Add support for multiple payers

[dcbr]

This PR adds support for multiple payers of a certain expense. The database changes are minimal and resemble the structure of the paidFor expense field. There's quite some changes to the interface, mostly to the expense form, which are showcased in the video below.

Spliit_multi_payer.mp4

The PR is in a finished state, however it is still marked as draft as I don't know how to provide a correct migration strategy for existing databases (the prisma generated one just seems to drop the paidById column entirely). Some help there would be appreciated. The necessary migration is not too complicated: for each existing expense a new ExpensePaidBy row must be created with participantId equal to the old paidById, expenseId equal to the corresponding expense id and amount equal to the expense's (total) amount.

Closes #14.

Additionally fixes some small bugs regarding amount and balance formatting (this might resolve issues #87 and #140). Also resolves #156 by increasing the upper bound to 10 billion.

[Maxco10]

Good job @dcbr . You should replace "Remove payer" option into dropdown with a "trash icon" close to amount.
An icon is more intuitive for my personal opinion.

[dcbr]

You mean something like this? (This is in mobile viewer)

Initially, I didn't opt to introduce an extra icon as I thought it would become too crowded on mobile, but maybe it's just doable.

[Maxco10]

@dcbr it is perfect with this layout for my personal opinion.

[justcallmelarry]

I would put the remove payer button either on the far right or the far left instead of in the middle, personally

[tasken]

Align to the right, together with the "add payer"

[dcbr]

This right alignment is already part of the last commit, I just haven't updated the previous screenshots.
Anybody knows how to implement the correct database migration? Is it the src/scripts/migrate.ts script that needs to be modified or appended to?

[shynst]

This looks like a great addition! Thank you!

This should do for the database migration: npx prisma migrate dev --name multiple_payers

See here for the docs on prisma: https://www.prisma.io/docs/orm/prisma-migrate/getting-started

[dcbr]

Yes, I already did that. The problem is that the generated migration commands just drop the old paidById column without transferring it to the new ExpensePaidBy table.
But I can manually modify this file to do so and that also seems to be suggested on their website. I will finish this once I have some more time then.

[shynst]

I see. You need to manually adjust the migration file. This should do (please test!):

-- CreateTable
CREATE TABLE "ExpensePaidBy" (
    "expenseId" TEXT NOT NULL,
    "participantId" TEXT NOT NULL,
    "amount" INTEGER NOT NULL,

    CONSTRAINT "ExpensePaidBy_pkey" PRIMARY KEY ("expenseId","participantId")
);

-- AddForeignKey
ALTER TABLE "ExpensePaidBy" ADD CONSTRAINT "ExpensePaidBy_expenseId_fkey" FOREIGN KEY ("expenseId") REFERENCES "Expense"("id") ON DELETE CASCADE ON UPDATE CASCADE;

-- AddForeignKey
ALTER TABLE "ExpensePaidBy" ADD CONSTRAINT "ExpensePaidBy_participantId_fkey" FOREIGN KEY ("participantId") REFERENCES "Participant"("id") ON DELETE CASCADE ON UPDATE CASCADE;

/*
step 2: copy values of old column "paidById" to new table
*/

INSERT INTO "ExpensePaidBy"
	SELECT "id" AS "expenseId", "paidById" AS "participantId", amount
	FROM "Expense";

/*
step 3: drop old column "paidById"
*/

-- DropForeignKey
ALTER TABLE "Expense" DROP CONSTRAINT "Expense_paidById_fkey";

-- AlterTable
ALTER TABLE "Expense" DROP COLUMN "paidById";

[dcbr]

I see. You need to manually adjust the migration file. This should do (please test!):

Thanks @shynst, that worked like a charm! :)

The merge conflicts with the main branch are resolved and the database migration is correctly configured now.
This is ready for review.

[pktiuk]

What is this PR waiting for?

[dcbr]

@scastiel could you let me know whether this is a feature you want in spliit or not? Because otherwise it's quite the hassle to continue resolving all conflicts introduced by later PRs.

[rock-meister]

This is one of the key feature that folks are missing (coming from Splitwise). Is there a decision from the the core contributors that can be shared to the community?

[sir-argupta]

Hi @dcbr
If you don't mind, then can you please reslove conflicts for this time ??🙏