Oli Sturm
94 lines
3.3 KiB
C#
94 lines
3.3 KiB
C#
using CsharpEs.Library;
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namespace CsharpEs.Domain;
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public sealed record AccountState(Guid Id);
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public abstract record AccountCommand
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{
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public sealed record OpenAccount(Guid AccountId, Money OpeningBalance) : AccountCommand;
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public sealed record WithdrawMoney(Guid AccountId, Money Amount) : AccountCommand;
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public sealed record DepositMoney(Guid AccountId, Money Amount) : AccountCommand;
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}
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public abstract record AccountEvent(Guid AccountId)
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{
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public sealed record AccountOpened(Guid AccountId, Money OpeningBalance)
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: AccountEvent(AccountId);
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public sealed record MoneyWithdrawn(Guid AccountId, Money Amount) : AccountEvent(AccountId);
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public sealed record MoneyDeposited(Guid AccountId, Money Amount) : AccountEvent(AccountId);
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}
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public abstract record AccountError
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{
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public sealed record AccountNotFound : AccountError;
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public sealed record AccountOpenAlready : AccountError;
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public sealed record OpeningBalanceMustBeNonNegative : AccountError;
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public sealed record InnerException(Exception exception) : AccountError;
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}
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public static class AccountDecider
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{
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public static Result<AccountEvent, AccountError> Decide(
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AccountState? state,
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AccountCommand command
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) =>
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Result<AccountEvent, AccountError>.Catch(
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() =>
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(state, command) switch
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{
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// if this is a new account, check for valid opening balance
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(null, AccountCommand.OpenAccount c) when c.OpeningBalance.Amount < 0m =>
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Result<AccountEvent, AccountError>.Fail(
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new AccountError.OpeningBalanceMustBeNonNegative()
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),
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// still a new account, now we can open it
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(null, AccountCommand.OpenAccount c) => Result<AccountEvent, AccountError>.Ok(
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new AccountEvent.AccountOpened(c.AccountId, c.OpeningBalance)
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),
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// if we have an account already, you can't open it
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(not null, AccountCommand.OpenAccount c) => Result<
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AccountEvent,
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AccountError
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>.Fail(new AccountError.AccountOpenAlready()),
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(null, _) => Result<AccountEvent, AccountError>.Fail(
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new AccountError.AccountNotFound()
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),
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(_, AccountCommand.WithdrawMoney c) => Result<AccountEvent, AccountError>.Ok(
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new AccountEvent.MoneyWithdrawn(c.AccountId, c.Amount)
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),
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(_, AccountCommand.DepositMoney c) => Result<AccountEvent, AccountError>.Ok(
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new AccountEvent.MoneyDeposited(c.AccountId, c.Amount)
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),
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_ => throw new InvalidOperationException("Unknown command."),
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},
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e => new AccountError.InnerException(e)
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);
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public static Result<AccountState?, AccountError> Evolve(
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AccountState? state,
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AccountEvent @event
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) =>
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(state, @event) switch
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{
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(null, AccountEvent.AccountOpened e) => Result<AccountState?, AccountError>.Ok(
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new AccountState(e.AccountId)
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),
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_ => Result<AccountState?, AccountError>.Ok(state),
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};
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}
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