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aj
0446127e11
The server stores only nest-level metadata, so a browser that shows a saved nest's plates and drawings has to read them from its archive. NestDetails.FromNest turns a nest into one row per plate (duplicates, size, parts and distinct drawings without cutoffs, utilization; 0 for a zero-size plate rather than NaN) and one row per non-cutoff drawing (required, nested across every plate's duplicates, remaining, area), plus the nest's units. NestDetailsSession loads the details of the highlighted nest. A new load or Clear supersedes the previous one before cancelling it, so a load that completes synchronously on cancellation and any late result or failure of a superseded load are discarded; IsLoading follows only the latest load.
109 lines
3.5 KiB
C#
109 lines
3.5 KiB
C#
namespace OpenNest.Data;
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/// <summary>
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/// Loads the details of the nest highlighted in the Database-mode nest browser. Moving
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/// the highlight starts a new load and cancels the previous one; a superseded load's
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/// result or failure is discarded, so details never belong to a nest that is no longer
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/// highlighted. Call from one thread (the UI thread).
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/// </summary>
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public sealed class NestDetailsSession : IDisposable
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{
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private readonly Func<Guid, CancellationToken, Task<NestDetails>> _load;
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private CancellationTokenSource? _pending;
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private int _generation;
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private bool _disposed;
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/// <param name="load">
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/// Builds the details of one nest; throws when the nest cannot be read (for example
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/// when it no longer exists on the server).
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/// </param>
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public NestDetailsSession(Func<Guid, CancellationToken, Task<NestDetails>> load)
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{
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ArgumentNullException.ThrowIfNull(load);
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_load = load;
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}
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/// <summary>The nest of the latest load; null before the first load and after <see cref="Clear"/>.</summary>
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public Guid? NestId { get; private set; }
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/// <summary>Details of <see cref="NestId"/>; null while loading, after a failure and after <see cref="Clear"/>.</summary>
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public NestDetails? Details { get; private set; }
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/// <summary>True while the latest load is outstanding; superseded loads do not count.</summary>
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public bool IsLoading { get; private set; }
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/// <summary>
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/// Loads one nest's details. Returns true when they were applied, false when a later
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/// load or <see cref="Clear"/> superseded this one. A failure of the latest load
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/// propagates; failures of superseded loads are ignored.
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/// </summary>
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public async Task<bool> LoadAsync(Guid id)
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{
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ObjectDisposedException.ThrowIf(_disposed, this);
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// Supersede before cancelling: a load that completes synchronously when cancelled
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// must already see itself as superseded. Each source is released by its own load.
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var cancellation = Supersede();
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var generation = _generation;
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NestId = id;
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IsLoading = true;
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try
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{
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var details = await _load(id, cancellation.Token);
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if (generation != _generation)
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return false;
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Details = details;
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return true;
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}
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catch (Exception) when (generation != _generation)
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{
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return false;
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}
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finally
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{
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if (ReferenceEquals(_pending, cancellation))
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_pending = null;
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if (generation == _generation)
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IsLoading = false;
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cancellation.Dispose();
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}
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}
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/// <summary>Forgets the current details and discards any load in flight (no nest highlighted).</summary>
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public void Clear()
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{
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if (_disposed)
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return;
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_generation++;
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var pending = _pending;
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_pending = null;
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NestId = null;
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Details = null;
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IsLoading = false;
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pending?.Cancel();
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}
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private CancellationTokenSource Supersede()
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{
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var previous = _pending;
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var cancellation = new CancellationTokenSource();
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_pending = cancellation;
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_generation++;
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Details = null;
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previous?.Cancel();
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return cancellation;
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}
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/// <summary>Cancels any load in flight (which releases its own source when it ends).</summary>
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public void Dispose()
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{
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if (_disposed)
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return;
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Clear();
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_disposed = true;
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}
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}
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