using System.Collections.Generic;
using System.Collections.ObjectModel;
using Google.ProtocolBuffers.Collections;

namespace Google.ProtocolBuffers {
  /// <summary>
  /// Represents a single field in an UnknownFieldSet.
  /// 
  /// An UnknownField consists of five lists of values. The lists correspond
   /// to the five "wire types" used in the protocol buffer binary format.
   /// The wire type of each field can be determined from the encoded form alone,
   /// without knowing the field's declared type. So, we are able to parse
   /// unknown values at least this far and separate them. Normally, only one
   /// of the five lists will contain any values, since it is impossible to
   /// define a valid message type that declares two different types for the
   /// same field number. However, the code is designed to allow for the case
   /// where the same unknown field number is encountered using multiple different
   /// wire types.
   /// 
   /// UnknownField is an immutable class. To construct one, you must use an
   /// UnknownField.Builder.
  /// </summary>
  public sealed class UnknownField {

    private static readonly UnknownField defaultInstance = CreateBuilder().Build();
    private readonly ReadOnlyCollection<ulong> varintList;
    private readonly ReadOnlyCollection<uint> fixed32List;
    private readonly ReadOnlyCollection<ulong> fixed64List;
    private readonly ReadOnlyCollection<ByteString> lengthDelimitedList;
    private readonly ReadOnlyCollection<UnknownFieldSet> groupList;

    private UnknownField(ReadOnlyCollection<ulong> varintList,
        ReadOnlyCollection<uint> fixed32List, 
        ReadOnlyCollection<ulong> fixed64List, 
        ReadOnlyCollection<ByteString> lengthDelimitedList, 
        ReadOnlyCollection<UnknownFieldSet> groupList) {
      this.varintList = varintList;
      this.fixed32List = fixed32List;
      this.fixed64List = fixed64List;
      this.lengthDelimitedList = lengthDelimitedList;
      this.groupList = groupList;
    }

    public static UnknownField DefaultInstance { 
      get { return defaultInstance; } 
    }

    /// <summary>
    /// The list of varint values for this field.
    /// </summary>
    public IList<ulong> VarintList {
      get { return varintList; }
    }

    /// <summary>
    /// The list of fixed32 values for this field.
    /// </summary>
    public IList<uint> Fixed32List {
      get { return fixed32List; }
    }

    /// <summary>
    /// The list of fixed64 values for this field.
    /// </summary>
    public IList<ulong> Fixed64List {
      get { return fixed64List; }
    }

    /// <summary>
    /// The list of length-delimited values for this field.
    /// </summary>
    public IList<ByteString> LengthDelimitedList {
      get { return lengthDelimitedList; }
    }

    /// <summary>
    /// The list of embedded group values for this field. These
    /// are represented using UnknownFieldSets rather than Messages
    /// since the group's type is presumably unknown.
    /// </summary>
    public IList<UnknownFieldSet> GroupList {
      get { return groupList; }
    }

    /// <summary>
    /// Constructs a new Builder.
    /// </summary>
    public static Builder CreateBuilder() {
      return new Builder();
    }

    /// <summary>
    /// Constructs a new Builder and initializes it to a copy of <paramref name="copyFrom"/>.
    /// </summary>
    public static Builder CreateBuilder(UnknownField copyFrom) {
      return new Builder().MergeFrom(copyFrom);
    }
   
    /// <summary>
    /// Serializes the field, including the field number, and writes it to
    /// <paramref name="output"/>.
    /// </summary>
    public void WriteTo(int fieldNumber, CodedOutputStream output) {
      foreach (ulong value in varintList) {
        output.WriteUInt64(fieldNumber, value);
      }
      foreach (uint value in fixed32List) {
        output.WriteFixed32(fieldNumber, value);
      }
      foreach (ulong value in fixed64List) {
        output.WriteFixed64(fieldNumber, value);
      }
      foreach (ByteString value in lengthDelimitedList) {
        output.WriteBytes(fieldNumber, value);
      }
      foreach (UnknownFieldSet value in groupList) {
        output.WriteUnknownGroup(fieldNumber, value);
      }
    }

    /// <summary>
    /// Computes the number of bytes required to encode this field, including field
    /// number.
    /// </summary>
    public int GetSerializedSize(int fieldNumber) {
      int result = 0;
      foreach (ulong value in varintList) {
        result += CodedOutputStream.ComputeUInt64Size(fieldNumber, value);
      }
      foreach (uint value in fixed32List) {
        result += CodedOutputStream.ComputeFixed32Size(fieldNumber, value);
      }
      foreach (ulong value in fixed64List) {
        result += CodedOutputStream.ComputeFixed64Size(fieldNumber, value);
      }
      foreach (ByteString value in lengthDelimitedList) {
        result += CodedOutputStream.ComputeBytesSize(fieldNumber, value);
      }
      foreach (UnknownFieldSet value in groupList) {
        result += CodedOutputStream.ComputeUnknownGroupSize(fieldNumber, value);
      }
      return result;
    }

    /// <summary>
    /// Serializes the length-delimited values of the field, including field
    /// number, and writes them to <paramref name="output"/> using the MessageSet wire format.
    /// </summary>
    /// <param name="fieldNumber"></param>
    /// <param name="output"></param>
    public void WriteAsMessageSetExtensionTo(int fieldNumber, CodedOutputStream output) {
      foreach (ByteString value in lengthDelimitedList) {
        output.WriteRawMessageSetExtension(fieldNumber, value);
      }
    }

    /// <summary>
    /// Get the number of bytes required to encode this field, incuding field number,
    /// using the MessageSet wire format.
    /// </summary>
    public int GetSerializedSizeAsMessageSetExtension(int fieldNumber) {
      int result = 0;
      foreach (ByteString value in lengthDelimitedList) {
        result += CodedOutputStream.ComputeRawMessageSetExtensionSize(fieldNumber, value);
      }
      return result;
    }

    /// <summary>
    /// Used to build instances of UnknownField.
    /// </summary>
    public class Builder {

      private List<ulong> varintList;
      private List<uint> fixed32List;
      private List<ulong> fixed64List;
      private List<ByteString> lengthDelimitedList;
      private List<UnknownFieldSet> groupList;

      /// <summary>
      /// Builds the field. After building, the builder is reset to an empty
      /// state. (This is actually easier than making it unusable.)
      /// </summary>
      public UnknownField Build() {
        return new UnknownField(MakeReadOnly(ref varintList),
            MakeReadOnly(ref fixed32List),
            MakeReadOnly(ref fixed64List),
            MakeReadOnly(ref lengthDelimitedList),
            MakeReadOnly(ref groupList));
      }

      /// <summary>
      /// Merge the values in <paramref name="other" /> into this field.  For each list
      /// of values, <paramref name="other"/>'s values are append to the ones in this
      /// field.
      /// </summary>
      public Builder MergeFrom(UnknownField other) {
        varintList = AddAll(varintList, other.VarintList);
        fixed32List = AddAll(fixed32List, other.Fixed32List);
        fixed64List = AddAll(fixed64List, other.Fixed64List);
        lengthDelimitedList = AddAll(lengthDelimitedList, other.LengthDelimitedList);
        groupList = AddAll(groupList, other.GroupList);
        return this;
      }

      /// <summary>
      /// Returns a new list containing all of the given specified values from
      /// both the <paramref name="current"/> and <paramref name="extras"/> lists.
      /// If <paramref name="current" /> is null and <paramref name="extras"/> is empty,
      /// null is returned. Otherwise, either a new list is created (if <paramref name="current" />
      /// is null) or the elements of <paramref name="extras"/> are added to <paramref name="current" />.
      /// </summary>
      private static List<T> AddAll<T>(List<T> current, IList<T> extras)
      {
        if (extras.Count == 0) {
          return current;
        }
 	      if (current == null) {
          current = new List<T>(extras);
        } else {
          current.AddRange(extras);
        }
        return current;
      }

      /// <summary>
      /// Clears the contents of this builder.
      /// </summary>
      public Builder Clear() {
        varintList = null;
        fixed32List = null;
        fixed64List = null;
        lengthDelimitedList = null;
        groupList = null;
        return this;
      }

      /// <summary>
      /// Adds a varint value.
      /// </summary>
      public Builder AddVarint(ulong value) {
        varintList = Add(varintList, value);
        return this;
      }

      /// <summary>
      /// Adds a fixed32 value.
      /// </summary>
      public Builder AddFixed32(uint value) {
        fixed32List = Add(fixed32List, value);
        return this;
      }

      /// <summary>
      /// Adds a fixed64 value.
      /// </summary>
      public Builder AddFixed64(ulong value) {
        fixed64List = Add(fixed64List, value);
        return this;
      }

      /// <summary>
      /// Adds a length-delimited value.
      /// </summary>
      public Builder AddLengthDelimited(ByteString value) {
        lengthDelimitedList = Add(lengthDelimitedList, value);
        return this;
      }

      /// <summary>
      /// Adds an embedded group.
      /// </summary>
      /// <param name="value"></param>
      /// <returns></returns>
      public Builder AddGroup(UnknownFieldSet value) {
        groupList = Add(groupList, value);
        return this;
      }

      /// <summary>
      /// Adds <paramref name="value"/> to the <paramref name="list"/>, creating
      /// a new list if <paramref name="list"/> is null. The list is returned - either
      /// the original reference or the new list.
      /// </summary>
      private static List<T> Add<T>(List<T> list, T value) {
        if (list == null) {
          list = new List<T>();
        }
        list.Add(value);
        return list;
      }

      /// <summary>
      /// Returns a read-only version of the given IList, and clears
      /// the field used for <paramref name="list"/>. If the value
      /// is null, an empty list is produced using Lists.Empty.
      /// </summary>
      /// <returns></returns>
      private static ReadOnlyCollection<T> MakeReadOnly<T>(ref List<T> list) {
        ReadOnlyCollection<T> ret = list == null ? Lists<T>.Empty : new ReadOnlyCollection<T>(list);
 	      list = null;
        return ret;
      }
    }
  }
}