From dd3c6c5e594291a8c5f0d30c3e84208b265fb2f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B8ren=20Siersted=20Mikkelsen?= <sami@wisehome.dk>
Date: Fri, 11 Apr 2025 10:08:44 +0200
Subject: [PATCH] feat: add JSON encoding support for Quantity

- implement Jason.Encoder for Quantity to allow JSON encoding
- add Jason as a dependency in mix.exs (it is part of mix already)
---
 lib/quantity.ex        | 11 ++++++++++-
 mix.exs                |  1 +
 test/quantity_test.exs |  4 ++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/quantity.ex b/lib/quantity.ex
index 9d2e131..b81c198 100644
--- a/lib/quantity.ex
+++ b/lib/quantity.ex
@@ -146,7 +146,7 @@ defmodule Quantity do
 
   @doc """
   Encodes the quantity as a string. The result is parsable with parse/1
-  If the exponent is positive, encode usinge the "raw" format to preserve precision
+  If the exponent is positive, encode using the "raw" format to preserve precision
 
   iex> Quantity.new(42, -1, "db") |> Quantity.to_string()
   "4.2 db"
@@ -351,6 +351,15 @@ defmodule Quantity do
     end
   end
 
+  defimpl Jason.Encoder do
+    @impl Jason.Encoder
+    def encode(value, opts) do
+      value
+      |> Quantity.to_string()
+      |> Jason.Encode.string(opts)
+    end
+  end
+
   # Normalizes unit to a standard form:
   # * Shorten unit as much as possible
   # * At most one :div (with possibly many :mults on each side)
diff --git a/mix.exs b/mix.exs
index 3ffc5e8..42e5a75 100644
--- a/mix.exs
+++ b/mix.exs
@@ -36,6 +36,7 @@ defmodule Quantity.MixProject do
     [
       # Decimal
       {:decimal, "~> 2.0"},
+      {:jason, "~> 1.4"},
 
       # Documentation
       {:ex_doc, "~> 0.21", only: :dev, runtime: false},
diff --git a/test/quantity_test.exs b/test/quantity_test.exs
index 6c8a934..c708770 100644
--- a/test/quantity_test.exs
+++ b/test/quantity_test.exs
@@ -55,6 +55,10 @@ defmodule QuantityTest do
     assert Quantity.to_string(~Q[42]) == "42"
   end
 
+  test "encode to json from map" do
+    assert %{quantity: ~Q[12.45 DKK]} |> Jason.encode!() == ~S|{"quantity":"12.45 DKK"}|
+  end
+
   test "for non-number decimals" do
     ["inf", "-inf", "nan"]
     |> Enum.each(fn not_number ->