# format.ludic - a kind of file, the steps that carry it forward, and how one read went

# how a read ended; a game's own refusals (another map, another account) start at SAVE_STATUS_COUNT
export const SAVE_OK: int = 0
export const SAVE_NONE: int = 1            # there is no file
export const SAVE_CORRUPT: int = 2         # it did not parse, is cut off, or is not this kind of file
export const SAVE_FUTURE: int = 3          # written by a later build: refused, and never written over
export const SAVE_STATUS_COUNT: int = 4

# a kind of file: which migrations are its, what this build writes, the oldest it will carry forward,
# the key its version is under (a file without one is version 1), and whether an object is one at all
export property SaveFormat {
  name: string = "",
  version: int = 1,
  oldest: int = 1,
  version_key: string = "version",
  is_one: fn(Val) -> bool = null
}

export function save_format(name: string, version: int) -> SaveFormat {
  let f = new SaveFormat
  f.name = name
  f.version = version
  return f
}

# One step: an object of `format` at version `from` rewritten in place into version from + 1. A
# version with no step is carried forward as it stands. The game writes these as defs.
export property SaveMigration {
  key: string = "",
  format: string = "",
  from: int = 0,
  run: fn(Val) -> void = null
}
export open registry SaveMigrations of SaveMigration as SMIG

# One read: what was found, the version it was written in, whether it had to be carried forward,
# whether it must never be written over, and whether it is the backup standing in for the file
export property SaveRead {
  status: int = 0,
  from: int = 0,
  migrated: bool = false,
  readonly: bool = false,
  from_backup: bool = false,
  intact: bool = true,        # save_read: whether the text was whole (the words for a refusal)
  value: Val = null
}

function read_new(status: int, v: Val) -> SaveRead {
  let r = new SaveRead
  r.status = status
  r.value = v
  return r
}