using System;
using WhiteMagic.Native;

namespace WhiteMagic.Memory;

/// <summary>
/// An immutable snapshot of a memory region as reported by <c>VirtualQueryEx</c>.
/// </summary>
public readonly record struct MemoryRegion
{
    /// <summary>The base address of the region of pages.</summary>
    public IntPtr BaseAddress { get; }

    /// <summary>The size of the region, in bytes.</summary>
    public nuint Size { get; }

    /// <summary>The access protection of the pages in the region.</summary>
    public MemoryProtectionType Protection { get; }

    /// <summary>The state of the pages in the region.</summary>
    public MemoryState State { get; }

    /// <summary>The type of pages in the region.</summary>
    public MemoryType Type { get; }

    /// <summary>The base address of a range of pages allocated by VirtualAllocEx.</summary>
    public IntPtr AllocationBase { get; }

    /// <summary>The memory protection option when the region was initially allocated.</summary>
    public MemoryProtectionType AllocationProtect { get; }

    /// <summary>
    /// Initializes a new <see cref="MemoryRegion"/> from explicit values.
    /// </summary>
    public MemoryRegion(
        IntPtr baseAddress,
        nuint size,
        MemoryProtectionType protection,
        MemoryState state,
        MemoryType type,
        IntPtr allocationBase,
        MemoryProtectionType allocationProtect)
    {
        BaseAddress = baseAddress;
        Size = size;
        Protection = protection;
        State = state;
        Type = type;
        AllocationBase = allocationBase;
        AllocationProtect = allocationProtect;
    }

    /// <summary>
    /// Initializes a new <see cref="MemoryRegion"/> from a raw <c>MEMORY_BASIC_INFORMATION</c>.
    /// </summary>
    internal MemoryRegion(MemoryBasicInformation info)
    {
        BaseAddress = info.BaseAddress;
        Size = info.RegionSize;
        AllocationBase = info.AllocationBase;
        AllocationProtect = (MemoryProtectionType)info.AllocationProtect;
        Protection = (MemoryProtectionType)info.Protect;
        State = (MemoryState)info.State;
        Type = (MemoryType)info.Type;
    }

    /// <summary>
    /// Returns <see langword="true"/> if <paramref name="address"/> is inside the region,
    /// defined as <c>[BaseAddress, BaseAddress + Size)</c>.
    /// </summary>
    public bool Contains(IntPtr address)
    {
        return (nuint)(address - BaseAddress) < Size;
    }
}