using System.Collections.Generic;
using System.Globalization;
using EmbyToolbox.Models;

namespace EmbyToolbox.Services;

public static class VideoBitratePolicy
{
    public const string Auto = "Auto";
    public const string Source = "Source";
    public const string Custom = "Custom";

    public static IReadOnlyList<string> UiOptions { get; } =
    [
        Auto,
        Source,
        "2 Mbps",
        "3 Mbps",
        "4 Mbps",
        "6 Mbps",
        "8 Mbps",
        "10 Mbps",
        "12 Mbps",
        "15 Mbps",
        "20 Mbps",
        Custom
    ];

    public static string NormalizeMode(string? mode) =>
        mode switch
        {
            Source => Source,
            Custom => Custom,
            _ => TryParseFixedModeKbps(mode) is { } fixedKbps
                ? $"{fixedKbps / 1000.0:0.###} Mbps".Replace(".000", string.Empty, StringComparison.Ordinal)
                : Auto
        };

    public static int? ResolveTargetKbps(string? mode, double? customMbps, MediaAnalysisResult? media)
    {
        var normalized = NormalizeMode(mode);
        if (normalized == Auto)
        {
            return null;
        }

        if (normalized == Source)
        {
            return media?.SourceVideoBitrateBps is { } bps && bps > 0
                ? Math.Max(1, (int)Math.Round(bps / 1000.0, MidpointRounding.AwayFromZero))
                : null;
        }

        if (normalized == Custom)
        {
            return customMbps is { } mbps && mbps > 0
                ? Math.Max(1, (int)Math.Round(mbps * 1000.0, MidpointRounding.AwayFromZero))
                : null;
        }

        return TryParseFixedModeKbps(normalized);
    }

    public static int? TryParseFixedModeKbps(string? mode)
    {
        if (string.IsNullOrWhiteSpace(mode))
        {
            return null;
        }

        var m = mode.Trim();
        if (m.Equals(Auto, StringComparison.OrdinalIgnoreCase)
            || m.Equals(Source, StringComparison.OrdinalIgnoreCase)
            || m.Equals(Custom, StringComparison.OrdinalIgnoreCase))
        {
            return null;
        }

        if (!m.EndsWith("Mbps", StringComparison.OrdinalIgnoreCase))
        {
            return null;
        }

        var number = m[..^4].Trim();
        if (!double.TryParse(number.Replace(',', '.'), NumberStyles.Any, CultureInfo.InvariantCulture, out var mbps) || mbps <= 0)
        {
            return null;
        }

        return Math.Max(1, (int)Math.Round(mbps * 1000.0, MidpointRounding.AwayFromZero));
    }

    public static string FormatCurrentSource(long? bps)
    {
        if (bps is not { } value || value <= 0)
        {
            return "Текущее: неизвестно";
        }

        var mbps = value / 1_000_000d;
        return $"Текущее: {mbps:0.###} Mbps";
    }
}