using System.Text.Json;
using Microsoft.AspNetCore.Mvc;
using RadicadeServer.API.Studio;

namespace RadicadeServer.CDN
{
	/// <summary>
	/// Step one of the client's two-step bundle download. The client asks
	/// <c>/rooms/unity_assets/{assetId}/{target}/{version}</c> and is handed a file name, then
	/// ranges over that file at <c>/data/{Filename}</c> (and, for a subroom's bundle, under the
	/// CDN's own <c>/unity/{Filename}</c> alias).
	///
	/// The id arrives in two shapes and both have to be answered. A Studio manifest id is 40
	/// alphanumerics and its baked bundles are named in the manifest's own metadata. A legacy
	/// bundle is stored under its file name (or that name minus <c>.assetbundle</c>), and that
	/// name is what the subroom's <c>UnityAssetId</c> carries - every imported room, the built-in
	/// rooms and every room bound from the admin panel. Answering only the 40-character shape
	/// leaves every legacy bundle unresolvable, and the client reports one 400 as
	/// "Error downloading room assets" for the whole room.
	/// </summary>
	[Route("rooms/")]
	public class UnityAssetsCDN : Controller
	{
		[HttpGet("unity_assets/{assetId}/{target}/{version}")]
		public async Task<IActionResult> GetUnityAsset(string assetId, int target, int version)
		{
			return await ServeMetadataAsync(assetId, target, version);
		}

		[HttpGet("unity_assets/{assetId}")]
		public async Task<IActionResult> GetUnityAsset(string assetId)
		{
			return await ServeMetadataAsync(assetId, 0, 1);
		}

		private async Task<IActionResult> ServeMetadataAsync(string assetId, int target, int version)
		{
			if (!CdnStorageNames.IsServable(assetId) || target < 0 || target > byte.MaxValue || version < 0)
				return BadRequest();

			string? filename = null;
			string? rejectedDependencies = null;

			if (StudioUnityAssetRegistry.IsValidAssetId(assetId))
			{
				var asset = await StudioUnityAssetRegistry.ReadAsync(assetId, HttpContext.RequestAborted);
				var baked = asset?.BakedUnityAssets.FirstOrDefault(x => x.Target == target && x.Version == version);

				if (baked != null)
				{
					filename = baked.Filename;
					rejectedDependencies = baked.RejectedDependenciesFilename;
				}
				else if (asset != null)
				{
					// The manifest exists, so the file on disk under this id is that JSON
					// manifest and not a bundle. A target/version it does not name is a 404:
					// handing the manifest over as the bundle would have the client parse
					// metadata as an asset bundle.
					return NotFound();
				}
			}

			// Reached for every legacy id, and for a 40-character id with no manifest behind it:
			// the bundle is the file stored under the name the subroom points at, with or without
			// the .assetbundle suffix an import appends.
			filename ??= CdnStorageNames.Resolve(assetId);
			if (filename == null) return NotFound();

			var body = JsonSerializer.Serialize(new
			{
				UnityAssetId = assetId,
				Target = target,
				Version = version,
				Filename = filename,
				RejectedDependenciesFilename = rejectedDependencies
			});
			return Content(body, "application/json");
		}
	}
}