using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.Logging;
using Npgsql;
using NpgsqlTypes;
using StellaOps.Scanner.Storage.Postgres;
using StellaOps.Scanner.WebService.Contracts;
using StellaOps.Scanner.WebService.Domain;

namespace StellaOps.Scanner.WebService.Services;

internal sealed class CallGraphIngestionService : ICallGraphIngestionService
{
    private const string TenantContext = "00000000-0000-0000-0000-000000000001";
    private static readonly Guid TenantId = Guid.Parse(TenantContext);

    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    private readonly ScannerDataSource _dataSource;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<CallGraphIngestionService> _logger;

    private string SchemaName => _dataSource.SchemaName ?? ScannerDataSource.DefaultSchema;
    private string CallGraphIngestionsTable => $"{SchemaName}.callgraph_ingestions";

    public CallGraphIngestionService(
        ScannerDataSource dataSource,
        TimeProvider timeProvider,
        ILogger<CallGraphIngestionService> logger)
    {
        _dataSource = dataSource ?? throw new ArgumentNullException(nameof(dataSource));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public CallGraphValidationResult Validate(CallGraphV1Dto callGraph)
    {
        ArgumentNullException.ThrowIfNull(callGraph);

        var errors = new List<string>();

        if (string.IsNullOrWhiteSpace(callGraph.Schema))
        {
            errors.Add("Schema is required.");
        }
        else if (!string.Equals(callGraph.Schema, "stella.callgraph.v1", StringComparison.Ordinal))
        {
            errors.Add($"Unsupported schema '{callGraph.Schema}'. Expected 'stella.callgraph.v1'.");
        }

        if (string.IsNullOrWhiteSpace(callGraph.ScanKey))
        {
            errors.Add("ScanKey is required.");
        }

        if (string.IsNullOrWhiteSpace(callGraph.Language))
        {
            errors.Add("Language is required.");
        }

        if (callGraph.Nodes is null || callGraph.Nodes.Count == 0)
        {
            errors.Add("At least one node is required.");
        }

        if (callGraph.Edges is null || callGraph.Edges.Count == 0)
        {
            errors.Add("At least one edge is required.");
        }

        return errors.Count == 0
            ? CallGraphValidationResult.Success()
            : CallGraphValidationResult.Failure(errors.ToArray());
    }

    public async Task<ExistingCallGraphDto?> FindByDigestAsync(
        ScanId scanId,
        string contentDigest,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(scanId.Value))
        {
            return null;
        }

        if (string.IsNullOrWhiteSpace(contentDigest))
        {
            return null;
        }

        var sql = $"""
            SELECT id, content_digest, created_at_utc
            FROM {CallGraphIngestionsTable}
            WHERE tenant_id = @tenant_id
              AND scan_id = @scan_id
              AND content_digest = @content_digest
            LIMIT 1
            """;

        await using var connection = await _dataSource.OpenConnectionAsync(TenantContext, "reader", cancellationToken)
            .ConfigureAwait(false);
        await using var command = new NpgsqlCommand(sql, connection);
        command.Parameters.AddWithValue("tenant_id", TenantId);
        command.Parameters.AddWithValue("scan_id", scanId.Value.Trim());
        command.Parameters.AddWithValue("content_digest", contentDigest.Trim());

        await using var reader = await command.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
        if (!await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
        {
            return null;
        }

        return new ExistingCallGraphDto(
            Id: reader.GetString(0),
            Digest: reader.GetString(1),
            CreatedAt: reader.GetFieldValue<DateTimeOffset>(2));
    }

    public async Task<CallGraphIngestionResult> IngestAsync(
        ScanId scanId,
        CallGraphV1Dto callGraph,
        string contentDigest,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(callGraph);
        ArgumentException.ThrowIfNullOrWhiteSpace(scanId.Value);
        ArgumentException.ThrowIfNullOrWhiteSpace(contentDigest);

        var normalizedDigest = contentDigest.Trim();
        var callgraphId = CreateCallGraphId(scanId, normalizedDigest);
        var now = _timeProvider.GetUtcNow();
        var nodeCount = callGraph.Nodes?.Count ?? 0;
        var edgeCount = callGraph.Edges?.Count ?? 0;
        var language = callGraph.Language?.Trim() ?? string.Empty;
        var payload = JsonSerializer.Serialize(callGraph, JsonOptions);

        var insertSql = $"""
            INSERT INTO {CallGraphIngestionsTable} (
                id,
                tenant_id,
                scan_id,
                content_digest,
                language,
                node_count,
                edge_count,
                created_at_utc,
                callgraph_json
            ) VALUES (
                @id,
                @tenant_id,
                @scan_id,
                @content_digest,
                @language,
                @node_count,
                @edge_count,
                @created_at_utc,
                @callgraph_json::jsonb
            )
            ON CONFLICT (tenant_id, scan_id, content_digest) DO NOTHING
            """;

        var selectSql = $"""
            SELECT id, content_digest, node_count, edge_count
            FROM {CallGraphIngestionsTable}
            WHERE tenant_id = @tenant_id
              AND scan_id = @scan_id
              AND content_digest = @content_digest
            LIMIT 1
            """;

        await using var connection = await _dataSource.OpenConnectionAsync(TenantContext, "writer", cancellationToken)
            .ConfigureAwait(false);

        await using (var insert = new NpgsqlCommand(insertSql, connection))
        {
            insert.Parameters.AddWithValue("id", callgraphId);
            insert.Parameters.AddWithValue("tenant_id", TenantId);
            insert.Parameters.AddWithValue("scan_id", scanId.Value.Trim());
            insert.Parameters.AddWithValue("content_digest", normalizedDigest);
            insert.Parameters.AddWithValue("language", language);
            insert.Parameters.AddWithValue("node_count", nodeCount);
            insert.Parameters.AddWithValue("edge_count", edgeCount);
            insert.Parameters.AddWithValue("created_at_utc", now.UtcDateTime);
            insert.Parameters.Add(new NpgsqlParameter<string>("callgraph_json", NpgsqlDbType.Jsonb) { TypedValue = payload });

            await insert.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
        }

        await using var select = new NpgsqlCommand(selectSql, connection);
        select.Parameters.AddWithValue("tenant_id", TenantId);
        select.Parameters.AddWithValue("scan_id", scanId.Value.Trim());
        select.Parameters.AddWithValue("content_digest", normalizedDigest);

        await using var reader = await select.ExecuteReaderAsync(cancellationToken).ConfigureAwait(false);
        if (!await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
        {
            throw new InvalidOperationException("Call graph ingestion row was not persisted.");
        }

        var persistedId = reader.GetString(0);
        var persistedDigest = reader.GetString(1);
        var persistedNodeCount = reader.GetInt32(2);
        var persistedEdgeCount = reader.GetInt32(3);

        _logger.LogInformation(
            "Ingested callgraph scan={ScanId} lang={Language} nodes={Nodes} edges={Edges} digest={Digest}",
            scanId.Value,
            language,
            persistedNodeCount,
            persistedEdgeCount,
            persistedDigest);

        return new CallGraphIngestionResult(
            CallgraphId: persistedId,
            NodeCount: persistedNodeCount,
            EdgeCount: persistedEdgeCount,
            Digest: persistedDigest);
    }

    private static string CreateCallGraphId(ScanId scanId, string contentDigest)
    {
        var bytes = Encoding.UTF8.GetBytes($"{scanId.Value.Trim()}:{contentDigest.Trim()}");
        var hash = SHA256.HashData(bytes);
        return $"cg_{Convert.ToHexString(hash).ToLowerInvariant()}";
    }
}