"""Live configuration of the two engines HyperSwap arbitrates between.

Arbitration behaviour is largely dictated by settings that live outside this codebase.
Working out why a yield behaved the way it did meant reading journald and the ollama
unit by hand: OLLAMA_NUM_PARALLEL decides whether an unload queues behind a running
generation, OLLAMA_MAX_LOADED_MODELS decides whether more than one model can be
resident, and a pinned n_gpu_layers decides whether a model that will not fit spills to
the CPU or fails outright. Those are worth reading and explaining rather than hardcoding
into a dashboard subtitle that silently goes stale.
"""
import json
import logging
import subprocess
from typing import Any, Dict, List, Optional

import httpx

import vram_arbitrator

logger = logging.getLogger("engines")

# Settings that change how the arbitrator must behave, with what they imply.
OLLAMA_SETTING_NOTES = {
    "OLLAMA_NUM_PARALLEL": (
        "Requests per model. At 1, a keep_alive:0 unload queues behind any running "
        "generation and applies when it finishes — which is why a busy model is "
        "reported as deferred rather than failed."),
    "OLLAMA_MAX_LOADED_MODELS": (
        "How many models may be resident at once. At 1, Ollama evicts the previous "
        "model on every swap."),
    "OLLAMA_KEEP_ALIVE": (
        "Default residency after a request. Long values keep VRAM occupied and make "
        "ComfyUI wait for an explicit yield."),
    "OLLAMA_FLASH_ATTENTION": "FlashAttention kernels for attention.",
    "OLLAMA_KV_CACHE_TYPE": "KV cache quantisation; smaller types cut VRAM per context.",
    "OLLAMA_NUM_BATCH": "Prompt-evaluation batch size.",
}


def _ollama_unit_environment() -> Dict[str, str]:
    """Read the ollama service's environment. Empty if it is not a systemd unit."""
    env: Dict[str, str] = {}
    try:
        proc = subprocess.run(["systemctl", "show", "ollama", "-p", "Environment",
                               "--value"], capture_output=True, text=True, timeout=8)
        for token in proc.stdout.split():
            if "=" in token and token.startswith("OLLAMA"):
                k, _, v = token.partition("=")
                env[k] = v
    except Exception as e:
        logger.debug(f"could not read ollama unit environment: {e}")
    return env


async def get_engine_config() -> Dict[str, Any]:
    """Real, live configuration of both engines, with arbitration implications."""
    ollama_env = _ollama_unit_environment()
    ollama_settings = [
        {"key": k, "value": v, "means": OLLAMA_SETTING_NOTES.get(k, "")}
        for k, v in sorted(ollama_env.items())
    ]

    # A short, honest summary line to replace the dashboard's hardcoded subtitle.
    feature_bits: List[str] = []
    if ollama_env.get("OLLAMA_FLASH_ATTENTION") == "1":
        feature_bits.append("FlashAttention")
    kv = ollama_env.get("OLLAMA_KV_CACHE_TYPE")
    if kv:
        feature_bits.append(f"{kv} KV cache")
    host = ollama_env.get("OLLAMA_HOST", "")
    port = host.rsplit(":", 1)[-1] if ":" in host else "11434"

    ollama = {
        "port": port,
        "settings": ollama_settings,
        "summary": " + ".join(feature_bits) if feature_bits else "default configuration",
        "max_loaded_models": ollama_env.get("OLLAMA_MAX_LOADED_MODELS"),
        "num_parallel": ollama_env.get("OLLAMA_NUM_PARALLEL"),
        "keep_alive": ollama_env.get("OLLAMA_KEEP_ALIVE"),
        "config_source": "systemd unit environment" if ollama_env else "unavailable",
    }

    comfy: Dict[str, Any] = {"online": False}
    try:
        async with httpx.AsyncClient(timeout=4.0) as c:
            r = await c.get(f"{vram_arbitrator.COMFY_API_BASE}/system_stats")
        if r.status_code == 200:
            data = r.json()
            system = data.get("system", {})
            argv = system.get("argv") or []
            devices = data.get("devices") or []
            dev = devices[0] if devices else {}
            # The allocator is named in the device string; it is the closest thing
            # ComfyUI reports to the "async offload" the old subtitle asserted.
            dev_name = dev.get("name", "")
            allocator = ("cudaMallocAsync" if "cudaMallocAsync" in dev_name
                         else "cudaMalloc" if "cudaMalloc" in dev_name else "unknown")
            vram_flags = [a for a in argv
                          if a in ("--lowvram", "--novram", "--highvram", "--normalvram",
                                   "--gpu-only", "--cpu")]
            comfy = {
                "online": True,
                "version": system.get("comfyui_version"),
                "pytorch": system.get("pytorch_version"),
                # split()[0] on an absent version raises IndexError, which would have
                # been swallowed by the except below and reported ComfyUI as offline.
                "python": ((system.get("python_version") or "").split() or [None])[0],
                "argv": argv,
                "vram_mode": vram_flags[0] if vram_flags else "default (auto)",
                "allocator": allocator,
                "device": dev_name,
                "summary": f"{allocator}, {vram_flags[0] if vram_flags else 'auto VRAM'}",
            }
    except Exception as e:
        comfy = {"online": False, "error": str(e)[:120]}

    return {"ollama": ollama, "comfyui": comfy}