using FileSignatures;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

namespace System.ComponentModel.DataAnnotations;

public class ImageFileValidationAttribute : ValidationAttribute
{
    public ImageFileValidationAttribute(long length)
    {
        Length = length;
    }

    public long Length { get; set; }

    protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
    {
        var fileInspector = validationContext.GetRequiredService<IFileFormatInspector>();
        if (null == fileInspector)
        {
            return new ValidationResult("未配置文件验证器");
        }
        if (value is IFormFile file)
        {
            var result = Validate(fileInspector, file);
            if (null != result)
                return result;
        }
        else if (value is IFormFileCollection files)
        {
            foreach (var f in files)
            {
                var result = Validate(fileInspector, f);
                if (null != result)
                    return result;
            }
        }

        return ValidationResult.Success;
    }

    private ValidationResult? Validate(IFileFormatInspector fileInspector, IFormFile file)
    {
        if (file.Length > Length)
            return new ValidationResult("文件太大");
        var format = fileInspector.DetermineFileFormat(file.OpenReadStream());
        if (null == format)
            return new ValidationResult("文件格式不支持");
        return null;
    }
}