using System;
using System.Collections.Generic;
using Jellyfin.Plugin.JRay.Models;

namespace Jellyfin.Plugin.JRay.Services;

/// <summary>
/// Resolves the effective prioritise/ignore action for an item from the
/// configured rules. More specific scopes win: an Item rule overrides a
/// Series rule, which overrides a Genre rule. Because a given scope+value can
/// hold only one action, the only conflicts possible are across scopes, and
/// specificity resolves those.
/// </summary>
public static class PolicyResolver
{
    /// <summary>
    /// Computes the effective action for an item, or <c>null</c> if no rule matches.
    /// </summary>
    /// <param name="rules">The configured rules.</param>
    /// <param name="itemId">The item's id.</param>
    /// <param name="seriesId">The item's series id, or <see cref="Guid.Empty"/> if it is not an episode.</param>
    /// <param name="genres">The item's genres.</param>
    /// <returns>The effective <see cref="PolicyAction"/>, or <c>null</c> when unruled.</returns>
    public static PolicyAction? Resolve(
        IReadOnlyList<MediaPolicyRule> rules,
        Guid itemId,
        Guid seriesId,
        IReadOnlyList<string> genres)
    {
        ArgumentNullException.ThrowIfNull(rules);

        PolicyAction? itemAction = null;
        PolicyAction? seriesAction = null;
        PolicyAction? genreAction = null;

        var itemIdStr = itemId.ToString("D");
        var seriesIdStr = seriesId == Guid.Empty ? null : seriesId.ToString("D");

        foreach (var rule in rules)
        {
            switch (rule.Scope)
            {
                case PolicyScope.Item:
                    if (string.Equals(rule.Value, itemIdStr, StringComparison.OrdinalIgnoreCase))
                    {
                        itemAction = rule.Action;
                    }

                    break;

                case PolicyScope.Series:
                    if (seriesIdStr is not null && string.Equals(rule.Value, seriesIdStr, StringComparison.OrdinalIgnoreCase))
                    {
                        seriesAction = rule.Action;
                    }

                    break;

                case PolicyScope.Genre:
                    if (genres is not null && MatchesGenre(genres, rule.Value))
                    {
                        genreAction = rule.Action;
                    }

                    break;
            }
        }

        return itemAction ?? seriesAction ?? genreAction;
    }

    private static bool MatchesGenre(IReadOnlyList<string> genres, string value)
    {
        for (var i = 0; i < genres.Count; i++)
        {
            if (string.Equals(genres[i], value, StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }
        }

        return false;
    }
}