"use strict";

// function prefixSearch(...) {
// 	...
// }

module.exports = function createLMDBBackend(instance) {
	return {
		getKey: function (key) {
			// return value, or throw if non-existent
			return instance.get(key);
		},
		putKey: function (key, value) {
			// TODO: compare-and-set in API?
			// NOTE: returns `false` if `ifVersion` check failed, but we are not currently using that feature
			return instance.put(key, value);
		},
		getKeyRange: function* (lowestKey, lowestInclusive, highestKey, highestInclusive) { 
			// NOTE: Range requests in lmdb are start-inclusive but end-exclusive
			yield* instance.getRange({ start: lowestKey, end: highestKey })
				.filter(({ key }) => {
					if (!lowestInclusive && lowestKey.equals(key)) {
						return false;
					} else {
						return true;
					}
				});

			if (highestInclusive && instance.doesExist(highestKey)) {
				yield { key: highestKey, value: instance.get(highestKey) };
			}

			return;
		},
		runInTransaction: function (callback) {
			
		}
	};
};