Support negative comment offsets

src/parser/parser.test.ts

@@ -555,6 +555,94 @@ Rest: 5:00 50%
     `);
   });
 
+  it("parses intervals with negative comment offsets", () => {
+    expect(
+      parse(`
+Name: My Workout
+Interval: 10:00 90%
+  @ 0:10 Find your rythm.
+  @ -0:10 Final push. YOU GOT IT!
+
+Rest: 5:00 50%
+  @ -4:30 Great effort!
+  @ -2:00 Cool down well after all of this.
+`),
+    ).toMatchInlineSnapshot(`
+      Object {
+        "author": "",
+        "description": "",
+        "intervals": Array [
+          Object {
+            "cadence": undefined,
+            "comments": Array [
+              Object {
+                "loc": Object {
+                  "col": 4,
+                  "row": 3,
+                },
+                "offset": Duration {
+                  "seconds": 10,
+                },
+                "text": "Find your rythm.",
+              },
+              Object {
+                "loc": Object {
+                  "col": 4,
+                  "row": 4,
+                },
+                "offset": Duration {
+                  "seconds": 590,
+                },
+                "text": "Final push. YOU GOT IT!",
+              },
+            ],
+            "duration": Duration {
+              "seconds": 600,
+            },
+            "intensity": ConstantIntensity {
+              "_value": 0.9,
+            },
+            "type": "Interval",
+          },
+          Object {
+            "cadence": undefined,
+            "comments": Array [
+              Object {
+                "loc": Object {
+                  "col": 4,
+                  "row": 7,
+                },
+                "offset": Duration {
+                  "seconds": 30,
+                },
+                "text": "Great effort!",
+              },
+              Object {
+                "loc": Object {
+                  "col": 4,
+                  "row": 8,
+                },
+                "offset": Duration {
+                  "seconds": 180,
+                },
+                "text": "Cool down well after all of this.",
+              },
+            ],
+            "duration": Duration {
+              "seconds": 300,
+            },
+            "intensity": ConstantIntensity {
+              "_value": 0.5,
+            },
+            "type": "Rest",
+          },
+        ],
+        "name": "My Workout",
+        "tags": Array [],
+      }
+    `);
+  });
+
   it("throws error when comment offset is outside of interval length", () => {
     expect(() =>
       parse(`

src/parser/parser.ts

@@ -57,7 +57,7 @@ const parseHeader = (tokens: Token[]): [Header, Token[]] => {
   return [header, tokens];
 };
 
-const parseIntervalComments = (tokens: Token[]): [Comment[], Token[]] => {
+const parseIntervalComments = (tokens: Token[], intervalDuration: Duration): [Comment[], Token[]] => {
   const comments: Comment[] = [];
   while (tokens[0]) {
     const [start, offset, text, ...rest] = tokens;
@@ -72,7 +72,8 @@ const parseIntervalComments = (tokens: Token[]): [Comment[], Token[]] => {
         throw new ParseError(`Expected [comment text] instead got ${tokenToString(text)}`, text?.loc || offset.loc);
       }
       comments.push({
-        offset: new Duration(offset.value),
+        // when offset is negative, recalculate it based on interval length
+        offset: new Duration(offset.value >= 0 ? offset.value : intervalDuration.seconds + offset.value),
         text: text.value,
         loc: offset.loc,
       });
@@ -115,7 +116,7 @@ const parseIntervalParams = (type: IntervalType, tokens: Token[], loc: SourceLoc
     intensity = new FreeIntensity();
   }
 
-  const [comments, rest] = parseIntervalComments(tokens);
+  const [comments, rest] = parseIntervalComments(tokens, duration);
 
   return [{ type, duration, intensity, cadence, comments }, rest];
 };

src/parser/tokenizer.ts

@@ -89,16 +89,17 @@ const tokenizeParams = (text: string, loc: SourceLocation): Token[] => {
 };
 
 const tokenizeComment = (line: string, row: number): Token[] | undefined => {
-  const [, commentHead, offset, commentText] = line.match(/^(\s*@\s*)([0-9:]+)(.*?)$/) || [];
+  const [, commentHead, minus, offset, commentText] = line.match(/^(\s*@\s*)(-?)([0-9:]+)(.*?)$/) || [];
   if (!commentHead) {
     return undefined;
   }
+  const sign = minus ? -1 : 1;
   if (!DURATION_REGEX.test(offset)) {
     throw new ParseError("Invalid comment offset", { row, col: commentHead.length });
   }
   return [
     { type: "comment-start", loc: { row, col: line.indexOf("@") } },
-    { type: "duration", value: toSeconds(offset), loc: { row, col: commentHead.length } },
+    { type: "duration", value: sign * toSeconds(offset), loc: { row, col: commentHead.length } },
     { type: "text", value: commentText.trim(), loc: { row, col: commentHead.length + offset.length } },
   ];
 };