From 235281daf9a6d67874f7ab78219c4e6dd4eb12ef Mon Sep 17 00:00:00 2001
From: Matthew O'Connor <matthew.oconnor@xledger.com>
Date: Fri, 25 Oct 2024 10:18:53 -0600
Subject: [PATCH] Implement ImmArray.Find and ImmSet.TryGetValue.

Closes #2.
---
 Xledger.Collections.Test/TestImmArray.cs | 15 +++++++++++++++
 Xledger.Collections.Test/TestImmSet.cs   | 19 +++++++++++++++++++
 Xledger.Collections/ImmArray.cs          |  7 +++++++
 Xledger.Collections/ImmSet.cs            |  7 +++++++
 4 files changed, 48 insertions(+)

diff --git a/Xledger.Collections.Test/TestImmArray.cs b/Xledger.Collections.Test/TestImmArray.cs
index cfcf592..3b7f673 100644
--- a/Xledger.Collections.Test/TestImmArray.cs
+++ b/Xledger.Collections.Test/TestImmArray.cs
@@ -146,6 +146,21 @@ public void TestCompareToRecord() {
         Assert.ThrowsAny<ArgumentException>(() => imm2 >= imm1);
     }
 
+    [Fact]
+    public void TestFind() {
+        var arr = Enumerable.Range(-1, 100).ToArray();
+        var imm = arr.ToImmArray();
+
+        Predicate<int> pred = i => i == -1;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 12;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 75;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+        pred = i => i == 1_000_000;
+        Assert.Equal(Array.Find(arr, pred), imm.Find(pred));
+    }
+
     public record Employee(int Id, string Name, decimal Salary);
 }
 
diff --git a/Xledger.Collections.Test/TestImmSet.cs b/Xledger.Collections.Test/TestImmSet.cs
index cd9462e..ced1dcc 100644
--- a/Xledger.Collections.Test/TestImmSet.cs
+++ b/Xledger.Collections.Test/TestImmSet.cs
@@ -79,6 +79,25 @@ public void TestContains() {
         Assert.True(lst.Contains(3));
     }
 
+    [Fact]
+    public void TestTryGetValue() {
+        var imm = ImmSet.Of("foo", "bar", "baz");
+
+        var lookup = "food".Substring(0, 3);
+        var found = imm.TryGetValue(lookup, out var actual);
+        Assert.True(found);
+        Assert.NotSame(lookup, actual);
+        Assert.Equal(lookup, actual);
+
+        found = imm.TryGetValue("foo", out actual);
+        Assert.True(found);
+        Assert.Same("foo", actual);
+        Assert.Equal("foo", actual);
+
+        found = imm.TryGetValue("food", out actual);
+        Assert.False(found);
+    }
+
     [Fact]
     public void TestNoOps() {
         var imm = ImmSet.Of(7, 6, 5, 4);
diff --git a/Xledger.Collections/ImmArray.cs b/Xledger.Collections/ImmArray.cs
index 9431b6a..d9caad4 100644
--- a/Xledger.Collections/ImmArray.cs
+++ b/Xledger.Collections/ImmArray.cs
@@ -121,6 +121,13 @@ public bool Contains(T item) {
         return this.data.Length > 0 && IndexOf(item) >= 0;
     }
 
+    /// <summary>
+    /// Returns the first matching element or default if none matches.
+    /// </summary>
+    public T Find(Predicate<T> pred) {
+        return Array.Find(this.data, pred);
+    }
+
     /// <inheritdoc />
     public int IndexOf(T item) {
         return Array.IndexOf<T>(this.data, item);
diff --git a/Xledger.Collections/ImmSet.cs b/Xledger.Collections/ImmSet.cs
index 4495c77..b7dbb30 100644
--- a/Xledger.Collections/ImmSet.cs
+++ b/Xledger.Collections/ImmSet.cs
@@ -182,6 +182,13 @@ public bool SetEquals(IEnumerable<T> other) {
         }
     }
 
+    /// <summary>
+    /// Searches the set for a given value and returns the equal value it finds, if any.
+    /// </summary>
+    public bool TryGetValue(T equalValue, out T actualValue) {
+        return this.data.TryGetValue(equalValue, out actualValue);
+    }
+
     /// <inheritdoc />
     public override string ToString() {
         return $"[{string.Join(", ", this.data)}]";