = (uint8_t*)buffer;

  for (size_t i = 0; i < size; i += 4)
  {
    uint32_t value = pci_config_read(bus, device, function, offset + i);

    size_t remaining = size - i;
    if (remaining >= 4)
    {
      *(uint32_t*)(buf + i) = value;
    }
    else
    {
      for (size_t j = 0; j < remaining; ++j)
      {
        buf[i + j] = (value >> (8 * j)) & 0xFF;
      }
    }
  }
}


void pci_enumerate(void)
{
  for (uint16_t bus = 0; bus < 256; bus++) /* Maximum 256 buses */
  {
    for (uint8_t device = 0; device < 32; device++) /* Maximum 32 devices per bus */
    {
      for (uint8_t function = 0; function < 8; function++) /* Maximum 8 functions per device */
      {
        struct pci_header pre_header;
        pci_config_read_block(bus, device, function, 0x00, &pre_header, sizeof(pre_header));

        if (pre_header.vendor_id == 0xFFFF)
        {
          continue; /* No device present */
        }
        
        if (pre_header.class_code == 0xB)
        {
          printf("Processor found on PCI bus, what?!?!\n");
          continue;
        }
      
        if (pre_header.header_type == 0x00)
        {
          struct pci_header_type_0 hdr;
          pci_config_read_block(bus, device, function, 0x00, &hdr, sizeof(hdr));

          if (hdr.class_code == 0x1 && hdr.subclass == 0x6 && hdr.prog_if == 0x1)
          {
            /*configure_ahci_controller(hdr);*/
          }
        }
      }
    }
  }
}