using System;

namespace StellaOps.Configuration;

/// <summary>
/// API lifecycle controls for the Authority service.
/// </summary>
public sealed class AuthorityApiLifecycleOptions
{
    /// <summary>
    /// Settings for the legacy OAuth endpoint shim (/oauth/* → canonical).
    /// </summary>
    public AuthorityLegacyAuthEndpointOptions LegacyAuth { get; } = new();

    internal void Validate()
    {
        LegacyAuth.Validate();
    }
}

/// <summary>
/// Configuration for legacy OAuth endpoint shims and deprecation signalling.
/// </summary>
public sealed class AuthorityLegacyAuthEndpointOptions
{
    private static readonly DateTimeOffset DefaultDeprecationDate = new(2025, 11, 1, 0, 0, 0, TimeSpan.Zero);
    private static readonly DateTimeOffset DefaultSunsetDate = new(2026, 5, 1, 0, 0, 0, TimeSpan.Zero);

    /// <summary>
    /// Enables the legacy endpoint shim that routes /oauth/* to the canonical endpoints.
    /// </summary>
    public bool Enabled { get; set; } = true;

    /// <summary>
    /// Date when clients should consider the legacy endpoints deprecated.
    /// </summary>
    public DateTimeOffset DeprecationDate { get; set; } = DefaultDeprecationDate;

    /// <summary>
    /// Date when legacy endpoints will be removed.
    /// </summary>
    public DateTimeOffset SunsetDate { get; set; } = DefaultSunsetDate;

    /// <summary>
    /// Optional documentation URL included in the Sunset link header.
    /// </summary>
    public string? DocumentationUrl { get; set; } = "https://docs.stella-ops.org/authority/legacy-auth";

    internal void Validate()
    {
        if (!Enabled)
        {
            return;
        }

        var normalizedDeprecation = DeprecationDate.ToUniversalTime();
        var normalizedSunset = SunsetDate.ToUniversalTime();

        if (normalizedSunset <= normalizedDeprecation)
        {
            throw new InvalidOperationException("Legacy auth sunset date must be after the deprecation date.");
        }

        DeprecationDate = normalizedDeprecation;
        SunsetDate = normalizedSunset;

        if (!string.IsNullOrWhiteSpace(DocumentationUrl))
        {
            if (!Uri.TryCreate(DocumentationUrl, UriKind.Absolute, out var uri) ||
                (uri.Scheme != Uri.UriSchemeHttps && uri.Scheme != Uri.UriSchemeHttp))
            {
                throw new InvalidOperationException("Legacy auth documentation URL must be an absolute HTTP or HTTPS URL.");
            }
        }
    }
}