// Copyright (C) 2024, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
// 
// Permission is hereby granted, free of charge, to any person obtaining a 
// copy of this software and associated documentation files (the "Software"), 
// to deal in the Software without restriction, including without limitation 
// the rights to use, copy, modify, merge, publish, distribute, sublicense, 
// and/or sell copies of the Software, and to permit persons to whom the 
// Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Specialized;
using System.Linq;
using System.Text;

namespace Duplicati.Library.Utility
{
    /// <summary>
    /// Represents a relaxed parsing of a URL.
    /// The goal is to cover as many types of url's as possible,
    /// without being ambiguous.
    /// The major limitations is that an embedded username may not contain a :,
    /// and the password may not contain a @.
    /// </summary>
    public struct Uri
    {
        /// <summary>
        /// A very lax version of a URL parser
        /// </summary>
        private static readonly System.Text.RegularExpressions.Regex URL_PARSER = new System.Text.RegularExpressions.Regex(@"(?<scheme>[^:]+)://(((?<username>[^\:\?/]+)(\:(?<password>[^@\:\?/]*))?\@))?((?<hostname>(?:[^\[/\?\:][^/\?\:]*)|(?:\[[^\]]+\]))(\:(?<port>\d+))?)?((?<path>[^\?]*))?(\?(?<query>.+))?");

        /// <summary>
        /// The URL scheme, e.g. http
        /// </summary>
        public readonly string Scheme;
        /// <summary>
        /// The server name, e.g. www.example.com
        /// </summary>
        public readonly string Host;
        /// <summary>
        /// The server path, e.g. index.html
        /// </summary>
        public readonly string Path;
        /// <summary>
        /// The server port, e.g. 80, is -1 if using the default port
        /// </summary>
        public readonly int Port;
        /// <summary>
        /// The querystring, e.g. ?id=1
        /// </summary>
        public readonly string Query;
        /// <summary>
        /// The username, if any
        /// </summary>
        public readonly string Username;
        /// <summary>
        /// The password, if any
        /// </summary>
        public readonly string Password;

        /// <summary>
        /// The original URI.
        /// </summary>
        public readonly string OriginalUri;

        /// <summary>
        /// Cache for the query parameters.
        /// </summary>
        private NameValueCollection m_queryParams;

        /// <summary>
        /// Gets the parameters in the query string
        /// </summary>
        /// <value>The query parameters.</value>
        public NameValueCollection QueryParameters
        {
            get
            {
                if (m_queryParams == null)
                {
                    if (Query == null)
                        m_queryParams = new NameValueCollection();
                    else
                        m_queryParams = ParseQueryString(Query);
                }

                return m_queryParams;
            }
        }

        /// <summary>
        /// Gets the host and path.
        /// </summary>
        /// <value>The host and path.</value>
        public string HostAndPath
        {
            get
            {
                if (string.IsNullOrEmpty(Path))
                    return Host;
                else if (string.IsNullOrEmpty(Host))
                    return Path;
                else
                    return Host + (Path == null ? "" : "/" + Path);
            }
        }

        /// <summary>
        /// Gets the path and query.
        /// </summary>
        /// <value>The path and query.</value>
        public string PathAndQuery
        {
            get
            {
                return (Path ?? "") + (Query == null ? "" : "?" + Query);
            }
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="Duplicati.Library.Utility.Uri"/> struct.
        /// </summary>
        /// <param name="url">The URL to parse</param>
        public Uri(string url)
        {
            if (string.IsNullOrEmpty(url))
                throw new ArgumentNullException(nameof(url));

            m_queryParams = null;
            this.OriginalUri = url;

            var m = URL_PARSER.Match(url);
            if (!m.Success || m.Length != url.Length)
            {
                var path = url;
                if (path.StartsWith("file://", StringComparison.OrdinalIgnoreCase))
                    path = path.Substring("file://".Length);

                if (path.IndexOfAny(System.IO.Path.GetInvalidPathChars()) < 0)
                    try
                    {
                        var fp = System.IO.Path.GetFullPath(path);
                        this.Scheme = "file";
                        this.Host = null;
                        this.Path = fp;
                        this.Port = -1;
                        this.Query = null;
                        this.Username = null;
                        this.Password = null;
                        return;
                    }
                    catch
                    {
                    }
                throw new ArgumentException(Strings.Uri.UriParseError(url), nameof(url));
            }

            this.Scheme = m.Groups["scheme"].Value;
            var h = m.Groups["hostname"].Success ? m.Groups["hostname"].Value : "";

            var p = m.Groups["path"].Success ? m.Groups["path"].Value : "";
            if (m.Groups["hostname"].Success && p.StartsWith("/", StringComparison.Ordinal))
                p = p.Substring(1);

            // file://c:\test support
            if (h.Length == 1 && p.StartsWith(":", StringComparison.Ordinal))
            {
                h = h + p;
                p = "";
            }

            this.Host = h;
            this.Path = p;

            this.Query = m.Groups["query"].Success ? m.Groups["query"].Value : null;
            this.Username = m.Groups["username"].Success ? UrlDecode(m.Groups["username"].Value) : null;
            this.Password = m.Groups["password"].Success ? UrlDecode(m.Groups["password"].Value) : null;
            if (m.Groups["port"].Success)
                this.Port = int.Parse(m.Groups["port"].Value);
            else
                this.Port = -1;
        }

        /// <summary>
        /// Constructs a free-form URI from components
        /// </summary>
        /// <param name="scheme">The url scheme, e.g. http</param>
        /// <param name="host">The hostname, e.g. www.example.com</param>
        /// <param name="path">The path, e.g. index.html</param>
        /// <param name="query">The query string, e.g. id=1</param>
        /// <param name="username">The username</param>
        /// <param name="password">The password</param>
        /// <param name="port">The port</param>
        public Uri(string scheme, string host, string path = null, string query = null, string username = null, string password = null, int port = -1)
        {
            m_queryParams = null;
            Scheme = scheme;
            Host = host;
            Path = path;
            Query = query;
            Username = username;
            Password = password;
            Port = port;
            OriginalUri = AsString(scheme, host, path, query, username, password, port);
        }

        /// <summary>
        /// Returns a <see cref="System.String"/> that represents the current <see cref="Duplicati.Library.Utility.Uri"/>.
        /// </summary>
        /// <returns>A <see cref="System.String"/> that represents the current <see cref="Duplicati.Library.Utility.Uri"/>.</returns>
        public override string ToString()
        {
            return AsString(Scheme, Host, Path, Query, Username, Password, Port);
        }

        /// <summary>
        /// Throws an exception if the host name is missing.
        /// </summary>
        public void RequireHost()
        {
            if (string.IsNullOrEmpty(Host))
                throw new ArgumentException(Strings.Uri.NoHostname(OriginalUri));
        }

        /// <summary>
        /// Constructs an url-like string from components.
        /// </summary>
        /// <returns>An url-like string</returns>
        /// <param name="scheme">The url scheme, e.g. http</param>
        /// <param name="host">The hostname, e.g. www.example.com</param>
        /// <param name="path">The path, e.g. index.html</param>
        /// <param name="query">The query string, e.g. id=1</param>
        /// <param name="username">The username</param>
        /// <param name="password">The password</param>
        /// <param name="port">The port</param>
        private static string AsString(string scheme, string host, string path, string query, string username, string password, int port)
        {
            var s = scheme + "://";
            if (!string.IsNullOrEmpty(username) || !string.IsNullOrEmpty(password))
            {

                s += UrlEncode(username ?? "");
                s += ":";
                s += UrlEncode(password ?? "");
                s += "@";
            }

            if (!string.IsNullOrEmpty(host))
            {
                s += host;
                if (port != -1)
                    s += ":" + port.ToString();
            }

            if (!string.IsNullOrEmpty(path))
            {
                if (!string.IsNullOrEmpty(host) && !path.StartsWith("/", StringComparison.Ordinal))
                    s += "/";
                s += path;
            }
            if (!string.IsNullOrEmpty(query))
                s += "?" + query;

            return s;
        }

        /// <summary>
        /// Creates a new instance with another scheme
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="scheme">The new scheme to use</param>
        public Uri SetScheme(string scheme)
        {
            return new Uri(scheme, Host, Path, Query, Username, Password, Port);
        }

        /// <summary>
        /// Creates a new instance with another host
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="host">The new hostname to use</param>
        public Uri SetHost(string host)
        {
            return new Uri(Scheme, host, Path, Query, Username, Password, Port);
        }

        /// <summary>
        /// Creates a new instance with another path
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="path">The new path to use</param>
        public Uri SetPath(string path)
        {
            return new Uri(Scheme, Host, path, Query, Username, Password, Port);
        }

        /// <summary>
        /// Creates a new instance with another query
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="query">The new query to use</param>
        public Uri SetQuery(string query)
        {
            return new Uri(Scheme, Host, Path, query, Username, Password, Port);
        }

        /// <summary>
        /// Creates a new instance with other credentials
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="username">The new username to use</param>
        /// <param name="password">The new password to use</param>
        public Uri SetCredentials(string username, string password)
        {
            return new Uri(Scheme, Host, Path, Query, username, password, Port);
        }

        /// <summary>
        /// Creates a new instance with another port
        /// </summary>
        /// <returns>A new instance</returns>
        /// <param name="port">The new port to use</param>
        public Uri SetPort(int port)
        {
            return new Uri(Scheme, Host, Path, Query, Username, Password, port);
        }

        /// <summary>
        /// The regular expression that matches %20 type values in a querystring
        /// </summary>
        private static readonly System.Text.RegularExpressions.Regex RE_ESCAPECHAR = new System.Text.RegularExpressions.Regex(@"[^0-9a-zA-Z\-_]", System.Text.RegularExpressions.RegexOptions.Compiled);

        /// <summary>
        /// Encodes a URL, like System.Web.HttpUtility.UrlEncode
        /// </summary>
        /// <returns>The encoded URL</returns>
        /// <param name="value">The URL fragment to encode</param>
        /// <param name="encoding">The encoding to use</param>
        public static string UrlPathEncode(string value, System.Text.Encoding encoding = null)
        {
            return UrlEncode(value, encoding, "%20");
        }

        /// <summary>
        /// Encodes a URL, like System.Web.HttpUtility.UrlEncode
        /// </summary>
        /// <returns>The encoded URL</returns>
        /// <param name="value">The URL fragment to encode</param>
        /// <param name="encoding">The encoding to use</param>
        public static string UrlEncode(string value, System.Text.Encoding encoding = null, string spacevalue = "+")
        {
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            encoding = encoding ?? System.Text.Encoding.UTF8;

            var encoder = encoding.GetEncoder();
            var inbuf = new char[1];
            var outbuf = new byte[4];

            return RE_ESCAPECHAR.Replace(value, (m) =>
            {
                if (m.Value == " ")
                    return spacevalue;

                inbuf[0] = m.Value[0];

                try
                {
                    var len = encoder.GetBytes(inbuf, 0, 1, outbuf, 0, true);
                    return "%" + BitConverter.ToString(outbuf, 0, len).Replace("-", "%");
                }
                catch
                {
                }

                //Fallback
                return m.Value;
            });

        }

        /// <summary>
        /// The regular expression that matches %20 type values in a querystring
        /// </summary>
        private static readonly System.Text.RegularExpressions.Regex RE_NUMBER = new System.Text.RegularExpressions.Regex(@"(\%(?<number>([0-9]|[a-f]|[A-F]){2}))|(\+)|(\%u(?<number>([0-9]|[a-f]|[A-F]){4}))", System.Text.RegularExpressions.RegexOptions.Compiled);

        /// <summary>
        /// Decodes a URL, like System.Web.HttpUtility.UrlDecode
        /// </summary>
        /// <returns>The decoded URL</returns>
        /// <param name="value">The URL fragment to decode</param>
        /// <param name="encoding">The encoding to use</param>
        public static string UrlDecode(string value, System.Text.Encoding encoding = null)
        {
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            encoding = encoding ?? System.Text.Encoding.UTF8;

            var decoder = encoding.GetDecoder();
            var inbuf = new byte[8];
            var outbuf = new char[8];

            return RE_NUMBER.Replace(value, (m) =>
            {
                if (m.Value == "+")
                    return " ";

                try
                {
                    var hex = m.Groups["number"].Value;
                    var bytelen = hex.Length / 2;
                    Utility.HexStringAsByteArray(hex, inbuf);
                    var c = decoder.GetChars(inbuf, 0, bytelen, outbuf, 0);
                    return new string(outbuf, 0, c);
                }
                catch
                {
                }

                //Fallback
                return m.Value;
            });

        }

        /// <summary>
        /// The regular expression that matches a=b type values in a querystring
        /// </summary>
        private static readonly System.Text.RegularExpressions.Regex RE_URLPARAM = new System.Text.RegularExpressions.Regex(@"(?<key>[^\=\&]+)(\=(?<value>[^\&]*))?", System.Text.RegularExpressions.RegexOptions.Compiled);

        /// <summary>
        /// Parses the query string.
        /// This is a duplicate of the System.Web.HttpUtility.ParseQueryString that does not work well on Mono
        /// </summary>
        /// <returns>The parsed query string</returns>
        /// <param name="query">The query to parse</param>
        public static NameValueCollection ParseQueryString(string query)
        {
            return Library.Utility.Uri.ParseQueryString(query, true);
        }

        /// <summary>
        /// Parses the query string.
        /// This is a duplicate of the System.Web.HttpUtility.ParseQueryString that does not work well on Mono
        /// </summary>
        /// <returns>The parsed query string</returns>
        /// <param name="query">The query to parse</param>
        /// <param name="decodeValues">Whether to the parameter values should be decoded or not.</param>
        public static NameValueCollection ParseQueryString(string query, bool decodeValues)
        {
            if (query == null)
                throw new ArgumentNullException(nameof(query));
            if (query.StartsWith("?", StringComparison.Ordinal))
                query = query.Substring(1);
            if (string.IsNullOrEmpty(query))
                return new NameValueCollection(StringComparer.OrdinalIgnoreCase);

            var result = new NameValueCollection(StringComparer.OrdinalIgnoreCase);
            foreach (System.Text.RegularExpressions.Match m in RE_URLPARAM.Matches(query))
            {
                string value = m.Groups["value"].Success ? m.Groups["value"].Value : "";
                if (decodeValues)
                {
                    value = UrlDecode(value);
                }

                result.Add(UrlDecode(m.Groups["key"].Value), value);
            }

            return result;
        }

        /// <summary>
        /// Build the querystring to be used in a URL
        /// </summary>
        /// <returns>The generated querystring</returns>
        /// <param name="query">A collection of name value pairs to be translated into a query string</param>
        /// <param name="delimiter">The delimiter to separate key value pairs in the query string</param>
        public static string BuildUriQuery(NameValueCollection query, string delimiter)
        {

            if (query == null)
                throw new ArgumentNullException(nameof(query));

            StringBuilder builder = new StringBuilder();
            foreach (var key in query.Cast<string>().Where(key => !string.IsNullOrEmpty(query[key])))
            {
                builder.Append(builder.Length == 0 ? string.Empty : delimiter)
                       .Append(key)
                       .Append("=")
                       .Append(query[key]);
            }

            return builder.ToString();
        }

        /// <summary>
        /// Build the querystring to be used in a URL
        /// </summary>
        /// <returns>The generated querystring</returns>
        /// <param name="query">A collection of name value pairs to be translated into a query string that is
        /// ampersand delimited.</param>
        public static string BuildUriQuery(NameValueCollection query)
        {
            return BuildUriQuery(query, "&");
        }

        /// <summary>
        /// Builds a URL together using a base URL, a path and a query.
        /// </summary>
        /// <returns>The built together URL.</returns>
        /// <param name="url">Base URL, containing schema, host, port.</param>
        /// <param name="path">Base path.</param>
        /// <param name="query">A collection of name value pairs to be translated into a query string.</param>
        public static string UriBuilder(string url, string path, NameValueCollection query)
        {
            var builder = new UriBuilder(url)
            {
                Path = (new UrlPath(ExtractPath(url)).Append(path)).ToString(),
                Query = query != null ? BuildUriQuery(query) : null
            };
            return builder.Uri.AbsoluteUri;
        }

        /// <summary>
        /// Grab path part of a URI.
        /// At the moment, simple implementation does not remove fragments.
        /// </summary>
        /// <returns>The path.</returns>
        /// <param name="url">URL.</param>
        public static string ExtractPath(string url)
        {
            return (new Uri(url)).Path;
        }

        /// <summary>
        /// Builds a URL together using a base URL and path.
        /// </summary>
        /// <returns>The built together URL.</returns>
        /// <param name="url">Base URL, containing schema, host, port.</param>
        /// <param name="path">Base path.</param>
        public static string UriBuilder(string url, string path)
        {
            return UriBuilder(url, path, null);
        }
    }
}