fix: validate reminder indexes and honor parsing time zones

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## Unreleased
 
 - Run developer checks once with the existing 90% coverage gate, pin CI to Swift 6.2 and current Node/pnpm tooling, and execute universal CLI smoke checks in CI.
+- Reject out-of-range numeric reminder indexes before converting them to array offsets, preventing an arithmetic-overflow crash for the minimum integer.
+- Honor the supplied calendar's time zone when RemindCore parses local dates, while retaining explicit ISO 8601 offsets.
 
 ## 0.3.6 - 2026-09-07
 

Sources/RemindCore/DateParsing.swift

@@ -19,6 +19,7 @@ public enum DateParsing {
     parseUserDateWithMetadata(input, now: now, calendar: calendar)?.date
   }
 
+  /// Interprets local dates in the supplied calendar's time zone; explicit ISO offsets take precedence.
   public static func parseUserDateWithMetadata(
     _ input: String,
     now: Date = Date(),
@@ -39,15 +40,15 @@ public enum DateParsing {
     }
 
     let localISO =
-      localISOFormatter(format: "yyyy-MM-dd'T'HH:mm:ss.SSSSSS").date(from: trimmed)
-      ?? localISOFormatter(format: "yyyy-MM-dd'T'HH:mm:ss.SSS").date(from: trimmed)
-      ?? localISOFormatter(format: "yyyy-MM-dd'T'HH:mm:ss").date(from: trimmed)
-      ?? localISOFormatter(format: "yyyy-MM-dd'T'HH:mm").date(from: trimmed)
+      localFormatter(format: "yyyy-MM-dd'T'HH:mm:ss.SSSSSS", calendar: calendar).date(from: trimmed)
+      ?? localFormatter(format: "yyyy-MM-dd'T'HH:mm:ss.SSS", calendar: calendar).date(from: trimmed)
+      ?? localFormatter(format: "yyyy-MM-dd'T'HH:mm:ss", calendar: calendar).date(from: trimmed)
+      ?? localFormatter(format: "yyyy-MM-dd'T'HH:mm", calendar: calendar).date(from: trimmed)
     if let localISO {
       return ParsedUserDate(date: localISO, isDateOnly: false)
     }
 
-    for (formatter, isDateOnly) in dateFormatters() {
+    for (formatter, isDateOnly) in dateFormatters(calendar: calendar) {
       if let date = formatter.date(from: trimmed) {
         return ParsedUserDate(date: date, isDateOnly: isDateOnly)
       }
@@ -91,15 +92,15 @@ public enum DateParsing {
     return formatter
   }
 
-  private static func localISOFormatter(format: String) -> DateFormatter {
+  private static func localFormatter(format: String, calendar: Calendar) -> DateFormatter {
     let formatter = DateFormatter()
     formatter.locale = Locale(identifier: "en_US_POSIX")
-    formatter.timeZone = TimeZone.current
+    formatter.timeZone = calendar.timeZone
     formatter.dateFormat = format
     return formatter
   }
 
-  private static func dateFormatters() -> [(DateFormatter, Bool)] {
+  private static func dateFormatters(calendar: Calendar) -> [(DateFormatter, Bool)] {
     let formats: [(String, Bool)] = [
       ("yyyy-MM-dd", true),
       ("yyyy-MM-dd HH:mm", false),
@@ -110,11 +111,7 @@ public enum DateParsing {
       ("dd-MM-yyyy", true),
     ]
     return formats.map { format, isDateOnly in
-      let formatter = DateFormatter()
-      formatter.locale = Locale(identifier: "en_US_POSIX")
-      formatter.timeZone = TimeZone.current
-      formatter.dateFormat = format
-      return (formatter, isDateOnly)
+      (localFormatter(format: format, calendar: calendar), isDateOnly)
     }
   }
 }

Sources/RemindCore/IDResolver.swift

@@ -14,11 +14,10 @@ public enum IDResolver {
     for input in inputs {
       let trimmed = input.trimmingCharacters(in: .whitespacesAndNewlines)
       if let index = Int(trimmed) {
-        let idx = index - 1
-        guard idx >= 0 && idx < numericSorted.count else {
+        guard index > 0 && index <= numericSorted.count else {
           throw RemindCoreError.invalidIdentifier(trimmed)
         }
-        resolved.append(numericSorted[idx])
+        resolved.append(numericSorted[index - 1])
         continue
       }
 

Tests/RemindCoreTests/DateParsingTests.swift

@@ -38,6 +38,26 @@ struct DateParsingTests {
     #expect(parsed?.isDateOnly == false)
   }
 
+  @Test("Local dates honor the supplied time zone", arguments: [14 * 3600, -10 * 3600])
+  func suppliedTimeZone(_ offset: Int) throws {
+    var calendar = Calendar(identifier: .gregorian)
+    calendar.timeZone = try #require(TimeZone(secondsFromGMT: offset))
+    let expected = try #require(
+      calendar.date(from: DateComponents(year: 2026, month: 1, day: 3, hour: 12, minute: 34)))
+
+    for input in ["2026-01-03T12:34", "2026-01-03 12:34", "01/03/2026 12:34"] {
+      let parsed = try #require(DateParsing.parseUserDateWithMetadata(input, calendar: calendar))
+      #expect(parsed.date == expected)
+      #expect(!parsed.isDateOnly)
+    }
+    let allDay = try #require(DateParsing.parseUserDateWithMetadata("2026-01-03", calendar: calendar))
+    #expect(allDay.date == calendar.startOfDay(for: expected))
+    #expect(allDay.isDateOnly)
+
+    let absolute = "2026-01-03T12:34:00Z"
+    #expect(DateParsing.parseUserDate(absolute, calendar: calendar) == ISO8601DateFormatter().date(from: absolute))
+  }
+
   @Test("Formatted date parsing")
   func formattedParsing() {
     let input = "2026-01-03 10:30"

Tests/RemindCoreTests/IDResolverTests.swift

@@ -45,6 +45,14 @@ struct IDResolverTests {
     #expect(resolved.first?.title == "Second")
   }
 
+  @Test("Reject out-of-range indexes without overflow", arguments: [Int.min, -1, 0, 3, Int.max])
+  func rejectInvalidIndex(_ index: Int) {
+    let input = String(index)
+    #expect(throws: RemindCoreError.invalidIdentifier(input)) {
+      _ = try IDResolver.resolve([input], from: sampleReminders())
+    }
+  }
+
   @Test("Resolve by prefix")
   func resolvePrefix() throws {
     let resolved = try IDResolver.resolve(["abcd"], from: sampleReminders())

docs/commands.md

@@ -72,6 +72,7 @@ remindctl edit 4A83 --no-repeat
 ```
 
 `edit`, `complete`, and `delete` accept indexes from the current default listing or ID prefixes.
+Numeric indexes must be positive and within the current view; out-of-range values return an error.
 
 If `add`, `edit`, or `complete` reports `Reminder is missing a calendar`, EventKit saved the reminder but returned it without its list. Check Reminders.app before retrying; this error does not roll back the saved change.