using Microsoft.AspNetCore.Http;

namespace PowderCoating.Application.Services;

/// <summary>
/// Shared file validation and content-type resolution used across all blob storage services.
/// </summary>
public static class BlobFileHelper
{
    /// <summary>
    /// Validates an uploaded file against an extension allowlist and a maximum size.
    /// Returns the normalized (lowercase) extension on success so callers do not re-derive it.
    /// </summary>
    public static (bool IsValid, string Extension, string Error) ValidateUpload(
        IFormFile? file,
        string[] allowedExtensions,
        long maxBytes)
    {
        if (file == null || file.Length == 0)
            return (false, string.Empty, "No file provided.");

        if (file.Length > maxBytes)
            return (false, string.Empty, $"File exceeds the {maxBytes / 1024 / 1024} MB limit.");

        var extension = Path.GetExtension(file.FileName).ToLowerInvariant();
        if (string.IsNullOrEmpty(extension) || !allowedExtensions.Contains(extension))
            return (false, string.Empty, $"File type not allowed. Allowed: {string.Join(", ", allowedExtensions)}.");

        return (true, extension, string.Empty);
    }

    /// <summary>
    /// Maps a file extension to its MIME content type, covering common image formats and
    /// document types. Falls back to <c>application/octet-stream</c>.
    /// </summary>
    public static string GetContentType(string extension) => extension switch
    {
        ".jpg" or ".jpeg" => "image/jpeg",
        ".png"            => "image/png",
        ".gif"            => "image/gif",
        ".webp"           => "image/webp",
        ".svg"            => "image/svg+xml",
        ".pdf"            => "application/pdf",
        ".doc"            => "application/msword",
        ".docx"           => "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
        ".txt"            => "text/plain",
        _                 => "application/octet-stream"
    };

    /// <summary>
    /// Strips OS-invalid filename characters from a base filename (no extension), replacing
    /// them with underscores to produce a safe blob path segment.
    /// </summary>
    public static string SanitizeFileName(string fileName)
    {
        var sanitized = string.Join("_", fileName.Split(Path.GetInvalidFileNameChars()));
        return string.IsNullOrWhiteSpace(sanitized) ? "file" : sanitized;
    }
}