Changes before error encountered

Co-authored-by: petesramek <2333452+petesramek@users.noreply.github.com>
Agent-Logs-Url: https://github.com/petesramek/polyline-algorithm-csharp/sessions/dffc0779-5a05-4dc6-bfc5-93a43db4236e

Author: Copilot

src/PolylineAlgorithm/Abstraction/AbstractPolylineDecoder.cs

@@ -11,16 +11,20 @@ namespace PolylineAlgorithm.Abstraction;
 using PolylineAlgorithm.Internal.Logging;
 using PolylineAlgorithm.Properties;
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
 
 /// <summary>
 /// Decodes encoded polyline strings into sequences of geographic coordinates.
-/// Implements the <see cref="IPolylineDecoder{TPolyline, TCoordinate}"/> interface.
+/// Implements the <see cref="IPolylineDecoder{TPolyline, TCoordinate}"/> and <see cref="IAsyncPolylineDecoder{TPolyline, TCoordinate}"/> interfaces.
 /// </summary>
 /// <remarks>
 /// This abstract class provides a base implementation for decoding polylines, allowing subclasses to define how to handle specific polyline formats.
 /// </remarks>
-public abstract class AbstractPolylineDecoder<TPolyline, TCoordinate> : IPolylineDecoder<TPolyline, TCoordinate> {
+public abstract class AbstractPolylineDecoder<TPolyline, TCoordinate> : IPolylineDecoder<TPolyline, TCoordinate>, IAsyncPolylineDecoder<TPolyline, TCoordinate> {
     /// <summary>
     /// Initializes a new instance of the <see cref="AbstractPolylineDecoder{TPolyline, TCoordinate}"/> class with default encoding options.
     /// </summary>
@@ -151,4 +155,25 @@ static void ValidateEmptySequence(ILogger<AbstractPolylineDecoder<TPolyline, TCo
     /// A coordinate instance of type <typeparamref name="TCoordinate"/>.
     /// </returns>
     protected abstract TCoordinate CreateCoordinate(double latitude, double longitude);
+
+    /// <summary>
+    /// Asynchronously decodes an encoded <typeparamref name="TPolyline"/> into a sequence of <typeparamref name="TCoordinate"/> instances.
+    /// </summary>
+    /// <param name="polyline">
+    /// The <typeparamref name="TPolyline"/> instance containing the encoded polyline string to decode.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// A <see cref="CancellationToken"/> to observe while waiting for the task to complete.
+    /// </param>
+    /// <returns>
+    /// An <see cref="IAsyncEnumerable{T}"/> of <typeparamref name="TCoordinate"/> representing the decoded latitude and longitude pairs.
+    /// </returns>
+    public async IAsyncEnumerable<TCoordinate> DecodeAsync(TPolyline polyline, [EnumeratorCancellation] CancellationToken cancellationToken = default) {
+        foreach (var coordinate in Decode(polyline)) {
+            cancellationToken.ThrowIfCancellationRequested();
+            yield return coordinate;
+        }
+
+        await Task.CompletedTask.ConfigureAwait(false);
+    }
 }

src/PolylineAlgorithm/Abstraction/AbstractPolylineEncoder.cs

@@ -14,15 +14,17 @@ namespace PolylineAlgorithm.Abstraction;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
 
 /// <summary>
 /// Provides functionality to encode a collection of geographic coordinates into an encoded polyline string.
-/// Implements the <see cref="IPolylineEncoder{TCoordinate, TPolyline}"/> interface.
+/// Implements the <see cref="IPolylineEncoder{TCoordinate, TPolyline}"/> and <see cref="IAsyncPolylineEncoder{TCoordinate, TPolyline}"/> interfaces.
 /// </summary>
 /// <remarks>
 /// This abstract class serves as a base for specific polyline encoders, allowing customization of the encoding process.
 /// </remarks>
-public abstract class AbstractPolylineEncoder<TCoordinate, TPolyline> : IPolylineEncoder<TCoordinate, TPolyline> {
+public abstract class AbstractPolylineEncoder<TCoordinate, TPolyline> : IPolylineEncoder<TCoordinate, TPolyline>, IAsyncPolylineEncoder<TCoordinate, TPolyline> {
     /// <summary>
     /// Initializes a new instance of the <see cref="AbstractPolylineEncoder{TCoordinate, TPolyline}"/> class with default encoding options.
     /// </summary>

src/PolylineAlgorithm/Abstraction/IAsyncPolylineDecoder.cs

@@ -0,0 +1,29 @@
+//
+// Copyright © Pete Sramek. All rights reserved.
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+//
+
+namespace PolylineAlgorithm.Abstraction;
+
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+/// <summary>
+/// Defines a contract for asynchronously decoding an encoded polyline into a sequence of geographic coordinates.
+/// </summary>
+public interface IAsyncPolylineDecoder<TPolyline, TCoordinate> {
+    /// <summary>
+    /// Asynchronously decodes the specified encoded polyline into a sequence of geographic coordinates.
+    /// </summary>
+    /// <param name="polyline">
+    /// The <typeparamref name="TPolyline"/> instance containing the encoded polyline string to decode.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// A <see cref="CancellationToken"/> to observe while waiting for the task to complete.
+    /// </param>
+    /// <returns>
+    /// An <see cref="IAsyncEnumerable{T}"/> of <typeparamref name="TCoordinate"/> representing the decoded latitude and longitude pairs.
+    /// </returns>
+    IAsyncEnumerable<TCoordinate> DecodeAsync(TPolyline polyline, [EnumeratorCancellation] CancellationToken cancellationToken = default);
+}

src/PolylineAlgorithm/Abstraction/IAsyncPolylineEncoder.cs

@@ -0,0 +1,30 @@
+//
+// Copyright © Pete Sramek. All rights reserved.
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+//
+
+namespace PolylineAlgorithm.Abstraction;
+
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+/// <summary>
+/// Defines a contract for asynchronously encoding a sequence of geographic coordinates into an encoded polyline string.
+/// </summary>
+public interface IAsyncPolylineEncoder<TCoordinate, TPolyline> {
+    /// <summary>
+    /// Asynchronously encodes a sequence of geographic coordinates into an encoded polyline representation.
+    /// </summary>
+    /// <param name="coordinates">
+    /// The asynchronous collection of <typeparamref name="TCoordinate"/> instances to encode into a polyline.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// A <see cref="CancellationToken"/> to observe while waiting for the task to complete.
+    /// </param>
+    /// <returns>
+    /// A <see cref="ValueTask{TResult}"/> representing the asynchronous operation, containing a <typeparamref name="TPolyline"/>
+    /// with the encoded polyline string that represents the input coordinates.
+    /// </returns>
+    ValueTask<TPolyline> EncodeAsync(IAsyncEnumerable<TCoordinate> coordinates, CancellationToken cancellationToken = default);
+}

src/PolylineAlgorithm/Internal/CoordinateVariance.cs

@@ -59,15 +59,7 @@ public void Next(int latitude, int longitude) {
     /// <param name="next">The next coordinate value.</param>
     /// <returns>The computed variance between <paramref name="initial"/> and <paramref name="next"/>.</returns>
 
-    private static int Variance(int initial, int next) => (initial, next) switch {
-        (0, 0) => 0,
-        (0, _) => next,
-        (_, 0) => -initial,
-        ( < 0, < 0) => -(Math.Abs(next) - Math.Abs(initial)),
-        ( < 0, > 0) => next + Math.Abs(initial),
-        ( > 0, < 0) => -(Math.Abs(next) + initial),
-        ( > 0, > 0) => next - initial,
-    };
+    private static int Variance(int initial, int next) => next - initial;
 
     /// <summary>
     /// Returns a string representation of the current coordinate variance.

src/PolylineAlgorithm/PolylineEncoding.cs

@@ -104,7 +104,7 @@ public static double Denormalize(int value, CoordinateValueType type) {
             return 0.0;
         }
 
-        return Math.Truncate((double)value) / Defaults.Algorithm.Precision;
+        return (double)value / Defaults.Algorithm.Precision;
     }
 
     /// <summary>