"""GPU resource management (REQ-010).

Manual, not automatic (Phase 13: "don't automate too much early on"). Three
named modes; a :class:`GpuMonitor` reports VRAM/util so a human (or a later
auto policy) can decide. The mode switch is a pure decision — no process
spawning here, so it's testable on a machine with no GPU.
"""
from __future__ import annotations

from dataclasses import dataclass


@dataclass
class GpuState:
    vram_total_gb: float
    vram_free_gb: float
    util_percent: int = 0
    stt_resident: bool = False
    tts_resident: bool = False
    comfyui_active: bool = False


class GpuMonitor:
    """Reads GPU state. ``mock`` for tests; a real one would shell to nvidia-smi."""

    def __init__(self, state: GpuState | None = None) -> None:
        self._state = state or GpuState(vram_total_gb=16.0, vram_free_gb=16.0)

    @property
    def state(self) -> GpuState:
        return self._state


class ResourceMode:
    FULL = "voice-full"
    LITE = "voice-lite"
    OFF = "voice-off"


class GpuResourceManager:
    """Decide which voice models should be resident for a given mode.

    * FULL  — STT + TTS resident (normal voice use).
    * LITE  — STT resident, TTS loaded on demand (for gaming; frees VRAM).
    * OFF   — nothing resident (ComfyUI / other GPU work).
    """

    def __init__(self, monitor: GpuMonitor) -> None:
        self.monitor = monitor

    def plan(self, mode: str) -> dict:
        if mode == ResourceMode.FULL:
            return {"stt": True, "tts": True, "unload_tts": False}
        if mode == ResourceMode.LITE:
            return {"stt": True, "tts": False, "unload_tts": True}
        if mode == ResourceMode.OFF:
            return {"stt": False, "tts": False, "unload_tts": True}
        raise ValueError(f"unknown gpu mode: {mode}")

    def can_fit(self, mode: str) -> bool:
        """Heuristic: does the current free VRAM fit the plan's budgets?"""
        s = self.monitor.state
        plan = self.plan(mode)
        needed = 0.0
        if plan["stt"]:
            needed += 2.0
        if plan["tts"]:
            needed += 4.0
        return s.vram_free_gb >= needed