//------------------------------------------------------------------------------
// <copyright file="DBConnectionString.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------

namespace System.Data.Common {

    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Data;
    using System.Data.Common;
    using System.Diagnostics;
    using System.Globalization;
    using System.Linq;
    using System.Runtime.Serialization;
    using System.Security.Permissions;
    using System.Text;
    using System.Text.RegularExpressions;

    [Serializable] // MDAC 83147
    internal sealed class DBConnectionString {
        // instances of this class are intended to be immutable, i.e readonly
        // used by permission classes so it is much easier to verify correctness
        // when not worried about the class being modified during execution

        private static class KEY {
            internal const string Password            = "password";
            internal const string PersistSecurityInfo = "persist security info";
            internal const string Pwd                 = "pwd";
        };

        // this class is serializable with Everett, so ugly field names can't be changed
        readonly private string        _encryptedUsersConnectionString;

        // hash of unique keys to values
        readonly private Hashtable     _parsetable;

        // a linked list of key/value and their length in _encryptedUsersConnectionString
        readonly private NameValuePair _keychain;

        // track the existence of "password" or "pwd" in the connection string
        // not used for anything anymore but must keep it set correct for V1.1 serialization
        readonly private bool          _hasPassword;

        readonly private string[] _restrictionValues;
        readonly private string   _restrictions;

        readonly private KeyRestrictionBehavior _behavior;

#pragma warning disable 169
        // this field is no longer used, hence the warning was disabled
        // however, it can not be removed or it will break serialization with V1.1
        readonly private string _encryptedActualConnectionString;
#pragma warning restore 169

        internal DBConnectionString(string value, string restrictions, KeyRestrictionBehavior behavior, Hashtable synonyms, bool useOdbcRules)
            : this(new DbConnectionOptions(value, synonyms, useOdbcRules), restrictions, behavior, synonyms, false)
        {
            // useOdbcRules is only used to parse the connection string, not to parse restrictions because values don't apply there
            // the hashtable doesn't need clone since it isn't shared with anything else
        }

        internal DBConnectionString(DbConnectionOptions connectionOptions)
            : this(connectionOptions, (string)null, KeyRestrictionBehavior.AllowOnly, (Hashtable)null, true)
        {
            // used by DBDataPermission to convert from DbConnectionOptions to DBConnectionString
            // since backward compatability requires Everett level classes
        }

        private DBConnectionString(DbConnectionOptions connectionOptions, string restrictions, KeyRestrictionBehavior behavior, Hashtable synonyms, bool mustCloneDictionary) { // used by DBDataPermission
            Debug.Assert(null != connectionOptions, "null connectionOptions");
            switch(behavior) {
            case KeyRestrictionBehavior.PreventUsage:
            case KeyRestrictionBehavior.AllowOnly:
                _behavior = behavior;
                break;
            default:
                throw ADP.InvalidKeyRestrictionBehavior(behavior);
            }

            // grab all the parsed details from DbConnectionOptions
            _encryptedUsersConnectionString = connectionOptions.UsersConnectionString(false);
            _hasPassword = connectionOptions.HasPasswordKeyword;
            _parsetable = connectionOptions.Parsetable;
            _keychain = connectionOptions._keyChain;

            // we do not want to serialize out user password unless directed so by "persist security info=true"
            // otherwise all instances of user's password will be replaced with "*"
            if (_hasPassword && !connectionOptions.HasPersistablePassword) {

                if (mustCloneDictionary) {
                    // clone the hashtable to replace user's password/pwd value with "*"
                    // we only need to clone if coming from DbConnectionOptions and password exists
                    _parsetable = (Hashtable) _parsetable.Clone();
                }

                // different than Everett in that instead of removing password/pwd from
                // the hashtable, we replace the value with '*'.  This is okay since we
                // serialize out with '*' so already knows what we do.  Better this way
                // than to treat password specially later on which causes problems.
                const string star = "*";
                if (_parsetable.ContainsKey(KEY.Password)) {
                    _parsetable[KEY.Password] = star;
                }
                if (_parsetable.ContainsKey(KEY.Pwd)) {
                    _parsetable[KEY.Pwd] = star;
                }

                // replace user's password/pwd value with "*" in the linked list and build a new string
                _keychain = connectionOptions.ReplacePasswordPwd(out _encryptedUsersConnectionString, true);
            }

            if (!ADP.IsEmpty(restrictions)) {
                _restrictionValues = ParseRestrictions(restrictions, synonyms);
                _restrictions = restrictions;
            }
        }

        private DBConnectionString(DBConnectionString connectionString, string[] restrictionValues, KeyRestrictionBehavior behavior) {
            // used by intersect for two equal connection strings with different restrictions
            _encryptedUsersConnectionString = connectionString._encryptedUsersConnectionString;
            _parsetable = connectionString._parsetable;
            _keychain = connectionString._keychain;
            _hasPassword = connectionString._hasPassword;

            _restrictionValues = restrictionValues;
            _restrictions = null;
            _behavior = behavior;

            Verify(restrictionValues);
        }

        internal KeyRestrictionBehavior Behavior {
            get { return _behavior; }
        }

        internal string ConnectionString {
            get { return _encryptedUsersConnectionString; }
        }

        internal bool IsEmpty {
            get { return (null == _keychain); }
        }

        internal NameValuePair KeyChain {
            get { return _keychain; }
        }

        internal string Restrictions {
            get {
                string restrictions = _restrictions;
                if (null == restrictions) {
                    string[] restrictionValues = _restrictionValues;
                    if ((null != restrictionValues) && (0 < restrictionValues.Length)) {
                        StringBuilder builder = new StringBuilder();
                        for(int i = 0; i < restrictionValues.Length; ++i) {
                            if (!ADP.IsEmpty(restrictionValues[i])) {
                                builder.Append(restrictionValues[i]);
                                builder.Append("=;");
                            }
#if DEBUG
                            else {
                                Debug.Assert(false, "empty restriction");
                            }
#endif
                        }
                        restrictions = builder.ToString();
                    }
                }
                return ((null != restrictions) ? restrictions: "");
            }
        }

        internal string this[string keyword] {
            get { return (string)_parsetable[keyword]; }
        }

        internal bool ContainsKey(string keyword) {
            return _parsetable.ContainsKey(keyword);
        }

        internal DBConnectionString Intersect(DBConnectionString entry) {
            KeyRestrictionBehavior behavior = _behavior;
            string[] restrictionValues = null;

            if (null == entry) {
                //Debug.WriteLine("0 entry AllowNothing");
                behavior = KeyRestrictionBehavior.AllowOnly;
            }
            else if (this._behavior != entry._behavior) { // subset of the AllowOnly array
                behavior = KeyRestrictionBehavior.AllowOnly;

                if (KeyRestrictionBehavior.AllowOnly == entry._behavior) { // this PreventUsage and entry AllowOnly
                    if (!ADP.IsEmptyArray(_restrictionValues)) {
                        if (!ADP.IsEmptyArray(entry._restrictionValues)) {
                            //Debug.WriteLine("1 this PreventUsage with restrictions and entry AllowOnly with restrictions");
                            restrictionValues = NewRestrictionAllowOnly(entry._restrictionValues, _restrictionValues);
                        }
                        else {
                            //Debug.WriteLine("2 this PreventUsage with restrictions and entry AllowOnly with no restrictions");
                        }
                    }
                    else {
                        //Debug.WriteLine("3/4 this PreventUsage with no restrictions and entry AllowOnly");
                        restrictionValues = entry._restrictionValues;
                    }
                }
                else if (!ADP.IsEmptyArray(_restrictionValues)) { // this AllowOnly and entry PreventUsage
                    if (!ADP.IsEmptyArray(entry._restrictionValues)) {
                        //Debug.WriteLine("5 this AllowOnly with restrictions and entry PreventUsage with restrictions");
                        restrictionValues = NewRestrictionAllowOnly(_restrictionValues, entry._restrictionValues);
                    }
                    else {
                        //Debug.WriteLine("6 this AllowOnly and entry PreventUsage with no restrictions");
                        restrictionValues = _restrictionValues;
                    }
                }
                else {
                    //Debug.WriteLine("7/8 this AllowOnly with no restrictions and entry PreventUsage");
                }
            }
            else if (KeyRestrictionBehavior.PreventUsage == this._behavior) { // both PreventUsage
                if (ADP.IsEmptyArray(_restrictionValues)) {
                    //Debug.WriteLine("9/10 both PreventUsage and this with no restrictions");
                    restrictionValues = entry._restrictionValues;
                }
                else if (ADP.IsEmptyArray(entry._restrictionValues)) {
                    //Debug.WriteLine("11 both PreventUsage and entry with no restrictions");
                    restrictionValues = _restrictionValues;
                }
                else {
                    //Debug.WriteLine("12 both PreventUsage with restrictions");
                    restrictionValues = NoDuplicateUnion(_restrictionValues, entry._restrictionValues);
                }
            }
            else if (!ADP.IsEmptyArray(_restrictionValues) && !ADP.IsEmptyArray(entry._restrictionValues)) { // both AllowOnly with restrictions
                if (this._restrictionValues.Length <= entry._restrictionValues.Length) {
                    //Debug.WriteLine("13a this AllowOnly with restrictions and entry AllowOnly with restrictions");
                    restrictionValues = NewRestrictionIntersect(_restrictionValues, entry._restrictionValues);
                }
                else {
                    //Debug.WriteLine("13b this AllowOnly with restrictions and entry AllowOnly with restrictions");
                    restrictionValues = NewRestrictionIntersect(entry._restrictionValues, _restrictionValues);
                }
            }
            else { // both AllowOnly
                //Debug.WriteLine("14/15/16 this AllowOnly and entry AllowOnly but no restrictions");
            }

            // verify _hasPassword & _parsetable are in sync between Everett/Whidbey
            Debug.Assert(!_hasPassword || ContainsKey(KEY.Password) || ContainsKey(KEY.Pwd), "OnDeserialized password mismatch this");
            Debug.Assert(null == entry || !entry._hasPassword || entry.ContainsKey(KEY.Password) || entry.ContainsKey(KEY.Pwd), "OnDeserialized password mismatch entry");

            DBConnectionString value = new DBConnectionString(this, restrictionValues, behavior);
            ValidateCombinedSet(this, value);
            ValidateCombinedSet(entry, value);
            
            return value;
        }

        [Conditional("DEBUG")]
        private void ValidateCombinedSet(DBConnectionString componentSet, DBConnectionString combinedSet) {
            Debug.Assert(combinedSet != null, "The combined connection string should not be null");
            if ((componentSet != null) && (combinedSet._restrictionValues != null) && (componentSet._restrictionValues != null)) {
                if (componentSet._behavior == KeyRestrictionBehavior.AllowOnly) {
                    if (combinedSet._behavior == KeyRestrictionBehavior.AllowOnly) {
                        // Component==Allow, Combined==Allow
                        // All values in the Combined Set should also be in the Component Set
                        // Combined - Component == null
                        Debug.Assert(combinedSet._restrictionValues.Except(componentSet._restrictionValues).Count() == 0, "Combined set allows values not allowed by component set");
                    }
                    else if (combinedSet._behavior == KeyRestrictionBehavior.PreventUsage) {
                        // Component==Allow, Combined==PreventUsage
                        // Preventions override allows, so there is nothing to check here
                    }
                    else {
                        Debug.Assert(false, string.Format("Unknown behavior for combined set: {0}", combinedSet._behavior));
                    }
                }
                else if (componentSet._behavior == KeyRestrictionBehavior.PreventUsage) {
                    if (combinedSet._behavior == KeyRestrictionBehavior.AllowOnly) {
                        // Component==PreventUsage, Combined==Allow
                        // There shouldn't be any of the values from the Component Set in the Combined Set
                        // Intersect(Component, Combined) == null
                        Debug.Assert(combinedSet._restrictionValues.Intersect(componentSet._restrictionValues).Count() == 0, "Combined values allows values prevented by component set");
                    }
                    else if (combinedSet._behavior == KeyRestrictionBehavior.PreventUsage) {
                        // Component==PreventUsage, Combined==PreventUsage
                        // All values in the Component Set should also be in the Combined Set
                        // Component - Combined == null
                        Debug.Assert(componentSet._restrictionValues.Except(combinedSet._restrictionValues).Count() == 0, "Combined values does not prevent all of the values prevented by the component set");
                    }
                    else {
                        Debug.Assert(false, string.Format("Unknown behavior for combined set: {0}", combinedSet._behavior));
                    }
                }
                else {
                    Debug.Assert(false, string.Format("Unknown behavior for component set: {0}", componentSet._behavior));
                }
            }
        }

        private bool IsRestrictedKeyword(string key) {
            // restricted if not found
            return ((null == _restrictionValues) || (0 > Array.BinarySearch(_restrictionValues, key, StringComparer.Ordinal)));
        }

        internal bool IsSupersetOf(DBConnectionString entry) {
            Debug.Assert(!_hasPassword || ContainsKey(KEY.Password) || ContainsKey(KEY.Pwd), "OnDeserialized password mismatch this");
            Debug.Assert(!entry._hasPassword || entry.ContainsKey(KEY.Password) || entry.ContainsKey(KEY.Pwd), "OnDeserialized password mismatch entry");

            switch(_behavior) {
            case KeyRestrictionBehavior.AllowOnly:
                // every key must either be in the resticted connection string or in the allowed keywords
                // keychain may contain duplicates, but it is better than GetEnumerator on _parsetable.Keys
                for(NameValuePair current = entry.KeyChain; null != current; current = current.Next) {
                    if (!ContainsKey(current.Name) && IsRestrictedKeyword(current.Name)) {
                        return false;
                    }
                }
                break;
            case KeyRestrictionBehavior.PreventUsage:
                // every key can not be in the restricted keywords (even if in the restricted connection string)
                if (null != _restrictionValues) {
                    foreach(string restriction in _restrictionValues) {
                        if (entry.ContainsKey(restriction)) {
                            return false;
                        }
                    }
                }
                break;
            default:
                Debug.Assert(false, "invalid KeyRestrictionBehavior");
                throw ADP.InvalidKeyRestrictionBehavior(_behavior);
            }
            return true;
        }

        static private string[] NewRestrictionAllowOnly(string[] allowonly, string[] preventusage) {
            List<string> newlist = null;
            for (int i = 0; i < allowonly.Length; ++i) {
                if (0 > Array.BinarySearch(preventusage, allowonly[i], StringComparer.Ordinal)) {
                    if (null == newlist) {
                        newlist = new List<string>();
                    }
                    newlist.Add(allowonly[i]);
                }
            }
            string[] restrictionValues = null;
            if (null != newlist) {
                restrictionValues = newlist.ToArray();
            }
            Verify(restrictionValues);
            return restrictionValues;
        }

        static private string[] NewRestrictionIntersect(string[] a, string[] b) {
            List<string> newlist = null;
            for (int i = 0; i < a.Length; ++i) {
                if (0 <= Array.BinarySearch(b, a[i], StringComparer.Ordinal)) {
                    if (null == newlist) {
                        newlist = new List<string>();
                    }
                    newlist.Add(a[i]);
                }
            }
            string[] restrictionValues = null;
            if (newlist != null) {
                restrictionValues = newlist.ToArray();
            }
            Verify(restrictionValues);
            return restrictionValues;
        }

        static private string[] NoDuplicateUnion(string[] a, string[] b) {
#if DEBUG
            Debug.Assert(null != a && 0 < a.Length, "empty a");
            Debug.Assert(null != b && 0 < b.Length, "empty b");
            Verify(a);
            Verify(b);
#endif
            List<string> newlist = new List<string>(a.Length + b.Length);
            for(int i = 0; i < a.Length; ++i) {
                newlist.Add(a[i]);
            }
            for(int i = 0; i < b.Length; ++i) { // find duplicates
                if (0 > Array.BinarySearch(a, b[i], StringComparer.Ordinal)) {
                    newlist.Add(b[i]);
                }
            }
            string[] restrictionValues = newlist.ToArray();
            Array.Sort(restrictionValues, StringComparer.Ordinal);
            Verify(restrictionValues);
            return restrictionValues;
        }

        private static string[] ParseRestrictions(string restrictions, Hashtable synonyms) {
#if DEBUG
            if (Bid.AdvancedOn) {
                Bid.Trace("<comm.DBConnectionString|INFO|ADV> Restrictions='%ls'\n", restrictions);
            }
#endif
            List<string> restrictionValues = new List<string>();
            StringBuilder buffer = new StringBuilder(restrictions.Length);

            int nextStartPosition = 0;
            int endPosition = restrictions.Length;
            while (nextStartPosition < endPosition) {
                int startPosition = nextStartPosition;

                string keyname, keyvalue; // since parsing restrictions ignores values, it doesn't matter if we use ODBC rules or OLEDB rules
                nextStartPosition = DbConnectionOptions.GetKeyValuePair(restrictions, startPosition, buffer, false, out keyname, out keyvalue);
                if (!ADP.IsEmpty(keyname)) {
#if DEBUG
                    if (Bid.AdvancedOn) {
                        Bid.Trace("<comm.DBConnectionString|INFO|ADV> KeyName='%ls'\n", keyname);
                    }
#endif
                    string realkeyname = ((null != synonyms) ? (string)synonyms[keyname] : keyname); // MDAC 85144
                    if (ADP.IsEmpty(realkeyname)) {
                        throw ADP.KeywordNotSupported(keyname);
                    }
                    restrictionValues.Add(realkeyname);
                }
            }
            return RemoveDuplicates(restrictionValues.ToArray());

        }

        static internal string[] RemoveDuplicates(string[] restrictions) {
            int count = restrictions.Length;
            if (0 < count) {
                Array.Sort(restrictions, StringComparer.Ordinal);

                for (int i = 1; i < restrictions.Length; ++i) {
                    string prev = restrictions[i-1];
                    if ((0 == prev.Length) || (prev == restrictions[i])) {
                        restrictions[i-1] = null;
                        count--;
                    }
                }
                if (0 == restrictions[restrictions.Length-1].Length) {
                    restrictions[restrictions.Length-1] = null;
                    count--;
                }
                if (count != restrictions.Length) {
                    string[] tmp = new String[count];
                    count = 0;
                    for (int i = 0; i < restrictions.Length; ++i) {
                        if (null != restrictions[i]) {
                            tmp[count++] = restrictions[i];
                        }
                    }
                    restrictions = tmp;
                }
            }
            Verify(restrictions);
            return restrictions;
        }

        [ConditionalAttribute("DEBUG")]
        private static void Verify(string[] restrictionValues) {
            if (null != restrictionValues) {
                for (int i = 1; i < restrictionValues.Length; ++i) {
                    Debug.Assert(!ADP.IsEmpty(restrictionValues[i-1]), "empty restriction");
                    Debug.Assert(!ADP.IsEmpty(restrictionValues[i]), "empty restriction");
                    Debug.Assert(0 >= StringComparer.Ordinal.Compare(restrictionValues[i-1], restrictionValues[i]));
                }
            }
        }
    }
}