From 39409a574500f4387bbdc337466261cf18aef374 Mon Sep 17 00:00:00 2001
From: Nathan Zimmerberg <39104088+nhz2@users.noreply.github.com>
Date: Sun, 24 Mar 2024 14:46:14 -0400
Subject: [PATCH] Implement `isreadable` and `iswritable` (#185)

---
 ext/TestExt.jl    |  1 +
 src/stream.jl     | 12 +++++++++++-
 test/codecnoop.jl | 28 ++++++++++++++++++----------
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/ext/TestExt.jl b/ext/TestExt.jl
index cac67dd8..71aa1226 100644
--- a/ext/TestExt.jl
+++ b/ext/TestExt.jl
@@ -90,6 +90,7 @@ function TranscodingStreams.test_chunked_read(Encoder, Decoder)
             stream = TranscodingStream(Decoder(), buffer, stop_on_end=true)
             ok &= hash(read(stream)) == hash(chunk)
             ok &= eof(stream)
+            ok &= isreadable(stream)
             close(stream)
         end
         Test.@test ok
diff --git a/src/stream.jl b/src/stream.jl
index d4d8625e..53dcd8e0 100644
--- a/src/stream.jl
+++ b/src/stream.jl
@@ -103,7 +103,7 @@ julia> using TranscodingStreams
 
 julia> file = open(joinpath(dirname(dirname(pathof(TranscodingStreams))), "README.md"));
 
-julia> stream = NoopStream(file);
+julia> stream = TranscodingStream(Noop(), file);
 
 julia> readline(file)
 "TranscodingStreams.jl"
@@ -182,6 +182,16 @@ function Base.isopen(stream::TranscodingStream)
     return stream.state.mode != :close && stream.state.mode != :panic
 end
 
+function Base.isreadable(stream::TranscodingStream)::Bool
+    mode = stream.state.mode
+    (mode === :idle || mode === :read || mode === :stop) && isreadable(stream.stream)
+end
+
+function Base.iswritable(stream::TranscodingStream)::Bool
+    mode = stream.state.mode
+    (mode === :idle || mode === :write) && iswritable(stream.stream)
+end
+
 function Base.close(stream::TranscodingStream)
     mode = stream.state.mode
     if mode != :panic
diff --git a/test/codecnoop.jl b/test/codecnoop.jl
index 1c4a0d77..2bff031e 100644
--- a/test/codecnoop.jl
+++ b/test/codecnoop.jl
@@ -240,18 +240,26 @@
     TranscodingStreams.test_roundtrip_write(NoopStream, NoopStream)
     TranscodingStreams.test_roundtrip_lines(NoopStream, NoopStream)
 
-    # switch write => read
-    stream = NoopStream(IOBuffer(b"foobar", read=true, write=true))
-    @test_throws ArgumentError begin
-        write(stream, b"xyz")
-        read(stream, 3)
+    @testset "switch write => read" begin
+        stream = NoopStream(IOBuffer(collect(b"foobar"), read=true, write=true))
+        @test isreadable(stream)
+        @test iswritable(stream)
+        @test_throws ArgumentError begin
+            write(stream, b"xyz")
+            read(stream, 3)
+        end
+        @test !isreadable(stream)
+        @test iswritable(stream)
     end
 
-    # switch read => write
-    stream = NoopStream(IOBuffer(b"foobar", read=true, write=true))
-    @test_throws ArgumentError begin
-        read(stream, 3)
-        write(stream, b"xyz")
+    @testset "switch read => write" begin
+        stream = NoopStream(IOBuffer(collect(b"foobar"), read=true, write=true))
+        @test_throws ArgumentError begin
+            read(stream, 3)
+            write(stream, b"xyz")
+        end
+        @test isreadable(stream)
+        @test !iswritable(stream)
     end
 
     stream = NoopStream(IOBuffer(""))