using System;
using MathNet.Numerics.Properties;

namespace MathNet.Numerics.LinearAlgebra.Storage
{
    internal class SparseDiagonalMatrixStorage<T> : MatrixStorage<T>
        where T : struct, IEquatable<T>, IFormattable
    {
        // [ruegg] public fields are OK here

        readonly T _zero;
        public readonly T[] Data;

        internal SparseDiagonalMatrixStorage(int rows, int columns, T zero)
            : base(rows, columns)
        {
            _zero = zero;
            Data = new T[Math.Min(rows, columns)];
        }

        internal SparseDiagonalMatrixStorage(int rows, int columns, T zero, T[] data)
            : base(rows, columns)
        {
            _zero = zero;
            Data = data;
        }

        /// <summary>
        /// Retrieves the requested element without range checking.
        /// </summary>
        public override T At(int row, int column)
        {
            return row == column ? Data[row] : _zero;
        }

        /// <summary>
        /// Sets the element without range checking.
        /// </summary>
        public override void At(int row, int column, T value)
        {
            if (row == column)
            {
                Data[row] = value;
            }
            else if (!_zero.Equals(value))
            {
                throw new IndexOutOfRangeException("Cannot set an off-diagonal element in a diagonal matrix.");
            }
        }

        public override void Clear()
        {
            Array.Clear(Data, 0, Data.Length);
        }

        public void CopyTo(MatrixStorage<T> target, bool skipClearing = false)
        {
            var diagonalTarget = target as SparseDiagonalMatrixStorage<T>;
            if (diagonalTarget != null)
            {
                CopyTo(diagonalTarget);
                return;
            }

            var denseTarget = target as DenseColumnMajorMatrixStorage<T>;
            if (denseTarget != null)
            {
                CopyTo(denseTarget, skipClearing);
                return;
            }

            var sparseTarget = target as SparseCompressedRowMatrixStorage<T>;
            if (sparseTarget != null)
            {
                CopyTo(sparseTarget, skipClearing);
                return;
            }

            // FALL BACK

            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            if (RowCount != target.RowCount || ColumnCount != target.ColumnCount)
            {
                var message = string.Format(Resources.ArgumentMatrixDimensions2, RowCount + "x" + ColumnCount, target.RowCount + "x" + target.ColumnCount);
                throw new ArgumentException(message, "target");
            }

            if (!skipClearing)
            {
                target.Clear();
            }

            for (int i = 0; i < Data.Length; i++)
            {
                target.At(i, i, Data[i]);
            }
        }

        public void CopyTo(SparseDiagonalMatrixStorage<T> target)
        {
            if (ReferenceEquals(this, target))
            {
                return;
            }

            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            if (RowCount != target.RowCount || ColumnCount != target.ColumnCount)
            {
                var message = string.Format(Resources.ArgumentMatrixDimensions2, RowCount + "x" + ColumnCount, target.RowCount + "x" + target.ColumnCount);
                throw new ArgumentException(message, "target");
            }

            //Buffer.BlockCopy(Data, 0, target.Data, 0, Data.Length * System.Runtime.InteropServices.Marshal.SizeOf(typeof(T)));
            Array.Copy(Data, 0, target.Data, 0, Data.Length);
        }

        public void CopyTo(SparseCompressedRowMatrixStorage<T> target, bool skipClearing = false)
        {
            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            if (RowCount != target.RowCount || ColumnCount != target.ColumnCount)
            {
                var message = string.Format(Resources.ArgumentMatrixDimensions2, RowCount + "x" + ColumnCount, target.RowCount + "x" + target.ColumnCount);
                throw new ArgumentException(message, "target");
            }

            if (!skipClearing)
            {
                target.Clear();
            }

            for (int i = 0; i < Data.Length; i++)
            {
                target.At(i, i, Data[i]);
            }
        }

        public void CopyTo(DenseColumnMajorMatrixStorage<T> target, bool skipClearing = false)
        {
            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            if (RowCount != target.RowCount || ColumnCount != target.ColumnCount)
            {
                var message = string.Format(Resources.ArgumentMatrixDimensions2, RowCount + "x" + ColumnCount, target.RowCount + "x" + target.ColumnCount);
                throw new ArgumentException(message, "target");
            }

            if (!skipClearing)
            {
                target.Clear();
            }

            for (int i = 0; i < Data.Length; i++)
            {
                target.Data[i*(target.RowCount + 1)] = Data[i];
            }
        }

        public void CopySubMatrixTo(DenseColumnMajorMatrixStorage<T> target,
            int sourceRowIndex, int targetRowIndex, int rowCount,
            int sourceColumnIndex, int targetColumnIndex, int columnCount,
            bool skipClearing = false)
        {
            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            ValidateSubMatrixRange(target,
                sourceRowIndex, targetRowIndex, rowCount,
                sourceColumnIndex, targetColumnIndex, columnCount);

            if (!skipClearing)
            {
                target.Clear();
            }

            if (sourceRowIndex > sourceColumnIndex && sourceColumnIndex + columnCount > sourceRowIndex)
            {
                // column by column, but skip resulting zero columns at the beginning

                int columnInit = sourceRowIndex - sourceColumnIndex;
                int offset = (columnInit + targetColumnIndex) * target.RowCount + targetRowIndex;
                int step = target.RowCount + 1;
                int end = Math.Min(columnCount - columnInit, rowCount) + sourceRowIndex;

                for (int i = sourceRowIndex, j = offset; i < end; i++, j += step)
                {
                    target.Data[j] = Data[i];
                }
            }
            else if (sourceRowIndex < sourceColumnIndex && sourceRowIndex + rowCount > sourceColumnIndex)
            {
                // row by row, but skip resulting zero rows at the beginning

                int rowInit = sourceColumnIndex - sourceRowIndex;
                int offset = targetColumnIndex*target.RowCount + rowInit + targetRowIndex;
                int step = target.RowCount + 1;
                int end = Math.Min(columnCount, rowCount - rowInit) + sourceColumnIndex;

                for (int i = sourceColumnIndex, j = offset; i < end; i++, j += step)
                {
                    target.Data[j] = Data[i];
                }
            }
            else
            {
                int offset = targetColumnIndex*target.RowCount + targetRowIndex;
                int step = target.RowCount + 1;
                var end = Math.Min(columnCount, rowCount) + sourceRowIndex;

                for (int i = sourceRowIndex, j = offset; i < end; i++, j += step)
                {
                    target.Data[j] = Data[i];
                }
            }
        }

        public void CopySubMatrixTo(SparseCompressedRowMatrixStorage<T> target,
            int sourceRowIndex, int targetRowIndex, int rowCount,
            int sourceColumnIndex, int targetColumnIndex, int columnCount,
            bool skipClearing = false)
        {
            if (target == null)
            {
                throw new ArgumentNullException("target");
            }

            ValidateSubMatrixRange(target,
                sourceRowIndex, targetRowIndex, rowCount,
                sourceColumnIndex, targetColumnIndex, columnCount);

            if (!skipClearing)
            {
                target.Clear();
            }

            if (sourceRowIndex > sourceColumnIndex && sourceColumnIndex + columnCount > sourceRowIndex)
            {
                // column by column, but skip resulting zero columns at the beginning
                int columnInit = sourceRowIndex - sourceColumnIndex;
                for (var i = 0; i < Math.Min(columnCount - columnInit, rowCount); i++)
                {
                    target.At(i + targetRowIndex, columnInit + i + targetColumnIndex, Data[sourceRowIndex + i]);
                }
            }
            else if (sourceRowIndex < sourceColumnIndex && sourceRowIndex + rowCount > sourceColumnIndex)
            {
                // row by row, but skip resulting zero rows at the beginning
                int rowInit = sourceColumnIndex - sourceRowIndex;
                for (var i = 0; i < Math.Min(columnCount, rowCount - rowInit); i++)
                {
                    target.At(rowInit + i + targetRowIndex, i + targetColumnIndex, Data[sourceColumnIndex + i]);
                }
            }
            else
            {
                for (var i = 0; i < Math.Min(columnCount, rowCount); i++)
                {
                    target.At(i + targetRowIndex, i + targetColumnIndex, Data[sourceRowIndex + i]);
                }
            }
        }
    }
}