Hastlayer-SDK

using Hast.Synthesis.Models;
using Microsoft.Extensions.Logging;
using System;
using System.Runtime.InteropServices;

namespace Hast.Transformer.SimpleMemory;

/// <summary>
/// Represents a simplified memory model available on the FPGA for transformed algorithms. WARNING: SimpleMemory is NOT
/// thread-safe, there shouldn't be any concurrent access to it.
/// </summary>
/// <remarks>
/// <para>
/// All read/write methods' name MUST follow the convention to begin with "Read" or "Write" respectively.
///
/// WARNING: changes here should be in sync with the VHDL library. The signatures of the methods of this class mustn't
/// be changed (i.e. no renames, new or re-ordered arguments) without making adequate changes to the VHDL library too.
/// </para>
/// </remarks>
public class SimpleMemory
{
    public const int MemoryCellSizeBytes = sizeof(int);

    /// <summary>
    /// Gets the span of memory at the cellIndex, the length is <see cref="MemoryCellSizeBytes"/>.
    /// </summary>
    /// <param name="cellIndex">The cell index where the memory span starts.</param>
    /// <returns>A span starting at cellIndex * MemoryCellSizeBytes.</returns>
    private Span<byte> this[int cellIndex] => Memory.Slice(cellIndex * MemoryCellSizeBytes, MemoryCellSizeBytes).Span;

    /// <summary>
    /// Gets the number of extra cells used for header information like memberId or data length.
    /// </summary>
    public int PrefixCellCount { get; internal set; }

    /// <summary>
    /// Gets or sets the full memory including the <see cref="PrefixCellCount"/> cells of extra memory that is to be
    /// used for passing in extra input parameters (like memberId) without having to copy the operative memory contents
    /// into an auxiliary array.
    /// </summary>
    internal Memory<byte> PrefixedMemory { get; set; }

    /// <summary>
    /// Gets the contents of the memory representation.
    /// </summary>
    /// <remarks>
    /// <para>
    /// This is internal so the property can be read when handling communication with the FPGA but not by user code.
    /// </para>
    /// </remarks>
    internal Memory<byte> Memory => PrefixedMemory[(PrefixCellCount * MemoryCellSizeBytes)..];

    /// <summary>
    /// Gets the number of bytes of this memory allocation.
    /// </summary>
    public int ByteCount => Memory.Length;

    /// <summary>
    /// Gets the number of cells of this memory allocation, indicating memory cells of size <see
    /// cref="MemoryCellSizeBytes"/>.
    /// </summary>
    public int CellCount => Memory.Length / MemoryCellSizeBytes;

    /// <summary>
    /// Initializes a new instance of the <see cref="SimpleMemory"/> class. It represents a simplified memory model
    /// available on the FPGA for transformed algorithms from an existing byte array.
    /// </summary>
    /// <param name="memory">The source data.</param>
    /// <param name="prefixCellCount">The amount of cells for header data. See <see cref="PrefixCellCount"/>.</param>
    /// <param name="alignment">
    /// The alignment value. If set to greater than 0, the starting address of the content is aligned to be a multiple
    /// of that number. It must be an integer and power of 2.
    /// </param>
    internal SimpleMemory(Memory<byte> memory, int prefixCellCount, int alignment)
    {
        if (alignment > 0)
        {
            IntPtr address;
            unsafe
            {
                fixed (byte* pointer = memory.Span)
                {
                    address = new IntPtr(pointer);
                }
            }

            var addressLong = Environment.Is64BitProcess ? address.ToInt64() : address.ToInt32();
            var alignmentOffset = Environment.Is64BitProcess
                ? alignment - (int)(address.ToInt64() % alignment)
                : alignment - (int)((uint)address % alignment);

            var expectedLength = alignmentOffset + memory.Length - alignment;
            if (expectedLength > 0 && expectedLength < memory.Length)
            {
                memory = memory.Slice(alignmentOffset, memory.Length - alignment);
            }
            else
            {
                // This should never happen in production.
#if DEBUG
                Console.Error.WriteLine("Alignment failed!");
                Console.Error.WriteLine("  64-bit: {0}", Environment.Is64BitProcess);
                Console.Error.WriteLine("  address: {0}", address);
                Console.Error.WriteLine("  addressLong: {0}", addressLong);
                Console.Error.WriteLine("  memory length: {0}", memory.Length);
                Console.Error.WriteLine("  alignment: {0}", alignment);
                Console.Error.WriteLine("  alignmentOffset: {0}", alignmentOffset);
                Console.Error.WriteLine("  expectedLength: {0}", expectedLength);
#else
                throw new InvalidOperationException(
                    "Alignment failed! (" +
                    FormattableString.Invariant($"64-bit: {Environment.Is64BitProcess}; ") +
                    FormattableString.Invariant($"address: {address}; ") +
                    FormattableString.Invariant($"addressLong: {addressLong}; ") +
                    FormattableString.Invariant($"{nameof(memory)} length: {memory.Length}; ") +
                    FormattableString.Invariant($"alignment: {alignment}; ") +
                    FormattableString.Invariant($"alignmentOffset: {alignmentOffset}; ") +
                    FormattableString.Invariant($"expectedLength: {expectedLength})"));
#endif
            }
        }

        PrefixedMemory = memory;
        PrefixCellCount = prefixCellCount;
    }

    public void Write4Bytes(int cellIndex, byte[] bytes)
    {
        var target = this[cellIndex];

        for (int i = 0; i < bytes.Length; i++) target[i] = bytes[i];
        for (int i = bytes.Length; i < MemoryCellSizeBytes; i++) target[i] = 0;
    }

    public byte[] Read4Bytes(int cellIndex)
    {
        var output = new byte[MemoryCellSizeBytes];
        this[cellIndex].CopyTo(output);
        return output;
    }

    public void WriteUInt32(int cellIndex, uint number) => MemoryMarshal.Write(this[cellIndex], ref number);

    public uint ReadUInt32(int cellIndex) => MemoryMarshal.Read<uint>(this[cellIndex]);

    public void WriteInt32(int cellIndex, int number) => Write4Bytes(cellIndex, BitConverter.GetBytes(number));

    public int ReadInt32(int cellIndex) => MemoryMarshal.Read<int>(this[cellIndex]);

    public void WriteBoolean(int cellIndex, bool boolean) =>
        // Since the implementation of a boolean can depend on the system rather hard-coding the expected values here so
        // on the FPGA-side we can depend on it. Can't call MemoryMarshal.Write directly because its second parameter
        // must be passed using "ref" and you can't pass in constants or expressions by reference.
        WriteUInt32(cellIndex, boolean ? uint.MaxValue : uint.MinValue);

    public bool ReadBoolean(int cellIndex) => MemoryMarshal.Read<uint>(this[cellIndex]) != uint.MinValue;

    /// <summary>
    /// Creates a new instance of <see cref="SimpleMemory"/> with a specific size of payload in cells using a device's
    /// <see cref="MemoryConfiguration"/>.
    /// </summary>
    /// <param name="memoryConfiguration">Creation parameters associated with the selected device.</param>
    /// <param name="cellCount">The size of the usable memory.</param>
    /// <returns>The instance with a byte[] of capacity for the require payload size.</returns>
    public static SimpleMemory Create(IMemoryConfiguration memoryConfiguration, int cellCount)
    {
        var memory = new byte[((cellCount + memoryConfiguration.MinimumPrefix) * MemoryCellSizeBytes) +
                              memoryConfiguration.Alignment];
        return new SimpleMemory(memory, memoryConfiguration.MinimumPrefix, memoryConfiguration.Alignment);
    }

    /// <summary>
    /// Creates a new instance of <see cref="SimpleMemory"/> which wraps the given memory as content.
    /// </summary>
    /// <param name="memoryConfiguration">Creation parameters associated with the selected device.</param>
    /// <param name="memory">The data to be assigned.</param>
    /// <param name="logger">Optional logger for reporting issues.</param>
    /// <param name="withPrefixCells">The number of cells already provisioned in the <paramref name="memory"/>.</param>
    /// <returns>A new instance that wraps the given memory.</returns>
    /// <remarks>
    /// <para>
    /// If the <see cref="IMemoryConfiguration"/> indicates that more prefix space is required than what is already
    /// provisioned in the <paramref name="memory"/> according to the <paramref name="withPrefixCells"/>, then an
    /// additional copy will occur. This is logged as a warning if a logger is given.
    /// </para>
    /// </remarks>
    public static SimpleMemory Create(
        IMemoryConfiguration memoryConfiguration,
        Memory<byte> memory,
        ILogger logger = null,
        int withPrefixCells = 0)
    {
        if (withPrefixCells < memoryConfiguration.MinimumPrefix)
        {
            logger?.LogWarning("Not enough prefix cells available. An extra copy occurs.");
            var additionalBytes = (memoryConfiguration.MinimumPrefix - withPrefixCells) * MemoryCellSizeBytes;
            Memory<byte> newMemory = new byte[memory.Length + additionalBytes];
            memory.CopyTo(newMemory[additionalBytes..]);

            memory = newMemory;
            withPrefixCells = memoryConfiguration.MinimumPrefix;
        }

        return new SimpleMemory(memory, withPrefixCells, 0);
    }

    /// <summary>
    /// Creates a new instance of <see cref="SimpleMemory"/> for use in software runs. It handles the content
    /// identically to an instance created for a specific device but has no specific optimizations.
    /// </summary>
    /// <param name="cellCount">The size of the usable memory.</param>
    /// <returns>The instance with a <c>byte[]</c> of capacity for the require payload size.</returns>
    public static SimpleMemory CreateSoftwareMemory(int cellCount) =>
        new(new byte[cellCount * MemoryCellSizeBytes], 0, 0);
}

/// <summary>
/// Extensions for older Framework features which don't support Memory or Span yet.
/// </summary>
public static class MemoryExtensions
{
    /// <summary>
    /// Gets the internal array to be used for <see cref="System.IO.Stream.Write(byte[], int, int)"/>.
    /// </summary>
    /// <param name="bytes">The source.</param>
    /// <returns>The underlying array.</returns>
    /// <remarks>
    /// <para>
    /// Don't use this for writing into streams, <see cref="ReadOnlySpan{T}"/> can do that now. Only for
    /// <c>System.IO.Ports.SerialPort</c> which as of yet doesn't support <see cref="Span{T}"/>. Follow <see
    /// href="https://github.com/dotnet/runtime/issues/27941">this issue</see> to see progress on the SerialPort API
    /// update.
    /// </para>
    /// </remarks>
    public static ArraySegment<byte> GetUnderlyingArray(this Memory<byte> bytes) => GetUnderlyingArray((ReadOnlyMemory<byte>)bytes);

    public static ArraySegment<byte> GetUnderlyingArray(this ReadOnlyMemory<byte> bytes)
    {
        if (!MemoryMarshal.TryGetArray(bytes, out var arraySegment))
        {
            throw new NotSupportedException("This Memory does not support exposing the underlying array.");
        }

        return arraySegment;
    }
}