package starssh

import (
	"bufio"
	"bytes"
	"io"
	"os"
	"testing"
	"time"
)

type terminalInputProvider struct {
	io.Reader
	source io.Reader
}

func (p terminalInputProvider) TerminalInputSource() io.Reader {
	return p.source
}

type prefixedReadCloser struct {
	io.Reader
	io.Closer
}

func TestPrepareTerminalInputReaderBufioReaderPreservesBufferedBytes(t *testing.T) {
	reader, writer, err := os.Pipe()
	if err != nil {
		t.Fatalf("create pipe: %v", err)
	}
	defer reader.Close()

	if _, err := writer.Write([]byte("hello world")); err != nil {
		writer.Close()
		t.Fatalf("write pipe: %v", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatalf("close writer: %v", err)
	}

	buffered := bufio.NewReaderSize(reader, 4)
	peeked, err := buffered.Peek(5)
	if err != nil {
		t.Fatalf("prime buffer: %v", err)
	}
	if string(peeked) != "hello" {
		t.Fatalf("unexpected buffered prefix: %q", string(peeked))
	}

	prepared, cancel, cancelable, err := prepareTerminalInputReader(buffered)
	if err != nil {
		t.Fatalf("prepare input: %v", err)
	}
	defer cancel()

	if !cancelable {
		t.Fatal("expected cancelable reader")
	}

	data, err := io.ReadAll(prepared)
	if err != nil {
		t.Fatalf("read prepared input: %v", err)
	}
	if string(data) != "hello world" {
		t.Fatalf("unexpected prepared input: %q", string(data))
	}
}

func TestPrepareTerminalInputReaderBufioReadWriterPreservesBufferedBytes(t *testing.T) {
	reader, writer, err := os.Pipe()
	if err != nil {
		t.Fatalf("create pipe: %v", err)
	}
	defer reader.Close()

	if _, err := writer.Write([]byte("buffered payload")); err != nil {
		writer.Close()
		t.Fatalf("write pipe: %v", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatalf("close writer: %v", err)
	}

	readWriter := bufio.NewReadWriter(bufio.NewReaderSize(reader, 8), bufio.NewWriter(io.Discard))
	if _, err := readWriter.Reader.Peek(8); err != nil {
		t.Fatalf("prime readwriter buffer: %v", err)
	}

	prepared, cancel, cancelable, err := prepareTerminalInputReader(readWriter)
	if err != nil {
		t.Fatalf("prepare readwriter input: %v", err)
	}
	defer cancel()

	if !cancelable {
		t.Fatal("expected cancelable readwriter input")
	}

	data, err := io.ReadAll(prepared)
	if err != nil {
		t.Fatalf("read prepared readwriter input: %v", err)
	}
	if string(data) != "buffered payload" {
		t.Fatalf("unexpected prepared readwriter input: %q", string(data))
	}
}

func TestPrepareTerminalInputReaderBufioReaderFallbackKeepsData(t *testing.T) {
	buffered := bufio.NewReader(bytes.NewBufferString("abc123"))
	if _, err := buffered.Peek(3); err != nil {
		t.Fatalf("prime buffer: %v", err)
	}

	prepared, cancel, cancelable, err := prepareTerminalInputReader(buffered)
	if err != nil {
		t.Fatalf("prepare fallback input: %v", err)
	}
	defer cancel()

	if cancelable {
		t.Fatal("expected non-cancelable reader")
	}

	data, err := io.ReadAll(prepared)
	if err != nil {
		t.Fatalf("read fallback input: %v", err)
	}
	if string(data) != "abc123" {
		t.Fatalf("unexpected fallback input: %q", string(data))
	}
}

func TestPrepareTerminalInputReaderProviderPrefersExplicitSource(t *testing.T) {
	reader, writer, err := os.Pipe()
	if err != nil {
		t.Fatalf("create pipe: %v", err)
	}
	defer reader.Close()

	if _, err := writer.Write([]byte("provider data")); err != nil {
		writer.Close()
		t.Fatalf("write pipe: %v", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatalf("close writer: %v", err)
	}

	buffered := bufio.NewReader(reader)
	prefix, err := buffered.Peek(len("provider data"))
	if err != nil {
		t.Fatalf("prime buffer: %v", err)
	}

	source := prefixedReadCloser{
		Reader: io.MultiReader(bytes.NewReader(append([]byte(nil), prefix...)), reader),
		Closer: reader,
	}
	provider := terminalInputProvider{
		Reader: buffered,
		source: source,
	}

	prepared, cancel, cancelable, err := prepareTerminalInputReader(provider)
	if err != nil {
		t.Fatalf("prepare provider input: %v", err)
	}
	defer cancel()

	if !cancelable {
		t.Fatal("expected provider-backed input to be cancelable")
	}

	data, err := io.ReadAll(prepared)
	if err != nil {
		t.Fatalf("read provider input: %v", err)
	}
	if string(data) != "provider data" {
		t.Fatalf("unexpected provider input: %q", string(data))
	}
}

func TestPrepareTerminalInputReaderProviderCancelUnblocksRead(t *testing.T) {
	reader, writer := io.Pipe()
	defer reader.Close()
	defer writer.Close()

	buffered := bufio.NewReader(reader)
	provider := terminalInputProvider{
		Reader: buffered,
		source: reader,
	}

	prepared, cancel, cancelable, err := prepareTerminalInputReader(provider)
	if err != nil {
		t.Fatalf("prepare input: %v", err)
	}

	if !cancelable {
		t.Fatal("expected provider-backed input to be cancelable")
	}

	done := make(chan error, 1)
	go func() {
		buf := make([]byte, 1)
		_, readErr := prepared.Read(buf)
		done <- readErr
	}()

	time.Sleep(50 * time.Millisecond)
	cancel()

	select {
	case readErr := <-done:
		if readErr == nil {
			t.Fatal("expected cancel to interrupt blocking read")
		}
	case <-time.After(time.Second):
		t.Fatal("blocking read did not unblock after cancel")
	}
}

func TestPrepareTerminalInputReaderBufioReaderCancelUnblocksRead(t *testing.T) {
	reader, writer := io.Pipe()
	defer reader.Close()
	defer writer.Close()

	buffered := bufio.NewReader(reader)
	prepared, cancel, cancelable, err := prepareTerminalInputReader(buffered)
	if err != nil {
		t.Fatalf("prepare input: %v", err)
	}

	if !cancelable {
		t.Fatal("expected bufio reader to be cancelable")
	}

	done := make(chan error, 1)
	go func() {
		buf := make([]byte, 1)
		_, readErr := prepared.Read(buf)
		done <- readErr
	}()

	time.Sleep(50 * time.Millisecond)
	cancel()

	select {
	case readErr := <-done:
		if readErr == nil {
			t.Fatal("expected cancel to interrupt blocking read")
		}
	case <-time.After(time.Second):
		t.Fatal("blocking bufio reader did not unblock after cancel")
	}
}

func TestPrepareTerminalInputReaderBufioReadWriterCancelUnblocksRead(t *testing.T) {
	reader, writer := io.Pipe()
	defer reader.Close()
	defer writer.Close()

	readWriter := bufio.NewReadWriter(bufio.NewReader(reader), bufio.NewWriter(io.Discard))
	prepared, cancel, cancelable, err := prepareTerminalInputReader(readWriter)
	if err != nil {
		t.Fatalf("prepare readwriter input: %v", err)
	}

	if !cancelable {
		t.Fatal("expected bufio readwriter to be cancelable")
	}

	done := make(chan error, 1)
	go func() {
		buf := make([]byte, 1)
		_, readErr := prepared.Read(buf)
		done <- readErr
	}()

	time.Sleep(50 * time.Millisecond)
	cancel()

	select {
	case readErr := <-done:
		if readErr == nil {
			t.Fatal("expected cancel to interrupt blocking read")
		}
	case <-time.After(time.Second):
		t.Fatal("blocking readwriter input did not unblock after cancel")
	}
}