/* Manages state for parsing operations outside of a Parser.
 *
 * The state is immutable; all update operations return a new state.
 *
 * Since #x is covariant, any ParseState can convert to ParseState<any>, and
 * ParseState<all> can convert to all other ParseState.
 */
concrete ParseState<|#x> {
  @category new (String) -> (ParseState<any>)

  @value run<#y>       (Parser<#y>) -> (ParseState<#y>)
  @value runAndGet<#y> (Parser<#y>) -> (ParseState<any>,ErrorOr<#y>)

  @value atEof       () -> (Bool)
  @value hasAnyError () -> (Bool)
  @value getError    () -> (Formatted)
}

/* A self-contained parser operation.
 *
 * Since #x is covariant, any Parser can convert to Parser<any>, and Parser<all>
 * can convert to all other Parser.
 */
@value interface Parser<|#x> {
  run (ParseContext<any>) -> (ParseState<#x>)
}

/* Parser context available when running a Parser.
 *
 * Since #x is covariant, any ParseContext can convert to ParseContext<any>, and
 * ParseContext<all> can convert to all other ParseContext.
 */
@value interface ParseContext<|#x> {
  run<#y>       (Parser<#y>) -> (ParseContext<#y>)
  runAndGet<#y> (Parser<#y>) -> (ParseContext<any>,ErrorOr<#y>)

  convertError<#y> ()            -> (ParseState<#y>)
  getValue         ()            -> (ErrorOr<#x>)
  setValue<#y>     (ErrorOr<#y>) -> (ParseState<#y>)
  setBrokenInput   (Formatted)   -> (ParseState<all>)
  toState          ()            -> (ParseState<#x>)

  getPosition () -> (String)

  atEof          () -> (Bool)
  hasAnyError    () -> (Bool)
  hasBrokenInput () -> (Bool)

  current () -> (Char)
  advance () -> (ParseContext<#x>)
}