using ClawdDotNet.Core.Organisation;
using ClawdDotNet.Core.Tasks;

namespace ClawdDotNet.Core.Cases;

/// <summary>Where a conflict goes: who decides, who is told, or why it is no conflict at all.</summary>
public sealed record ConflictRoute(string Decider, IReadOnlyList<string> Informed, string? Refusal)
{
    public bool DecidedByHuman => string.IsNullOrWhiteSpace(Decider);
}

/// <summary>
/// #689: The rules of escalation, conflict and decision — all of them read off the tree, none
/// of them configured (Organisation-Konzept, section 5). Pure, so each rule can be tested on an
/// organisation chart alone.
/// </summary>
public static class CaseRules
{
    /// <summary>The human, as a holder or a decider.</summary>
    public const string Human = "";

    /// <summary>
    /// Who an escalation goes to next: the agent's own lead — never sideways, never past a level.
    /// Without a lead above, a human.
    /// </summary>
    public static string NextHolder(OrgChart? org, string agentId)
        => org?.EffectiveLeaderOf(agentId)?.AgentId ?? Human;

    /// <summary>
    /// A conflict is decided at the lowest place above both sides. It is delivered there
    /// directly — the levels in between cannot decide it and are told, not asked.
    /// </summary>
    public static ConflictRoute RouteConflict(OrgChart? org, string a, string b)
    {
        if (string.Equals(a, b, StringComparison.OrdinalIgnoreCase))
            return new ConflictRoute(Human, [], "A conflict needs two sides.");
        if (org is not { HasUnits: true })
            return new ConflictRoute(Human, [], null);

        if (ReportingLine.IsAbove(org, b, a))
            return new ConflictRoute(Human, [], $"'{a}' stands above '{b}' and can decide this itself — that is no conflict.");
        if (ReportingLine.IsAbove(org, a, b))
            return new ConflictRoute(Human, [], $"'{b}' stands above '{a}' and decides this — escalate to it instead.");

        var pathA = PathUp(org, a);
        var pathB = PathUp(org, b);
        var commonIndex = pathA.FindIndex(u => pathB.Contains(u, StringComparer.OrdinalIgnoreCase));

        var decider = Human;
        if (commonIndex >= 0)
        {
            for (var i = commonIndex; i < pathA.Count; i++)
            {
                if (org.LeaderOf(pathA[i]) is { } lead
                    && !string.Equals(lead.AgentId, a, StringComparison.OrdinalIgnoreCase)
                    && !string.Equals(lead.AgentId, b, StringComparison.OrdinalIgnoreCase))
                {
                    decider = lead.AgentId;
                    break;
                }
            }
        }

        // The leads between each side and the common place: concerned, told, not asked.
        var informed = new List<string>();
        void Between(List<string> path, int stopAt)
        {
            for (var i = 0; i < stopAt && i < path.Count; i++)
                if (org.LeaderOf(path[i]) is { } lead
                    && !string.Equals(lead.AgentId, a, StringComparison.OrdinalIgnoreCase)
                    && !string.Equals(lead.AgentId, b, StringComparison.OrdinalIgnoreCase)
                    && !string.Equals(lead.AgentId, decider, StringComparison.OrdinalIgnoreCase)
                    && !informed.Contains(lead.AgentId, StringComparer.OrdinalIgnoreCase))
                    informed.Add(lead.AgentId);
        }

        var common = commonIndex >= 0 ? pathA[commonIndex] : null;
        Between(pathA, common is null ? pathA.Count : commonIndex);
        Between(pathB, common is null ? pathB.Count : pathB.FindIndex(u => string.Equals(u, common, StringComparison.OrdinalIgnoreCase)));

        return new ConflictRoute(decider, informed, null);
    }

    /// <summary>The unit of the agent and all units above it, nearest first.</summary>
    private static List<string> PathUp(OrgChart org, string agentId)
        => org.UnitOf(agentId) is { } unit
            ? [unit.Id, .. org.Ancestors(unit.Id).Select(u => u.Id)]
            : [];

    /// <summary>
    /// How far a decision reaches: the unit the deciding lead leads, with everything below it.
    /// A human decides for the whole instance.
    /// </summary>
    public static string? ScopeOf(OrgChart? org, string decider)
    {
        if (string.IsNullOrWhiteSpace(decider) || org is not { HasUnits: true })
            return null;
        return org.LedBy(decider)?.Id ?? org.UnitOf(decider)?.Id;
    }

    /// <summary>Whether a decision binds the agent: it is in the decision's unit or below it.</summary>
    public static bool Binds(OrgChart? org, Decision decision, string agentId)
    {
        if (decision.ScopeUnitId is null)
            return true;
        if (org is null)
            return false;
        return PathUp(org, agentId).Contains(decision.ScopeUnitId, StringComparer.OrdinalIgnoreCase);
    }

    /// <summary>
    /// Decisions that answer the question, closest first. Deliberately shallow, like the
    /// duplicate check of the board (#674): the subject compared as a title, or at least two
    /// telling words shared with subject and question.
    /// </summary>
    public static IReadOnlyList<Decision> Find(IEnumerable<Decision> decisions, string subject, string? question = null)
    {
        var wanted = Words(subject + " " + question);
        return decisions
            .Select(d => (Decision: d, Score: Score(d, subject, wanted)))
            .Where(x => x.Score > 0)
            .OrderByDescending(x => x.Score)
            .ThenByDescending(x => x.Decision.DecidedAt)
            .Select(x => x.Decision)
            .ToList();
    }

    private static int Score(Decision decision, string subject, HashSet<string> wanted)
    {
        var match = TaskSimilarity.Compare(decision.Subject, subject);
        if (match == TaskTitleMatch.Duplicate) return 100;
        if (match == TaskTitleMatch.Similar) return 50;

        var shared = Words(decision.Subject + " " + decision.Question).Count(wanted.Contains);
        return shared >= 2 ? shared : 0;
    }

    /// <summary>The words worth comparing: normalised, four letters or more.</summary>
    private static HashSet<string> Words(string text)
        => TaskSimilarity.Normalize(text)
            .Split(' ', StringSplitOptions.RemoveEmptyEntries)
            .Where(w => w.Length >= 4)
            .ToHashSet(StringComparer.Ordinal);
}