// This file provides functions for the wetterhorn harness that are not
// expressible directly in haskell.
//
// Currently these functions exclusively enable/disable the Haskell runtime.

#include "HsFFI.h"
#include "plugin_interface.h"
#include <unistd.h>

const char *plugin_name = "Wetterhorn";

void* foreign_interface;

void* get_foreign_interface()
{
  return foreign_interface;
}

extern void performMajorGC();

void plugin_metaload(int argc, char** argv)
{
  hs_init(&argc, &argv);
}

void plugin_load(int argc, char **argv, foreign_interface_t* fintf) {
  hs_init(&argc, &argv);
  foreign_interface = fintf;
}

void plugin_teardown(opqst_t st) {
  // the opaque state should be dereferenced by now. Perform a major GC to help
  // clean up before doing a reload.
  //
  // Used primarily in the case where the RTS is kept alive when performing a
  // hot-reload.
  performMajorGC();
  hs_exit();

  // There's a race condition between when this shared library is unloaded and
  // when the haskell runtime actually exits. Don't have a good solution for
  // this at the moment, so just sleep for a second.
  sleep(1);
}

static const char msg[] =
    "Wetterhorn Plugin v 0.01\n\n"
    "Welcome, and thank you for your interest.\n\n"
    "This is merely a plugin to the Wetterhorn Compositor and not meant to be\n"
    "executed as a standalone binary. This plugin requires a harness to run\n"
    "To use this file, please use './wtr_harness [full-path-to-wtr.so]'\n"
    "That will allow you to see how this compositor works in all its glory!\n";
static const int msg_sz = sizeof(msg);

/*
 * Implemens a basic _start that prints inforamtion and exits for users on an
 * x86_64 system.
 */
__attribute__((naked)) void _start()
{

  // Make system call to print the message
  asm(
      // Load the address of the string into rsi
      "mov %0, %%rsi\n"
      // Load the string length into edx
      "mov %1, %%edx\n"
      // Load the file descriptor for stdout into edi
      "mov $1, %%edi\n"
      // Load the syscall number for sys_write into eax
      "mov $1, %%eax\n"
      // Make the syscall
      "syscall\n"

      // Exit the program.
      "mov $0, %%rdi\n"
      "mov $60, %%rax\n"
      "syscall\n"
      :
      : "r"(msg), "r"(msg_sz)  // Input: address of msg
      : "%rsi", "%edx", "%edi" // Clobbered registers
  );
}