using System.Text.Json;
using System.Text.Json.Serialization;

namespace PrivaPub.Infrastructure.Backup
{
	// What a backup holds (manifest.json at its root): enough to check it is whole, to restore it on this host only, and to
	// rebuild what Mongo had (each collection's indexes).
	public sealed class ArchiveManifest
	{
		public const int CurrentFormat = 1;
		public const string FileName = "manifest.json";

		public int Format { get; set; } = CurrentFormat;
		public string Kind { get; set; }//nightly, manual, pre-deploy, pre-restore, uploaded
		public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
		public string Host { get; set; }//BackendBaseAddress: URIs and media URLs are stored whole, so only this host can restore it
		public string AppCommit { get; set; }
		public string AppRef { get; set; }
		public string NewestMigration { get; set; }
		public int MigrationNumber { get; set; }
		public bool Consistent { get; set; }//read at one instant (a snapshot session on a replica set)
		public bool DbOnly { get; set; }//no media files, only their list (the deploy's, which can't link www-data's files)
		public List<CollectionEntry> Collections { get; set; } = [];
		public List<ExcludedEntry> Excluded { get; set; } = [];
		public MediaEntry Media { get; set; } = new();

		public sealed class CollectionEntry
		{
			public string Name { get; set; }
			public long Count { get; set; }
			public long Bytes { get; set; }
			public string Sha256 { get; set; }
			public List<string> Indexes { get; set; } = [];//each as canonical Extended JSON
		}

		public sealed class ExcludedEntry
		{
			public string Name { get; set; }
			public string Why { get; set; }
		}

		public sealed class MediaEntry
		{
			public int Files { get; set; }
			public long Bytes { get; set; }
			public int Missing { get; set; }
			public List<string> List { get; set; } = [];
		}

		static readonly JsonSerializerOptions Json = new() { WriteIndented = true, PropertyNamingPolicy = JsonNamingPolicy.CamelCase, DefaultIgnoreCondition = JsonIgnoreCondition.Never };

		public static ArchiveManifest Read(string directory)
		{
			var path = Path.Combine(directory, FileName);
			return File.Exists(path) ? JsonSerializer.Deserialize<ArchiveManifest>(File.ReadAllText(path), Json) : default;
		}

		public void Write(string directory)
		{
			using var file = new FileStream(Path.Combine(directory, FileName), FileMode.Create, FileAccess.Write);
			JsonSerializer.Serialize(file, this, Json);
			file.Flush(flushToDisk: true);
		}
	}
}