bsky-app/src/lib/strings/handles.ts

// Regex from the go implementation
// https://github.com/bluesky-social/indigo/blob/main/atproto/syntax/handle.go#L10
const VALIDATE_REGEX =
  /^([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?$/

export function makeValidHandle(str: string): string {
  if (str.length > 20) {
    str = str.slice(0, 20)
  }
  str = str.toLowerCase()
  return str.replace(/^[^a-z0-9]+/g, '').replace(/[^a-z0-9-]/g, '')
}

export function createFullHandle(name: string, domain: string): string {
  name = (name || '').replace(/[.]+$/, '')
  domain = (domain || '').replace(/^[.]+/, '')
  return `${name}.${domain}`
}

export function isInvalidHandle(handle: string): boolean {
  return handle === 'handle.invalid'
}

export function sanitizeHandle(handle: string, prefix = ''): string {
  return isInvalidHandle(handle) ? '⚠Invalid Handle' : `${prefix}${handle}`
}

export interface IsValidHandle {
  handleChars: boolean
  hyphenStartOrEnd: boolean
  frontLength: boolean
  totalLength: boolean
  overall: boolean
}

// More checks from https://github.com/bluesky-social/atproto/blob/main/packages/pds/src/handle/index.ts#L72
export function validateHandle(str: string, userDomain: string): IsValidHandle {
  const fullHandle = createFullHandle(str, userDomain)

  const results = {
    handleChars:
      !str || (VALIDATE_REGEX.test(fullHandle) && !str.includes('.')),
    hyphenStartOrEnd: !str.startsWith('-') && !str.endsWith('-'),
    frontLength: str.length >= 3,
    totalLength: fullHandle.length <= 253,
  }

  return {
    ...results,
    overall: !Object.values(results).includes(false),
  }
}