import json
import logging
import os
from typing import Optional

import httpx


log = logging.getLogger("docker_logs")


def _docker_transport() -> httpx.AsyncHTTPTransport:
    sock_path = os.getenv("DOCKER_SOCK", "/var/run/docker.sock")
    return httpx.AsyncHTTPTransport(uds=sock_path)


async def _docker_get(path: str, params: Optional[dict] = None) -> httpx.Response:
    timeout = httpx.Timeout(10.0, read=10.0)
    async with httpx.AsyncClient(transport=_docker_transport(), base_url="http://docker", timeout=timeout) as client:
        resp = await client.get(path, params=params)
        resp.raise_for_status()
        return resp


def _decode_docker_stream(data: bytes) -> str:
    if not data:
        return ""
    out = bytearray()
    idx = 0
    while idx + 8 <= len(data):
        stream_type = data[idx]
        size = int.from_bytes(data[idx + 4: idx + 8], "big")
        idx += 8
        if idx + size > len(data):
            break
        chunk = data[idx: idx + size]
        idx += size
        if stream_type in (1, 2):
            out.extend(chunk)
        else:
            out.extend(chunk)
    if out:
        return out.decode("utf-8", errors="replace")
    return data.decode("utf-8", errors="replace")


async def docker_container_logs(container_name: str, tail_lines: int = 200) -> str:
    filters = json.dumps({"name": [container_name]})
    resp = await _docker_get("/containers/json", params={"filters": filters})
    containers = resp.json() or []
    if not containers:
        log.info("No docker container found for name=%s", container_name)
        return ""
    container_id = containers[0].get("Id")
    if not container_id:
        return ""
    resp = await _docker_get(
        f"/containers/{container_id}/logs",
        params={"stdout": 1, "stderr": 1, "tail": tail_lines},
    )
    return _decode_docker_stream(resp.content)