using System;

using System.Collections.Generic;

using System.Security.Principal;

using System.Linq;

using Raven.Abstractions.Data;

using Raven.Database.Server.Abstractions;

using Raven.Database.Extensions;



namespace Raven.Database.Server.Security.OAuth

{

	public class OAuthRequestAuthorizer : AbstractRequestAuthorizer

	{

		public bool Authorize(IHttpContext ctx, bool hasApiKey)

		{

			var httpRequest = ctx.Request;



			var isGetRequest = IsGetRequest(httpRequest.HttpMethod, httpRequest.Url.AbsolutePath);

			var allowUnauthenticatedUsers = // we need to auth even if we don't have to, for bundles that want the user 

				Settings.AnonymousUserAccessMode == AnonymousUserAccessMode.All ||

				Settings.AnonymousUserAccessMode == AnonymousUserAccessMode.Admin || 

			        Settings.AnonymousUserAccessMode == AnonymousUserAccessMode.Get &&

			        isGetRequest;



			var token = GetToken(ctx);

			

			if (token == null)

			{

				if (allowUnauthenticatedUsers)

					return true;



				WriteAuthorizationChallenge(ctx, hasApiKey ? 412 : 401, "invalid_request", "The access token is required");

				

				return false;

			}



			AccessTokenBody tokenBody;

			if (!AccessToken.TryParseBody(Settings.OAuthTokenKey, token, out tokenBody))

			{

				if (allowUnauthenticatedUsers)

					return true;

				WriteAuthorizationChallenge(ctx, 401, "invalid_token", "The access token is invalid");



				return false;

			}



			if (tokenBody.IsExpired())

			{

				if (allowUnauthenticatedUsers)

					return true;

				WriteAuthorizationChallenge(ctx, 401, "invalid_token", "The access token is expired");



				return false;

			}



			var writeAccess = isGetRequest == false;

			if(!tokenBody.IsAuthorized(TenantId, writeAccess))

			{

				if (allowUnauthenticatedUsers)

					return true;



				WriteAuthorizationChallenge(ctx, 403, "insufficient_scope", 

					writeAccess ?

					"Not authorized for read/write access for tenant " + TenantId :

					"Not authorized for tenant " + TenantId);

	   

				return false;

			}

			

			ctx.User = new OAuthPrincipal(tokenBody, TenantId);

			CurrentOperationContext.Headers.Value[Constants.RavenAuthenticatedUser] = tokenBody.UserId;

			CurrentOperationContext.User.Value = ctx.User;

			return true;

		}



		public override List<string> GetApprovedDatabases(IHttpContext context)

		{

			var user = context.User as OAuthPrincipal;

			if(user == null)

				return new List<string>();

			return user.GetApprovedDatabases();

		}



		public override void Dispose()

		{

			

		}



		static string GetToken(IHttpContext ctx)

		{

			const string bearerPrefix = "Bearer ";



			var auth = ctx.Request.Headers["Authorization"];

			if(auth == null)

			{

				auth = ctx.Request.GetCookie("OAuth-Token");

				if (auth != null)

					auth = Uri.UnescapeDataString(auth);

			}

			if (auth == null || auth.Length <= bearerPrefix.Length ||

				!auth.StartsWith(bearerPrefix, StringComparison.OrdinalIgnoreCase))

				return null;



			var token = auth.Substring(bearerPrefix.Length, auth.Length - bearerPrefix.Length);

			

			return token;

		}



		void WriteAuthorizationChallenge(IHttpContext ctx, int statusCode, string error, string errorDescription)

		{

			if (string.IsNullOrEmpty(Settings.OAuthTokenServer) == false)

			{

				ctx.Response.AddHeader("OAuth-Source", Settings.OAuthTokenServer);

			}

			ctx.Response.StatusCode = statusCode;

			ctx.Response.AddHeader("WWW-Authenticate", string.Format("Bearer realm=\"Raven\", error=\"{0}\",error_description=\"{1}\"", error, errorDescription));

		}

	}



	public class OAuthPrincipal : IPrincipal, IIdentity

	{

		private readonly AccessTokenBody tokenBody;

		private readonly string tenantId;



		public OAuthPrincipal(AccessTokenBody tokenBody, string tenantId)

		{

			this.tokenBody = tokenBody;

			this.tenantId = tenantId;

		}



		public bool IsInRole(string role)

		{

			if ("Administrators".Equals(role, StringComparison.OrdinalIgnoreCase) == false)

				return false;



			var databaseAccess = tokenBody.AuthorizedDatabases

				.Where(x=>

					string.Equals(x.TenantId, tenantId, StringComparison.OrdinalIgnoreCase) ||

					x.TenantId == "*");



			return databaseAccess.Any(access => access.Admin);

		}



		public IIdentity Identity

		{

			get { return this; }

		}



		public string Name

		{

			get { return tokenBody.UserId; }

		}



		public string AuthenticationType

		{

			get { return "OAuth"; }

		}



		public bool IsAuthenticated

		{

			get { return true; }

		}



		public List<string> GetApprovedDatabases()

		{

			return tokenBody.AuthorizedDatabases.Select(access => access.TenantId).ToList();

		}



		public AccessTokenBody TokenBody

		{

			get { return tokenBody; }

		}

	}

}