From e30793b5be3646c31b68484593fa847e82d60fe9 Mon Sep 17 00:00:00 2001
From: Chris Wegrzyn <chris.wegrzyn@gmail.com>
Date: Thu, 23 May 2024 08:48:23 -0400
Subject: [PATCH] ProgressTrack: enforce upper/lower bound when using
 advancement methods (#77)

Fixes #64
---
 src/tracks/progress.test.ts |  4 ++++
 src/tracks/progress.ts      | 16 +++++++---------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/tracks/progress.test.ts b/src/tracks/progress.test.ts
index c0b1c312..bcdb674a 100644
--- a/src/tracks/progress.test.ts
+++ b/src/tracks/progress.test.ts
@@ -74,6 +74,10 @@ describe("ProgressTrack", () => {
     expect(track.advancedByTicks(10)).toBe(track);
   });
 
+  it("won't advance negatively below 0 ticks", () => {
+    expect(make({ progress: 1 }).advancedByTicks(-2).progress).toBe(0);
+  });
+
   it("won't advance past 40 ticks", () => {
     expect(make({ progress: 39 }).advancedByTicks(2).progress).toBe(40);
   });
diff --git a/src/tracks/progress.ts b/src/tracks/progress.ts
index b33ceb6d..add23550 100644
--- a/src/tracks/progress.ts
+++ b/src/tracks/progress.ts
@@ -164,26 +164,24 @@ export class ProgressTrack {
     return Math.ceil(this.ticksRemaining / this.ticksPerStep);
   }
 
+  /** Set the meter directly to a specific number of ticks, ensuring legal range for this meter. */
   withTicks(ticks: number): ProgressTrack {
-    const newProgress = Math.min(
-      this.unbounded ? Number.MAX_SAFE_INTEGER : MAX_TICKS,
-      ticks,
+    const newProgress = Math.max(
+      0,
+      Math.min(this.unbounded ? Number.MAX_SAFE_INTEGER : MAX_TICKS, ticks),
     );
     if (this.complete || newProgress === this.progress) return this;
     return new ProgressTrack({ ...this, progress: newProgress });
   }
 
+  /** Advance the meter by `steps`, ensuring legal range for this meter. */
   advanced(steps: number): ProgressTrack {
     return this.advancedByTicks(steps * this.ticksPerStep);
   }
 
+  /** Advance the meter by `ticks`, ensuring legal range for this meter. */
   advancedByTicks(ticks: number): ProgressTrack {
-    const newProgress = Math.min(
-      this.unbounded ? Number.MAX_SAFE_INTEGER : MAX_TICKS,
-      this.progress + ticks,
-    );
-    if (this.complete || newProgress === this.progress) return this;
-    return new ProgressTrack({ ...this, progress: newProgress });
+    return this.withTicks(this.progress + ticks);
   }
 
   completed(): ProgressTrack {