import asyncio
import struct

import pytest

from browser_cli.framing import (
    async_recv_frame,
    frame,
    recv_frame,
    send_frame,
)
from browser_cli.version_manager import MAX_MSG_BYTES

class FakeRecv:
    def __init__(self, chunks):
        self.chunks = list(chunks)

    def recv(self, n):
        if not self.chunks:
            return b""
        chunk = self.chunks.pop(0)
        if len(chunk) > n:
            self.chunks.insert(0, chunk[n:])
            return chunk[:n]
        return chunk

def test_frame_prefixes_payload_length():
    assert frame(b"abc") == b"\x03\x00\x00\x00abc"

def test_recv_frame_reads_chunked_socket_payload():
    sock = FakeRecv([b"\x05", b"\x00\x00\x00he", b"llo"])
    assert recv_frame(sock) == b"hello"

def test_recv_frame_allow_eof_returns_none():
    assert recv_frame(FakeRecv([]), allow_eof=True) is None

def test_recv_frame_rejects_oversized_payload():
    sock = FakeRecv([struct.pack("<I", MAX_MSG_BYTES + 1)])
    with pytest.raises(ConnectionError, match="too large"):
        recv_frame(sock, label="message")

def test_send_frame_writes_prefixed_payload():
    sent = []

    class FakeSend:
        def sendall(self, data):
            sent.append(data)

    send_frame(FakeSend(), b"ok")
    assert sent == [b"\x02\x00\x00\x00ok"]

def test_async_recv_frame_reads_payload():
    async def run():
        reader = asyncio.StreamReader()
        reader.feed_data(frame(b"async"))
        reader.feed_eof()
        return await async_recv_frame(reader)

    assert asyncio.run(run()) == b"async"