using System.Collections.Immutable;
using ScadaLink.Commons.Types.Audit;
using ScadaLink.Commons.Types.Enums;

namespace ScadaLink.CentralUI.Components.Audit;

/// <summary>
/// UI-side binding model for <see cref="AuditFilterBar"/> (#23 M7-T2).
///
/// <para>
/// The model mirrors <see cref="AuditLogQueryFilter"/> but allows multi-select chip
/// state for Channel / Kind / Status / Site (each a <see cref="HashSet{T}"/>) plus
/// extra UI-only fields the underlying filter does not carry: the Errors-only toggle,
/// the time-range preset, and free-text Instance / Script searches.
/// </para>
///
/// <para>
/// The repository filter contract (<see cref="AuditLogQueryFilter"/>) is single-value
/// per dimension today; the chip multi-selects therefore collapse to the FIRST
/// selected chip when the model is published via <see cref="ToFilter"/>. That is a
/// deliberate Bundle B scope decision — the chip UI is preserved so a follow-up can
/// either repeat the query per chip or widen the filter contract without rewriting
/// the form. Instance and Script free-text are also UI-only today: the underlying
/// filter has no matching columns, so they are dropped during collapse.
/// </para>
///
/// <para>
/// The Errors-only toggle is a convenience: when true AND no explicit Status chips
/// are selected, the collapsed filter pins <see cref="AuditStatus.Failed"/> (the
/// first of {Failed, Parked, Discarded}). When Status chips ARE selected the toggle
/// is a no-op — the explicit Status filter wins.
/// </para>
/// </summary>
public sealed class AuditQueryModel
{
    public HashSet<AuditChannel> Channels { get; } = new();
    public HashSet<AuditKind> Kinds { get; } = new();
    public HashSet<AuditStatus> Statuses { get; } = new();
    public HashSet<string> SiteIdentifiers { get; } = new(StringComparer.OrdinalIgnoreCase);

    public AuditTimeRangePreset TimeRange { get; set; } = AuditTimeRangePreset.LastHour;
    public DateTime? CustomFromUtc { get; set; }
    public DateTime? CustomToUtc { get; set; }

    public string InstanceSearch { get; set; } = string.Empty;
    public string ScriptSearch { get; set; } = string.Empty;
    public string TargetSearch { get; set; } = string.Empty;
    public string ActorSearch { get; set; } = string.Empty;

    public bool ErrorsOnly { get; set; }

    /// <summary>
    /// Maps each channel to the kinds it can emit (per Component-AuditLog.md §4).
    /// <c>CachedSubmit</c> and <c>CachedResolve</c> appear under both
    /// <see cref="AuditChannel.ApiOutbound"/> and <see cref="AuditChannel.DbOutbound"/>
    /// because the cached-call lifecycle is channel-agnostic at submit/resolve time.
    /// Used by the filter bar to narrow the Kind chip list once Channels are picked.
    /// </summary>
    public static readonly IReadOnlyDictionary<AuditChannel, ImmutableList<AuditKind>> KindsByChannel =
        new Dictionary<AuditChannel, ImmutableList<AuditKind>>
        {
            [AuditChannel.ApiOutbound] = ImmutableList.Create(
                AuditKind.ApiCall, AuditKind.ApiCallCached,
                AuditKind.CachedSubmit, AuditKind.CachedResolve),
            [AuditChannel.DbOutbound] = ImmutableList.Create(
                AuditKind.DbWrite, AuditKind.DbWriteCached,
                AuditKind.CachedSubmit, AuditKind.CachedResolve),
            [AuditChannel.Notification] = ImmutableList.Create(
                AuditKind.NotifySend, AuditKind.NotifyDeliver),
            [AuditChannel.ApiInbound] = ImmutableList.Create(
                AuditKind.InboundRequest, AuditKind.InboundAuthFailure),
        };

    /// <summary>
    /// Returns the kinds visible in the Kind chip list given the currently selected
    /// Channels. With no Channel selected, all 10 kinds are visible (no narrowing).
    /// With one or more Channels selected, the union of the channel-specific kind
    /// lists is returned (deduplicated and order-stable on first-seen).
    /// </summary>
    public IReadOnlyList<AuditKind> VisibleKinds()
    {
        if (Channels.Count == 0)
        {
            return Enum.GetValues<AuditKind>();
        }

        var seen = new HashSet<AuditKind>();
        var result = new List<AuditKind>();
        foreach (var ch in Channels)
        {
            if (!KindsByChannel.TryGetValue(ch, out var kinds))
            {
                continue;
            }
            foreach (var k in kinds)
            {
                if (seen.Add(k))
                {
                    result.Add(k);
                }
            }
        }
        return result;
    }

    /// <summary>
    /// Collapses this UI model to the repository's single-value filter.
    /// See class doc for the multi-select → single-value contract.
    /// </summary>
    public AuditLogQueryFilter ToFilter(DateTime utcNow)
    {
        var status = ResolveStatus();

        var (fromUtc, toUtc) = ResolveTimeWindow(utcNow);

        return new AuditLogQueryFilter(
            Channel: Channels.Count > 0 ? Channels.First() : null,
            Kind: Kinds.Count > 0 ? Kinds.First() : null,
            Status: status,
            SourceSiteId: SiteIdentifiers.Count > 0 ? SiteIdentifiers.First() : null,
            Target: string.IsNullOrWhiteSpace(TargetSearch) ? null : TargetSearch.Trim(),
            Actor: string.IsNullOrWhiteSpace(ActorSearch) ? null : ActorSearch.Trim(),
            CorrelationId: null,
            FromUtc: fromUtc,
            ToUtc: toUtc);
    }

    private AuditStatus? ResolveStatus()
    {
        if (Statuses.Count > 0)
        {
            // Explicit chips win — Errors-only is a no-op.
            return Statuses.First();
        }

        if (ErrorsOnly)
        {
            // Single-value filter contract: Failed is the lead non-success status.
            // When the filter widens to multi-value the full {Failed, Parked, Discarded}
            // set will flow through.
            return AuditStatus.Failed;
        }

        return null;
    }

    private (DateTime? From, DateTime? To) ResolveTimeWindow(DateTime utcNow)
    {
        return TimeRange switch
        {
            AuditTimeRangePreset.Last5Minutes => (utcNow.AddMinutes(-5), null),
            AuditTimeRangePreset.LastHour => (utcNow.AddHours(-1), null),
            AuditTimeRangePreset.Last24Hours => (utcNow.AddHours(-24), null),
            AuditTimeRangePreset.Custom => (CustomFromUtc, CustomToUtc),
            _ => (null, null),
        };
    }
}

/// <summary>
/// Time-range presets surfaced in the filter bar. <see cref="Custom"/> reveals the
/// FromUtc / ToUtc datetime pickers; the other presets compute From relative to
/// "now" at the moment Apply is clicked.
/// </summary>
public enum AuditTimeRangePreset
{
    Last5Minutes,
    LastHour,
    Last24Hours,
    Custom,
}