#include "vm.h"
#include "lib/commons.h"
#include "lib/fun.h"
#include "lib/heap.h"
#include "lib/locals.h"
#include "lib/mod.h"
#include "lib/type.h"
#include "lib/tysy.h"
#include "program.h"
#include "value.h"

void vm_init(vm_t* vm, sym_t* sym, tysy_t* tysy, err_t* err)
{
  assert(vm);
  assert(sym);
  assert(tysy);

  vm->top_frame = NULL;
  locals_init(&vm->locals);
  vm_frame_push(vm, NULL);

  vm->tysy = tysy;
  vm->err = err;

  heap_init(&vm->heap);
}

void vm_free(vm_t* vm)
{
  assert(vm);

  while (vm_frame_pop(vm))
    {
    }

  if (vm->top_frame)
    {
      vm_frame_free(vm->top_frame);
      free(vm->top_frame);
    }

  vm->top_frame = NULL;

  heap_free(&vm->heap);

  locals_free(&vm->locals);
}

void vm_frame_init(frame_t* frame)
{
  assert(frame);

  frame->fun = NULL;

  frame->pc = 0;
  frame->bp = 0;
  frame->sp = 0;

  frame->prev = NULL;
  frame->program = NULL;

  frame->locals = NULL;

  frame->alloc.cap = 0;
  frame->alloc.size = 0;
  frame->alloc.data = NULL;
}

void vm_frame_free(frame_t* frame)
{
  if (frame->prev != NULL)
    {
      vm_frame_free((frame_t*) frame->prev);
      frame->prev = NULL;
    }
}

void vm_frame_push(vm_t* vm, fun_t* fun)
{
  assert(vm);

  frame_t* frame = malloc(sizeof(frame_t));
  vm_frame_init(frame);

  frame->prev = (struct frame*) vm->top_frame;

  if (fun != NULL)
    {
      frame->program = fun->program;
      frame->locals = (locals_t*) fun->locals;
    }
  else
    {
      frame->locals = &vm->locals;
    }

  vm->top_frame = frame;
}

int vm_frame_pop(vm_t* vm)
{
  assert(vm);

  if (vm->top_frame->fun)
    {
      vm->top_frame->fun = NULL;
    }

  if (vm->top_frame)
    {
      vm_clear_alloc(vm->top_frame);
    }

  if (vm->top_frame && vm->top_frame->prev)
    {
      frame_t* prev = (frame_t*) vm->top_frame->prev;
      vm->top_frame->prev = NULL;

      vm_frame_free(vm->top_frame);
      free(vm->top_frame);
      vm->top_frame = NULL;

      vm->top_frame = prev;

      return 1;
    }

  return 0;
}

void vm_push_new(vm_t* vm, value_t* value)
{
  assert(value);
  vm->top_frame->stack[vm->top_frame->sp] = value;

  vm_push_alloc(vm->top_frame, value);

  vm->top_frame->sp++;
}

void vm_push(vm_t* vm, value_t* value)
{
  assert(value);
  vm->top_frame->stack[vm->top_frame->sp] = value;
  vm->top_frame->allocated[vm->top_frame->sp] = 0;
  vm->top_frame->sp++;
}

value_t* vm_pop(vm_t* vm)
{
  assert(vm);

  if (vm->top_frame->sp == 0)
    {
      assert(0);
    }

  value_t* val = vm->top_frame->stack[vm->top_frame->sp - 1];

  vm->top_frame->sp--;

  return val;
}

size_t vm_stack_str(vm_t* vm, char* buffer, size_t size)
{
  assert(vm);
  assert(buffer);

  size_t sz = 0;

  if (vm->top_frame->sp == 0)
    {
      sz += snprintf(buffer + sz, size - sz, "** empty **\n");
      return sz;
    }

  for (size_t i=0; i<vm->top_frame->sp; i++)
    {
      value_t* val = vm->top_frame->stack[vm->top_frame->sp - 1 - i];

      sz += snprintf(buffer + sz, size - sz, "| ");
      value_str(val, buffer + sz, size - sz);
      sz += snprintf(buffer + sz, size - sz, " |");
    }

  return sz;
}

int vm_exec_mod(vm_t* vm, mod_t* mod)
{
  assert(vm);
  vm->top_frame->pc = 0;
  vm->top_frame->program = &mod->program;

  while (vm->top_frame->pc < vm->top_frame->program->size)
    {
      program_t* program = vm->top_frame->program;

      int status = vm_exec_instr(vm,
                                 program->ops[vm->top_frame->pc],
                                 program->params[vm->top_frame->pc]);

      if (status != 0)
        {
          return status;
        }
    }

  return 0;
}

int vm_exec_instr(vm_t* vm, Opcode op, param_t param)
{
  assert(vm);

  switch (op)
    {
    case OP_PUSH: {
      if (vm->top_frame->sp + 1 >= RZ_STACK_LIMIT)
        {
          fprintf(stderr, "Stack overflow\n");
          abort();
        }

      value_t* val = (value_t*) vm->top_frame->program->values.data[param];
      vm_push(vm, val);
      vm->top_frame->pc++;
    } break;

    case OP_ASSERT: {
      value_t* value = vm_pop(vm);

      if (value->type->kind != TYPE_BOOL)
        {
          vm_ensure_type(vm, value, TYPE_BOOL);

          vm->top_frame->pc++;
          break;
        }

      if (!value->value.bool)
        {
          fprintf(stderr, "\33[31mASSERT\33[0m[:%d] assertion failed\n",
                  value->line);
          return -1;
        }

      vm_push(vm, value);
      vm->top_frame->pc++;

    } break;

    case OP_NE:
    case OP_EQ: {
      value_t* rhs = vm_pop(vm);
      value_t* lhs = vm_pop(vm);

      int same_type = lhs->type->kind == rhs->type->kind;
      int eq = value_eq(lhs, rhs);

      value_t* res = tysy_new_bool(vm->tysy,
                                   (op == OP_EQ
                                    ? (same_type && eq)
                                    : (!same_type || !eq)),
                                   rhs->line);

      vm_push_new(vm, res);

      vm->top_frame->pc++;
    } break;

    case OP_LT:
    case OP_LE:
    case OP_GT:
    case OP_GE: {
      value_t* rhs = vm_pop(vm);
      value_t* lhs = vm_pop(vm);

      vm_ensure_type(vm, lhs, TYPE_NUM);
      vm_ensure_type(vm, rhs, TYPE_NUM);

      int val = 0;

      switch (op)
        {
        case OP_LT: val = lhs->value.num < rhs->value.num; break;
        case OP_LE: val = lhs->value.num <= rhs->value.num; break;
        case OP_GT: val = lhs->value.num > rhs->value.num; break;
        case OP_GE: val = lhs->value.num >= rhs->value.num; break;
        default: break;
        }

      value_t* res = tysy_new_bool(vm->tysy, val, lhs->line);
      vm_push_new(vm, res);

      vm->top_frame->pc++;
    } break;

    case OP_ADD:
    case OP_SUB:
    case OP_MUL:
    case OP_DIV:
    case OP_MODULO:
    case OP_POW: {
      value_t* rhs = vm_pop(vm);
      value_t* lhs = vm_pop(vm);

      vm_ensure_type(vm, lhs, TYPE_NUM);
      vm_ensure_type(vm, rhs, TYPE_NUM);

      double val = 0;

      switch (op)
        {
        case OP_ADD: val = lhs->value.num + rhs->value.num; break;
        case OP_SUB: val = lhs->value.num - rhs->value.num; break;
        case OP_MUL: val = lhs->value.num * rhs->value.num; break;
        case OP_DIV: val = lhs->value.num / rhs->value.num; break;
        case OP_MODULO: val = fmod(lhs->value.num, rhs->value.num); break;
        case OP_POW: val = powf(lhs->value.num, rhs->value.num); break;
        default: assert(0); break;
        }

      value_t* res = tysy_new_num(vm->tysy, val, lhs->line);
      vm_push_new(vm, res);

      vm->top_frame->pc++;
    } break;

    case OP_STRCAT: {
      value_t* rhs = vm_pop(vm);
      value_t* lhs = vm_pop(vm);

      vm_ensure_type(vm, lhs, TYPE_STR);
      vm_ensure_type(vm, rhs, TYPE_STR);

      str_t res;
      str_init(&res);
      str_append(&res, lhs->value.str);
      str_append(&res, rhs->value.str);

      value_t* value = tysy_new_str(vm->tysy, res.data, lhs->line);
      str_free(&res);

      vm_push_new(vm, value);

      vm->top_frame->pc++;
    } break;

    case OP_STRDUP: {
      value_t* rhs = vm_pop(vm);
      value_t* lhs = vm_pop(vm);

      if (lhs->type->kind != TYPE_NUM)
        {
          value_t* tmp = lhs;
          lhs = rhs;
          rhs = tmp;
        }

      vm_ensure_type(vm, lhs, TYPE_NUM);
      vm_ensure_type(vm, rhs, TYPE_STR);

      str_t res;
      str_init(&res);

      for (int i=0; i<(int) lhs->value.num; i++)
        {
          str_append(&res, rhs->value.str);
        }

      value_t* value = tysy_new_str(vm->tysy, res.data, lhs->line);
      str_free(&res);

      vm_push_new(vm, value);

      vm->top_frame->pc++;
    } break;

    case OP_USUB: {
      value_t* lhs = vm_pop(vm);

      vm_ensure_type(vm, lhs, TYPE_NUM);

      double val = -lhs->value.num;

      value_t* res = tysy_new_num(vm->tysy, val, lhs->line);
      vm_push_new(vm, res);

      vm->top_frame->pc++;
    } break;

    case OP_NOT: {
      value_t* lhs = vm_pop(vm);
      vm_ensure_type(vm, lhs, TYPE_BOOL);

      int val = !lhs->value.bool;

      value_t* res = tysy_new_bool(vm->tysy, val, lhs->line);
      vm_push_new(vm, res);

      vm->top_frame->pc++;
    } break;

    case OP_BRT:
    case OP_BRF: {
      value_t* value = vm_pop(vm);

      vm_ensure_type(vm, value, TYPE_BOOL);

      if (op == OP_BRT && value->value.bool)
        {
          vm->top_frame->pc = param;
        }
      else if (op == OP_BRF && !value->value.bool)
        {
          vm->top_frame->pc = param;
        }
      else
        {
          vm->top_frame->pc++;
        }

    } break;

    case OP_BR: {
      vm->top_frame->pc = param;
    } break;

    case OP_LOAD: {
      local_t* local = locals_try_load(vm->top_frame->locals, param);

      if (!local && vm->top_frame->fun)
        {
          fun_t* fun = vm->top_frame->fun;
          closure_entry_t* e = fun_try_find_closure(fun, param);

          if (e)
            {
              vm_push(vm, e->value);
              vm->top_frame->pc++;
              break;
            }
        }

      if (!local)
        {
          local = locals_try_load(&vm->locals, param);
        }

      if (!local)
        {
          char msg[RZ_STR_LIMIT];

          snprintf(msg, RZ_STR_LIMIT, "Cannot load local variable '%d'.",
                   param);

          if (vm->top_frame->sp == 0)
            {
              err_fatal(vm->err, msg, -1);
              err_dump(vm->err);
              abort();
            }
          else
            {
              value_t* val = vm->top_frame->stack[vm->top_frame->sp - 1];
              int line = val->line;

              err_fatal(vm->err, msg, line);
              err_dump(vm->err);
              abort();
            }
        }
      else
        {
          assert(local->addr < vm->top_frame->sp);
          vm_push(vm, vm->top_frame->stack[local->addr]);
        }

      vm->top_frame->pc++;
    } break;

    case OP_STORE: {
      assert(vm->top_frame->sp > 0);

      if (vm->top_frame->fun)
        {
          fun_t* fun = vm->top_frame->fun;

          closure_entry_t* closure = fun_try_find_closure(fun, param);

          if (closure)
            {
              value_t* value = vm->top_frame->stack[vm->top_frame->sp - 1];
              value_free(closure->value);
              free(closure->value);
              closure->value = value_new_clone(value);
              vm->top_frame->pc++;
              break;
            }
        }

      locals_store(vm->top_frame->locals, param, vm->top_frame->sp - 1);
      vm->top_frame->pc++;
    } break;

    case OP_MKFUN: {
      value_t* value = value_new_clone(vm_pop(vm));

      assert(value->type->kind == TYPE_FUN);
      size_t addr = heap_alloc(&vm->heap, value);

      value_t* ref = tysy_new_ref(vm->tysy, addr, value->line);
      vm_push_new(vm, ref);

      frame_t* prev = (frame_t*) vm->top_frame->prev;
      locals_t* loc = &vm->locals;

      assert(value->type->kind == TYPE_FUN);

      fun_t* fun = value->value.fun;
      frame_t* frame = vm->top_frame;

      if (vm->top_frame->fun)
        {
          loc = (locals_t*) vm->top_frame->fun->locals;
        }
      else if (prev && prev->fun)
        {
          loc = (locals_t*) prev->fun->locals;
          frame = prev;
        }
      else if (prev)
        {
          loc = prev->locals;
          frame = prev;
        }

      if (loc)
        {
          for (size_t i=0; i<loc->size; i++)
            {
              int id = frame->locals->data[i]->id;
              value_t* loc_val = frame->stack[loc->data[i]->addr];

              fun_capture(fun, id, loc_val);
            }
        }

      vm->top_frame->pc++;
    } break;

    case OP_DEREF: {
      value_t* value = vm_pop(vm);

      assert(value->type->kind == TYPE_REF);

      size_t addr = value->value.ref;

      vm_push(vm, heap_deref(&vm->heap, addr));
      vm->top_frame->pc++;
    } break;

    case OP_CALL: {
      size_t const ARG_SZ = param;
      value_t* args[ARG_SZ];

      value_t* fun_ref = vm_pop(vm);

      for (size_t i=0; i<ARG_SZ; i++)
        {
          value_t* val = vm_pop(vm);
          args[i] = val;
        }

      value_t* fun_val = heap_deref(&vm->heap, fun_ref->value.ref);
      assert(fun_val);

      assert(fun_val->type->kind == TYPE_FUN);

      assert(fun_val->value.fun);
      fun_t* fun = fun_val->value.fun;

      vm->top_frame->pc++;
      vm_frame_push(vm, fun);
      vm->top_frame->fun = fun;

      vm_push(vm, fun_ref);
      locals_store(vm->top_frame->locals, fun->base, vm->top_frame->sp - 1);

      for (size_t i=0; i<ARG_SZ; i++)
        {
          value_t* arg = args[i];
          size_t addr = fun->arg_base + (ARG_SZ - 1 - i);

          vm_push(vm, arg);

          locals_store(vm->top_frame->locals,
                       addr,
                       vm->top_frame->sp - 1);
        }


    } break;

    case OP_RET: {
      frame_t* frame = (frame_t*) vm->top_frame;
      frame_t* prev = (frame_t*) vm->top_frame->prev;

      value_t* ret = frame->stack[frame->sp - 1];
      prev->stack[prev->sp] = ret;
      prev->sp++;

      for (size_t i=0; i<frame->alloc.size; i++)
        {
          if (frame->alloc.data[i] == ret)
            {
              frame->alloc.data[i] = NULL;
              vm_push_alloc(prev, ret);
            }
        }

      vm_frame_pop(vm);
    } break;

    default: {
      fprintf(stderr, "Cannot execute unknown opcode '%s'.\n",
              OpcodeStr[op]);
      abort();
    };
    }

  return 0;
}

void vm_ensure_type(vm_t* vm, value_t* value, TypeKind want)
{
  assert(vm);
  assert(value);

  TypeKind got = value->type->kind;
  int line = value->line;

  if (got != want)
    {
      char msg[RZ_STR_LIMIT];
      snprintf(msg, RZ_STR_LIMIT,
               "type mismatch: %s expected, got %s.",
               TypeKindStr[want] + strlen("TYPE_"),
               TypeKindStr[got] + strlen("TYPE_"));

      err_fatal(vm->err, msg, line);
      err_dump(vm->err);
    }
}

void vm_push_alloc(frame_t* frame, value_t* value)
{
  assert(frame);
  assert(value);

  if (frame->alloc.cap == 0)
    {
      frame->alloc.cap = 2;
      frame->alloc.data = malloc(sizeof(value_t*) * frame->alloc.cap);
    }

  if (frame->alloc.size >= frame->alloc.cap)
    {
      frame->alloc.cap *= 2;
      frame->alloc.data = realloc(frame->alloc.data,
                               sizeof(value_t*) * frame->alloc.cap);
    }

  frame->alloc.data[frame->alloc.size] = value;
  frame->alloc.size++;
}

void vm_clear_alloc(frame_t* frame)
{
  assert(frame);
  for (size_t i=0; i<frame->alloc.size; i++)
    {
      value_t* val = frame->alloc.data[i];

      if (val)
        {
          value_free(val);
          free(val);
        }
    }

  free(frame->alloc.data);
  frame->alloc.data = NULL;
}