!759

// Example input:

// If the available commands are "load", "save" and "quit", which command is "q" likely to mean?

static S parsingRules = [[

  case-insensitive

  if the available commands are <cmdlist>, which command is <cmd> likely to mean? = question

  <quoted> = cmd

  <cmd> = cmdlist

  <cmd> <and> <cmdlist> = cmdlist

  , = and

  and = and

]];

// returns null if className is not a parsed main class

static Explain explainFull(O parseResult, S className) {

  L exp = cast call(parseResult, "explainFull", className);

  if (exp == null) ret null;

  ret new Explain(parseResult, exp);

}

static S findBestMatch(S query, L<S> cmds) {

  query = query.toLowerCase();

  new Map<S, Integer> map;

  for (S cmd : cmds)

    map.put(cmd, l(commonPrefix(cmd.toLowerCase(), query)));

  ret highest(map);

}

static O parser;

p {

  parser = newParser();

}

synchronized answer {

  // prematching to not fire up the parser every time...

  if (matchStart("If the available commands are", s)) {

    O parseResult = call(parser, "parse", s, parsingRules);

    Explain explain = explainFull(parseResult, "question");

    if (explain != null) {

      Explain dehlist = explain.sub(0);

      L<S> quotedCmds = dehlist.findAll("cmd");

      S query = unquote(explain.sub(1).string());

      new L<S> cmds;

      for (S cmd : quotedCmds) cmds.add(unquote(cmd));

      ret structure(findBestMatch(query, cmds));

    } else

      ret "No parse: " + structure(parseResult);

  }

}