// Copyright (c) Microsoft Corporation. All rights reserved. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Microsoft.Web.Mvc.Properties;

namespace Microsoft.Web.Mvc
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public sealed class FileExtensionsAttribute : DataTypeAttribute, IClientValidatable
    {
        private string _extensions;

        public FileExtensionsAttribute()
            : base("upload")
        {
            ErrorMessage = MvcResources.FileExtensionsAttribute_Invalid;
        }

        public string Extensions
        {
            get { return String.IsNullOrWhiteSpace(_extensions) ? "png,jpg,jpeg,gif" : _extensions; }
            set { _extensions = value; }
        }

        private string ExtensionsFormatted
        {
            get { return ExtensionsParsed.Aggregate((left, right) => left + ", " + right); }
        }

        [SuppressMessage("Microsoft.Globalization", "CA1308:NormalizeStringsToUppercase", Justification = "These strings are normalized to lowercase because they are presented to the user in lowercase format")]
        private string ExtensionsNormalized
        {
            get { return Extensions.Replace(" ", String.Empty).Replace(".", String.Empty).ToLowerInvariant(); }
        }

        private IEnumerable<string> ExtensionsParsed
        {
            get { return ExtensionsNormalized.Split(',').Select(e => "." + e); }
        }

        public override string FormatErrorMessage(string name)
        {
            return String.Format(CultureInfo.CurrentCulture, ErrorMessageString, name, ExtensionsFormatted);
        }

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var rule = new ModelClientValidationRule
            {
                ValidationType = "accept",
                ErrorMessage = FormatErrorMessage(metadata.GetDisplayName())
            };
            rule.ValidationParameters["exts"] = ExtensionsNormalized;
            yield return rule;
        }

        public override bool IsValid(object value)
        {
            if (value == null)
            {
                return true;
            }

            HttpPostedFileBase valueAsFileBase = value as HttpPostedFileBase;
            if (valueAsFileBase != null)
            {
                return ValidateExtension(valueAsFileBase.FileName);
            }

            string valueAsString = value as string;
            if (valueAsString != null)
            {
                return ValidateExtension(valueAsString);
            }

            return false;
        }

        [SuppressMessage("Microsoft.Globalization", "CA1308:NormalizeStringsToUppercase", Justification = "These strings are normalized to lowercase because they are presented to the user in lowercase format")]
        private bool ValidateExtension(string fileName)
        {
            try
            {
                return ExtensionsParsed.Contains(Path.GetExtension(fileName).ToLowerInvariant());
            }
            catch (ArgumentException)
            {
                return false;
            }
        }
    }
}