using System.Diagnostics.CodeAnalysis;
using System.Text;
using Microsoft.AspNetCore.WebUtilities;

namespace Houston.Model.Documents;

/// <summary>
/// Public URL id of a customer document.
/// </summary>
/// <remarks>
/// The identifier used in URLs (e.g. <c>/document/{id}/download</c> or <c>/document/{id}/share</c>)
/// is the URL base64 encoding of the document path <em>without</em> the customer/organization
/// folder. For an object stored at <c>OrgX/TypeY/FileZ.pdf</c> the id therefore encodes
/// <c>TypeY/FileZ.pdf</c>. The organization part is never part of the id, so it can only ever be
/// derived server side from the authenticated user.
/// </remarks>
public readonly record struct DocumentId(string Value)
{
    public static DocumentId Encode(DocumentRelativePath relativePath)
        => new(WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(relativePath.ToString())));

    public bool TryDecode([NotNullWhen(true)] out DocumentRelativePath? relativePath)
    {
        relativePath = null;

        if (String.IsNullOrEmpty(Value))
            return false;

        try
        {
            var decoded = Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(Value));
            return DocumentRelativePath.TryFromS3Key(decoded, out relativePath);
        }
        catch (FormatException)
        {
            relativePath = null;
            return false;
        }
    }

    public override string ToString() => Value;
}