//------------------------------------------------------------------------------
// <copyright file="ConfigDefinitionUpdates.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//------------------------------------------------------------------------------

namespace System.Configuration {
    using System.Configuration.Internal;
    using System.Collections;
    using System.Collections.Generic;
    using System.Collections.Specialized;
    using System.Configuration;
    using System.Globalization;
    using System.IO;
    using System.Reflection;
    using System.Runtime.InteropServices;
    using System.Security.Permissions;
    using System.Security;
    using System.Text;
    using System.Xml;


    // This is the public type of the override mode enum visible to the API users
    // The override mode is an attribute of a <location> tag and controls if the sections inside this tag
    // can be defined in child web.config files
    public enum OverrideMode {
        // Default ( aka Indiferent ) - When specified on a location tag means the location tag will not alter
        // the locking mode ( locked or unlocked ). Rather, the locking mode should be picked
        // from the <location> tag with the closest parent path in the current file, or the parent file if no such location in the current one,
        // or the default for the specific section ( section.OverrideModeDefault )
        Inherit     = 0,
        // Allow overriding in child config files. I.e. unlock the settings for overridiing
        Allow       = 1,
        // Deny overriding of the settings defined in the <location> tag. It is an error for the sections in the <location> tag
        // to appear in a child config file. It is not an error for them to appear in another <lcoation> tag in the current file
        Deny        = 2,
    }

    

    // This is a class that abstracts the usage of the override mode setting
    internal struct OverrideModeSetting {

        private const byte  ApiDefinedLegacy    = 0x10;    // allowOverride was set thourhg the API  
        private const byte  ApiDefinedNewMode   = 0x20;    // overrideMode was set thourhg the API  
        private const byte  ApiDefinedAny       = ApiDefinedLegacy | ApiDefinedNewMode;    // allowOverride or overrideMode was set through the API  
        
        private const byte  XmlDefinedLegacy    = 0x40;    // allowOverride was defined in the XML
        private const byte  XmlDefinedNewMode   = 0x80;    // overrideMode was defined in the XML
        private const byte  XmlDefinedAny       = XmlDefinedLegacy | XmlDefinedNewMode;    // overrideMode or allowOverride was defined in the XML
        
        private const byte  ModeMask            = 0x0f;    // logical AND this with the current value to get the mode part only       


        private byte                _mode;


        internal static OverrideModeSetting  SectionDefault;
        internal static OverrideModeSetting  LocationDefault;

        static OverrideModeSetting() {
            
            SectionDefault = new OverrideModeSetting();
            // Default for section is ALLOW ( to be consistent with Whidbey )
            SectionDefault._mode = (byte)OverrideMode.Allow;


            LocationDefault = new OverrideModeSetting();
            // Default for location tags is INHERIT. Note that we do not make the value as existant in the XML or specified by the API
            LocationDefault._mode = (byte)OverrideMode.Inherit;
        }

        static internal OverrideModeSetting CreateFromXmlReadValue(bool allowOverride) {
            // Create a mode from the old "allowOverride" attribute in the xml

            // The conversion is true -> OverrideMode.Inherit
            // The conversion is false -> OverrideMode.Deny
            // This is consistent with Whidbey where true means true unless there is a false somewhere above
            OverrideModeSetting result = new OverrideModeSetting();

            result.SetMode(allowOverride ? OverrideMode.Inherit : OverrideMode.Deny);
            result._mode |= XmlDefinedLegacy;

            return result;
        }

        static internal OverrideModeSetting CreateFromXmlReadValue(OverrideMode mode) {
            OverrideModeSetting result = new OverrideModeSetting();
            
            result.SetMode(mode);        
            result._mode |= XmlDefinedNewMode;

            return result;
        }

         internal static OverrideMode ParseOverrideModeXmlValue(string value, XmlUtil xmlUtil) {
            // 'value' is the string representation of OverrideMode enum
            // Try to parse the string to the enum and generate errors if not possible

            switch (value) {
                case BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_INHERIT:
                    return OverrideMode.Inherit;

                case BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_ALLOW:
                    return OverrideMode.Allow;

                case BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_DENY:
                    return OverrideMode.Deny;

                default:
                    throw new ConfigurationErrorsException(
                            SR.GetString(SR.Config_section_override_mode_attribute_invalid), 
                            xmlUtil);
            }
        }

        internal static bool CanUseSameLocationTag(OverrideModeSetting x, OverrideModeSetting y) {
            // This function tells if the two OverrideModeSettings are compatible enough to be used in only one location tag
            // or each of them should go to a separate one

            // The rules here are ( in order of importance )
            // 1. The effective mode is the same ( we will use only the new OverrideMode to compare )
            // 2. When the mode was changed( i.e. API change ) - both must be changed the same way ( i.e. using either allowOverride or OverrideMode )
            // 3. When mode was not changed the XML - they must've been the same in the xml ( i.e. allowOverride specified on both, or overrideMode or neither of them )

            bool result = false;

            result = (x.OverrideMode == y.OverrideMode);

            if (result == true) {
                
                result = false;
                
                // Check for an API change for each setting first
                // If one mode was set through the API - the other mode has to be set in the same way through the API or has to be using the same type in the xml

                // Handle case where "x" was API modified
                if ((x._mode & ApiDefinedAny) != 0) {

                    result = IsMatchingApiChangedLocationTag(x, y);
                }
                // Handle case where "y" was API modified
                else if ((y._mode & ApiDefinedAny) != 0) {
                    
                    result = IsMatchingApiChangedLocationTag(y, x);
                }
                // Handle case where neither "x" nor "y" was API modified
                else {

                    // If one of the settings was XML defined - they are a match only if both were XML defined in the same way
                    if (    ((x._mode & XmlDefinedAny) != 0) || 
                            ((y._mode & XmlDefinedAny) != 0)) {

                        result = (x._mode & XmlDefinedAny) == (y._mode & XmlDefinedAny);
                    }
                    // Neither "x" nor "y" was XML defined - they are a match since they can both go 
                    // to a default <location> with no explicit mode setting written out
                    else {
                        result = true;
                    }
                }
            }

            return result;
        }

        private static bool IsMatchingApiChangedLocationTag(OverrideModeSetting x, OverrideModeSetting y) {
            // x must be a changed through the API setting
            // Returns true if x and y can share the same location tag

            Debug.Assert((x._mode & ApiDefinedAny) != 0);

            bool result = false;

            // If "y" was modified through the API as well - the modified setting must be the same ( i.e. allowOvverride or overrideMode must be modified in both settings )
            if ((y._mode & ApiDefinedAny) != 0) {
                
                result = (x._mode & ApiDefinedAny) == (y._mode & ApiDefinedAny);
            }
            // "y" was not API modified  - they are still a match if "y" was a XML setting from the same mode
            else if ((y._mode & XmlDefinedAny) != 0) {
                
                result = (  (((x._mode & ApiDefinedLegacy) != 0) && ((y._mode & XmlDefinedLegacy) != 0)) || // "x" was API changed in Legacy and "y" was XML defined in Legacy
                            (((x._mode & ApiDefinedNewMode) != 0) && ((y._mode & XmlDefinedNewMode) != 0)));         // "x" was API changed in New and "y" was XML defined in New
                            
            }
            // "y" was not API or XML modified - since "x" was API modified - they are not a match ( i.e. "y" should go to an <location> with no explicit mode written out )
            else {
            }                    

            return result;
        }

        internal bool IsDefaultForSection {
            get {
                // Returns true if the current value of the overrideMode setting is the default one on a section declaration

                // The current default value for a section's overrideMode ( i.e. overrideModeDefault ) is Allow ( see CreateDefaultForSection )
                // It would've been nice not to repeat that rule here but since OverrideMode.Inherited means the same in this specific context we have to
                // I.e. the default for a section is both Allow and Inherited. In this case they mean the same
                
                OverrideMode mode = OverrideMode;

                // Return  true if mode is Allow or Inherit
                return ((mode == OverrideMode.Allow) || (mode == OverrideMode.Inherit));
            }
        }

        internal bool IsDefaultForLocationTag {
            get {
                // Returns true if the current setting is the same as the default value for a location tag
                // Note that if the setting was an API modified or XmlDefined  it is not a default since it
                // cannot go to the default <location> tag which does not explicitlly specify a mode

                OverrideModeSetting defaultSetting = LocationDefault;

                return  (defaultSetting.OverrideMode == this.OverrideMode) &&
                        ((_mode & ApiDefinedAny) == 0) &&
                        ((_mode & XmlDefinedAny) == 0);
            }
        }

        internal bool IsLocked {
            get { return OverrideMode == OverrideMode.Deny;}
        }

        internal string LocationTagXmlString {
            get {
                // Returns the string for this setting which is to be written in the xml <location> tag

                string  result      = String.Empty;
                string  value       = null;
                string  attrib      = null;

                bool    needToWrite = false;
                bool    useLegacy   = false;
                
                // If there was an API change - it has highest priority
                if ((_mode & ApiDefinedAny) != 0) {
                    // Whichever was changed by the API dictates what is to be written
                    useLegacy   = (_mode & ApiDefinedLegacy) != 0;
                    needToWrite = true;
                        
                    Debug.Assert(useLegacy || (_mode & ApiDefinedNewMode) != 0);
                }
                // It wasn't changed through the API - check if it was read originally from the XML
                else if ((_mode & XmlDefinedAny) != 0) {
                    // Whatever was defined in the XML is to be written out

                    useLegacy   = (_mode & XmlDefinedLegacy) != 0;
                    needToWrite = true;

                    Debug.Assert(useLegacy || (_mode & XmlDefinedNewMode) != 0);
                }

                if (needToWrite) {
                    // Legacy - allowOverride
                    if (useLegacy) {
                        attrib  = BaseConfigurationRecord.KEYWORD_LOCATION_ALLOWOVERRIDE;
                        value   = AllowOverride ? BaseConfigurationRecord.KEYWORD_TRUE : BaseConfigurationRecord.KEYWORD_FALSE;
                    }
                    else {
                        attrib  = BaseConfigurationRecord.KEYWORD_LOCATION_OVERRIDEMODE;
                        value   = OverrideModeXmlValue;
                    }

                    result = String.Format(CultureInfo.InvariantCulture, BaseConfigurationRecord.KEYWORD_LOCATION_OVERRIDEMODE_STRING, attrib, value);
                }

                return result;                    
            }
        }

        internal string OverrideModeXmlValue {
            get {
                // Returns the xml (string) value of the current setting for override mode

                switch(OverrideMode) {
                    case OverrideMode.Inherit:
                        return BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_INHERIT;

                    case OverrideMode.Allow:
                        return BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_ALLOW;

                    case OverrideMode.Deny:
                        return BaseConfigurationRecord.KEYWORD_OVERRIDEMODE_DENY;

                    default:
                        Debug.Assert(false, "Missing xml keyword for OverrideMode enum value");
                        break;
                }

                return null;
            }
        }

        // Use this method to change only the value of the setting when not done through the public API
        internal void ChangeModeInternal(OverrideMode mode) {
            SetMode(mode);
        }

        // Properties to enable external chnages to the mode.
        // Note that those changes will be tracked as made by the public API
        // There shouldn't be a reason for those to be used except in this specific case
        internal OverrideMode OverrideMode {
            get {
                return (OverrideMode)(_mode & ModeMask);
            }
            set {
                // Note that changing the mode through the API ( which is the purpose of this setter )
                // overrides the setting in the XML ( if any )
                // and hence we dont keep a track of it anymore

                // Error condition: We do not allow changes to the mode through both AllowOverride and OverrideMode
                // If one was changed first we require that API users stick with it
                VerifyConsistentChangeModel(ApiDefinedNewMode);

                SetMode(value);
                _mode |= ApiDefinedNewMode;
            }
        }

        internal bool AllowOverride {
            get {
                bool                    result  = true;

                switch(OverrideMode) {
                    case OverrideMode.Inherit:
                    case OverrideMode.Allow:
                        result = true;
                        break;

                    case OverrideMode.Deny:
                        result = false;
                        break;

                    default:
                        Debug.Assert(false, "Unrecognized OverrideMode");
                        break;
                }

                return result;
            }
            set {
                // Note that changing the mode through the API ( which is the purpose of this setter )
                // overrides the setting in the XML ( if any )
                // and hence we dont keep a track of it anymore

                // Error condition: We do not allow changes to the mode through both AllowOverride and OverrideMode
                // If one was changed first we require that API users stick with it
                VerifyConsistentChangeModel(ApiDefinedLegacy);

                SetMode(value ? OverrideMode.Inherit : OverrideMode.Deny);
                _mode |= ApiDefinedLegacy;
            }
        }


        private void SetMode(OverrideMode mode) {
            _mode = (byte)mode;
        }

        private void VerifyConsistentChangeModel(byte required) {
            // The required API change model ( i.e. was allowOverride used or OverrideMode ) should be consistent
            // I.e. its not possible to change both on the same OverrideModeSetting object
            
            byte current = (byte)(_mode & ApiDefinedAny);   // Shows whats the current setting: 0 ( none ), ApiDefinedLegacy or ApiDefinedNew

            if (current != 0 && current != required) {
                throw new ConfigurationErrorsException(SR.GetString(SR.Cannot_change_both_AllowOverride_and_OverrideMode));
            }
        }

    }
}