firebird

defmodule Firebird.WasmModules.Physics do
  Module.register_attribute(__MODULE__, :wasm, accumulate: true)

  @moduledoc """
  Simple physics calculations compiled to WebAssembly.

  Demonstrates integer-based physics computations. Uses scaled integers
  (multiply by 1000) for fixed-point arithmetic since the WASM target
  only supports integers and floats.
  """

  @wasm true
  def distance(velocity, time), do: velocity * time

  @wasm true
  def kinetic_energy(mass, velocity) do
    # KE = 1/2 * m * v^2 (returns 2x for integer math)
    mass * velocity * velocity
  end

  @wasm true
  def gravitational_force(m1, m2, r) do
    # F ∝ m1 * m2 / r^2 (simplified, no G constant)
    div(m1 * m2, r * r)
  end

  @wasm true
  def projectile_range(v0, angle_deg) do
    # Simplified: range = v0^2 * sin(2*angle) / g
    # For 45 degrees (optimal): range = v0^2 / g
    # Using g = 10 for simplicity
    if angle_deg == 45 do
      div(v0 * v0, 10)
    else
      # Approximate for other angles
      div(v0 * v0 * angle_deg * (90 - angle_deg), 10 * 45 * 45)
    end
  end

  @wasm true
  def momentum(mass, velocity), do: mass * velocity

  @wasm true
  def acceleration(force, mass), do: div(force, mass)

  @wasm true
  def work(force, displacement), do: force * displacement

  @wasm true
  def manhattan_distance(x1, y1, x2, y2) do
    abs_diff(x1, x2) + abs_diff(y1, y2)
  end

  @wasm true
  def abs_diff(a, b) do
    if a >= b do
      a - b
    else
      b - a
    end
  end
end