using Microsoft.EntityFrameworkCore;

namespace StellaOps.Provcache.Postgres;

public sealed partial class PostgresEvidenceChunkRepository
{
    /// <inheritdoc />
    public async Task<ChunkManifest?> GetManifestAsync(
        string proofRoot,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(proofRoot);

        // Get metadata without loading blobs
        var chunks = await _context.EvidenceChunks
            .Where(e => e.ProofRoot == proofRoot)
            .OrderBy(e => e.ChunkIndex)
            .Select(e => new
            {
                e.ChunkId,
                e.ChunkIndex,
                e.ChunkHash,
                e.BlobSize,
                e.ContentType,
                e.CreatedAt
            })
            .AsNoTracking()
            .ToListAsync(cancellationToken)
            .ConfigureAwait(false);

        if (chunks.Count == 0)
        {
            return null;
        }

        var metadata = chunks
            .Select(c => new ChunkMetadata
            {
                ChunkId = c.ChunkId,
                Index = c.ChunkIndex,
                Hash = c.ChunkHash,
                Size = c.BlobSize,
                ContentType = c.ContentType
            })
            .ToList();

        return new ChunkManifest
        {
            ProofRoot = proofRoot,
            TotalChunks = chunks.Count,
            TotalSize = chunks.Sum(c => (long)c.BlobSize),
            Chunks = metadata,
            GeneratedAt = _timeProvider.GetUtcNow()
        };
    }
}