defmodule WaspVM.Executor do
  alias WaspVM.Frame
  alias WaspVM.Memory
  alias WaspVM.HostFunction.API
  use Bitwise
  require Logger
  require IEx
  alias Decimal, as: D

  @moduledoc false

  # Reference for tests being used: https://github.com/WebAssembly/wabt/tree/master/test

  def create_frame_and_execute(vm, addr, gas_limit, opts, gas \\ 0, stack \\ []) do
    case elem(vm.store.funcs, addr) do
      {{inputs, _outputs}, module_ref, instr, locals} ->
        {args, stack} = Enum.split(stack, tuple_size(inputs))

        %{^module_ref => module} = vm.modules

        frame = %Frame{
          module: module,
          instructions: instr,
          locals: List.to_tuple(args ++ locals),
          gas_limit: gas_limit
        }

        total_instr = map_size(instr)

        execute(frame, vm, gas, stack, total_instr, gas_limit, opts)
      {:hostfunc, {inputs, _outputs}, mname, fname, module_ref} ->
        # TODO: How should we handle gas for host functions? Does gas price get passed in?
        # Do we default to a gas value?

        {args, stack} = Enum.split(stack, tuple_size(inputs))

        %{^module_ref => module} = vm.modules

        func =
          module.resolved_imports
          |> Map.get(mname)
          |> Map.get(fname)

        # Start an API agent that isolates VM state until the host function
        # finishes running.
        {:ok, ctx} = API.start_link(vm)

        return_val = apply(func, [ctx, args])

        # Get updated state from the API agent
        vm = API.state(ctx)

        # Kill the API agent now that it's served it's purpose
        API.stop(ctx)

        # TODO: Gas needs to be updated based on the comment above instead of
        # just getting passed through
        if !is_number(return_val) do
          {vm, gas, stack}
        else
          {vm, gas, [return_val | stack]}
        end
    end
  end

  # What happens is we pass in the main limit for the gas & the gas_limit,
  # then every iteration before we procedd we check the gas limit and the
  # returned op_gas (gas accumulted from executing that opcode)
  # Example List Options [trace: false]
  def execute(frame, vm, gas, stack, total_instr, gas_limit, opts, next_instr \\ 0)
  def execute(_frame, vm, gas, stack, _total, gas_limit, opts, _next) when gas_limit != :infinity and gas > gas_limit, do: IEx.pry #{:error, :reached_gas_limit}
  def execute(_frame, vm, gas, stack, total_instr, _gas_limit, _opts, next_instr) when next_instr >= total_instr or next_instr < 0, do: {vm, gas, stack}
  def execute(frame, vm, gas, stack, total_instr, gas_limit, opts, next_instr) do
    %{^next_instr => instr} = frame.instructions

    {{frame, vm, next_instr}, gas, stack} = instruction(instr, frame, vm, gas, stack, next_instr, opts)

    if opts[:trace] do
      write_to_file(instr, gas)
    end

    execute(frame, vm, gas, stack, total_instr, gas_limit, opts, next_instr + 1)
  end

  def instruction(opcode, f, v, g, s, n, opts) when is_atom(opcode), do: exec_inst({f, v, n}, g, s, opts, opcode)
  def instruction(opcode, f, v, g, s, n, opts) when is_tuple(opcode), do: exec_inst({f, v, n}, g, s, opts, opcode)

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_add), do: {ctx, gas + 3, [(a + b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_sub), do: {ctx, gas + 3, [a - b | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_mul), do: {ctx, gas + 5, [a * b | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_add), do: {ctx, gas + 3, [a + b | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_sub), do: {ctx, gas + 3, [a - b | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_mul), do: {ctx, gas + 5, [a * b | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_le_s) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_ge_s) when a >= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_lt_u) when a < b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_lt_u) when a < b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_gt_u) when a > b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_gt_u) when a > b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_le_u) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_le_u) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_ge_u) when a >= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_ge_u) when a >= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_eq) when a === b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_eq) when a === b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_ne) when a !== b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_eq) when a === b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_eq) when a === b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_ne) when a !== b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_lt) when a < b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_lt) when a < b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_le) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_le) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_ge) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_ge) when a <= b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_gt) when a > b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_gt) when a > b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_ne) when a !== b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_ne) when a !== b, do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_add), do: {ctx, gas + 3, [float_point_op(a + b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_sub), do: {ctx, gas + 3, [float_point_op(b - a) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_mul), do: {ctx, gas + 5, [float_point_op(a * b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_add), do: {ctx, gas + 3, [float_point_op(a + b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_sub), do: {ctx, gas + 3, [float_point_op(b - a) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_mul), do: {ctx, gas + 5, [float_point_op(a * b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_min), do: {ctx, gas + 5, [float_point_op(min(a, b)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_max), do: {ctx, gas + 5, [float_point_op(max(a, b)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_min), do: {ctx, gas + 5, [float_point_op(min(a, b)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_max), do: {ctx, gas + 5, [float_point_op(max(a, b)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_copysign), do: {ctx, gas + 5, [float_point_op(copysign(b, a)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f64_copysign), do: {ctx, gas + 5, [float_point_op(copysign(b, a)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :f32_div), do: {ctx, gas + 5, [float_point_op(a / b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_rotl), do: {ctx, gas + 5, [rotl(b, a) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_rotr), do: {ctx, gas + 5, [rotr(b, a) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_and), do: {ctx, gas + 3, [band(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_or), do: {ctx, gas + 3, [bor(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_xor), do: {ctx, gas + 3, [bxor(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_and), do: {ctx, gas + 3, [band(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_or), do: {ctx, gas + 3, [bor(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_xor), do: {ctx, gas + 3, [bxor(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_shl), do: {ctx, gas + 5, [bsl(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_shl), do: {ctx, gas + 5, [bsl(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_shr_u), do: {ctx, gas + 5, [log_shr(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_shr_u), do: {ctx, gas + 5, [bsr(a, b) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_shr_s), do: {ctx, gas + 5, [bsr(a, Integer.mod(b, 32)) | stack]}
  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_shr_s), do: {ctx, gas + 5, [bsr(a, Integer.mod(b, 64)) | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_eq), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_eq), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_ne), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_le_s), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_ge_s), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_lt_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_lt_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_gt_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_gt_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_le_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_le_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_ge_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i64_ge_u), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_eq), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_eq), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :i32_ne), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_lt), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_lt), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_le) , do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_le), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_ge), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_ge), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_gt), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_gt), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f32_ne), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [_, _ | stack], _opts, :f64_ne), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [0 | stack], _opts, :i32_eqz), do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [_ | stack], _opts, :i32_eqz), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [0 | stack], _opts, :i64_eqz), do: {ctx, gas + 3, [1 | stack]}
  defp exec_inst(ctx, gas, [_ | stack], _opts, :i64_eqz), do: {ctx, gas + 3, [0 | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_nearest), do: {ctx, gas + 5, [round(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_nearest), do: {ctx, gas + 5, [round(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_trunc), do: {ctx, gas + 5, [trunc(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_trunc), do: {ctx, gas + 5, [trunc(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_floor), do: {ctx, gas + 5, [Float.floor(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_floor), do: {ctx, gas + 5, [Float.floor(a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_neg), do: {ctx, gas + 5, [float_point_op(a * -1) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_neg), do: {ctx, gas + 5, [float_point_op(a * -1) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_abs), do: {ctx, gas + 5, [float_point_op(abs(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_abs), do: {ctx, gas + 5, [float_point_op(abs(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_sqrt), do: {ctx, gas + 5, [float_point_op(:math.sqrt(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_sqrt), do: {ctx, gas + 5, [float_point_op(:math.sqrt(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_popcnt), do: {ctx, gas + 5, [popcnt(a, 32) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_popcnt), do: {ctx, gas + 5, [popcnt(a, 64) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_ceil), do: {ctx, gas + 5, [float_point_op(Float.ceil(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_ceil), do: {ctx, gas + 5, [float_point_op(Float.ceil(a)) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_wrap_i64), do: {ctx, gas + 5, [bin_wrap(:i64, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_trunc_u_f32), do: {ctx, gas + 5, [bin_trunc(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_trunc_s_f32), do: {ctx, gas + 5, [bin_trunc(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_trunc_u_f64), do: {ctx, gas + 5, [bin_trunc(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_trunc_s_f64), do: {ctx, gas + 5, [bin_trunc(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_trunc_u_f32), do: {ctx, gas + 5, [bin_trunc(:f32, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_trunc_s_f32), do: {ctx, gas + 5, [bin_trunc(:f32, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_trunc_u_f64), do: {ctx, gas + 5, [bin_trunc(:f64, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_trunc_s_f64), do: {ctx, gas + 5, [bin_trunc(:f64, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_convert_s_i32), do: {ctx, gas + 5, [float_point_op(a * 1.000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_convert_u_i32), do: {ctx, gas + 5, [float_point_op(band(a, 0xFFFFFFFF) * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_convert_s_i64), do: {ctx, gas + 5, [float_point_op(a * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_convert_u_i64), do: {ctx, gas + 5, [float_point_op(band(a, 0xFFFFFFFFFFFFFF) * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_convert_s_i64), do: {ctx, gas + 5, [float_point_op(a * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_convert_u_i64), do: {ctx, gas + 5, [float_point_op(band(a, 0xFFFFFFFFFFFFFF) * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_convert_s_i32), do: {ctx, gas + 5, [float_point_op(a * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_convert_u_i32), do: {ctx, gas + 5, [float_point_op(band(a, 0xFFFFFFFF) * 1.000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_extend_u_i32), do: {ctx, gas + 5, [round(:math.pow(2, 32) + a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_extend_s_i32), do: {ctx, gas + 5, [band(a, 0xFFFFFFFFFFFFFFFF) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_demote_f64), do: {ctx, gas + 5, [float_demote(a * 1.0000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_promote_f32), do: {ctx, gas + 5, [float_promote(a * 1.0000000) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_reinterpret_f32), do: {ctx, gas + 5, [reint(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_reinterpret_f32), do: {ctx, gas + 5, [reint(:f32, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f64_reinterpret_i64), do: {ctx, gas + 5, [reint(:f64, :i64, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :f32_reinterpret_i32), do: {ctx, gas + 5, [reint(:f32, :i32, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_clz), do: {ctx, gas + 5, [count_bits(:l, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_clz), do: {ctx, gas + 5, [count_bits(:l, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i32_ctz), do: {ctx, gas + 5, [count_bits(:t, a) | stack]}
  defp exec_inst(ctx, gas, [a | stack], _opts, :i64_ctz), do: {ctx, gas + 5, [count_bits(:t, a) | stack]}
  defp exec_inst(ctx, gas, [0, b, _ | stack], _opts, :select), do: {ctx, gas, [b | stack]}
  defp exec_inst(ctx, gas, [1, _ | stack], _opts, :select), do: {ctx, gas, stack}
  defp exec_inst(ctx, gas, [1 | stack], _opts, {:br_if, label_idx}), do: break_to(ctx, gas, stack, label_idx)
  defp exec_inst(ctx, gas, [_ | stack], _opts, {:br_if, _label_idx}), do: {ctx, gas, stack}
  defp exec_inst(ctx, gas, stack, _opts, {:i32_const, i32}), do: {ctx, gas + 3, [i32 | stack]}
  defp exec_inst(ctx, gas, stack, _opts, {:i64_const, i64}), do: {ctx, gas + 3, [i64 | stack]}
  defp exec_inst(ctx, gas, stack, _opts, {:f32_const, f32}), do: {ctx, gas + 3, [f32 | stack]}
  defp exec_inst(ctx, gas, stack, _opts, {:f64_const, f64}), do: {ctx, gas + 3, [f64 | stack]}
  defp exec_inst({_frame, vm, _n} = ctx, gas, stack, _opts, :current_memory),  do: {ctx, gas + 3, [length(vm.memory.pages) | stack]}
  defp exec_inst({frame, _vm, _n} = ctx, gas, stack, _opts, {:get_local, idx}), do: {ctx, gas + 3, [elem(frame.locals, idx) | stack]}
  defp exec_inst({_frame, vm, _n} = ctx, gas, stack, _opts, {:get_global, idx}), do: {ctx, gas + 3, [Enum.at(vm.globals, idx) | stack]}
  defp exec_inst(ctx, gas, [_ | stack], _opts, :drop), do: {ctx, gas, stack}
  defp exec_inst(ctx, gas, stack, _opts, {:br, label_idx}), do: break_to(ctx, gas, stack, label_idx)
  defp exec_inst({%{labels: []} = frame, vm, n}, gas, stack, _opts, :end), do: {{frame, vm, n}, gas, stack}
  defp exec_inst({frame, vm, _n}, gas, stack, _opts, {:else, end_idx}), do: {{frame, vm, end_idx}, gas, stack}
  defp exec_inst({frame, vm, _n}, gas, stack, _opts, :return), do: {{frame, vm, -10}, gas, stack}
  defp exec_inst(ctx, gas, stack, _opts, :unreachable), do: {ctx, gas, stack}
  defp exec_inst(ctx, gas, stack, _opts, :nop), do: {ctx, gas, stack}
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i32_div_u), do: trap("Divide by zero in i32.div_u")
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i32_rem_s), do: trap("Divide by zero in i32.rem_s")
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i64_rem_s), do: trap("Divide by zero in i64.rem_s")
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i64_div_u), do: trap("Divide by zero in i64.div_u")
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i32_rem_u), do: trap("Divide by zero in i32.rem_u")
  defp exec_inst(_ctx, _gas, [0 | _], _opts, :i64_rem_u), do: trap("Divide by zero in i64.rem_u")

  defp exec_inst({frame, vm, n}, gas, [1 | stack], _opts, {:if, _type, _else_idx, end_idx}) do
    labels = [{n, end_idx} | frame.labels]
    snapshots = [stack | frame.snapshots]

    {{Map.merge(frame, %{labels: labels, snapshots: snapshots}), vm, n}, gas + 2, stack}
  end

  defp exec_inst({frame, vm, _n}, gas, [_val | stack], _opts, {:if, _type, else_idx, end_idx}) do
    next_instr = if else_idx != :none, do: else_idx, else: end_idx
    {{frame, vm, next_instr}, gas + 2, stack}
  end

  defp exec_inst({frame, vm, n}, gas, stack, _opts, :end) do
    [corresponding_label | labels] = frame.labels

    case corresponding_label do
      {:loop, _instr} -> {{Map.put(frame, :labels, labels), vm, n}, gas, stack}
      _ -> {{frame, vm, n}, gas, stack}
    end
  end

  defp exec_inst({frame, vm, n}, gas, stack, opts, {:call, funcidx}) do
    %{^funcidx => func_addr} = frame.module.funcaddrs

    # TODO: Maybe this shouldn't pass the existing stack in?
    {vm, gas, stack} = create_frame_and_execute(vm, func_addr, frame.gas_limit, opts, gas, stack)

    {{frame, vm, n}, gas, stack}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_div_s) do
    j1 = sign_value(a, 32)
    j2 = sign_value(b, 32)

    if j2 == 0 do
      trap("Divide by zero in i32.div_s")
    else
      if j1 / j2 == 2147483648 do
        trap("Out of bounds in i32.div_s")
      else
        res = trunc(j1 / j2)
        ans = sign_value(res, 32)

        {ctx, gas + 5, [ans | stack]}
      end
    end
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_div_s) do
    j1 = sign_value(a, 64)
    j2 = sign_value(b, 64)

    if j2 == 0 do
      trap("Divide by zero in i64.div_s")
    else
      if j1 / j2 == 9.223372036854776e18 do
        trap("Out of bounds in i64.div_s")
      else
        res = trunc(j1 / j2)
        ans = sign_value(res, 64)

        {ctx, gas + 5, [ans | stack]}
      end
    end
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_div_u) do
    rem = a - (b * trunc(a / b))
    result = Integer.floor_div((a - rem), b)
    {ctx, gas + 5, [result | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_rem_s) do
    j1 = sign_value(a, 32)
    j2 = sign_value(b, 32)

    rem = j1 - (j2 * trunc(j1 / j2))

    {ctx, gas + 5, [rem | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_rem_s) do
    j1 = sign_value(a, 64)
    j2 = sign_value(b, 64)

    rem = j1 - (j2 * trunc(j1 / j2))
    res = 1.8446744073709552e19 - rem

    {ctx, gas + 5, [res | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_div_u) do
    rem = a - (b * trunc(a / b))
    result = Integer.floor_div((a - rem), b)
    {ctx, gas + 5, [result | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_rem_u) do
    c =
      a
      |> Kernel./(b)
      |> trunc()
      |> Kernel.*(b)

    res = a - c

    {ctx, gas + 5, [res | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_rem_u) do
    c =
      a
      |> Kernel./(b)
      |> trunc()
      |> Kernel.*(b)

    res = a - c

    {ctx, gas + 5, [res | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_le_s) do
    val = if sign_value(a, 32) <= sign_value(b, 32), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_ge_s) do
    val = if sign_value(a, 32) >= sign_value(b, 32), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_lt_s) do
    val = if sign_value(a, 32) < sign_value(b, 32), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_lt_s) do
    val = if sign_value(a, 64) < sign_value(b, 64), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i32_gt_s) do
    val = if sign_value(a, 32) > sign_value(b, 32), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst(ctx, gas, [b, a | stack], _opts, :i64_gt_s) do
    val = if sign_value(a, 64) > sign_value(b, 64), do: 1, else: 0
    {ctx, gas + 3, [val | stack]}
  end

  defp exec_inst({frame, vm, n}, gas, [value | stack], _opts, {:set_global, idx}) do
    globals = List.replace_at(vm.globals, idx, value)

    {{frame, Map.put(vm, :globals, globals), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value | stack], _opts, {:set_local, idx}) do
    locals = put_elem(frame.locals, idx, value)

    {{Map.put(frame, :locals, locals), vm, n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value | _] = stack, _opts, {:tee_local, idx}) do
    locals = put_elem(frame.locals, idx, value)

    {{Map.put(frame, :locals, locals), vm, n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [pages | stack], _opts, :grow_memory) do
    {{frame, Map.put(vm, :memory, Memory.grow(vm.memory, pages)), n}, gas + 3, [length(vm.memory) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i32_load8_s, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i8::8>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 1)

    {ctx, gas + 5, [bin_wrap_signed(:i32, :i8, i8) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i32_load16_s, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i16::16>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 2)

    {ctx, gas + 5, [bin_wrap_signed(:i32, :i16, i16) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load8_s, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i8::8>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 1)

    {ctx, gas + 5, [bin_wrap_signed(:i64, :i8, i8) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load16_s, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i16::16>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 2)

    {ctx, gas + 5, [bin_wrap_signed(:i64, :i16, i16) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load32_s, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i32::32>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 4)

    {ctx, gas + 5, [bin_wrap_signed(:i64, :i32, i32) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i32_load8_u, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i8::8>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 1)

    {ctx, gas + 5, [bin_wrap_unsigned(:i32, :i8, abs(i8)) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i32_load16_u, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i16::16>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 2)

    {ctx, gas + 5, [bin_wrap_unsigned(:i32, :i16, abs(i16)) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load8_u, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i8::8>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 1)

    {ctx, gas + 5, [bin_wrap_unsigned(:i64, :i8, abs(i8)) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load16_u, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i16::16>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 2)

    {ctx, gas + 5, [bin_wrap_unsigned(:i64, :i16, abs(i16)) | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load32_u, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i32::32>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 4)

    {ctx, gas + 5, [bin_wrap_unsigned(:i64, :i32, abs(i32)) | stack]}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i32_store, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, <<value::32>>)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i32_store8, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, <<wrap_to_value(:i8, value)::8>>)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i32_store16, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    value =
      <<wrap_to_value(:i16, value)::16>>
      |> Binary.to_list
      |> Enum.reverse()
      |> Binary.from_list

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, value)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i64_store8, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)
    value = <<wrap_to_value(:i8, value)::8>>

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, value)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i64_store16, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    value =
      <<wrap_to_value(:i16, value)::16>>
      |> Binary.to_list
      |> Enum.reverse()
      |> Binary.from_list

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, value)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 5, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i64_store32, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    value =
      <<wrap_to_value(:i32, value)::32>>
      |> Binary.to_list
      |> Enum.reverse()
      |> Binary.from_list

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, value)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 5, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:i64_store, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, <<value::64>>)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:f32_store, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, <<value::32>>)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, n}, gas, [value, address | stack], _opts, {:f64_store, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    mem =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.put_at(address + offset, <<value::64>>)

    store_mems = List.replace_at(vm.store.mems, mem_addr, mem)
    store = Map.put(vm.store, :mems, store_mems)

    {{frame, Map.put(vm, :store, store), n}, gas + 3, stack}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i32_load, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i32::32>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 4)

    {ctx, gas + 3, [i32 | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:i64_load, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<i64::64>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 8)

    {ctx, gas + 3, [i64 | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:f32_load, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<f32::32-float>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 4)

    {ctx, gas + 3, [f32 | stack]}
  end

  defp exec_inst({frame, vm, _n} = ctx, gas, [address | stack], _opts, {:f64_load, _alignment, offset}) do
    mem_addr = hd(frame.module.memaddrs)

    <<f64::64-float>> =
      vm.store.mems
      |> Enum.at(mem_addr)
      |> Memory.get_at(address + offset, 8)

    {ctx, gas + 3, [f64 | stack]}
  end

  defp exec_inst({frame, vm, n}, gas, stack, _opts, {:loop, _result_type}) do
    labels = [{n, n} | frame.labels]
    snapshots = [stack | frame.snapshots]

    {{Map.merge(frame, %{labels: labels, snapshots: snapshots}), vm, n}, gas + 2, stack}
  end

  defp exec_inst({frame, vm, n}, gas, stack, _opts, {:block, _result_type, end_idx}) do
    labels = [{n, end_idx - 1} | frame.labels]
    snapshots = [stack | frame.snapshots]

    {{Map.merge(frame, %{labels: labels, snapshots: snapshots}), vm, n}, gas + 2, stack}
  end

  defp exec_inst({frame, vm, n}, gas, stack, _opts, :end) do
    [_ | labels] = frame.labels
    [_ | snapshots] = frame.snapshots

    {{Map.merge(frame, %{labels: labels, snapshots: snapshots}), vm, n}, gas + 2, stack}
  end

  defp exec_inst(ctx, gas, stack, opts, op) do
    IO.inspect op
    IEx.pry
  end

  defp break_to({frame, vm, _n}, gas, stack, label_idx) do
    {label_instr_idx, next_instr} = Enum.at(frame.labels, label_idx)
    snapshot = Enum.at(frame.snapshots, label_idx)

    %{^label_instr_idx => instr} = frame.instructions

    drop_changes =
      fn type ->
        if type != :no_res do
          [res | _] = stack
          [res | snapshot]
        else
          snapshot
        end
      end

    stack =
      case instr do
        {:loop, _} -> snapshot
        {:if, res_type, _, _} -> drop_changes.(res_type)
        {:block, res_type, _} -> drop_changes.(res_type)
      end

    {{frame, vm, next_instr}, gas + 2, stack}
  end

  # Reference https://lemire.me/blog/2017/05/29/unsigned-vs-signed-integer-arithmetic/
  defp reint(:f32, :i32, float), do: reint(float)
  defp reint(:f32, :i64, float), do: reint(float)
  defp reint(:f64, :i64, float), do: reint(float)
  defp reint(float) do
    float
    |> :erlang.float_to_binary()
    |> :binary.decode_unsigned()
  end

  defp sign_value(integer, n), do: sign_value(integer, n, :math.pow(2, 31), :math.pow(2, 32))
  defp sign_value(integer, _n, lower, _upper) when integer >= 0 and integer < lower, do: integer
  defp sign_value(integer, _n, lower, _upper) when integer < 0 and integer > -lower, do: integer
  defp sign_value(integer, _n, lower, upper) when integer > lower and integer < upper, do: :math.pow(2, 32) + integer
  defp sign_value(integer, _n, lower, upper) when integer > -lower and integer < -upper, do: :math.pow(2, 32) + integer

  defp popcnt(integer, 32), do: popcnt(<<integer::32>>)
  defp popcnt(integer, 64), do: popcnt(<<integer::64>>)
  defp popcnt(binary) do
    binary
    |> Binary.to_list()
    |> Enum.reject(& &1 == 0)
    |> Enum.count()
  end

  defp rotl(number, shift), do: (number <<< shift) ||| (number >>> (0x1F &&& (32 + ~~~(shift + 1)))) &&& ~~~(0xFFFFFFFF <<< shift)
  defp rotr(number, shift), do: (number >>> shift) ||| (number <<< (0x1F &&& (32 + ~~~(-shift + 1)))) &&& ~~~(0xFFFFFFFF <<< -shift)

  def float_point_op(number) do
    D.set_context(%D.Context{D.get_context | precision: 6})

    number
    |> :erlang.float_to_binary([decimals: 6])
    |> D.new()
  end

  def float_demote(number) do
    D.set_context(%D.Context{D.get_context | precision: 6})

    number * 10
    |> :erlang.float_to_binary([decimals: 6])
    |> D.new()
  end

  def float_promote(number) do
    D.set_context(%D.Context{D.get_context | precision: 6})

    number
    |> :erlang.float_to_binary([decimals: 6])
    |> D.new()
  end

  defp copysign(a, b) do
    a_truth =
      to_string(a)
      |> String.codepoints
      |> Enum.any?(&(&1 == "-"))

    b_truth =
      to_string(b)
      |> String.codepoints
      |> Enum.any?(&(&1 == "-"))

    if a_truth == true && b_truth == true || a_truth == false && b_truth == false  do
      a
    else
      if a_truth == true && b_truth == false || a_truth == false && b_truth == true do
        b * -1
      end
    end
  end

  defp trap(reason), do: raise "Runtime Error -- #{reason}"

  defp check_value([0, 0, 0, 0]), do: 4
  defp check_value([0, 0, 0, _]), do: 3
  defp check_value([0, 0, _, _]), do: 2
  defp check_value([0, _, _, _]), do: 1
  defp check_value(_), do: 0

  defp count_bits(:l, number) do
    <<number::32>>
    |> Binary.to_list
    |> check_value
  end

  defp count_bits(:t, number) do
    <<number::32>>
    |> Binary.to_list
    |> Enum.reverse
    |> check_value
  end

  defp wrap_to_value(:i8, integer), do: integer &&& 0xFF
  defp wrap_to_value(:i16, integer), do: integer &&& 0xFFFF
  defp wrap_to_value(:i32, integer), do: integer &&& 0xFFFFFFFF

  defp bin_wrap(:i64, :i32, integer) do
    <<integer::64>>
    |> Binary.to_list()
    |> Enum.reverse
    |> Binary.from_list
    |> :binary.decode_unsigned()
    |> Bitwise.band(0xFFFFFFFF)
  end

  defp bin_wrap(:i8, integer), do: :binary.decode_unsigned(<<integer::8>>)
  defp bin_wrap(:i16, integer), do: :binary.decode_unsigned(<<integer::16>>)
  defp bin_wrap(:i32, integer), do: :binary.decode_unsigned(<<integer::32>>)

  defp bin_wrap_signed(:i32, :i8, integer), do: bin_wrap(:i8, integer) &&& 0xFFFFFFFF
  defp bin_wrap_signed(:i32, :i16, integer), do: bin_wrap(:i16, integer) &&& 0xFFFFFFFF
  defp bin_wrap_signed(:i64, :i8, integer), do: bin_wrap(:i8, integer) &&& 0xFFFFFFFFFFFFFFFF
  defp bin_wrap_signed(:i64, :i16, integer), do: bin_wrap(:i16, integer) &&& 0xFFFFFFFFFFFFFFFF
  defp bin_wrap_signed(:i64, :i32, integer), do: bin_wrap(:i32, integer) &&& 0xFFFFFFFFFFFFFFFF

  defp bin_wrap_unsigned(:i32, :i8, integer), do: bin_wrap(:i8, integer) &&& 0xFF
  defp bin_wrap_unsigned(:i32, :i16, integer), do: bin_wrap(:i16, integer) &&& 0xFFFF
  defp bin_wrap_unsigned(:i64, :i8, integer), do: bin_wrap(:i8, integer) &&& 0xFFFF
  defp bin_wrap_unsigned(:i64, :i16, integer), do: bin_wrap(:i16, integer) &&& 0xFFFF
  defp bin_wrap_unsigned(:i64, :i32, integer), do: bin_wrap(:i32, integer) &&& 0xFFFFFFFF

  defp bin_trunc(:f32, :i32, float), do: round(float)
  defp bin_trunc(:f32, :i64, float), do: round(float)
  defp bin_trunc(:f64, :i64, float), do: round(float)

  defp log_shr(integer, shift) do
    bin =
      integer
      |> Integer.to_string(2)
      |> String.codepoints
      |> Enum.reverse
      |> Enum.drop((shift))
      |> Enum.map(fn str -> String.to_integer(str) end)

    bin_size = Enum.count(bin)
    target = 32 - bin_size - shift
    zero_leading_map = Enum.map(1..target, fn _ -> 1 end)

    Integer.undigits(zero_leading_map ++ bin, 2)
  end

  defp create_entry(instruction) when not is_tuple(instruction), do: to_string(instruction)
  defp create_entry({instruction, _variable}), do: create_entry(instruction)
  defp create_entry({:if, _rtype, _else_idx, _end_idx}), do: create_entry(:if)
  defp create_entry(other), do: create_entry("Trace not implemented for: #{inspect(other)}")

  defp write_to_file(instruction, gas) do
    './trace.log'
    |> Path.expand()
    |> Path.absname()
    |> File.write("#{create_entry(instruction)} #{gas}\n", [:append])
  end
end