using FinancialApi.Application;
using Microsoft.EntityFrameworkCore;
using Wolverine.Attributes;
using Wolverine.Persistence;

namespace FinancialApi.Infrastructure;

public record TransferFundsCommand(int SourceAccountId, int DestinationAccountId, decimal Amount);

public record FundsTransferredEvent(int SourceAccountId, int DestinationAccountId, decimal Amount);

// A simple container to pass our loaded entities into the pure function
public record TransferPair(Account Source, Account Destination);

public static class TransferFundsHandler
{
    public static async Task<TransferPair?> LoadAsync(TransferFundsCommand cmd, AccountDbContext db)
    {
        var source = await db.Accounts.AsNoTracking().FirstOrDefaultAsync(x => x.Id == cmd.SourceAccountId);
        var dest = await db.Accounts.AsNoTracking().FirstOrDefaultAsync(x => x.Id == cmd.DestinationAccountId);

        if (source == null || dest == null) return null; // Wolverine drops into a 404/Problem if null

        return new TransferPair(source, dest);
    }

    [Transactional]
    public static (
        IStorageAction<Account> SourceWrite,
        IStorageAction<Account> DestWrite,
        IStorageAction<JournalEntry> JournalWrite,
        FundsTransferredEvent Event
        ) Handle(TransferFundsCommand cmd, TransferPair pair)
    {
        var updatedSource = pair.Source.Debit(cmd.Amount);
        var updatedDest = pair.Destination.Credit(cmd.Amount);

        var lines = new List<JournalLine>
        {
            new (pair.Source.Id, cmd.Amount, EntryType.Debit),
            new (pair.Destination.Id, cmd.Amount, EntryType.Credit)
        };

        var journalEntry =
            BalancedJournal.Create(Guid.NewGuid(),
                $"Transfer: {cmd.Amount} from {cmd.SourceAccountId} to {cmd.DestinationAccountId}",
                DateTimeOffset.UtcNow, lines);

        var @event = new FundsTransferredEvent(cmd.SourceAccountId, cmd.DestinationAccountId, cmd.Amount);

        return (
            Storage.Update(updatedSource),
            Storage.Update(updatedDest),
            Storage.Insert(journalEntry.Entry),
            @event
        );
    }
}