From 7409e6b3117c7885edbb60911e47e4e8475accab Mon Sep 17 00:00:00 2001
From: Lumi Pakkanen <lumi.pakkanen@gmail.com>
Date: Mon, 13 May 2024 16:22:46 +0300
Subject: [PATCH] JSON serialize NaN and Infinity

ref #318
---
 src/__tests__/monzo.spec.ts | 16 +++++++++++++---
 src/monzo.ts                | 26 ++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/src/__tests__/monzo.spec.ts b/src/__tests__/monzo.spec.ts
index 7a05f2cb..6f344346 100644
--- a/src/__tests__/monzo.spec.ts
+++ b/src/__tests__/monzo.spec.ts
@@ -461,16 +461,18 @@ describe('JSON serialization', () => {
       3.5,
       TimeMonzo.fromFraction('81/80'),
       null,
+      new TimeReal(0, NaN),
+      new TimeReal(1, Infinity),
     ];
     const serialized = JSON.stringify(data);
     expect(serialized).toBe(
-      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null]'
+      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null,{"type":"TimeReal","timeExponent":0,"value":"NaN"},{"type":"TimeReal","timeExponent":1,"value":"Infinity"}]'
     );
   });
 
   it('can deserialize an array of primitives, fractions and monzos', () => {
     const serialized =
-      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null]';
+      '["Hello, world!",{"n":10,"d":7},{"type":"TimeReal","timeExponent":-1,"value":777},3.5,{"type":"TimeMonzo","timeExponent":{"n":0,"d":1},"primeExponents":[{"n":-4,"d":1},{"n":4,"d":1},{"n":-1,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1},{"n":0,"d":1}],"residual":{"n":1,"d":1}},null,{"type":"TimeReal","timeExponent":0,"value":"NaN"},{"type":"TimeReal","timeExponent":1,"value":"Infinity"}]';
     function reviver(key: string, value: any) {
       return TimeMonzo.reviver(
         key,
@@ -478,7 +480,7 @@ describe('JSON serialization', () => {
       );
     }
     const data = JSON.parse(serialized, reviver);
-    expect(data).toHaveLength(6);
+    expect(data).toHaveLength(8);
 
     expect(data[0]).toBe('Hello, world!');
 
@@ -495,5 +497,13 @@ describe('JSON serialization', () => {
     expect(data[4].toFraction().toFraction()).toBe('81/80');
 
     expect(data[5]).toBeNull();
+
+    expect(data[6]).toBeInstanceOf(TimeReal);
+    expect(data[6].timeExponent).toBe(0);
+    expect(data[6].value).toBeNaN();
+
+    expect(data[7]).toBeInstanceOf(TimeReal);
+    expect(data[7].timeExponent).toBe(1);
+    expect(data[7].value).toBe(Infinity);
   });
 });
diff --git a/src/monzo.ts b/src/monzo.ts
index 25dd03bd..cf071867 100644
--- a/src/monzo.ts
+++ b/src/monzo.ts
@@ -184,6 +184,10 @@ export class TimeReal {
     if (!value) {
       timeExponent = 0;
     }
+    // Checks for Infinity and NaN
+    if (!isFinite(timeExponent)) {
+      throw new Error('Time exponent must be finite.');
+    }
     this.timeExponent = timeExponent;
     this.value = value;
   }
@@ -233,7 +237,15 @@ export class TimeReal {
       value !== null &&
       value.type === 'TimeReal'
     ) {
-      return new TimeReal(value.timeExponent, value.value);
+      let v: number | string = value.value;
+      if (v === 'NaN') {
+        v = NaN;
+      } else if (v === 'Infinity') {
+        v = Infinity;
+      } else if (v === '-Infinity') {
+        v = -Infinity;
+      }
+      return new TimeReal(value.timeExponent, v as number);
     }
     return value;
   }
@@ -243,10 +255,20 @@ export class TimeReal {
    * @returns The serialized object with property `type` set to `'TimeReal'`.
    */
   toJSON() {
+    let value: number | string = this.value;
+    // JSON sure is a standard
+    if (isNaN(value)) {
+      value = 'NaN';
+    } else if (value === Infinity) {
+      value = 'Infinity';
+    } else if (value === -Infinity) {
+      value = '-Infinity';
+    }
+
     return {
       type: 'TimeReal',
       timeExponent: this.timeExponent,
-      value: this.value,
+      value,
     };
   }