using System.Diagnostics.CodeAnalysis;
using Npgsql.BackendMessages;

namespace Npgsql.Internal.TypeHandling;

/// <summary>
/// Type handlers that wish to support reading other types in additional to the main one can
/// implement this interface for all those types.
/// </summary>
public interface INpgsqlSimpleTypeHandler<T>
{
    /// <summary>
    /// Reads a value of type <typeparamref name="T"/> with the given length from the provided buffer,
    /// with the assumption that it is entirely present in the provided memory buffer and no I/O will be
    /// required.
    /// </summary>
    /// <param name="buf">The buffer from which to read.</param>
    /// <param name="len">The byte length of the value. The buffer might not contain the full length, requiring I/O to be performed.</param>
    /// <param name="fieldDescription">Additional PostgreSQL information about the type, such as the length in varchar(30).</param>
    /// <returns>The fully-read value.</returns>
    T Read(NpgsqlReadBuffer buf, int len, FieldDescription? fieldDescription = null);

    /// <summary>
    /// Responsible for validating that a value represents a value of the correct and which can be
    /// written for PostgreSQL - if the value cannot be written for any reason, an exception should be thrown.
    /// Also returns the byte length needed to write the value.
    /// </summary>
    /// <param name="value">The value to be written to PostgreSQL</param>
    /// <param name="parameter">
    /// The <see cref="NpgsqlParameter"/> instance where this value resides. Can be used to access additional
    /// information relevant to the write process (e.g. <see cref="NpgsqlParameter.Size"/>).
    /// </param>
    /// <returns>The number of bytes required to write the value.</returns>
    int ValidateAndGetLength([DisallowNull] T value, NpgsqlParameter? parameter);

    /// <summary>
    /// Writes a value to the provided buffer, with the assumption that there is enough space in the buffer
    /// (no I/O will occur). The Npgsql core will have taken care of that.
    /// </summary>
    /// <param name="value">The value to write.</param>
    /// <param name="buf">The buffer to which to write.</param>
    /// <param name="parameter">
    /// The <see cref="NpgsqlParameter"/> instance where this value resides. Can be used to access additional
    /// information relevant to the write process (e.g. <see cref="NpgsqlParameter.Size"/>).
    /// </param>
    void Write([DisallowNull] T value, NpgsqlWriteBuffer buf, NpgsqlParameter? parameter);
}