using System.Collections.Immutable;
using System.Security.Cryptography;
using System.Text;
using StellaOps.AirGap.Bundle.Models;
using StellaOps.AirGap.Bundle.Serialization;

namespace StellaOps.AirGap.Bundle.Services;

public sealed class BundleBuilder : IBundleBuilder
{
    public async Task<BundleManifest> BuildAsync(
        BundleBuildRequest request,
        string outputPath,
        CancellationToken ct = default)
    {
        Directory.CreateDirectory(outputPath);

        var feeds = new List<FeedComponent>();
        var policies = new List<PolicyComponent>();
        var cryptoMaterials = new List<CryptoComponent>();

        foreach (var feedConfig in request.Feeds)
        {
            var component = await CopyComponentAsync(feedConfig, outputPath, ct).ConfigureAwait(false);
            feeds.Add(new FeedComponent(
                feedConfig.FeedId,
                feedConfig.Name,
                feedConfig.Version,
                component.RelativePath,
                component.Digest,
                component.SizeBytes,
                feedConfig.SnapshotAt,
                feedConfig.Format));
        }

        foreach (var policyConfig in request.Policies)
        {
            var component = await CopyComponentAsync(policyConfig, outputPath, ct).ConfigureAwait(false);
            policies.Add(new PolicyComponent(
                policyConfig.PolicyId,
                policyConfig.Name,
                policyConfig.Version,
                component.RelativePath,
                component.Digest,
                component.SizeBytes,
                policyConfig.Type));
        }

        foreach (var cryptoConfig in request.CryptoMaterials)
        {
            var component = await CopyComponentAsync(cryptoConfig, outputPath, ct).ConfigureAwait(false);
            cryptoMaterials.Add(new CryptoComponent(
                cryptoConfig.ComponentId,
                cryptoConfig.Name,
                component.RelativePath,
                component.Digest,
                component.SizeBytes,
                cryptoConfig.Type,
                cryptoConfig.ExpiresAt));
        }

        var totalSize = feeds.Sum(f => f.SizeBytes) +
                        policies.Sum(p => p.SizeBytes) +
                        cryptoMaterials.Sum(c => c.SizeBytes);

        var manifest = new BundleManifest
        {
            BundleId = Guid.NewGuid().ToString(),
            SchemaVersion = "1.0.0",
            Name = request.Name,
            Version = request.Version,
            CreatedAt = DateTimeOffset.UtcNow,
            ExpiresAt = request.ExpiresAt,
            Feeds = feeds.ToImmutableArray(),
            Policies = policies.ToImmutableArray(),
            CryptoMaterials = cryptoMaterials.ToImmutableArray(),
            TotalSizeBytes = totalSize
        };

        return BundleManifestSerializer.WithDigest(manifest);
    }

    private static async Task<CopiedComponent> CopyComponentAsync(
        BundleComponentSource source,
        string outputPath,
        CancellationToken ct)
    {
        var targetPath = Path.Combine(outputPath, source.RelativePath);
        Directory.CreateDirectory(Path.GetDirectoryName(targetPath) ?? outputPath);

        await using var input = File.OpenRead(source.SourcePath);
        await using var output = File.Create(targetPath);
        await input.CopyToAsync(output, ct).ConfigureAwait(false);

        await using var digestStream = File.OpenRead(targetPath);
        var hash = await SHA256.HashDataAsync(digestStream, ct).ConfigureAwait(false);
        var digest = Convert.ToHexString(hash).ToLowerInvariant();

        var info = new FileInfo(targetPath);
        return new CopiedComponent(source.RelativePath, digest, info.Length);
    }

    private sealed record CopiedComponent(string RelativePath, string Digest, long SizeBytes);
}

public interface IBundleBuilder
{
    Task<BundleManifest> BuildAsync(BundleBuildRequest request, string outputPath, CancellationToken ct = default);
}

public sealed record BundleBuildRequest(
    string Name,
    string Version,
    DateTimeOffset? ExpiresAt,
    IReadOnlyList<FeedBuildConfig> Feeds,
    IReadOnlyList<PolicyBuildConfig> Policies,
    IReadOnlyList<CryptoBuildConfig> CryptoMaterials);

public abstract record BundleComponentSource(string SourcePath, string RelativePath);

public sealed record FeedBuildConfig(
    string FeedId,
    string Name,
    string Version,
    string SourcePath,
    string RelativePath,
    DateTimeOffset SnapshotAt,
    FeedFormat Format)
    : BundleComponentSource(SourcePath, RelativePath);

public sealed record PolicyBuildConfig(
    string PolicyId,
    string Name,
    string Version,
    string SourcePath,
    string RelativePath,
    PolicyType Type)
    : BundleComponentSource(SourcePath, RelativePath);

public sealed record CryptoBuildConfig(
    string ComponentId,
    string Name,
    string SourcePath,
    string RelativePath,
    CryptoComponentType Type,
    DateTimeOffset? ExpiresAt)
    : BundleComponentSource(SourcePath, RelativePath);