"""Worker-child resource de-prioritization (S4): the encoder thread cap, the `-threads` flag on the
browser-safe re-encode, and the child's startup renice/ionice/OMP handicap. These keep a CPU-heavy
transcode from pegging every core on the box it shares with the API, Postgres, and Plex playback."""

import subprocess

import pytest

from app.config import settings
from app.downloads import edit as editmod
from app.downloads import runner


class TestEncodeThreadCap:
    def test_pinned_setting_wins(self, monkeypatch):
        monkeypatch.setattr(settings, "download_ffmpeg_threads", 3)
        assert editmod.encode_thread_cap() == 3

    def test_zero_reserves_one_core(self, monkeypatch):
        monkeypatch.setattr(settings, "download_ffmpeg_threads", 0)
        monkeypatch.setattr(editmod.os, "cpu_count", lambda: 8)
        assert editmod.encode_thread_cap() == 7

    def test_single_core_box_never_caps_below_one(self, monkeypatch):
        monkeypatch.setattr(settings, "download_ffmpeg_threads", 0)
        monkeypatch.setattr(editmod.os, "cpu_count", lambda: 1)
        assert editmod.encode_thread_cap() == 1

    def test_unknown_cpu_count_falls_back(self, monkeypatch):
        monkeypatch.setattr(settings, "download_ffmpeg_threads", 0)
        monkeypatch.setattr(editmod.os, "cpu_count", lambda: None)
        assert editmod.encode_thread_cap() == 1  # max(1, 2 - 1)


class TestBrowserSafeThreads:
    def test_threads_flag_added_when_capped(self):
        cmd = editmod.build_browser_safe_cmd(
            "/in.mkv", "/out.mp4", reencode_video=True, reencode_audio=False, threads=2
        )
        assert "-threads" in cmd
        assert cmd[cmd.index("-threads") + 1] == "2"
        # The cap precedes the output file, so it binds the encoder (not input decoding).
        assert cmd.index("-threads") < cmd.index("/out.mp4")

    @pytest.mark.parametrize("threads", [0, None])
    def test_no_threads_flag_when_uncapped(self, threads):
        cmd = editmod.build_browser_safe_cmd(
            "/in.mkv", "/out.mp4", reencode_video=True, reencode_audio=False, threads=threads
        )
        assert "-threads" not in cmd


class TestDeprioritize:
    def test_renices_by_configured_increment(self, monkeypatch):
        monkeypatch.setattr(settings, "download_child_nice", 12)
        monkeypatch.setattr(settings, "download_child_ionice_class", 0)  # skip ionice branch
        calls = []
        monkeypatch.setattr(runner.os, "nice", lambda n: calls.append(n))
        monkeypatch.setattr(runner.os, "environ", {})
        runner._deprioritize()
        assert calls == [12]

    def test_nice_zero_does_not_renice(self, monkeypatch):
        monkeypatch.setattr(settings, "download_child_nice", 0)
        monkeypatch.setattr(settings, "download_child_ionice_class", 0)
        calls = []
        monkeypatch.setattr(runner.os, "nice", lambda n: calls.append(n))
        monkeypatch.setattr(runner.os, "environ", {})
        runner._deprioritize()
        assert calls == []

    def test_sets_omp_budget_to_thread_cap(self, monkeypatch):
        monkeypatch.setattr(settings, "download_child_nice", 0)
        monkeypatch.setattr(settings, "download_child_ionice_class", 0)
        monkeypatch.setattr(settings, "download_ffmpeg_threads", 4)
        env: dict = {}
        monkeypatch.setattr(runner.os, "environ", env)
        runner._deprioritize()
        assert env["OMP_NUM_THREADS"] == "4"

    def test_ionice_invoked_when_binary_present(self, monkeypatch):
        monkeypatch.setattr(settings, "download_child_nice", 0)
        monkeypatch.setattr(settings, "download_child_ionice_class", 3)
        monkeypatch.setattr(runner.os, "environ", {})
        monkeypatch.setattr(runner.shutil, "which", lambda name: "/usr/bin/ionice")
        ran = []
        monkeypatch.setattr(
            runner.subprocess,
            "run",
            lambda cmd, **kw: ran.append(cmd) or subprocess.CompletedProcess(cmd, 0),
        )
        runner._deprioritize()
        assert ran and ran[0][:3] == ["ionice", "-c", "3"]

    def test_ionice_skipped_when_binary_absent(self, monkeypatch):
        monkeypatch.setattr(settings, "download_child_nice", 0)
        monkeypatch.setattr(settings, "download_child_ionice_class", 3)
        monkeypatch.setattr(runner.os, "environ", {})
        monkeypatch.setattr(runner.shutil, "which", lambda name: None)
        ran = []
        monkeypatch.setattr(runner.subprocess, "run", lambda cmd, **kw: ran.append(cmd))
        runner._deprioritize()
        assert ran == []