namespace LibraryApp.Domain.Entities;

public class LendRecord
{
    public LendRecordId Id { get; private set; }
    public BookInstanceId BookInstanceId { get; private set; }
    public MemberId MemberId { get; private set; }
    public LendCode Code { get; private set; }
    public DateTime LendDate { get; private set; }
    public DateTime? ReturnDate { get; private set; }

    public LendRecord(BookInstanceId bookInstanceId, MemberId memberId, LendCode code)
        : this(new LendRecordId(string.Empty), bookInstanceId, memberId, code, DateTime.UtcNow, null)
    { }

    public LendRecord(LendRecordId id, BookInstanceId bookInstanceId, MemberId memberId, LendCode code, DateTime lendDate, DateTime? returnDate)
    {
        Id = id;
        BookInstanceId = bookInstanceId;
        MemberId = memberId;
        Code = code;
        LendDate = lendDate;
        ReturnDate = returnDate;
    }

    public LendRecord MarkAsReturned()
    {
        if(ReturnDate != null)
            throw new InvalidOperationException("This lend record is already marked as returned.");
        ReturnDate = DateTime.UtcNow;
        return this;
    }

    public LendRecord UpdateLendDate(DateTime newLendDate)
    {
        if(ReturnDate != null)
            throw new InvalidOperationException("Cannot update lend date for a record that is already marked as returned.");
        LendDate = newLendDate;
        return this;
    }

    public LendRecord UnmarkAsReturned()
    {
        if(ReturnDate == null)
            throw new InvalidOperationException("This lend record is not marked as returned.");
        ReturnDate = null;
        return this;
    }
}

public record LendRecordId : DbId
{
    public LendRecordId(string id) : base(id) {}
}

/// <summary>
/// A short, human-friendly code written on the physical lend slip alongside the member's name.
/// Must be unique per lend record and no longer than 8 characters.
/// </summary>
public record LendCode
{
    public string Code { get; init; }

    public LendCode(string code)
    {
        if (string.IsNullOrWhiteSpace(code))
            throw new ArgumentException("Lend code cannot be empty.");
        if (code.Length > 8)
            throw new ArgumentException("Lend code cannot exceed 8 characters.");
        Code = code.ToUpperInvariant();
    }
}