fix: repair failing utility tests and implement missing functions

src/calculator.ts

@@ -15,7 +15,7 @@ export function multiply(a: number, b: number): number {
   return a * b
 }
 
-// BUG: Division by zero is not handled
 export function divide(a: number, b: number): number {
+  if (b === 0) throw new Error("Division by zero")
   return a / b
 }

src/date-utils.ts

@@ -6,15 +6,14 @@
  * Format a date as a human-readable relative string.
  * e.g. "2 days ago", "just now", "in 3 hours"
  *
- * BUG: off-by-one — uses Math.floor where Math.round is needed for days,
- * causing "1 day ago" to appear for anything from 12h to 47h.
+ * Uses Math.round for days, so "1 day ago" appears for differences closest to 1 day.
  */
 export function formatRelative(date: Date, now: Date = new Date()): string {
   const diffMs = now.getTime() - date.getTime()
   const diffSec = diffMs / 1000
   const diffMin = diffSec / 60
   const diffHours = diffMin / 60
-  const diffDays = Math.floor(diffHours / 24) // BUG: should be Math.round
+  const diffDays = Math.round(Math.abs(diffHours) / 24)
 
   if (Math.abs(diffSec) < 60) return "just now"
   if (Math.abs(diffMin) < 60) {

src/string-utils.ts

@@ -14,7 +14,19 @@ export function reverse(str: string): string {
 // TODO: implement truncate — should truncate at a word boundary, with "..."
 // counting toward maxLength. Return unchanged if str.length <= maxLength.
 export function truncate(str: string, maxLength: number): string {
-  throw new Error("not implemented")
+  if (str.length <= maxLength) return str
+  const budget = maxLength - 3
+  const words = str.trim().split(/\s+/)
+  let accumulated = ""
+  for (const word of words) {
+    const candidate = accumulated ? accumulated + " " + word : word
+    if (candidate.length <= budget) {
+      accumulated = candidate
+    } else {
+      break
+    }
+  }
+  return accumulated + "..."
 }
 
 export function slugify(str: string): string {
@@ -24,8 +36,7 @@ export function slugify(str: string): string {
     .replace(/^-|-$/g, "")
 }
 
-// BUG: This doesn't handle multiple consecutive spaces
 export function wordCount(str: string): number {
   if (!str.trim()) return 0
-  return str.split(" ").length
+  return str.trim().split(/\s+/).length
 }

src/task-manager.ts

@@ -54,18 +54,35 @@ export class TaskManager {
 
   // TODO: implement — remove a task by id, return true if removed, false if not found
   remove(id: string): boolean {
-    throw new Error("not implemented")
+    if (!this.tasks.has(id)) return false
+    this.tasks.delete(id)
+    return true
   }
 
   // TODO: implement — update title/description/priority of a task
   // return true if updated, false if not found
   update(id: string, changes: Partial<Pick<Task, "title" | "description" | "priority">>): boolean {
-    throw new Error("not implemented")
+    const task = this.tasks.get(id)
+    if (!task) return false
+    for (const key of Object.keys(changes) as Array<keyof typeof changes>) {
+      if (changes[key] !== undefined) {
+        (task as Record<string, unknown>)[key] = changes[key]
+      }
+    }
+    return true
   }
 
   // TODO: implement — return all tasks sorted by the given field
   // priority sort order: high > medium > low
   sortBy(field: "priority" | "createdAt" | "status"): Task[] {
-    throw new Error("not implemented")
+    const all = Array.from(this.tasks.values())
+    if (field === "priority") {
+      const weight: Record<Priority, number> = { high: 0, medium: 1, low: 2 }
+      return [...all].sort((a, b) => weight[a.priority] - weight[b.priority])
+    }
+    if (field === "createdAt") {
+      return [...all].sort((a, b) => a.createdAt.getTime() - b.createdAt.getTime())
+    }
+    return [...all].sort((a, b) => a.status.localeCompare(b.status))
   }
 }

src/validator.ts

@@ -4,13 +4,9 @@
 
 /**
  * Returns true if the string is a valid email address.
- *
- * BUG: the regex does not allow subdomains (e.g. user@mail.example.com fails)
- * and rejects valid TLDs longer than 4 chars (e.g. .museum, .travel).
  */
 export function isEmail(value: string): boolean {
-  // BUG: too restrictive — missing subdomain support and long TLDs
-  return /^[^\s@]+@[^\s@]+\.[a-zA-Z]{2,4}$/.test(value)
+  return /^[^\s@]+@[^\s@]+\.[a-zA-Z]{2,}$/.test(value)
 }
 
 /**
@@ -22,7 +18,7 @@ export function isUrl(value: string): boolean {
   try {
     const url = new URL(value)
     // BUG: only allows http/https but also rejects valid port usage
-    return (url.protocol === "http:" || url.protocol === "https:") && url.port === ""
+    return url.protocol === "http:" || url.protocol === "https:"
   } catch {
     return false
   }