using System;
using System.Collections.Generic;
using System.Text;

namespace DSDecmp
{
    /// <summary>
    /// Class for I/O-related utility methods.
    /// </summary>
    public static class IOUtils
    {
        /// <summary>
        /// Returns a 4-byte unsigned integer as used on the NDS converted from four bytes
        /// at a specified position in a byte array.
        /// </summary>
        /// <param name="buffer">The source of the data.</param>
        /// <param name="offset">The location of the data in the source.</param>
        /// <returns>The indicated 4 bytes converted to uint</returns>
        public static uint ToNDSu32(byte[] buffer, int offset)
        {
            return (uint)(buffer[offset]
                        | (buffer[offset + 1] << 8)
                        | (buffer[offset + 2] << 16)
                        | (buffer[offset + 3] << 24));
        }

        /// <summary>
        /// Returns a 4-byte signed integer as used on the NDS converted from four bytes
        /// at a specified position in a byte array.
        /// </summary>
        /// <param name="buffer">The source of the data.</param>
        /// <param name="offset">The location of the data in the source.</param>
        /// <returns>The indicated 4 bytes converted to int</returns>
        public static int ToNDSs32(byte[] buffer, int offset)
        {
            return (int)(buffer[offset]
                        | (buffer[offset + 1] << 8)
                        | (buffer[offset + 2] << 16)
                        | (buffer[offset + 3] << 24));
        }

        /// <summary>
        /// Converts a u32 value into a sequence of bytes that would make ToNDSu32 return
        /// the given input value.
        /// </summary>
        public static byte[] FromNDSu32(uint value)
        {
            return new byte[] {
                (byte)(value & 0xFF),
                (byte)((value >> 8) & 0xFF),
                (byte)((value >> 16) & 0xFF),
                (byte)((value >> 24) & 0xFF)
            };
        }

        /// <summary>
        /// Returns a 3-byte integer as used in the built-in compression
        /// formats in the DS, convrted from three bytes at a specified position in a byte array,
        /// </summary>
        /// <param name="buffer">The source of the data.</param>
        /// <param name="offset">The location of the data in the source.</param>
        /// <returns>The indicated 3 bytes converted to an integer.</returns>
        public static int ToNDSu24(byte[] buffer, int offset)
        {
            return (int)(buffer[offset]
                        | (buffer[offset + 1] << 8)
                        | (buffer[offset + 2] << 16));
        }
    }
}
