from datetime import datetime
import asyncio
import json

async def get_systemd_logs(lines: int = 200, service_name: str = "smartwave") -> list[dict]:
    """
    Asynchronously fetches the last N log entries from a systemd service 
    using native asyncio subprocess execution.
    """
    cmd = (
        "journalctl",
        "-u", service_name,
        "-n", str(lines),
        "-o", "json",
        "--no-pager"
    )
    
    try:
        # Create non-blocking child process
        proc = await asyncio.create_subprocess_exec(
            *cmd,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.PIPE
        )
        
        # Await completion and read output non-blockingly
        stdout_bytes, stderr_bytes = await proc.communicate()
        
        if proc.returncode != 0:
            print(f"[Logs] journalctl error (code {proc.returncode}): {stderr_bytes.decode('utf-8', errors='replace')}")
            return []
            
        structured_logs = []
        stdout_text = stdout_bytes.decode("utf-8", errors="replace")
        
        for line in stdout_text.strip().split("\n"):
            if not line:
                continue
            try:
                entry = json.loads(line)
                
                raw_ts = entry.get("__REALTIME_TIMESTAMP")
                timestamp_iso = None
                if raw_ts:
                    timestamp_iso = datetime.fromtimestamp(int(raw_ts) / 1_000_000).isoformat()
                
                structured_logs.append({
                    "timestamp": timestamp_iso,
                    "timestamp_us": int(raw_ts) if raw_ts else None,
                    "message": entry.get("MESSAGE", ""),
                    "priority": entry.get("PRIORITY"),
                    "pid": entry.get("_PID"),
                })
            except (json.JSONDecodeError, ValueError):
                continue
                
        return structured_logs

    except Exception as e:
        print(f"[Logs] Failed to read systemd logs for '{service_name}': {e}")
        return []