Added AnyReadableSequence

Author: dimitribouniol

Sources/AsyncSequenceReader/AnyReadableSequence.swift

@@ -0,0 +1,59 @@
+//
+//  AnyReadableSequence.swift
+//  AsyncSequenceReader
+//
+//  Created by Dimitri Bouniol on 2023-06-26.
+//  Copyright © 2021-23 Mochi Development, Inc. All rights reserved.
+//
+
+/// A type-erased convenience type to normalize synchronous and asynchronous sequences into a common async type.
+public struct AnyReadableSequence<Element>: AsyncSequence {
+    @usableFromInline
+    let makeUnderlyingIterator: () -> () async throws -> Element?
+    
+    public struct AsyncIterator: AsyncIteratorProtocol {
+        @usableFromInline
+        let makeUnderlyingNext: () async throws -> Element?
+        
+        @inlinable
+        init(_ makeUnderlyingNext: @escaping () async throws -> Element?) {
+            self.makeUnderlyingNext = makeUnderlyingNext
+        }
+        
+        @inlinable
+        public mutating func next() async throws -> Element? {
+            try await makeUnderlyingNext()
+        }
+    }
+    
+    @inlinable
+    public func makeAsyncIterator() -> AsyncIterator {
+        AsyncIterator(makeUnderlyingIterator())
+    }
+    
+    @inlinable
+    init(_ makeUnderlyingIterator: @escaping () -> () async throws -> Element?) {
+        self.makeUnderlyingIterator = makeUnderlyingIterator
+    }
+    
+    /// Initialize ``AnyReadableSequence`` with a sequence.
+    @inlinable
+    public init<S: Sequence>(_ sequence: S) where S.Element == Element {
+        self.init {
+            var iterator = sequence.makeIterator()
+            
+            return { iterator.next() }
+        }
+    }
+    
+    /// Initialize ``AnyReadableSequence`` with an async sequence.
+    @inlinable
+    public init<S: AsyncSequence>(_ sequence: S) where S.Element == Element {
+        self.init {
+            var iterator = sequence.makeAsyncIterator()
+            
+            return { try await iterator.next() }
+        }
+    }
+}
+