Initial commit

utils/usernameSuggestions.js

@@ -0,0 +1,69 @@
+const { validateUsername, USERNAME_MAX_LENGTH } = require('./usernameValidation')
+
+const escapeRegex = (value) => value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
+
+const isUsernameTaken = async (UserModel, userName, excludeUserId) => {
+  const existing = await UserModel.findOne({
+    user_name: { $regex: new RegExp(`^${escapeRegex(userName)}$`, 'i') }
+  })
+
+  if (!existing) return false
+  if (excludeUserId && existing._id.toString() === excludeUserId) return false
+  return true
+}
+
+const buildCandidates = (base, attempt) => {
+  const random2 = () => String(Math.floor(Math.random() * 90 + 10))
+  const random3 = () => String(Math.floor(Math.random() * 900 + 100))
+  const random4 = () => String(Math.floor(Math.random() * 9000 + 1000))
+
+  const builders = [
+    (b) => `${b}${random2()}`,
+    (b) => `${b}_${random3()}`,
+    (b) => `${b}.${random2()}`,
+    (b) => `${b}-${random2()}`,
+    (b) => `${b}${random4()}`,
+    (b) => `${b}_m${random2()}`,
+    (b) => `${b}${attempt}`,
+  ]
+
+  return builders.map((fn) => {
+    let candidate = fn(base)
+    if (candidate.length > USERNAME_MAX_LENGTH) {
+      candidate = candidate.slice(0, USERNAME_MAX_LENGTH)
+    }
+    return candidate
+  })
+}
+
+const generateUsernameSuggestions = async (
+  UserModel,
+  baseUsername,
+  excludeUserId,
+  count = 3
+) => {
+  const base = baseUsername.trim().toLowerCase()
+  const suggestions = []
+  const tried = new Set([base])
+
+  for (let attempt = 1; attempt <= 60 && suggestions.length < count; attempt++) {
+    const candidates = buildCandidates(base, attempt)
+
+    for (const candidate of candidates) {
+      if (suggestions.length >= count) break
+      if (tried.has(candidate)) continue
+      tried.add(candidate)
+      if (validateUsername(candidate)) continue
+
+      const taken = await isUsernameTaken(UserModel, candidate, excludeUserId)
+      if (!taken) suggestions.push(candidate)
+    }
+  }
+
+  return suggestions
+}
+
+module.exports = {
+  generateUsernameSuggestions,
+  isUsernameTaken
+}