using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
using System.Linq;
using System.Data.Linq.Mapping;
using System.Data.Linq.Provider;

namespace System.Data.Linq.SqlClient {
    /// <summary>
    /// This class defines the rules for inheritance behaviors. The rules:
    /// 
    ///  (1) The same field may not be mapped to different database columns.    
    ///      The DistinguishedMemberName and AreSameMember methods describe what 'same' means between two MemberInfos.
    ///  (2) Discriminators held in fixed-length fields in the database don't need
    ///      to be manually padded in inheritance mapping [InheritanceMapping(Code='x')]. 
    ///  
    /// </summary>
    static class InheritanceRules {
        /// <summary>
        /// Creates a name that is the same when the member should be considered 'same'
        /// for the purposes of the inheritance feature.
        /// </summary>
        internal static object DistinguishedMemberName(MemberInfo mi) {
            PropertyInfo pi = mi as PropertyInfo;
            FieldInfo fi = mi as FieldInfo;
            if (fi != null) {
                // Human readable variant:
                // return "fi:" + mi.Name + ":" + mi.DeclaringType;
                return new MetaPosition(mi);
            }
            else if (pi != null) {
                MethodInfo meth = null;

                if (pi.CanRead) {
                    meth = pi.GetGetMethod();
                }
                if (meth == null && pi.CanWrite) {
                    meth = pi.GetSetMethod();
                }
                bool isVirtual = meth != null && meth.IsVirtual;
                
                // Human readable variant:
                // return "pi:" + mi.Name + ":" + (isVirtual ? "virtual" : mi.DeclaringType.ToString());

                if (isVirtual) {
                    return mi.Name;
                } else {
                    return new MetaPosition(mi);
                }
            }
            else {
                throw Error.ArgumentOutOfRange("mi");
            }
        }

        /// <summary>
        /// Compares two MemberInfos for 'same-ness'.
        /// </summary>
        internal static bool AreSameMember(MemberInfo mi1, MemberInfo mi2) {
            return DistinguishedMemberName(mi1).Equals(DistinguishedMemberName(mi2));
        }
        
        /// <summary>
        /// The representation of a inheritance code when mapped to a specific provider type.
        /// </summary>
        internal static object InheritanceCodeForClientCompare(object rawCode, System.Data.Linq.SqlClient.ProviderType providerType) {
            // If its a fixed-size string type in the store then pad it with spaces so that 
            // comparing the string on the client agrees with the value returnd on the store.
            if (providerType.IsFixedSize && rawCode.GetType()==typeof(string)) {
                string s = (string) rawCode;
                if (providerType.Size.HasValue && s.Length!=providerType.Size) {
                    s = s.PadRight(providerType.Size.Value).Substring(0,providerType.Size.Value);
                }
                return s;
            }
            return rawCode;
        }


    }
}