using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Jellyfin.Database.Implementations.Entities;
using Jellyfin.Plugin.WatchedTogether.Configuration;

namespace Jellyfin.Plugin.WatchedTogether.Services;

/// <summary>
/// Computes, applies and checks the content restrictions a shared account should have.
/// </summary>
public interface IRestrictionService
{
    /// <summary>
    /// Computes the strictest combination of the given members' restrictions.
    /// </summary>
    /// <param name="memberIds">The members to combine.</param>
    /// <returns>Restrictions at least as strict as every member's.</returns>
    ContentRestrictions ComputeStrictest(IReadOnlyList<Guid> memberIds);

    /// <summary>
    /// Finds the range the members' parental rating caps span.
    /// </summary>
    /// <param name="memberIds">The members to inspect.</param>
    /// <returns>The strictest and loosest caps among them.</returns>
    RatingRange GetRatingRange(IReadOnlyList<Guid> memberIds);

    /// <summary>
    /// Writes the restrictions a group's shared account should have: the strictest member's,
    /// except for the rating cap when the group has chosen its own.
    /// </summary>
    /// <param name="group">The group whose shared account to update.</param>
    /// <returns>
    /// The restrictions written, and whether the group's chosen cap had to be adjusted to stay
    /// within its members' range - in which case <paramref name="group"/> has been updated in
    /// place and the caller should persist it.
    /// </returns>
    Task<RestrictionApplyResult> ApplyAsync(SharedGroup group);

    /// <summary>
    /// Determines whether <paramref name="candidate"/> hides at least everything
    /// <paramref name="member"/> cannot see, reading both users live.
    /// </summary>
    /// <param name="candidate">The shared account being unlocked.</param>
    /// <param name="member">The member whose password matched.</param>
    /// <returns><c>true</c> if the member may unlock the account.</returns>
    bool IsAtLeastAsStrict(User candidate, User member);
}

/// <summary>
/// The range spanned by a set of members' parental rating caps.
/// </summary>
/// <param name="Strictest">The lowest cap, or <c>null</c> if no member has one.</param>
/// <param name="Loosest">The highest cap, or <c>null</c> if any member has none.</param>
public readonly record struct RatingRange(int? Strictest, int? Loosest)
{
    /// <summary>
    /// Gets a value indicating whether there is anything to choose: at least one member is capped.
    /// </summary>
    public bool HasChoice => Strictest is not null;
}

/// <summary>
/// The outcome of applying a group's restrictions to its shared account.
/// </summary>
/// <param name="Restrictions">What was written.</param>
/// <param name="CapAdjusted">Whether the group's chosen cap was changed to fit its members' range.</param>
public sealed record RestrictionApplyResult(ContentRestrictions Restrictions, bool CapAdjusted);