using StellaOps.Policy.Engine.Domain;
using System.Collections.Concurrent;

namespace StellaOps.Policy.Engine.Services;

internal sealed class InMemoryPolicyPackRepository : IPolicyPackRepository
{
    private readonly ConcurrentDictionary<string, PolicyPackRecord> packs = new(StringComparer.OrdinalIgnoreCase);
    private readonly TimeProvider _timeProvider;

    public InMemoryPolicyPackRepository(TimeProvider timeProvider)
    {
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
    }

    public Task<PolicyPackRecord> CreateAsync(string packId, string? displayName, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(packId);

        var created = packs.GetOrAdd(packId, id => new PolicyPackRecord(id, displayName, _timeProvider.GetUtcNow()));
        return Task.FromResult(created);
    }

    public Task<IReadOnlyList<PolicyPackRecord>> ListAsync(CancellationToken cancellationToken)
    {
        IReadOnlyList<PolicyPackRecord> list = packs.Values
            .OrderBy(pack => pack.PackId, StringComparer.Ordinal)
            .ToList();
        return Task.FromResult(list);
    }

    public Task<PolicyRevisionRecord> UpsertRevisionAsync(string packId, int version, bool requiresTwoPersonApproval, PolicyRevisionStatus initialStatus, CancellationToken cancellationToken)
    {
        var pack = packs.GetOrAdd(packId, id => new PolicyPackRecord(id, null, _timeProvider.GetUtcNow()));
        int revisionVersion = version > 0 ? version : pack.GetNextVersion();
        var revision = pack.GetOrAddRevision(
            revisionVersion,
            v => new PolicyRevisionRecord(v, requiresTwoPersonApproval, initialStatus, _timeProvider.GetUtcNow()));

        if (revision.Status != initialStatus)
        {
            revision.SetStatus(initialStatus, _timeProvider.GetUtcNow());
        }

        return Task.FromResult(revision);
    }

    public Task<PolicyRevisionRecord?> GetRevisionAsync(string packId, int version, CancellationToken cancellationToken)
    {
        if (!packs.TryGetValue(packId, out var pack))
        {
            return Task.FromResult<PolicyRevisionRecord?>(null);
        }

        return Task.FromResult(pack.TryGetRevision(version, out var revision) ? revision : null);
    }

    public Task<PolicyActivationResult> RecordActivationAsync(string packId, int version, string actorId, DateTimeOffset timestamp, string? comment, CancellationToken cancellationToken)
    {
        if (!packs.TryGetValue(packId, out var pack))
        {
            return Task.FromResult(new PolicyActivationResult(PolicyActivationResultStatus.PackNotFound, null));
        }

        if (!pack.TryGetRevision(version, out var revision))
        {
            return Task.FromResult(new PolicyActivationResult(PolicyActivationResultStatus.RevisionNotFound, null));
        }

        if (revision.Status == PolicyRevisionStatus.Active)
        {
            return Task.FromResult(new PolicyActivationResult(PolicyActivationResultStatus.AlreadyActive, revision));
        }

        if (revision.Status != PolicyRevisionStatus.Approved)
        {
            return Task.FromResult(new PolicyActivationResult(PolicyActivationResultStatus.NotApproved, revision));
        }

        var approvalStatus = revision.AddApproval(new PolicyActivationApproval(actorId, timestamp, comment));
        return Task.FromResult(approvalStatus switch
        {
            PolicyActivationApprovalStatus.Duplicate => new PolicyActivationResult(PolicyActivationResultStatus.DuplicateApproval, revision),
            PolicyActivationApprovalStatus.Pending when revision.RequiresTwoPersonApproval
                => new PolicyActivationResult(PolicyActivationResultStatus.PendingSecondApproval, revision),
            PolicyActivationApprovalStatus.Pending =>
                ActivateRevision(revision, timestamp),
            PolicyActivationApprovalStatus.ThresholdReached =>
                ActivateRevision(revision, timestamp),
            _ => throw new InvalidOperationException("Unknown activation approval status.")
        });
    }

    private static PolicyActivationResult ActivateRevision(PolicyRevisionRecord revision, DateTimeOffset timestamp)
    {
        revision.SetStatus(PolicyRevisionStatus.Active, timestamp);
        return new PolicyActivationResult(PolicyActivationResultStatus.Activated, revision);
    }

    public Task<PolicyBundleRecord> StoreBundleAsync(string packId, int version, PolicyBundleRecord bundle, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(bundle);

        var pack = packs.GetOrAdd(packId, id => new PolicyPackRecord(id, null, _timeProvider.GetUtcNow()));
        var revision = pack.GetOrAddRevision(version > 0 ? version : pack.GetNextVersion(),
            v => new PolicyRevisionRecord(v, requiresTwoPerson: false, status: PolicyRevisionStatus.Draft, _timeProvider.GetUtcNow()));

        revision.SetBundle(bundle);
        return Task.FromResult(bundle);
    }

    public Task<PolicyBundleRecord?> GetBundleAsync(string packId, int version, CancellationToken cancellationToken)
    {
        if (!packs.TryGetValue(packId, out var pack))
        {
            return Task.FromResult<PolicyBundleRecord?>(null);
        }

        if (!pack.TryGetRevision(version, out var revision))
        {
            return Task.FromResult<PolicyBundleRecord?>(null);
        }

        return Task.FromResult(revision.Bundle);
    }
}