using System;
using System.Text;
 
namespace System.Net.NetworkInformation
{
 
    public class PhysicalAddress    {
    
        byte[] address = null;
        bool changed = true;
        int hash = 0;
 
        // FxCop: if this class is ever made mutable (like, given any non-readonly fields),
        // the readonly should be removed from the None decoration.
        public static readonly  PhysicalAddress None = new PhysicalAddress(new byte[0]);
 
    	// constructors
    	public PhysicalAddress(byte[] address){
            this.address = address;
        }
 
        public override int GetHashCode() {
            if (changed) {
                changed = false;
                hash = 0;
 
                int i;
                int size = address.Length & ~3;
 
                for (i = 0; i < size; i += 4) {
                    hash ^= (int)address[i]
                            | ((int)address[i+1] << 8)
                            | ((int)address[i+2] << 16)
                            | ((int)address[i+3] << 24);
                }
                if ((address.Length & 3) != 0) {
 
                    int remnant = 0;
                    int shift = 0;
 
                    for (; i < address.Length; ++i) {
                        remnant |= ((int)address[i]) << shift;
                        shift += 8;
                    }
                    hash ^= remnant;
                }
            }
            return hash;
        }
        
        public override bool Equals(object comparand) {
            PhysicalAddress address = comparand as PhysicalAddress;
            if (address == null)
                return false;
 
            if (this.address.Length != address.address.Length) {
                return false;
            }
            for (int i = 0; i < address.address.Length; i++) {
                if(this.address[i] != address.address[i])
                    return false;
            }
            return true;
        }
 
 
        public override string ToString(){
            StringBuilder addressString = new StringBuilder();
 
            foreach (byte value in address ) {
 
                int tmp = (value >> 4) & 0x0F;
 
                for (int i = 0; i<2; i++) {
                    if (tmp < 0x0A ) {
                        addressString.Append((char)(tmp+0x30));
                    }
                    else{
                        addressString.Append((char)(tmp+0x37));
                    }
                    tmp = ((int)value & 0x0F);
                }
            }
            return addressString.ToString();
        }
 
        public byte[] GetAddressBytes(){
            byte[] tmp = new byte[address.Length];
            Buffer.BlockCopy(address,0,tmp,0,address.Length);
            return tmp;
        }
 
 
 
        public static PhysicalAddress Parse(string address) {
            int validCount = 0;
            bool hasDashes = false;
            byte[] buffer = null;
 
            if(address == null)
            {
                return PhysicalAddress.None;
            }
 
            //has dashes?
            if (address.IndexOf('-') >= 0 ){
                hasDashes = true;
                buffer = new byte[(address.Length+1)/3];
            }
            else{
 
                if(address.Length % 2 > 0){  //should be even
                    throw new FormatException(SR.GetString(SR.net_bad_mac_address));
                }
 
                buffer = new byte[address.Length/2];
            }
 
            int j = 0;
            for (int i = 0; i < address.Length; i++ ) {
 
                int value = (int)address[i];
                
                if (value >= 0x30 && value <=0x39){
                    value -= 0x30;
                }
                else if (value >= 0x41 && value <= 0x46) {
                    value -= 0x37;
                }
                else if (value == (int)'-'){
                    if (validCount == 2) {
                        validCount = 0;
                        continue;
                    }
                    else{
                        throw new FormatException(SR.GetString(SR.net_bad_mac_address));
                    }
                }
                else{
                    throw new FormatException(SR.GetString(SR.net_bad_mac_address));
                }
 
                //we had too many characters after the last dash
                if(hasDashes && validCount >= 2){
                    throw new FormatException(SR.GetString(SR.net_bad_mac_address));
                }
 
                if (validCount%2 == 0) {
                    buffer[j] = (byte) (value << 4);
                }
                else{
                    buffer[j++] |= (byte) value;
                }
 
                validCount++;
            }
 
            //we too few characters after the last dash
            if(validCount < 2){
                throw new FormatException(SR.GetString(SR.net_bad_mac_address));
            }
 
            return new PhysicalAddress(buffer);
        }
    }
}