using System;
using System.Security.Cryptography;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Globalization;

namespace Google.GData.Client {
    /// <summary>
    /// The original OAuth code from http://eran.sandler.co.il/, hosted at http://oauth.net
    /// Modified only to change namespace.
    /// Written by Eran Sandler (http://eran.sandler.co.il)
    /// </summary>
	public class OAuthBase {

        /// <summary>
        /// Provides a predefined set of algorithms that are supported officially by the protocol
        /// </summary>
        public enum SignatureTypes {
            HMACSHA1,
            PLAINTEXT,
            RSASHA1
        }

        /// <summary>
        /// Provides an internal structure to sort the query parameter
        /// </summary>
        protected class QueryParameter {
            private string name = null;
            private string value = null;

            public QueryParameter(string name, string value) {
                this.name = name;
                this.value = value;
            }

            public string Name {
                get { return name; }
            }

            public string Value {
                get { return value; }
            }            
        }

        /// <summary>
        /// Comparer class used to perform the sorting of the query parameters
        /// </summary>
        protected class QueryParameterComparer : IComparer<QueryParameter> {

            #region IComparer<QueryParameter> Members

            public int Compare(QueryParameter x, QueryParameter y) {
                if (x.Name == y.Name) {
                    return string.Compare(x.Value, y.Value);
                } else {
                    return string.Compare(x.Name, y.Name);
                }
            }

            #endregion
        }

		protected const string OAuthVersion = "1.0";
        protected const string OAuthParameterPrefix = "oauth_";

        //
        // List of know and used oauth parameters' names
        //        
		protected const string OAuthConsumerKeyKey = "oauth_consumer_key";
		protected const string OAuthCallbackKey = "oauth_callback";
		protected const string OAuthVersionKey = "oauth_version";
		protected const string OAuthSignatureMethodKey = "oauth_signature_method";
		protected const string OAuthSignatureKey = "oauth_signature";
		protected const string OAuthTimestampKey = "oauth_timestamp";
		protected const string OAuthNonceKey = "oauth_nonce";
		protected const string OAuthTokenKey = "oauth_token";
		protected const string OAuthTokenSecretKey = "oauth_token_secret";

        protected const string HMACSHA1SignatureType = "HMAC-SHA1";
        protected const string PlainTextSignatureType = "PLAINTEXT";
        protected const string RSASHA1SignatureType = "RSA-SHA1";

        protected Random random = new Random();

        protected string unreservedChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~";

        /// <summary>
        /// Helper function to compute a hash value
        /// </summary>
        /// <param name="hashAlgorithm">The hashing algoirhtm used. If that algorithm needs some initialization, like HMAC and its derivatives, they should be initialized prior to passing it to this function</param>
        /// <param name="data">The data to hash</param>
        /// <returns>a Base64 string of the hash value</returns>
        private string ComputeHash(HashAlgorithm hashAlgorithm, string data) {
            if (hashAlgorithm == null) {
                throw new ArgumentNullException("hashAlgorithm");
            }

            if (string.IsNullOrEmpty(data)) {
                throw new ArgumentNullException("data");
            }

            byte[] dataBuffer = System.Text.Encoding.ASCII.GetBytes(data);
            byte[] hashBytes = hashAlgorithm.ComputeHash(dataBuffer);

            return Convert.ToBase64String(hashBytes);
        }

        /// <summary>
        /// Internal function to cut out all non oauth query string parameters (all parameters not begining with "oauth_")
        /// </summary>
        /// <param name="parameters">The query string part of the Url</param>
        /// <returns>A list of QueryParameter each containing the parameter name and value</returns>
        private List<QueryParameter> GetQueryParameters(string parameters) {
            if (parameters.StartsWith("?")) {
                parameters = parameters.Remove(0, 1);
            }

            List<QueryParameter> result = new List<QueryParameter>();

            if (!string.IsNullOrEmpty(parameters)) {
                string[] p = parameters.Split('&');
                foreach (string s in p) {
                    if (!string.IsNullOrEmpty(s) && !s.StartsWith(OAuthParameterPrefix)) {
                        if (s.IndexOf('=') > -1) {
                            string[] temp = s.Split('=');
                            result.Add(new QueryParameter(temp[0], temp[1]));
                        } else {
                            result.Add(new QueryParameter(s, string.Empty));
                        }
                    }
                }
            }

            return result;
        }

        /// <summary>
        /// This is a different Url Encode implementation since the default .NET one outputs the percent encoding in lower case.
        /// While this is not a problem with the percent encoding spec, it is used in upper case throughout OAuth
        /// </summary>
        /// <param name="value">The value to Url encode</param>
        /// <returns>Returns a Url encoded string</returns>
        protected string UrlEncode(string value) {
            StringBuilder result = new StringBuilder();

            foreach (char symbol in value) {
                if (unreservedChars.IndexOf(symbol) != -1) {
                    result.Append(symbol);
                } else {
                    result.Append('%' + String.Format("{0:X2}", (int)symbol));
                }
            }

            return result.ToString();
        }
                        
        /// <summary>
        /// Normalizes the request parameters according to the spec
        /// </summary>
        /// <param name="parameters">The list of parameters already sorted</param>
        /// <returns>a string representing the normalized parameters</returns>
		protected string NormalizeRequestParameters(IList<QueryParameter> parameters) {			
			StringBuilder sb = new StringBuilder();
            QueryParameter p = null;
            for (int i = 0; i < parameters.Count; i++) {
                p = parameters[i];
                sb.AppendFormat(CultureInfo.InvariantCulture, "{0}={1}", p.Name, p.Value);

                if (i < parameters.Count - 1) {
                    sb.Append("&");
                }
            }

            return sb.ToString();
		}

        /// <summary>
        /// Generate the signature base that is used to produce the signature
        /// </summary>
        /// <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
        /// <param name="consumerKey">The consumer key</param>        
        /// <param name="token">The token, if available. If not available pass null or an empty string</param>
        /// <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
        /// <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
        /// <param name="signatureType">The signature type. To use the default values use <see cref="OAuthBase.SignatureTypes">OAuthBase.SignatureTypes</see>.</param>
        /// <returns>The signature base</returns>
        public string GenerateSignatureBase(Uri url, string consumerKey, string token, string tokenSecret, string httpMethod, string timeStamp, string nonce, string signatureType, out string normalizedUrl, out string normalizedRequestParameters) {
            if (token == null) {
                token = string.Empty;
            }

            if (tokenSecret == null) {
                tokenSecret = string.Empty;
            }

            if (string.IsNullOrEmpty(consumerKey)) {
                throw new ArgumentNullException("consumerKey");
            }

            if (string.IsNullOrEmpty(httpMethod)) {
                throw new ArgumentNullException("httpMethod");
            }

            if (string.IsNullOrEmpty(signatureType)) {
                throw new ArgumentNullException("signatureType");
            }

			normalizedUrl = null;
			normalizedRequestParameters = null;

            List<QueryParameter> parameters = GetQueryParameters(url.Query);
            parameters.Add(new QueryParameter(OAuthVersionKey, OAuthVersion));
            parameters.Add(new QueryParameter(OAuthNonceKey, nonce));
            parameters.Add(new QueryParameter(OAuthTimestampKey, timeStamp));
            parameters.Add(new QueryParameter(OAuthSignatureMethodKey, signatureType));
            parameters.Add(new QueryParameter(OAuthConsumerKeyKey, consumerKey));

            if (!string.IsNullOrEmpty(token)) {
                parameters.Add(new QueryParameter(OAuthTokenKey, token));
            }

            parameters.Sort(new QueryParameterComparer());

            normalizedUrl = string.Format("{0}://{1}", url.Scheme, url.Host);
            if (!((url.Scheme == "http" && url.Port == 80) || (url.Scheme == "https" && url.Port == 443)))
            {
                normalizedUrl += ":" + url.Port;
            }
            normalizedUrl += url.AbsolutePath;
            normalizedRequestParameters = NormalizeRequestParameters(parameters);

            StringBuilder signatureBase = new StringBuilder();
            signatureBase.AppendFormat(CultureInfo.InvariantCulture, "{0}&", httpMethod.ToUpper());
            signatureBase.AppendFormat(CultureInfo.InvariantCulture, "{0}&", UrlEncode(normalizedUrl));
            signatureBase.AppendFormat(CultureInfo.InvariantCulture, "{0}", UrlEncode(normalizedRequestParameters));

            return signatureBase.ToString();
        }

        /// <summary>
        /// Generate the signature value based on the given signature base and hash algorithm
        /// </summary>
        /// <param name="signatureBase">The signature based as produced by the GenerateSignatureBase method or by any other means</param>
        /// <param name="hash">The hash algorithm used to perform the hashing. If the hashing algorithm requires initialization or a key it should be set prior to calling this method</param>
        /// <returns>A base64 string of the hash value</returns>
        public string GenerateSignatureUsingHash(string signatureBase, HashAlgorithm hash) {
            return ComputeHash(hash, signatureBase);
        }

        /// <summary>
        /// Generates a signature using the HMAC-SHA1 algorithm
        /// </summary>		
        /// <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
        /// <param name="consumerKey">The consumer key</param>
        /// <param name="consumerSecret">The consumer seceret</param>
        /// <param name="token">The token, if available. If not available pass null or an empty string</param>
        /// <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
        /// <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
        /// <returns>A base64 string of the hash value</returns>
		public string GenerateSignature(Uri url, string consumerKey, string consumerSecret, string token, string tokenSecret, string httpMethod, string timeStamp, string nonce, out string normalizedUrl, out string normalizedRequestParameters) {            
			return GenerateSignature(url, consumerKey, consumerSecret, token, tokenSecret, httpMethod, timeStamp, nonce, SignatureTypes.HMACSHA1, out normalizedUrl, out normalizedRequestParameters);
        }

        /// <summary>
        /// Generates a signature using the specified signatureType 
        /// </summary>		
        /// <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
        /// <param name="consumerKey">The consumer key</param>
        /// <param name="consumerSecret">The consumer seceret</param>
        /// <param name="token">The token, if available. If not available pass null or an empty string</param>
        /// <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
        /// <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
        /// <param name="signatureType">The type of signature to use</param>
        /// <returns>A base64 string of the hash value</returns>
		public string GenerateSignature(Uri url, string consumerKey, string consumerSecret, string token, string tokenSecret, string httpMethod, string timeStamp, string nonce, SignatureTypes signatureType, out string normalizedUrl, out string normalizedRequestParameters) {
			normalizedUrl = null;
			normalizedRequestParameters = null;

            switch (signatureType) {
                case SignatureTypes.PLAINTEXT:					
                    return HttpUtility.UrlEncode(string.Format("{0}&{1}", consumerSecret, tokenSecret));
                case SignatureTypes.HMACSHA1:					
					string signatureBase = GenerateSignatureBase(url, consumerKey, token, tokenSecret, httpMethod, timeStamp, nonce, HMACSHA1SignatureType, out normalizedUrl, out normalizedRequestParameters);

                    HMACSHA1 hmacsha1 = new HMACSHA1();
                    hmacsha1.Key = Encoding.ASCII.GetBytes(string.Format("{0}&{1}", UrlEncode(consumerSecret), string.IsNullOrEmpty(tokenSecret) ? "" : UrlEncode(tokenSecret)));

                    return GenerateSignatureUsingHash(signatureBase, hmacsha1);                                        
                case SignatureTypes.RSASHA1:
                    throw new NotImplementedException();
                default:
                    throw new ArgumentException("Unknown signature type", "signatureType");
            }
        }

        /// <summary>
        /// Generate the timestamp for the signature        
        /// </summary>
        /// <returns></returns>
        public virtual string GenerateTimeStamp() {
            // Default implementation of UNIX time of the current UTC time
            TimeSpan ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            return Convert.ToInt64(ts.TotalSeconds).ToString();            
        }

        /// <summary>
        /// Generate a nonce
        /// </summary>
        /// <returns></returns>
        public virtual string GenerateNonce() {
            // Just a simple implementation of a random number between 123400 and 9999999
            return random.Next(123400, 9999999).ToString();            
        }

	}
}

