(** Module for handling phonological features and segments *)

(* module Feature = struct *)

(** Type representing a phonological feature value *)
type feature_value = Plus | Minus | Zero

(** Type representing a phonological feature *)
type feature =
  | Syllabic
  | Sonorant
  | Consonantal
  | Continuant
  | DelayedRelease
  | Lateral
  | Nasal
  | Strident
  | Voiced
  | SpreadGlottis
  | ConstrictedGlottis
  | Anterior
  | Coronal
  | Distributed
  | Labial
  | High
  | Low
  | Back
  | Rounded
  | Velaric
  | Tense
  | Long
  | HighTone
  | HighReg (*high registry?*)

type feature_spec = feature * feature_value
(** Type representing a feature specification as a (value, feature) pair *)

type segment = feature_spec list

(** Convert a string feature value to the feature_value type *)
let value_of_string = function
  | "+" -> Plus
  | "-" -> Minus
  | "0" -> Zero
  | s -> failwith (Printf.sprintf "Invalid feature value: %s" s)

let string_of_feature = function
  | "syl" -> Syllabic
  | "son" -> Sonorant
  | "cons" -> Consonantal
  | "cont" -> Continuant
  | "delrel" -> DelayedRelease
  | "lat" -> Lateral
  | "nas" -> Nasal
  | "strid" -> Strident
  | "voi" -> Voiced
  | "sg" -> SpreadGlottis
  | "cg" -> ConstrictedGlottis
  | "ant" -> Anterior
  | "cor" -> Coronal
  | "distr" -> Distributed
  | "lab" -> Labial
  | "hi" -> High
  | "lo" -> Low
  | "back" -> Back
  | "round" -> Rounded
  | "velaric" -> Velaric
  | "tense" -> Tense
  | "long" -> Long
  | "hitone" -> HighTone
  | "hireg" -> HighReg
  | _ -> failwith "not a valid feature"

(** Check if a segment has a specific feature with a given value *)
let has_feature (value, feature_name) segment =
  List.exists (fun (v, f) -> v = value && f = feature_name) segment

(** Create a feature test function for use in the decision tree *)
let test feature_spec segment = has_feature feature_spec segment
(* end *)