/*
 * decaffeinate suggestions:
 * DS101: Remove unnecessary use of Array.from
 * DS102: Remove unnecessary code created because of implicit returns
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
let DiffCodec;
const {
    diff_match_patch
} = require("../lib/diff_match_patch");
const dmp = new diff_match_patch();

module.exports = (DiffCodec = {
	ADDED: 1,
	REMOVED: -1,
	UNCHANGED: 0,

	diffAsShareJsOp(before, after, callback) {
		if (callback == null) { callback = function(error, ops) {}; }
		const diffs = dmp.diff_main(before.join("\n"), after.join("\n"));
		dmp.diff_cleanupSemantic(diffs);

		const ops = [];
		let position = 0;
		for (let diff of Array.from(diffs)) {
			const type = diff[0];
			const content = diff[1];
			if (type === this.ADDED) {
				ops.push({
					i: content,
					p: position
				});
				position += content.length;
			} else if (type === this.REMOVED) {
				ops.push({
					d: content,
					p: position
				});
			} else if (type === this.UNCHANGED) {
				position += content.length;
			} else {
				throw "Unknown type";
			}
		}
		return callback(null, ops);
	}
});