ReC/src/ReC.Application/Common/Behaviors/Action/HeaderQueryBehavior.cs

using MediatR;
using Microsoft.EntityFrameworkCore;
using ReC.Application.Common.Dto;
using ReC.Application.Common.Exceptions;
using ReC.Application.Common.Interfaces;
using System.Text.Json;

namespace ReC.Application.Common.Behaviors.Action;

public class HeaderQueryBehavior<TRequest, TResponse>(IRecDbContext dbContext) : IPipelineBehavior<TRequest, TResponse>
    where TRequest : notnull
    where TResponse : IEnumerable<RecActionViewDto>
{
    public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancel)
    {
        var actions = await next(cancel);

        foreach (var action in actions)
            await SetHeader(action, cancel);

        return actions;
    }

    private async Task SetHeader(RecActionViewDto action, CancellationToken cancel)
    {
        if (action.HeaderQuery is not string headerQuery)
            return;

        await using var command = dbContext.Database.GetDbConnection().CreateCommand();
        command.CommandText = headerQuery;

        await dbContext.Database.OpenConnectionAsync(cancel);
        try
        {
            object? scalar;
            try
            {
                scalar = await command.ExecuteScalarAsync(cancel);
            }
            catch (Exception ex)
            {
                throw new DataIntegrityException(
                    $"Header query execution failed. The stored SQL may be malformed. ActionId: {action.Id}, ProfileId: {action.ProfileId}, Error: {ex.Message}");
            }

            if (scalar is not string rawHeader)
                throw new DataIntegrityException(
                    $"Header query returned no result or a null value. ActionId: {action.Id}, ProfileId: {action.ProfileId}");

            var headerDict = JsonSerializer.Deserialize<Dictionary<string, JsonElement>>(rawHeader)
                ?? throw new DataIntegrityException(
                    $"Header query returned invalid JSON. ActionId: {action.Id}, ProfileId: {action.ProfileId}");

            action.Headers = headerDict.ToDictionary(header => header.Key, kvp => kvp.Value.ToString());
        }
        finally
        {
            await dbContext.Database.CloseConnectionAsync();
        }
    }
}