using System.Collections.Concurrent;
using System.Text.Json;

namespace StellaOps.Scanner.Analyzers.Lang.Rust.Internal;

internal static class RustFingerprintScanner
{
    private static readonly EnumerationOptions Enumeration = new()
    {
        MatchCasing = MatchCasing.CaseSensitive,
        IgnoreInaccessible = true,
        RecurseSubdirectories = true,
        AttributesToSkip = FileAttributes.Device | FileAttributes.ReparsePoint,
    };

    private static readonly string FingerprintSegment = $"{Path.DirectorySeparatorChar}.fingerprint{Path.DirectorySeparatorChar}";
    private static readonly ConcurrentDictionary<RustFileCacheKey, RustFingerprintRecord?> Cache = new();

    public static IReadOnlyList<RustFingerprintRecord> Scan(string rootPath, CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(rootPath))
        {
            throw new ArgumentException("Root path is required", nameof(rootPath));
        }

        var results = new List<RustFingerprintRecord>();
        foreach (var path in Directory.EnumerateFiles(rootPath, "*.json", Enumeration))
        {
            cancellationToken.ThrowIfCancellationRequested();

            if (!path.Contains(FingerprintSegment, StringComparison.Ordinal))
            {
                continue;
            }

            if (!RustFileCacheKey.TryCreate(path, out var key))
            {
                continue;
            }

            var record = Cache.GetOrAdd(
                key,
                static (_, state) => ParseFingerprint(state),
                path);

            if (record is not null)
            {
                results.Add(record);
            }
        }

        return results;
    }

    private static RustFingerprintRecord? ParseFingerprint(string path)
    {
        try
        {
            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
            using var document = JsonDocument.Parse(stream);
            var root = document.RootElement;

            var pkgId = TryGetString(root, "pkgid")
                ?? TryGetString(root, "package_id")
                ?? TryGetString(root, "packageId");

            var (name, version, source) = ParseIdentity(pkgId, path);
            if (string.IsNullOrWhiteSpace(name))
            {
                return null;
            }

            var profile = TryGetString(root, "profile");
            var targetKind = TryGetKind(root);

            return new RustFingerprintRecord(
                Name: name!,
                Version: version,
                Source: source,
                TargetKind: targetKind,
                Profile: profile,
                AbsolutePath: path);
        }
        catch (JsonException)
        {
            return null;
        }
        catch (IOException)
        {
            return null;
        }
        catch (UnauthorizedAccessException)
        {
            return null;
        }
    }

    private static (string? Name, string? Version, string? Source) ParseIdentity(string? pkgId, string filePath)
    {
        if (!string.IsNullOrWhiteSpace(pkgId))
        {
            var span = pkgId.AsSpan().Trim();
            var firstSpace = span.IndexOf(' ');
            if (firstSpace > 0 && firstSpace < span.Length - 1)
            {
                var name = span[..firstSpace].ToString();
                var remaining = span[(firstSpace + 1)..].Trim();

                var secondSpace = remaining.IndexOf(' ');
                if (secondSpace < 0)
                {
                    return (name, remaining.ToString(), null);
                }

                var version = remaining[..secondSpace].ToString();
                var potentialSource = remaining[(secondSpace + 1)..].Trim();

                if (potentialSource.Length > 1 && potentialSource[0] == '(' && potentialSource[^1] == ')')
                {
                    potentialSource = potentialSource[1..^1].Trim();
                }

                var source = potentialSource.Length == 0 ? null : potentialSource.ToString();
                return (name, version, source);
            }
        }

        var directory = Path.GetDirectoryName(filePath);
        if (string.IsNullOrEmpty(directory))
        {
            return (null, null, null);
        }

        var crateDirectory = Path.GetFileName(directory);
        if (string.IsNullOrWhiteSpace(crateDirectory))
        {
            return (null, null, null);
        }

        var dashIndex = crateDirectory.LastIndexOf('-');
        if (dashIndex <= 0)
        {
            return (crateDirectory, null, null);
        }

        var maybeName = crateDirectory[..dashIndex];
        return (maybeName, null, null);
    }

    private static string? TryGetKind(JsonElement root)
    {
        if (root.TryGetProperty("target_kind", out var array) && array.ValueKind == JsonValueKind.Array && array.GetArrayLength() > 0)
        {
            var first = array[0];
            if (first.ValueKind == JsonValueKind.String)
            {
                return first.GetString();
            }
        }

        if (root.TryGetProperty("target", out var target) && target.ValueKind == JsonValueKind.String)
        {
            return target.GetString();
        }

        return null;
    }

    private static string? TryGetString(JsonElement element, string propertyName)
    {
        if (element.TryGetProperty(propertyName, out var value) && value.ValueKind == JsonValueKind.String)
        {
            return value.GetString();
        }

        return null;
    }
}

internal sealed record RustFingerprintRecord(
    string Name,
    string? Version,
    string? Source,
    string? TargetKind,
    string? Profile,
    string AbsolutePath);