export const WORKTREE_CREATE_PREPARATION_DIRECTORY = '.orca-preparing'
export const WORKTREE_CREATE_PREPARATION_LOCK_PREFIX = 'orca-create-preparation:v1:'
const WORKTREE_CREATE_PREPARATION_ID_PATTERN =
  /^(\d+)-[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i

// Appended last so older builds, which read only the pid field, still parse the reason.
const WORKTREE_CREATE_PREPARATION_MACHINE_FIELD = ':machine='

/** The machine is what makes the pid meaningful: a repo on a shared disk is seen by other hosts. */
export function createWorktreePreparationLockReason(
  sessionId: string,
  machineIdentity?: string | null
): string {
  const machine = machineIdentity
    ? `${WORKTREE_CREATE_PREPARATION_MACHINE_FIELD}${machineIdentity}`
    : ''
  return `${WORKTREE_CREATE_PREPARATION_LOCK_PREFIX}${process.pid}:${sessionId}${machine}`
}

/** Null for reasons older builds wrote, or a writer that could not read its machine identity. */
export function parseWorktreePreparationOwnerMachine(lockReason?: string): string | null {
  if (!lockReason || parseWorktreePreparationOwnerPid(lockReason) === null) {
    return null
  }
  const at = lockReason.indexOf(WORKTREE_CREATE_PREPARATION_MACHINE_FIELD)
  return at === -1
    ? null
    : lockReason.slice(at + WORKTREE_CREATE_PREPARATION_MACHINE_FIELD.length) || null
}

export function parseWorktreePreparationOwnerPid(lockReason?: string): number | null {
  if (!lockReason?.startsWith(WORKTREE_CREATE_PREPARATION_LOCK_PREFIX)) {
    return null
  }
  const pid = Number(lockReason.slice(WORKTREE_CREATE_PREPARATION_LOCK_PREFIX.length).split(':')[0])
  return Number.isSafeInteger(pid) && pid > 0 ? pid : null
}

export function parseWorktreePreparationPathOwnerPid(path: string): number | null {
  const pathParts = path.split(/[\\/]+/)
  const preparationIndex = pathParts.lastIndexOf(WORKTREE_CREATE_PREPARATION_DIRECTORY)
  if (preparationIndex === -1) {
    return null
  }
  const preparationId = pathParts[preparationIndex + 1]
  if (!preparationId || !WORKTREE_CREATE_PREPARATION_ID_PATTERN.test(preparationId)) {
    return null
  }
  const pid = Number(preparationId.split('-')[0])
  return Number.isSafeInteger(pid) && pid > 0 ? pid : null
}

export function isWorktreeCreatePreparation(worktree: {
  path: string
  lockReason?: string
  branch?: string
}): boolean {
  // The Git lock reason is the durable ownership proof. A path can be chosen
  // by a user (including for an uncommitted detached worktree), so path shape
  // alone must never hide or force-remove it. A crash before locking may leave
  // an unlocked detached entry for manual cleanup, but cannot delete user data.
  return parseWorktreePreparationOwnerPid(worktree.lockReason) !== null
}