using System.Text.Json.Nodes;
using Microsoft.Extensions.Logging;
using StellaOps.Findings.Ledger.Domain;
using StellaOps.Findings.Ledger.Infrastructure;
using StellaOps.Findings.Ledger.Infrastructure.Attestation;
using StellaOps.Findings.Ledger.Observability;

namespace StellaOps.Findings.Ledger.Services;

/// <summary>
/// Service for managing attestation pointers linking findings to verification reports and attestation envelopes.
/// </summary>
public sealed class AttestationPointerService
{
    private readonly ILedgerEventRepository _ledgerEventRepository;
    private readonly ILedgerEventWriteService _writeService;
    private readonly IAttestationPointerRepository _repository;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<AttestationPointerService> _logger;

    public AttestationPointerService(
        ILedgerEventRepository ledgerEventRepository,
        ILedgerEventWriteService writeService,
        IAttestationPointerRepository repository,
        TimeProvider timeProvider,
        ILogger<AttestationPointerService> logger)
    {
        _ledgerEventRepository = ledgerEventRepository ?? throw new ArgumentNullException(nameof(ledgerEventRepository));
        _writeService = writeService ?? throw new ArgumentNullException(nameof(writeService));
        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// Creates an attestation pointer linking a finding to a verification report or attestation envelope.
    /// </summary>
    public async Task<AttestationPointerResult> CreatePointerAsync(
        AttestationPointerInput input,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(input);
        ArgumentException.ThrowIfNullOrWhiteSpace(input.TenantId);
        ArgumentException.ThrowIfNullOrWhiteSpace(input.FindingId);
        ArgumentException.ThrowIfNullOrWhiteSpace(input.AttestationRef.Digest);

        var now = _timeProvider.GetUtcNow();
        var createdBy = input.CreatedBy ?? "attestation-linker";

        // Check for idempotency
        var exists = await _repository.ExistsAsync(
            input.TenantId,
            input.FindingId,
            input.AttestationRef.Digest,
            input.AttestationType,
            cancellationToken).ConfigureAwait(false);

        if (exists)
        {
            _logger.LogDebug(
                "Attestation pointer already exists for finding {FindingId} with digest {Digest}",
                input.FindingId, input.AttestationRef.Digest);

            // Find and return the existing pointer
            var existing = await _repository.GetByDigestAsync(
                input.TenantId,
                input.AttestationRef.Digest,
                cancellationToken).ConfigureAwait(false);

            var match = existing.FirstOrDefault(p =>
                p.FindingId == input.FindingId && p.AttestationType == input.AttestationType);

            return new AttestationPointerResult(true, match?.PointerId, match?.LedgerEventId, null);
        }

        var pointerId = Guid.NewGuid();

        // Create ledger event for the attestation pointer
        var chainId = LedgerChainIdGenerator.FromTenantSubject(
            input.TenantId, $"attestation::{input.FindingId}");

        var chainHead = await _ledgerEventRepository.GetChainHeadAsync(
            input.TenantId, chainId, cancellationToken).ConfigureAwait(false);

        var sequence = (chainHead?.SequenceNumber ?? 0) + 1;
        var previousHash = chainHead?.EventHash ?? LedgerEventConstants.EmptyHash;

        var eventId = Guid.NewGuid();

        var attestationPayload = BuildAttestationPayload(input, pointerId);
        var envelope = BuildEnvelope(eventId, input, chainId, sequence, now, attestationPayload);

        var draft = new LedgerEventDraft(
            input.TenantId,
            chainId,
            sequence,
            eventId,
            LedgerEventConstants.EventAttestationPointerLinked,
            "attestation-pointer",
            input.FindingId,
            input.FindingId,
            SourceRunId: null,
            ActorId: createdBy,
            ActorType: "system",
            OccurredAt: now,
            RecordedAt: now,
            Payload: attestationPayload,
            CanonicalEnvelope: envelope,
            ProvidedPreviousHash: previousHash);

        var writeResult = await _writeService.AppendAsync(draft, cancellationToken).ConfigureAwait(false);

        if (writeResult.Status is not (LedgerWriteStatus.Success or LedgerWriteStatus.Idempotent))
        {
            var error = string.Join(";", writeResult.Errors);
            _logger.LogWarning(
                "Failed to write ledger event for attestation pointer {PointerId}: {Error}",
                pointerId, error);
            return new AttestationPointerResult(false, null, null, error);
        }

        var ledgerEventId = writeResult.Record?.EventId;

        var record = new AttestationPointerRecord(
            input.TenantId,
            pointerId,
            input.FindingId,
            input.AttestationType,
            input.Relationship,
            input.AttestationRef,
            input.VerificationResult,
            now,
            createdBy,
            input.Metadata,
            ledgerEventId);

        await _repository.InsertAsync(record, cancellationToken).ConfigureAwait(false);

        LedgerTimeline.EmitAttestationPointerLinked(
            _logger,
            input.TenantId,
            input.FindingId,
            pointerId,
            input.AttestationType.ToString(),
            input.AttestationRef.Digest);

        return new AttestationPointerResult(true, pointerId, ledgerEventId, null);
    }

    /// <summary>
    /// Gets attestation pointers for a finding.
    /// </summary>
    public async Task<IReadOnlyList<AttestationPointerRecord>> GetPointersAsync(
        string tenantId,
        string findingId,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
        ArgumentException.ThrowIfNullOrWhiteSpace(findingId);

        return await _repository.GetByFindingIdAsync(tenantId, findingId, cancellationToken)
            .ConfigureAwait(false);
    }

    /// <summary>
    /// Gets an attestation pointer by ID.
    /// </summary>
    public async Task<AttestationPointerRecord?> GetPointerAsync(
        string tenantId,
        Guid pointerId,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);

        return await _repository.GetByIdAsync(tenantId, pointerId, cancellationToken)
            .ConfigureAwait(false);
    }

    /// <summary>
    /// Searches attestation pointers.
    /// </summary>
    public async Task<IReadOnlyList<AttestationPointerRecord>> SearchAsync(
        AttestationPointerQuery query,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(query);

        return await _repository.SearchAsync(query, cancellationToken).ConfigureAwait(false);
    }

    /// <summary>
    /// Gets attestation summary for a finding.
    /// </summary>
    public async Task<FindingAttestationSummary> GetSummaryAsync(
        string tenantId,
        string findingId,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
        ArgumentException.ThrowIfNullOrWhiteSpace(findingId);

        return await _repository.GetSummaryAsync(tenantId, findingId, cancellationToken)
            .ConfigureAwait(false);
    }

    /// <summary>
    /// Gets attestation summaries for multiple findings.
    /// </summary>
    public async Task<IReadOnlyList<FindingAttestationSummary>> GetSummariesAsync(
        string tenantId,
        IReadOnlyList<string> findingIds,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
        ArgumentNullException.ThrowIfNull(findingIds);

        return await _repository.GetSummariesAsync(tenantId, findingIds, cancellationToken)
            .ConfigureAwait(false);
    }

    /// <summary>
    /// Updates the verification result for an attestation pointer.
    /// </summary>
    public async Task<bool> UpdateVerificationResultAsync(
        string tenantId,
        Guid pointerId,
        VerificationResult verificationResult,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
        ArgumentNullException.ThrowIfNull(verificationResult);

        var existing = await _repository.GetByIdAsync(tenantId, pointerId, cancellationToken)
            .ConfigureAwait(false);

        if (existing is null)
        {
            _logger.LogWarning(
                "Attestation pointer {PointerId} not found for tenant {TenantId}",
                pointerId, tenantId);
            return false;
        }

        await _repository.UpdateVerificationResultAsync(
            tenantId, pointerId, verificationResult, cancellationToken).ConfigureAwait(false);

        _logger.LogInformation(
            "Updated verification result for attestation pointer {PointerId}, verified={Verified}",
            pointerId, verificationResult.Verified);

        return true;
    }

    /// <summary>
    /// Gets findings that have attestations matching the criteria.
    /// </summary>
    public async Task<IReadOnlyList<string>> GetFindingIdsWithAttestationsAsync(
        string tenantId,
        AttestationVerificationFilter? verificationFilter = null,
        IReadOnlyList<AttestationType>? attestationTypes = null,
        int limit = 100,
        int offset = 0,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);

        return await _repository.GetFindingIdsWithAttestationsAsync(
            tenantId, verificationFilter, attestationTypes, limit, offset, cancellationToken)
            .ConfigureAwait(false);
    }

    private static JsonObject BuildAttestationPayload(AttestationPointerInput input, Guid pointerId)
    {
        var attestationRefNode = new JsonObject
        {
            ["digest"] = input.AttestationRef.Digest
        };

        if (input.AttestationRef.AttestationId.HasValue)
        {
            attestationRefNode["attestation_id"] = input.AttestationRef.AttestationId.Value.ToString();
        }

        if (!string.IsNullOrEmpty(input.AttestationRef.StorageUri))
        {
            attestationRefNode["storage_uri"] = input.AttestationRef.StorageUri;
        }

        if (!string.IsNullOrEmpty(input.AttestationRef.PayloadType))
        {
            attestationRefNode["payload_type"] = input.AttestationRef.PayloadType;
        }

        if (!string.IsNullOrEmpty(input.AttestationRef.PredicateType))
        {
            attestationRefNode["predicate_type"] = input.AttestationRef.PredicateType;
        }

        if (input.AttestationRef.SubjectDigests is { Count: > 0 })
        {
            var subjectsArray = new JsonArray();
            foreach (var subject in input.AttestationRef.SubjectDigests)
            {
                subjectsArray.Add(subject);
            }
            attestationRefNode["subject_digests"] = subjectsArray;
        }

        if (input.AttestationRef.SignerInfo is not null)
        {
            var signerNode = new JsonObject();
            if (!string.IsNullOrEmpty(input.AttestationRef.SignerInfo.KeyId))
            {
                signerNode["key_id"] = input.AttestationRef.SignerInfo.KeyId;
            }
            if (!string.IsNullOrEmpty(input.AttestationRef.SignerInfo.Issuer))
            {
                signerNode["issuer"] = input.AttestationRef.SignerInfo.Issuer;
            }
            if (!string.IsNullOrEmpty(input.AttestationRef.SignerInfo.Subject))
            {
                signerNode["subject"] = input.AttestationRef.SignerInfo.Subject;
            }
            if (input.AttestationRef.SignerInfo.SignedAt.HasValue)
            {
                signerNode["signed_at"] = FormatTimestamp(input.AttestationRef.SignerInfo.SignedAt.Value);
            }
            attestationRefNode["signer_info"] = signerNode;
        }

        if (input.AttestationRef.RekorEntry is not null)
        {
            var rekorNode = new JsonObject();
            if (input.AttestationRef.RekorEntry.LogIndex.HasValue)
            {
                rekorNode["log_index"] = input.AttestationRef.RekorEntry.LogIndex.Value;
            }
            if (!string.IsNullOrEmpty(input.AttestationRef.RekorEntry.LogId))
            {
                rekorNode["log_id"] = input.AttestationRef.RekorEntry.LogId;
            }
            if (!string.IsNullOrEmpty(input.AttestationRef.RekorEntry.Uuid))
            {
                rekorNode["uuid"] = input.AttestationRef.RekorEntry.Uuid;
            }
            if (input.AttestationRef.RekorEntry.IntegratedTime.HasValue)
            {
                rekorNode["integrated_time"] = input.AttestationRef.RekorEntry.IntegratedTime.Value;
            }
            attestationRefNode["rekor_entry"] = rekorNode;
        }

        var pointerNode = new JsonObject
        {
            ["pointer_id"] = pointerId.ToString(),
            ["attestation_type"] = input.AttestationType.ToString(),
            ["relationship"] = input.Relationship.ToString(),
            ["attestation_ref"] = attestationRefNode
        };

        if (input.VerificationResult is not null)
        {
            var verificationNode = new JsonObject
            {
                ["verified"] = input.VerificationResult.Verified,
                ["verified_at"] = FormatTimestamp(input.VerificationResult.VerifiedAt)
            };

            if (!string.IsNullOrEmpty(input.VerificationResult.Verifier))
            {
                verificationNode["verifier"] = input.VerificationResult.Verifier;
            }

            if (!string.IsNullOrEmpty(input.VerificationResult.VerifierVersion))
            {
                verificationNode["verifier_version"] = input.VerificationResult.VerifierVersion;
            }

            if (!string.IsNullOrEmpty(input.VerificationResult.PolicyRef))
            {
                verificationNode["policy_ref"] = input.VerificationResult.PolicyRef;
            }

            if (input.VerificationResult.Checks is { Count: > 0 })
            {
                var checksArray = new JsonArray();
                foreach (var check in input.VerificationResult.Checks)
                {
                    var checkNode = new JsonObject
                    {
                        ["check_type"] = check.CheckType.ToString(),
                        ["passed"] = check.Passed
                    };
                    if (!string.IsNullOrEmpty(check.Details))
                    {
                        checkNode["details"] = check.Details;
                    }
                    checksArray.Add(checkNode);
                }
                verificationNode["checks"] = checksArray;
            }

            if (input.VerificationResult.Warnings is { Count: > 0 })
            {
                var warningsArray = new JsonArray();
                foreach (var warning in input.VerificationResult.Warnings)
                {
                    warningsArray.Add(warning);
                }
                verificationNode["warnings"] = warningsArray;
            }

            if (input.VerificationResult.Errors is { Count: > 0 })
            {
                var errorsArray = new JsonArray();
                foreach (var error in input.VerificationResult.Errors)
                {
                    errorsArray.Add(error);
                }
                verificationNode["errors"] = errorsArray;
            }

            pointerNode["verification_result"] = verificationNode;
        }

        return new JsonObject
        {
            ["attestation"] = new JsonObject
            {
                ["pointer"] = pointerNode
            }
        };
    }

    private static JsonObject BuildEnvelope(
        Guid eventId,
        AttestationPointerInput input,
        Guid chainId,
        long sequence,
        DateTimeOffset now,
        JsonObject payload)
    {
        return new JsonObject
        {
            ["event"] = new JsonObject
            {
                ["id"] = eventId.ToString(),
                ["type"] = LedgerEventConstants.EventAttestationPointerLinked,
                ["tenant"] = input.TenantId,
                ["chainId"] = chainId.ToString(),
                ["sequence"] = sequence,
                ["policyVersion"] = "attestation-pointer",
                ["artifactId"] = input.FindingId,
                ["finding"] = new JsonObject
                {
                    ["id"] = input.FindingId,
                    ["artifactId"] = input.FindingId,
                    ["vulnId"] = "attestation-pointer"
                },
                ["actor"] = new JsonObject
                {
                    ["id"] = input.CreatedBy ?? "attestation-linker",
                    ["type"] = "system"
                },
                ["occurredAt"] = FormatTimestamp(now),
                ["recordedAt"] = FormatTimestamp(now),
                ["payload"] = payload.DeepClone()
            }
        };
    }

    private static string FormatTimestamp(DateTimeOffset value)
        => value.ToUniversalTime().ToString("yyyy-MM-dd'T'HH:mm:ss.fff'Z'");
}