Sort by a new 'priority' parameter

[tomap]

Bump minor, because there could be a minor change in behavior
if some user already have a priority parameter
on their posts

Based upon the work of #6

[coveralls]

Coverage decreased (-25.0%) to 75.0% when pulling 69992b0 on tomap:master into e4129ae on hexojs:master.

[YunYouJun]

I've been looking forward to this feature for a long time.
The earlier merged, the better.

---

By the way, I found some theme such as hexo-theme-next, hexo-theme-melody etc.
They had added sticky style.
Maybe use sticky replace priority is ok?

[stevenjoezhang]

The parameter config.index_generator.order_by is ignored

[curbengh]

The parameter config.index_generator.order_by is ignored

That's the intention.

note that if your posts have a `priority` property, it will be used to order your post taking precedence over `order_by`.

[stevenjoezhang]

That's the intention.

note that if your posts have a priority property, it will be used to order your post taking precedence over order_by.

But how about posts with same priority? It does not match the description.

[tomap]

well, I just looked at the code again, and it is not what I intended...
I was trying to reproduce the work of #6
But what we have here is something that will break the parameter config.index_generator.order_by in all cases, which is not good

I believe the configuration config.index_generator.order_by can be used to order by priority, if a priority has been defined on all posts
What might be missing is a was to order by priority first, if there is a priority defined, it goes on top
If not, the config.index_generator.order_by is used
I'm not sure how to code that :)

[stevenjoezhang]

Yes, the issue is: When two or more posts have the same priority, the sorting should fall back to config.index_generator.order_by, but not

if(a.priority == b.priority) return b.date - a.date;

[stevenjoezhang]

But what we have here is something that will break the parameter config.index_generator.order_by in all cases, which is not good

@tomap I think you are talking about the stability of the sorting algorithm. Node.js 12+ uses stable sorting algorithms by default: https://v8.dev/features/stable-sort . Therefore, you can sort locals.posts by config.index_generator.order_by (e.g. '-date') first, and then sort locals.posts.data according to the value of sticky or priority parameter. For older Nodejs versions, lodash is required to implement this method.

[stevenjoezhang]

Suggested change

	const posts = locals.posts;
	posts.data = posts.data.sort(function(a, b) {
	if(a.priority && b.priority) {
	if(a.priority == b.priority) return b.date - a.date;
	else return b.priority - a.priority;
	}
	else if(a.priority && !b.priority) {
	return -1;
	}
	else if(!a.priority && b.priority) {
	return 1;
	}
	else return b.date - a.date;
	});
	const posts = locals.posts.sort(config.index_generator.order_by);
	posts.data.sort((a, b) => (b.sticky || 0) - (a.sticky || 0));

Stable sorting requires Node.js 12+.

[curbengh]

@stevenjoezhang

can you create another PR with your patch? This PR has been inactive for a while...

[SukkaW]

cc @stevenjoezhang

[stevenjoezhang]

@curbengh @SukkaW Superseded by #51