using System;
using Paca.Core;
using Paca.Core.Platform;
using Xunit;

namespace Paca.Tests.Core;

public class BatterySaverPowerManagerTests
{
    [Fact]
    public void 정상_상태_완전한_동시성_유지_및_백그라운드_작업_허용()
    {
        var manager = new BatterySaverPowerManager();
        manager.UpdateBatteryState(percent: 85, isCharging: false);

        Assert.False(manager.IsLowPowerModeActive);
        Assert.False(manager.ShouldDeferBackgroundProcessing);
        Assert.Equal(8, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
        Assert.True(manager.CanExecuteCpuIntensiveTask());
    }

    [Fact]
    public void 충전_중일_때는_배터리_15퍼센트여도_풀파워_유지()
    {
        var manager = new BatterySaverPowerManager();
        manager.UpdateBatteryState(percent: 15, isCharging: true);

        Assert.False(manager.IsLowPowerModeActive);
        Assert.False(manager.ShouldDeferBackgroundProcessing);
        Assert.Equal(8, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
        Assert.True(manager.CanExecuteCpuIntensiveTask());
    }

    [Fact]
    public void 배터리_20퍼센트_이하_방전_중_동시성_감축_및_백그라운드_유예()
    {
        var manager = new BatterySaverPowerManager(lowBatteryThresholdPercent: 20);
        manager.UpdateBatteryState(percent: 18, isCharging: false);

        Assert.True(manager.IsLowPowerModeActive);
        Assert.True(manager.ShouldDeferBackgroundProcessing);
        // 8개의 병렬 다운로드 -> 2개로 자동 감축 (전력 및 RF 소모 75% 절감)
        Assert.Equal(2, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
        Assert.False(manager.CanExecuteCpuIntensiveTask());
    }

    [Fact]
    public void 배터리_10퍼센트_이하_크리티컬_단일_스트림_최소_전력_모드()
    {
        var manager = new BatterySaverPowerManager();
        manager.UpdateBatteryState(percent: 8, isCharging: false);

        Assert.True(manager.IsLowPowerModeActive);
        // 크리티컬 상황에서는 최소 1개 스트림으로 다운로드 중단 방지
        Assert.Equal(1, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
        Assert.True(manager.ShouldDeferBackgroundProcessing);
    }

    [Fact]
    public void OS_절전_모드_활성화시_배터리_잔량_무관_절전_진입()
    {
        var manager = new BatterySaverPowerManager();
        manager.UpdateBatteryState(percent: 60, isCharging: false, isOsPowerSaverEnabled: true);

        Assert.True(manager.IsLowPowerModeActive);
        Assert.True(manager.ShouldDeferBackgroundProcessing);
        Assert.Equal(2, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
    }

    [Fact]
    public void 충전기_연결시_즉시_풀파워_복구_및_이벤트_발행()
    {
        var manager = new BatterySaverPowerManager();
        manager.UpdateBatteryState(percent: 12, isCharging: false);
        Assert.True(manager.IsLowPowerModeActive);

        bool eventFired = false;
        PowerStateChangedEventArgs? capturedArgs = null;
        manager.PowerStateChanged += (s, e) =>
        {
            eventFired = true;
            capturedArgs = e;
        };

        // 충전기 연결
        manager.UpdateBatteryState(percent: 12, isCharging: true);

        Assert.True(eventFired);
        Assert.NotNull(capturedArgs);
        Assert.False(capturedArgs!.IsLowPowerModeActive);
        Assert.False(manager.IsLowPowerModeActive);
        Assert.Equal(8, manager.CalculateOptimalConcurrency(baseConcurrency: 8));
    }

    [Fact]
    public void 절전_모드_대역폭_권장_제한치_계산_검증()
    {
        var manager = new BatterySaverPowerManager();
        
        // 정상 상태에서는 설정된 대역폭 유지
        manager.UpdateBatteryState(percent: 90, isCharging: false);
        Assert.Equal(10000, manager.CalculateBandwidthLimitKbps(baseLimitKbps: 10000));
        Assert.Null(manager.CalculateBandwidthLimitKbps(baseLimitKbps: null));

        // 절전 모드에서는 대역폭 상한 제안 (무제한일 경우 2000 Kbps로 쓰로틀링)
        manager.UpdateBatteryState(percent: 15, isCharging: false);
        Assert.Equal(2000, manager.CalculateBandwidthLimitKbps(baseLimitKbps: null));
        // 기존 제한이 더 크면 2000으로 강제
        Assert.Equal(2000, manager.CalculateBandwidthLimitKbps(baseLimitKbps: 8000));
        // 기존 제한이 이미 2000보다 작으면 기존 것 존중
        Assert.Equal(1000, manager.CalculateBandwidthLimitKbps(baseLimitKbps: 1000));
    }

    [Fact]
    public void HlsDownloader_배터리_절전모드_연동_동시성_감축_검증()
    {
        var powerManager = new BatterySaverPowerManager();
        var config = new Paca.Core.Config.AppConfig { Concurrency = 8 };
        var http = new System.Net.Http.HttpClient();
        var downloader = new Paca.Core.Hls.HlsDownloader(http, config, Paca.Core.Platform.DesktopMediaMuxer.Default, powerManager);

        // 정상 상태: 8
        powerManager.UpdateBatteryState(percent: 90, isCharging: false);
        Assert.Equal(8, downloader.GetEffectiveConcurrency());

        // 배터리 15% 방전 중: 2로 감축
        powerManager.UpdateBatteryState(percent: 15, isCharging: false);
        Assert.Equal(2, downloader.GetEffectiveConcurrency());

        // 충전기 연결: 8로 즉시 복귀
        powerManager.UpdateBatteryState(percent: 15, isCharging: true);
        Assert.Equal(8, downloader.GetEffectiveConcurrency());
    }

    [Fact]
    public void VideoPosterExtractor_배터리_절전모드시_썸네일_추출_유예_판정_검증()
    {
        var powerManager = new BatterySaverPowerManager();
        powerManager.UpdateBatteryState(percent: 15, isCharging: false);

        Assert.True(VideoPosterExtractor.ShouldDeferExtraction(powerManager));

        powerManager.UpdateBatteryState(percent: 15, isCharging: true);
        Assert.False(VideoPosterExtractor.ShouldDeferExtraction(powerManager));
        Assert.False(VideoPosterExtractor.ShouldDeferExtraction(null));
    }
}