using Microsoft.Extensions.Logging;
using StellaOps.Scanner.Analyzers.Native.Index;

namespace StellaOps.Scanner.Emit.Native;

/// <summary>
/// Emits native binary components for SBOM generation.
/// Uses the Build-ID index to resolve PURLs when possible.
/// </summary>
public sealed class NativeComponentEmitter : INativeComponentEmitter
{
    private readonly IBuildIdIndex _buildIdIndex;
    private readonly NativePurlBuilder _purlBuilder;
    private readonly ILogger<NativeComponentEmitter> _logger;

    /// <summary>
    /// Creates a new native component emitter.
    /// </summary>
    public NativeComponentEmitter(
        IBuildIdIndex buildIdIndex,
        ILogger<NativeComponentEmitter> logger)
    {
        ArgumentNullException.ThrowIfNull(buildIdIndex);
        ArgumentNullException.ThrowIfNull(logger);

        _buildIdIndex = buildIdIndex;
        _purlBuilder = new NativePurlBuilder();
        _logger = logger;
    }

    /// <inheritdoc />
    public async Task<NativeComponentEmitResult> EmitAsync(
        NativeBinaryMetadata metadata,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(metadata);

        // Try to resolve via Build-ID index
        BuildIdLookupResult? lookupResult = null;

        if (!string.IsNullOrWhiteSpace(metadata.BuildId))
        {
            lookupResult = await _buildIdIndex.LookupAsync(metadata.BuildId, cancellationToken).ConfigureAwait(false);
        }

        string purl;
        string? version = null;
        bool indexMatch = false;

        if (lookupResult is not null)
        {
            // Index match - use the resolved PURL
            purl = _purlBuilder.FromIndexResult(lookupResult);
            version = lookupResult.Version;
            indexMatch = true;

            _logger.LogDebug(
                "Resolved binary {FilePath} via Build-ID index: {Purl}",
                metadata.FilePath,
                purl);
        }
        else
        {
            // No match - generate generic PURL
            purl = _purlBuilder.FromUnresolvedBinary(metadata);
            version = metadata.ProductVersion ?? metadata.FileVersion;

            _logger.LogDebug(
                "Unresolved binary {FilePath}, generated generic PURL: {Purl}",
                metadata.FilePath,
                purl);
        }

        var name = Path.GetFileName(metadata.FilePath);

        return new NativeComponentEmitResult(
            Purl: purl,
            Name: name,
            Version: version,
            Metadata: metadata,
            IndexMatch: indexMatch,
            LookupResult: lookupResult);
    }

    /// <inheritdoc />
    public async Task<IReadOnlyList<NativeComponentEmitResult>> EmitBatchAsync(
        IEnumerable<NativeBinaryMetadata> metadataList,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(metadataList);

        var metadataArray = metadataList.ToArray();
        if (metadataArray.Length == 0)
        {
            return Array.Empty<NativeComponentEmitResult>();
        }

        // Batch lookup for all Build-IDs
        var buildIds = metadataArray
            .Where(m => !string.IsNullOrWhiteSpace(m.BuildId))
            .Select(m => m.BuildId!)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToArray();

        var lookupResults = await _buildIdIndex.BatchLookupAsync(buildIds, cancellationToken).ConfigureAwait(false);
        var lookupMap = lookupResults.ToDictionary(
            r => r.BuildId,
            StringComparer.OrdinalIgnoreCase);

        _logger.LogDebug(
            "Batch lookup: {Total} binaries, {Resolved} resolved via index",
            metadataArray.Length,
            lookupMap.Count);

        // Emit components
        var results = new List<NativeComponentEmitResult>(metadataArray.Length);

        foreach (var metadata in metadataArray)
        {
            BuildIdLookupResult? lookupResult = null;

            if (!string.IsNullOrWhiteSpace(metadata.BuildId) &&
                lookupMap.TryGetValue(metadata.BuildId, out var result))
            {
                lookupResult = result;
            }

            string purl;
            string? version = null;
            bool indexMatch = false;

            if (lookupResult is not null)
            {
                purl = _purlBuilder.FromIndexResult(lookupResult);
                version = lookupResult.Version;
                indexMatch = true;
            }
            else
            {
                purl = _purlBuilder.FromUnresolvedBinary(metadata);
                version = metadata.ProductVersion ?? metadata.FileVersion;
            }

            results.Add(new NativeComponentEmitResult(
                Purl: purl,
                Name: Path.GetFileName(metadata.FilePath),
                Version: version,
                Metadata: metadata,
                IndexMatch: indexMatch,
                LookupResult: lookupResult));
        }

        return results;
    }
}