// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Collections.Generic;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.Shared.Collections;
using Roslyn.Utilities;
using Xunit;
 
namespace Microsoft.CodeAnalysis.UnitTests.UtilityTest;
 
public sealed class BKTreeTests
{
    private static ImmutableArray<string> Find(BKTree tree, string value, int? threshold)
    {
        using var results = TemporaryArray<string>.Empty;
        tree.Find(ref results.AsRef(), value, threshold);
        return results.ToImmutableAndClear();
    }
 
    [Fact]
    public void SimpleTests()
    {
        string[] testValues = ["cook", "book", "books", "cake", "what", "water", "Cape", "Boon", "Cook", "Cart"];
        var tree = BKTree.Create(testValues);
 
        var results1 = Find(tree, "wat", threshold: 1);
        Assert.Single(results1, "what");
 
        var results2 = Find(tree, "wat", threshold: 2);
        Assert.True(results2.SetEquals(Expected("cart", "what", "water")));
 
        var results3 = Find(tree, "caqe", threshold: 1);
        Assert.True(results3.SetEquals(Expected("cake", "cape")));
    }
 
    [Fact]
    public void PermutationTests()
    {
        string[] testValues = ["cook", "book", "books", "cake", "what", "water", "Cape", "Boon", "Cook", "Cart"];
        TestTreeInvariants(testValues);
    }
 
    private static void TestTreeInvariants(string[] testValues)
    {
        var tree = BKTree.Create(testValues);
 
        foreach (var value in testValues)
        {
            // With a threshold of 0, we should only find exactly the item we're searching for.
            Assert.Single(Find(tree, value, threshold: 0), value.ToLower());
        }
 
        foreach (var value in testValues)
        {
            // With a threshold of 1, we should always at least find the item we're looking for.
            // But we may also find additional items along with it.
            var items = Find(tree, value, threshold: 1);
            Assert.Contains(value.ToLower(), items);
 
            // We better not be finding all items.
            Assert.NotEqual(testValues.Length, items.Length);
        }
 
        foreach (var value in testValues)
        {
            // If we delete each individual character in each search string, we should still
            // find the value in the tree.
            for (var i = 0; i < value.Length; i++)
            {
                var items = Find(tree, Delete(value, i), threshold: null);
                Assert.Contains(value.ToLower(), items);
 
                // We better not be finding all items.
                Assert.NotEqual(testValues.Length, items.Length);
            }
        }
 
        foreach (var value in testValues)
        {
            // If we add a random character at any location in a string, we should still 
            // be able to find it.
            for (var i = 0; i <= value.Length; i++)
            {
                var items = Find(tree, Insert(value, i, 'Z'), threshold: null);
                Assert.Contains(value.ToLower(), items);
 
                // We better not be finding all items.
                Assert.NotEqual(testValues.Length, items.Length);
            }
        }
 
        foreach (var value in testValues)
        {
            // If we transpose any characters in a string, we should still 
            // be able to find it.
            for (var i = 0; i < value.Length - 1; i++)
            {
                var items = Find(tree, Transpose(value, i), threshold: null);
                Assert.Contains(value.ToLower(), items);
            }
        }
    }
 
    private static string Transpose(string value, int i)
        => value[..i] + value[i + 1] + value[i] + value[(i + 2)..];
 
    private static string Insert(string value, int i, char v)
        => value[..i] + v + value[i..];
 
    private static string Delete(string value, int i)
        => value[..i] + value[(i + 1)..];
 
    [Fact]
    public void Test2()
    {
        string[] testValues = ["Leeds", "York", "Bristol", "Leicester", "Hull", "Durham"];
        var tree = BKTree.Create(testValues);
 
        var results = Find(tree, "hill", threshold: null);
        Assert.True(results.SetEquals(Expected("hull")));
 
        results = Find(tree, "liecester", threshold: null);
        Assert.True(results.SetEquals(Expected("leicester")));
 
        results = Find(tree, "leicestre", threshold: null);
        Assert.True(results.SetEquals(Expected("leicester")));
 
        results = Find(tree, "lecester", threshold: null);
        Assert.True(results.SetEquals(Expected("leicester")));
    }
 
    [Fact]
    public void TestSpillover()
    {
#pragma warning disable format // https://github.com/dotnet/roslyn/issues/70711 tracks removing this suppression.
        string[] testValues = [
            /*root:*/ "Four",
            /*d=1*/ "Fou", "For", "Fur", "Our", "FourA", "FouAr", "FoAur", "FAour", "AFour", "Tour",
            /*d=2*/ "Fo", "Fu", "Fr", "or", "ur", "ou", "FourAb", "FouAbr", "FoAbur", "FAbour", "AbFour", "oFour", "Fuor", "Foru", "ours",
            /*d=3*/ "F", "o", "u", "r", "Fob", "Fox", "bur", "urn", "hur", "foraa", "found"
        ];
#pragma warning restore format
 
        TestTreeInvariants(testValues);
    }
 
    [Fact]
    public void Top1000()
        => TestTreeInvariants(EditDistanceTests.Top1000);
 
    private static IEnumerable<string> Expected(params string[] values)
        => values;
}