#include "drive.h"
#include "elf.h"
#include "util.h"
#include "idt.h"
#include "log.h"
#include "panic.h"
#include "task.h"
#include "paging.h"
#include "pmap.h"
#include "kbd.h"

enum {
  IDT_PRESENT = 0x80,
  IDT_INT     = 0x0e,
};

struct idt_entry {
  uint16_t addr_low;
  uint16_t cs;
  uint8_t zero;
  uint8_t flags;
  uint16_t addr_high;
} __attribute__ ((packed));

struct idt_entry idt[256];

struct {
  uint16_t limit;
  uint32_t start;
} __attribute__ ((packed)) idtr = {
  .limit = 256 * sizeof(struct idt_entry) - 1,
  .start = (uint32_t)idt
};

//file handles as (drive_number << 8) + file_id_t

static uint32_t sc_open_file(uint32_t drive_number, char *path) {
  return (drive_number << 8) + drives[drive_number].get_file(drives + drive_number, path);
}

static void sc_close_file(uint32_t handle) {
  drives[handle >> 8].free_file(drives + (handle >> 8), handle & 0xff);
}

static uint32_t sc_file_get_size(uint32_t handle) {
  return drives[handle >> 8].get_file_length(drives + (handle >> 8), handle & 0xff);
}

static uint32_t sc_file_read(uint32_t handle, uint32_t file_offset, uint32_t count, void *buffer) {
  uint32_t len = sc_file_get_size(handle);
  if (file_offset + count > len)
    count = len - file_offset;
  fmcpy(buffer, drives + (handle >> 8), handle & 0xff, file_offset, count);
  return count;
}

static uint32_t sc_start_task(uint32_t drive_number, char *path, const char *pass) {
  switch_to_kernel_cr3();
  uint32_t process_id = try_elf_run(drives + drive_number, vma_to_pma(active_task->page_directory, path), pass);
  switch_to_task_cr3();
  return process_id;
}

static void *sc_allocate_ram(uint32_t pages) {
  return pd_user_allocate_anywhere_writable(active_task->page_directory, pages);
}

enum mi_arg {
  MI_KERNEL_MAX,
  MI_KERNEL_LEFT,
  MI_USER_MAX,
  MI_USER_LEFT,
  MI_TASK_LEFT
};

__attribute__ ((pure))
static uint32_t sc_memory_info(enum mi_arg arg) {
  switch (arg) {
  case MI_KERNEL_MAX:
    return max_kernel_pages;
  case MI_KERNEL_LEFT:
    return kernel_pages_left;
  case MI_USER_MAX:
    return max_user_pages;
  case MI_USER_LEFT:
    return user_pages_left;
  case MI_TASK_LEFT:
    PANIC("TODO: memory info task left");
  default:
    return -1;
  }
}

static void sc_wait_for_task(uint32_t handle) {
  active_task->wait_mode = PROCESS_END;
  active_task->wait_arg = handle;
}

void const *syscall_table[] = {
  &sc_open_file,
  &sc_close_file,
  &sc_file_read,
  &sc_file_get_size,
  &sc_start_task,
  &logsz,
  &get_key_code,
  &sc_allocate_ram,
  &sc_memory_info,
  &sc_wait_for_task
};

//these aren't really void ()'s, but gcc complains if we take an address of a void, so we give it a type
typedef void isr_t();

extern isr_t syscall_isr;
extern isr_t quit_isr;
extern isr_t yield_isr;

extern isr_t kbd_isr;

extern isr_t udf_isr;
extern isr_t dfa_isr;
extern isr_t tsf_isr;
extern isr_t npf_isr;
extern isr_t ssf_isr;
extern isr_t gpf_isr;
extern isr_t pff_isr;

__attribute__ ((noreturn))
void exception_halt(const char *id, uint32_t code, uint32_t eip, uint32_t cs) {
  char nbuf[11];

  set_log_mode(LOG_PANIC);
  logsz("Exception #");
  logsz(id);
  logsz(" at 0x");
  u8_hex(cs, nbuf);
  logsz(nbuf);
  logsz(":0x");
  u32_hex(eip, nbuf);
  logsz(nbuf);

  logsz("\nerror code = 0x");
  u32_hex(code, nbuf);
  logsz(nbuf);

  logsz("\ntask name = ");
  logsz(active_task->name);

  logsz("\ncr3 = 0x");
  uint32_t cr3;
  asm (
    "mov %%cr3, %0"
  : "=r" (cr3));
  u32_hex(cr3, nbuf);
  logsz(nbuf);

  logsz("\nHalting.");
  while (1)
    asm ("hlt");
}

static void register_int(uint8_t n, isr_t *isr, uint8_t dpl) {
  idt[n].addr_low = (uint32_t)isr & 0xffff;
  idt[n].addr_high = (uint32_t)isr >> 16;
  idt[n].cs = 0x10;
  idt[n].flags = IDT_PRESENT | (dpl << 5) | IDT_INT;
}

enum {
  PIC_MCMD  = 0x0020,
  PIC_MDATA = 0x0021,
  PIC_SCMD  = 0x00a0,
  PIC_SDATA = 0x00a1
};

enum {
  PIC_RESET = 0x11
};

void init_idt() {
  for (uint16_t i = 0; i < 256; ++i) {
    idt[i].flags = 0;
    idt[i].zero = 0;
  }

  register_int(0x30, &syscall_isr, 3);
  register_int(0x38, &quit_isr, 3);
  register_int(0x39, &yield_isr, 3);

  register_int(0x21, &kbd_isr, 0);

  register_int(0x08, &udf_isr, 0);
  register_int(0x08, &dfa_isr, 0);
  register_int(0x0a, &tsf_isr, 0);
  register_int(0x0b, &npf_isr, 0);
  register_int(0x0c, &ssf_isr, 0);
  register_int(0x0d, &gpf_isr, 0);
  register_int(0x0e, &pff_isr, 0);

  outb(PIC_MCMD, PIC_RESET);
  outb(PIC_SCMD, PIC_RESET);

  outb(PIC_MDATA, 0x20);
  outb(PIC_SDATA, 0x28);

  outb(PIC_MDATA, 0x04);
  outb(PIC_SDATA, 0x02);

  outb(PIC_MDATA, 0x01);
  outb(PIC_SDATA, 0x01);

  outb(PIC_MDATA, 0xfd);
  outb(PIC_SDATA, 0xff);

  asm volatile (
    "lidt %0"
  : : "m" (idtr) : "al");
}