Implement the Wondrous/Badi calendar

[glittle]

How can I help to implement the Badi (Wondrous) calendar? It is the official calendar of the Baha'i Faith, and has fairly simple rules.

I've implemented the calendar in .NET and Javascript in a number of systems already, and would like to see it in NodaTime as well.

[jskeet]

I'm quite happy for us to do this, but I'd rather not do it before 2.0. It would probably be reasonable to start a Badi branch though.

Implementing a calendar basically consists of implementing a YearMonthDayCalculator - have a look at the abstract methods in that for examples. If you're able to either create a pull request or provide appropriate information so I can implement it myself, that would be great - although in the latter case I probably won't get round to it until the second half of 2017.

[glittle]

Thanks, Jon! I should be able to do a pull request to get it started. I probably won't start for a couple of weeks yet, as I've got other projects to tend to first.

Is the main branch here (https://github.com/nodatime/nodatime) destined to be version 2? Or should I look somewhere else? (If you could "start the branch" and point me there, that might save us both some time!)

[jskeet]

Yes, that's the branch that will be 2.0. I've just created a new "badi" branch - if you create pull requests targeting that, that would be ideal.

[glittle]

I just tried to push to the "badi" branch and got this: "remote: Permission to nodatime/nodatime.git denied to glittle". I'm a novice with git... is there something I need to do instead, or do you need to give me access to that branch?

I'm wondering if I should have forked your "badi" branch and done my work there. Is that right?

[jskeet]

You don't want to push directly to that branch - you want to create your own fork in github, then push to that fork. Then you can create a pull request from your fork to that branch in nodatime/nodatime.

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On 22 February 2017 at 15:40, Glen Little ***@***.***> wrote: I just tried to push to the "badi" branch and got this: "remote: Permission to nodatime/nodatime.git denied to glittle". I'm a novice with git... is there something I need to do instead, or do you need to give me access to that branch? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#652 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABCc5sBcUAHYrAVBwU6Vsjc1oABhn-Qks5rfFb2gaJpZM4MFo3V> .

[glittle]

Unfortunately, I've run into what might be a show-stopping roadblock.

The underlying YearMonthDay struct does not support month numbers beyond 16. The Wondrous calendar requires 19 months (+ another for Ayyam-i-Ha).

I've committed working code into the badi branch in my fork (https://github.com/glittle/nodatime).

Until a workaround or another approach is identified, I cannot do any more development or testing. There are a number of tests that I want to add, but can't until the YearMonthDay struct works.

[glittle]

Unfortunately, this looks like a case of optimization that later proves to be 'premature'!

[jskeet]

Well, it wasn't premature in that it definitely improved performance - it just relied on an assumption that would apparently be invalid under the Wondrous calendar. I'll have a look and see whether it's feasible to give the month number another bit...

[jskeet]

Hmm. It looks like we could reduce the number of "day bits" to 5, allowing up to 32 days per month, and up to 32 months per year. I don't think we can reduce the year range.

I'm somewhat nervous about a maximum of 32 days per month though, given that there are up to 31 in the Gregorian calendar. Will have to think about this a bit more and do some more research. It would be annoying to change this for the Wondrous calendar in a way that then made other calendars impossible to implement...

[jskeet]

https://en.wikipedia.org/wiki/List_of_calendars has a list of calendars we'd want to consider.
There's a lot to look through, but will do what I can...

[glittle]

From the comment in the code, it looks like the year could be adjusted...

private const int YearBits = 15; // 32K range; only need -10K to +10K.

If that were reduced to 14, you'd have a 16K range, still bigger than what is needed.

Would changing the bits affect current implementations? If someone serializes a date, is it stored in the internal bit pattern, or otherwise?

My first thought was to overload the YearMonthDate class and adjust the internal representation when used for this calendar, but it is a struct. I was also not sure of the implications of doing so!

[jskeet]

No, we need -9998 to 9999, which is nearly 20K of range.

Changing the bit pattern now would be just about okay - doing it after 2.0 has been released wouldn't be. So we definitely need to get it right now :)

Adjusting the internal representation on a per calendar basis would inflict quite a nasty performance penalty, unfortunately. The reason for using this representation is to make it really really quick to get at each component. Adding any branching would slow things down quite a bit :(

[jskeet]

Ah, I'm silly - we can just add another bit for months... we've got lots of space, as it were, in YearMonthDay. YearMonthDayCalendar is where it gets tighter, and currently we have 7 bits for the calendar system ID... I think it's absolutely fine to reduce that to 6. I doubt that we'll need more than 64 calendar systems, ever!

Will do this in the master branch, and then would could rebase your branch - are you sufficiently comfortable with git to do that part yourself? (I'll cc you on the pull request, so you'll know when it's done.)

[glittle]

Great news! I'll see what I can do for the rebase...

[jskeet]

It's not in yet :) But when it is in, I'd expect you to be able to do:

git checkout master
git pull upstream master
git checkout badi
git rebase master
git push -f origin badi

That's assuming you have remotes setup as upstream=nodatime, origin=your fork.

The rebase may have merge conflicts, of course, at which point things get slightly trickier.

[jskeet]

Right, that PR is now merged. Good luck :)

[glittle]

I had merge conflicts. I also had a number of commits that I'd rather squash. To keep it simple, I've "manually stashed" the changes and files that I need to touch then deleted my fork, and reforked nodatime. However, I think your "badi" branch is no longer up-to-date. Could you update it, or should I not use that branch?

[jskeet]

Have rebased the badi branch.

[glittle]

Thanks. I think I'm on track now... The only real setback is that neglected to "stash" my unit tests file. It will take a while to rebuild all the tests. :(

[glittle]

How do I define DateTimeFormat.MonthNames for a new calendar? I haven't found it for any of the other calendars...

[jskeet]

Unfortunately, the .NET support for calendar localization is pretty poor. We effectively don't support localization on a per-calendar basis, because .NET just isn't geared up for it. At some point we'd like to support names via CLDR, but it's not on the immediate roadmap. For now, I'm afraid that will leave the Wondrous calendar without text support - just like there's no reliable text handling for the Hebrew calendar :(

[jskeet]

@glittle: Can I check whether this is still of interest? I'm doing a bit of housekeeping, and if you've now decided not go ahead with this, I'll close this issue and related ones.

[glittle]

Hi @jskeet. I was actually thinking of Noda Time recently and was planning to try again and see whether I could get it finished. So I'd like to keep it open for a bit longer. I expect to work on it in November.

Since version 2.2 is now current, should I start over with a current codebase? Can you bring the 'badi' branch up-to-date for me?

Thanks!

[jskeet]

I've brought the badi branch up to date with 2.2.x. Is that what you're after, or would you like me to rebase it to master? (2.2.x will give you some more stability while developing; master would be more up-to-date.)

Good to hear you're still considering it :)

[glittle]

As per my previous comments in this thread, I'm a novice with the nuances of git! What would you recommend for this?

[jskeet]

Probably simplest to work on a 2.2 base at the moment then. I can handle the rebasing later to bring it up to master when you're ready.

[glittle]

Took me a while to figure out why the instructions here (http://nodatime.org/developer/building) were not working!

Turns out that this file (https://github.com/nodatime/nodatime/blob/badi/global.json) was not updated, so 'dotnet' was reverting to version 1 whenever I was in the solution's folder! Back on track again now...

[glittle]

This thread can likely be closed now as #689 is also about the Wondrous calendar.