using StellaOps.PacksRegistry.Core.Contracts;
using StellaOps.PacksRegistry.Core.Models;
using System.Text.Json;

namespace StellaOps.PacksRegistry.Infrastructure.FileSystem;

public sealed class FilePackRepository : IPackRepository
{
    private readonly string _root;
    private readonly string _indexPath;
    private readonly JsonSerializerOptions _jsonOptions;
    private readonly SemaphoreSlim _mutex = new(1, 1);

    public FilePackRepository(string root)
    {
        _root = string.IsNullOrWhiteSpace(root) ? Path.GetFullPath("data/packs") : Path.GetFullPath(root);
        _indexPath = Path.Combine(_root, "index.ndjson");
        _jsonOptions = new JsonSerializerOptions
        {
            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
            WriteIndented = false
        };

        Directory.CreateDirectory(_root);
        Directory.CreateDirectory(Path.Combine(_root, "blobs"));
    }

    public async Task UpsertAsync(PackRecord record, byte[] content, byte[]? provenance, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(record);
        ArgumentNullException.ThrowIfNull(content);

        await _mutex.WaitAsync(cancellationToken).ConfigureAwait(false);
        try
        {
            var blobPath = Path.Combine(_root, "blobs", record.Digest.Replace(':', '_'));
            await File.WriteAllBytesAsync(blobPath, content, cancellationToken).ConfigureAwait(false);

            if (provenance is { Length: > 0 } && record.ProvenanceDigest is not null)
            {
                var provPath = Path.Combine(_root, "provenance", record.ProvenanceDigest.Replace(':', '_'));
                Directory.CreateDirectory(Path.GetDirectoryName(provPath)!);
                await File.WriteAllBytesAsync(provPath, provenance, cancellationToken).ConfigureAwait(false);
            }

        await using var stream = new FileStream(_indexPath, FileMode.Append, FileAccess.Write, FileShare.Read);
        await using var writer = new StreamWriter(stream);
        var json = JsonSerializer.Serialize(record, _jsonOptions);
        await writer.WriteLineAsync(json.AsMemory(), cancellationToken).ConfigureAwait(false);
    }
    finally
    {
        _mutex.Release();
    }
    }

    public async Task<PackRecord?> GetAsync(string packId, CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(packId);
        var records = await ReadAllAsync(cancellationToken).ConfigureAwait(false);
        return records.LastOrDefault(r => string.Equals(r.PackId, packId, StringComparison.OrdinalIgnoreCase));
    }

    public async Task<IReadOnlyList<PackRecord>> ListAsync(string? tenantId = null, CancellationToken cancellationToken = default)
    {
        var records = await ReadAllAsync(cancellationToken).ConfigureAwait(false);
        if (!string.IsNullOrWhiteSpace(tenantId))
        {
            records = records.Where(r => string.Equals(r.TenantId, tenantId, StringComparison.OrdinalIgnoreCase));
        }

        return records
            .OrderBy(r => r.TenantId, StringComparer.OrdinalIgnoreCase)
            .ThenBy(r => r.Name, StringComparer.OrdinalIgnoreCase)
            .ThenBy(r => r.Version, StringComparer.OrdinalIgnoreCase)
            .ToArray();
    }

    private async Task<IEnumerable<PackRecord>> ReadAllAsync(CancellationToken cancellationToken)
    {
        if (!File.Exists(_indexPath))
        {
            return Array.Empty<PackRecord>();
        }

        await _mutex.WaitAsync(cancellationToken).ConfigureAwait(false);
        try
        {
            var lines = await File.ReadAllLinesAsync(_indexPath, cancellationToken).ConfigureAwait(false);
            return lines
                .Where(line => !string.IsNullOrWhiteSpace(line))
                .Select(line => JsonSerializer.Deserialize<PackRecord>(line, _jsonOptions))
                .Where(r => r is not null)!;
        }
        finally
        {
            _mutex.Release();
        }
    }

    public async Task<byte[]?> GetContentAsync(string packId, CancellationToken cancellationToken = default)
    {
        var record = await GetAsync(packId, cancellationToken).ConfigureAwait(false);
        if (record is null)
        {
            return null;
        }

        var blobPath = Path.Combine(_root, "blobs", record.Digest.Replace(':', '_'));
        if (!File.Exists(blobPath))
        {
            return null;
        }

        return await File.ReadAllBytesAsync(blobPath, cancellationToken).ConfigureAwait(false);
    }

    public async Task<byte[]?> GetProvenanceAsync(string packId, CancellationToken cancellationToken = default)
    {
        var record = await GetAsync(packId, cancellationToken).ConfigureAwait(false);
        if (record?.ProvenanceDigest is null)
        {
            return null;
        }

        var provPath = Path.Combine(_root, "provenance", record.ProvenanceDigest.Replace(':', '_'));
        if (!File.Exists(provPath))
        {
            return null;
        }

        return await File.ReadAllBytesAsync(provPath, cancellationToken).ConfigureAwait(false);
    }
}