/* Copyright (C) 2023, 2024 Aryadev Chavali

 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
 * more details.

 * You should have received a copy of the GNU General Public License Version 2
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 * Created: 2023-10-15
 * Author: Aryadev Chavali
 * Description: Entrypoint to program
 */

#include "lib/base.h"
#include <stdio.h>
#include <stdlib.h>

#include <vm/runtime.h>
#include <vm/struct.h>

void usage(const char *program_name, FILE *out)
{
  fprintf(out,
          "Usage: %s [OPTIONS] FILE\n"
          "\t FILE: Bytecode file to execute\n"
          "\tOptions:\n"
          "\t\t To be developed...\n",
          program_name);
}

int main(int argc, char *argv[])
{
  if (argc == 1)
  {
    usage(argv[0], stderr);
    return 1;
  }
  const char *filename = argv[1];

#if VERBOSE >= 1
  INFO("INTERPRETER", "`%s`\n", filename);
#endif

  FILE *fp        = fopen(filename, "rb");
  darr_t fp_bytes = darr_read_file(fp);
  fclose(fp);

  prog_t program = {0};
  size_t header_read =
      prog_read_header(&program, fp_bytes.data, fp_bytes.available);

  if (!header_read)
  {
    FAIL("ERROR", "Could not deserialise program header in `%s`\n", filename);
    return 1;
  }
  // Ensure that we MUST have something to read
  else if (program.count == 0)
    return 0;

  // After reading header, we can allocate the buffer of instrutions exactly
  program.instructions = calloc(program.count, sizeof(*program.instructions));
  size_t bytes_read    = 0;
  read_err_prog_t read_err =
      prog_read_instructions(&program, &bytes_read, fp_bytes.data + header_read,
                             fp_bytes.available - header_read);

  if (bytes_read == 0)
  {
    FAIL("ERROR", "%s [%lu]:", filename, read_err.index);
    switch (read_err.type)
    {
    case READ_ERR_INVALID_OPCODE:
      fprintf(stderr, "INVALID_OPCODE");
      break;
    case READ_ERR_OPERAND_NO_FIT:
      fprintf(stderr, "OPERAND_NO_FIT");
      break;
    case READ_ERR_EXPECTED_MORE:
      fprintf(stderr, "EXPECTED_MORE");
      break;
    case READ_ERR_END:
    default:
      fprintf(stderr, "UNKNOWN");
      break;
    }
    fprintf(stderr, "\n");
    return 1;
  }

#if VERBOSE >= 1
  SUCCESS("SETUP", "Read %lu instructions\n", program.count);
#endif

  size_t stack_size     = 256;
  byte_t *stack         = calloc(stack_size, 1);
  size_t registers_size = 8 * WORD_SIZE;
  byte_t *registers     = calloc(registers_size, 1);
  heap_t heap           = {0};
  heap_create(&heap);
  size_t call_stack_size = 256;
  word_t *call_stack     = calloc(call_stack_size, sizeof(call_stack));

  vm_t vm = {0};
  vm_load_stack(&vm, stack, stack_size);
  vm_load_program(&vm, program);
  vm_load_registers(&vm, registers, registers_size);
  vm_load_heap(&vm, heap);
  vm_load_call_stack(&vm, call_stack, call_stack_size);

#if VERBOSE >= 1
  SUCCESS("SETUP", "Loaded internals\n%s", "");
  INFO("INTERPRETER", "Beginning execution\n%s", "");
#endif
  err_t err = vm_execute_all(&vm);

  int ret = 0;
  if (err)
  {
    const char *error_str = err_as_cstr(err);
    FAIL("ERROR", "%s\n", error_str);
    vm_print_all(&vm, stderr);
    ret = 255 - err;
  }

  vm_stop(&vm);

#if VERBOSE >= 1
  SUCCESS("INTEPRETER", "Finished execution\n%s", "");
#endif
  return ret;
}