storage.opajs

storage.js

/**
 * Add a path called [/storage] to the schema of our graph database.
 *
 * This path is is a dictionary indexed by [string]s of values
 * of type [option(string)], i.e. values that may either be
 * a string or omitted. To find out whether the value is present,
 * one should use pattern-matching - case [{some: ...}] if the
 * value is present, [{none}] if the value is omitted.
 *
 * Note: db is a keyword.
 */
db {
  option(string) /storage[string];
}

/**
 * Handle requests.
 *
 * @param request The uri of the request. The URI is converted to
 * a key in [/storage], the method determines what should be done,
 * and in the case of [{post}] requests, the body is used to set
 * the value in the db.
 *
 * @return If the request is rejected, [{method_not_allowed}].
 * If the request is a successful [{get}], a "text/plain" resource
 * with the value previously stored. If the request is a [{get}] to
 * an unknown key, a [{wrong_address}].
 * Otherwise, a [{success}].
 */
dispatch(request) {
  key = List.to_string(request.uri.path);
  match(request.method) {
    case {some: {get}}:
        match(/storage[key]) {
           {none}:  Resource.raw_status({wrong_address});
           {some: value}: Resource.raw_response(value, "text/plain", {success});
        }
    case {some: {post}}:
         /storage[key] <- request.body;
         Resource.raw_status({success});
    case {some: {delete}}:
         Db.remove(@/storage[key]);
         Resource.raw_status({success});
    case *: Resource.raw_status({method_not_allowed});
  }
}


/**
 * Main entry point: launching the server.
 */
start_server(Server.simple_request_dispatch(dispatch)).