package lsp

import (
	"bufio"
	"bytes"
	"testing"
)

func TestReadMessage_ParsesContentLength(t *testing.T) {
	body := []byte(`{"jsonrpc":"2.0","id":1,"method":"initialize"}`)
	frame := []byte("Content-Length: ")
	frame = append(frame, []byte(stringInt(len(body)))...)
	frame = append(frame, []byte("\r\n\r\n")...)
	frame = append(frame, body...)
	s := &Server{in: bufio.NewReader(bytes.NewReader(frame))}
	got, err := s.readMessage()
	if err != nil || string(got) != string(body) {
		t.Fatalf("readMessage failed: %v %q", err, string(got))
	}
}

func TestWriteMessage_FramesJSON(t *testing.T) {
	var out bytes.Buffer
	s := &Server{out: &out}
	payload := struct {
		JSONRPC string `json:"jsonrpc"`
		Ping    string `json:"ping"`
	}{JSONRPC: "2.0", Ping: "pong"}
	s.writeMessage(payload)
	got := out.String()
	if !bytes.HasPrefix([]byte(got), []byte("Content-Length: ")) {
		t.Fatalf("missing Content-Length header: %q", got)
	}
	// Header/body delimiter must be present
	idx := bytes.Index([]byte(got), []byte("\r\n\r\n"))
	if idx < 0 {
		t.Fatalf("missing CRLFCRLF delimiter: %q", got)
	}
	body := got[idx+4:]
	if body == "" || body[0] != '{' || body[len(body)-1] != '}' {
		t.Fatalf("body not JSON: %q", body)
	}
}

func stringInt(n int) string {
	if n == 0 {
		return "0"
	}
	var b [20]byte
	i := len(b)
	for n > 0 {
		i--
		b[i] = byte('0' + n%10)
		n /= 10
	}
	return string(b[i:])
}