using System;
using System.Text;

namespace NetVips;

/// <summary>
/// An output connection.
/// </summary>
public class Target : Connection
{
    /// <inheritdoc cref="Connection"/>
    internal Target(nint pointer) : base(pointer)
    {
    }

    /// <summary>
    /// Get the memory object held by the target when using <see cref="NewToMemory"/>.
    /// </summary>
    public byte[] Blob => (byte[])Get("blob");

    /// <summary>
    /// Make a new target to write to a file descriptor (a small integer).
    /// </summary>
    /// <remarks>
    /// Make a new target that is attached to the descriptor. For example:
    /// <code language="lang-csharp">
    /// using var target = Target.NewToDescriptor(1);
    /// </code>
    /// Makes a descriptor attached to stdout.
    ///
    /// You can pass this target to (for example) <see cref="Image.WriteToTarget"/>.
    /// </remarks>
    /// <param name="descriptor">Write to this file descriptor.</param>
    /// <returns>A new <see cref="Target"/>.</returns>
    /// <exception cref="VipsException">If unable to create a new <see cref="Target"/> from <paramref name="descriptor"/>.</exception>
    public static Target NewToDescriptor(int descriptor)
    {
        var pointer = Internal.VipsTarget.NewToDescriptor(descriptor);
        if (pointer == IntPtr.Zero)
        {
            throw new VipsException($"can't create output target to descriptor {descriptor}");
        }

        return new Target(pointer);
    }

    /// <summary>
    /// Make a new target to write to a file.
    /// </summary>
    /// <remarks>
    /// Make a new target that will write to the named file. For example:
    /// <code language="lang-csharp">
    /// using var target = Target.NewToFile("myfile.jpg");
    /// </code>
    /// You can pass this target to (for example) <see cref="Image.WriteToTarget"/>.
    /// </remarks>
    /// <param name="filename">Write to this this file.</param>
    /// <returns>A new <see cref="Target"/>.</returns>
    /// <exception cref="VipsException">If unable to create a new <see cref="Target"/> from <paramref name="filename"/>.</exception>
    public static Target NewToFile(string filename)
    {
        var bytes = Encoding.UTF8.GetBytes(filename + char.MinValue); // Ensure null-terminated string
        var pointer = Internal.VipsTarget.NewToFile(bytes);
        if (pointer == IntPtr.Zero)
        {
            throw new VipsException($"can't create output target to filename {filename}");
        }

        return new Target(pointer);
    }

    /// <summary>
    /// Make a new target to write to an area of memory.
    /// </summary>
    /// <remarks>
    /// Make a new target that will write to memory. For example:
    /// <code language="lang-csharp">
    /// using var target = Target.NewToMemory();
    /// </code>
    /// You can pass this target to (for example) <see cref="Image.WriteToTarget"/>.
    ///
    /// After writing to the target, fetch the bytes from the target object with:
    /// <code language="lang-csharp">
    /// var bytes = target.Blob;
    /// </code>
    /// </remarks>
    /// <returns>A new <see cref="Target"/>.</returns>
    /// <exception cref="VipsException">If unable to create a new <see cref="Target"/>.</exception>
    public static Target NewToMemory()
    {
        var pointer = Internal.VipsTarget.NewToMemory();
        if (pointer == IntPtr.Zero)
        {
            throw new VipsException("can't create output target to memory");
        }

        return new Target(pointer);
    }
}