package selector

import (
	"context"
	"net"
	"testing"

	"github.com/go-gost/core/chain"
	"github.com/go-gost/core/connector"
)

// mockTransport implements chain.Transporter for testing.
type mockTransport struct {
	dialResult   net.Conn
	dialErr      error
	handshakeErr error
	connectErr   error
	bindErr      error
}

func (m *mockTransport) Dial(ctx context.Context, addr string) (net.Conn, error) {
	if m.dialErr != nil {
		return nil, m.dialErr
	}
	return m.dialResult, nil
}

func (m *mockTransport) Handshake(ctx context.Context, conn net.Conn) (net.Conn, error) {
	if m.handshakeErr != nil {
		return nil, m.handshakeErr
	}
	return conn, nil
}

func (m *mockTransport) Connect(ctx context.Context, conn net.Conn, network, address string) (net.Conn, error) {
	if m.connectErr != nil {
		return nil, m.connectErr
	}
	return conn, nil
}

func (m *mockTransport) Bind(ctx context.Context, conn net.Conn, network, address string, opts ...connector.BindOption) (net.Listener, error) {
	if m.bindErr != nil {
		return nil, m.bindErr
	}
	return net.Listen("tcp", "127.0.0.1:0")
}

func (m *mockTransport) Multiplex() bool                    { return false }
func (m *mockTransport) Options() *chain.TransportOptions   { return &chain.TransportOptions{} }
func (m *mockTransport) Copy() chain.Transporter            { return m }

func makeNode(tr chain.Transporter) *chain.Node {
	return chain.NewNode("test", "127.0.0.1:0", chain.TransportNodeOption(tr))
}

// --- ParallelStrategy ---

func TestParallelStrategy_Empty(t *testing.T) {
	s := ParallelStrategy[*chain.Node]()
	if v := s.Apply(context.Background()); v != nil {
		t.Fatalf("expected nil, got %v", v)
	}
}

func TestParallelStrategy_Single(t *testing.T) {
	s := ParallelStrategy[*chain.Node]()
	tr := &mockTransport{}
	node := makeNode(tr)

	result := s.Apply(context.Background(), node)
	if result == nil {
		t.Fatal("expected non-nil result for single node")
	}
}

func TestParallelStrategy_MultipleNodes(t *testing.T) {
	s := ParallelStrategy[*chain.Node]()
	nodes := []*chain.Node{
		makeNode(&mockTransport{}),
		makeNode(&mockTransport{}),
		makeNode(&mockTransport{}),
	}

	result := s.Apply(context.Background(), nodes[0], nodes[1], nodes[2])
	if result == nil {
		t.Fatal("expected non-nil result")
	}
}

func TestParallelStrategy_NonNodeInput(t *testing.T) {
	s := ParallelStrategy[string]()
	// Single non-node input: len==1 returns vs[0] directly
	if v := s.Apply(context.Background(), "hello"); v != "hello" {
		t.Fatalf("expected 'hello' for single input, got %q", v)
	}

	// Multiple non-node inputs: type assertion fails, returns zero value
	if v := s.Apply(context.Background(), "a", "b"); v != "" {
		t.Fatalf("expected zero value for multiple non-node inputs, got %q", v)
	}
}

// --- parallelTransporter unit tests ---

func TestParallelTransporter_Dial_NoNodes(t *testing.T) {
	tr := &parallelTransporter{nodes: nil}
	_, err := tr.Dial(context.Background(), "")
	if err == nil {
		t.Fatal("expected error with no nodes")
	}
}

func TestParallelTransporter_Copy(t *testing.T) {
	nodes := []*chain.Node{makeNode(&mockTransport{}), makeNode(&mockTransport{})}
	tr := &parallelTransporter{nodes: nodes}

	cp := tr.Copy()
	cpTr := cp.(*parallelTransporter)

	if len(cpTr.nodes) != len(tr.nodes) {
		t.Fatalf("copy should have same number of nodes: %d vs %d", len(cpTr.nodes), len(tr.nodes))
	}

	// Should be a shallow copy of the slice (different backing array)
	cpTr.nodes[0] = nil
	if tr.nodes[0] == nil {
		t.Fatal("copy should not share backing array")
	}
}

func TestParallelTransporter_Multiplex(t *testing.T) {
	tr := &parallelTransporter{}
	if tr.Multiplex() {
		t.Fatal("parallel transporter should not multiplex")
	}
}

func TestParallelTransporter_Options(t *testing.T) {
	tr := &parallelTransporter{}
	if opts := tr.Options(); opts == nil {
		t.Fatal("expected non-nil options")
	}
}

func TestParallelTransporter_Handshake_NonParallelConn(t *testing.T) {
	tr := &parallelTransporter{}
	c1, c2 := net.Pipe()
	defer c1.Close()
	defer c2.Close()

	conn, err := tr.Handshake(context.Background(), c1)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	// Non-parallelConn should be returned as-is
	if conn != c1 {
		t.Fatal("expected original conn for non-parallelConn")
	}
}

func TestParallelTransporter_Connect_NonParallelConn(t *testing.T) {
	tr := &parallelTransporter{}
	c1, _ := net.Pipe()
	defer c1.Close()

	_, err := tr.Connect(context.Background(), c1, "tcp", "addr")
	if err == nil {
		t.Fatal("expected error for non-parallelConn")
	}
}

func TestParallelTransporter_Bind_NonParallelConn(t *testing.T) {
	tr := &parallelTransporter{}
	c1, _ := net.Pipe()
	defer c1.Close()

	_, err := tr.Bind(context.Background(), c1, "tcp", "addr")
	if err == nil {
		t.Fatal("expected error for non-parallelConn")
	}
}

// --- parallelConn tests ---

func TestParallelConn_Handshake_Delegates(t *testing.T) {
	tr := &parallelTransporter{
		nodes: []*chain.Node{makeNode(&mockTransport{})},
	}

	c1, c2 := net.Pipe()
	defer c2.Close()

	pc := &parallelConn{Conn: c1, node: makeNode(&mockTransport{})}
	conn, err := tr.Handshake(context.Background(), pc)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if conn == nil {
		t.Fatal("expected non-nil conn after handshake")
	}
	conn.Close()
}

func TestParallelConn_Connect_Delegates(t *testing.T) {
	tr := &parallelTransporter{
		nodes: []*chain.Node{makeNode(&mockTransport{})},
	}

	c1, c2 := net.Pipe()
	defer c2.Close()

	pc := &parallelConn{Conn: c1, node: makeNode(&mockTransport{})}
	conn, err := tr.Connect(context.Background(), pc, "tcp", "127.0.0.1:80")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if conn == nil {
		t.Fatal("expected non-nil conn after connect")
	}
	conn.Close()
}

func TestParallelConn_Bind_Delegates(t *testing.T) {
	tr := &parallelTransporter{
		nodes: []*chain.Node{makeNode(&mockTransport{})},
	}

	c1, c2 := net.Pipe()
	defer c2.Close()

	pc := &parallelConn{Conn: c1, node: makeNode(&mockTransport{})}
	ln, err := tr.Bind(context.Background(), pc, "tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	ln.Close()
}