using System.Security.Cryptography;

namespace Launcher.Next.Application;

public sealed record LegacySettingsSnapshot(string SourceEndpoint, string SourceFingerprint, string Sha256, long Length, DateTimeOffset LastWriteUtc, DateTimeOffset AcquiredUtc, string LocalSnapshotPath, bool OfflineFallback);

public static class LegacyNetworkConfiguration
{
    public const string ApprovedSettingsEndpoint = @"\\phimproject.com\common\BIM\save\All_Serv_Install\Settings.xml";
    public const string LegacyBimAlias = @"N:\BIM";
    public const string ApprovedBimEndpoint = @"\\phimproject.com\common\BIM";

    public static string ResolveApprovedAlias(string legacyPath)
    {
        if (string.IsNullOrWhiteSpace(legacyPath)) throw new InvalidOperationException("LEGACY_NETWORK_PATH_INVALID");
        var normalized = legacyPath.Replace('/', '\\');
        if (string.Equals(normalized, LegacyBimAlias, StringComparison.OrdinalIgnoreCase)) return ApprovedBimEndpoint;
        var prefix = LegacyBimAlias + "\\";
        if (!normalized.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)) throw new InvalidOperationException("LEGACY_NETWORK_ALIAS_NOT_APPROVED");
        return ApprovedBimEndpoint + normalized[(prefix.Length - 1)..];
    }

    public static LegacySettingsSnapshot AcquireApprovedSnapshot(string endpoint, string localRoot)
    {
        if (!string.Equals(endpoint, ApprovedSettingsEndpoint, StringComparison.OrdinalIgnoreCase)) throw new InvalidOperationException("LEGACY_SETTINGS_ENDPOINT_NOT_APPROVED");
        if (!Path.IsPathFullyQualified(endpoint) || !endpoint.StartsWith(@"\\", StringComparison.Ordinal) || endpoint.Contains('?') || endpoint.Contains('*')) throw new InvalidOperationException("LEGACY_SETTINGS_ENDPOINT_INVALID");
        if (!File.Exists(endpoint) || File.GetAttributes(endpoint).HasFlag(FileAttributes.ReparsePoint)) return OfflineSnapshot(endpoint, localRoot);
        var first = new FileInfo(endpoint);
        var sourceHashBefore = Hash(endpoint);
        var snapshots = Path.Combine(Path.GetFullPath(localRoot), "configuration-snapshots");
        Directory.CreateDirectory(snapshots);
        var temporary = Path.Combine(snapshots, Guid.NewGuid().ToString("N") + ".tmp");
        File.Copy(endpoint, temporary, false);
        var copiedHash = Hash(temporary);
        var after = new FileInfo(endpoint);
        var sourceHashAfter = Hash(endpoint);
        if (first.Length != after.Length || first.LastWriteTimeUtc != after.LastWriteTimeUtc || !string.Equals(sourceHashBefore, sourceHashAfter, StringComparison.Ordinal) || !string.Equals(copiedHash, sourceHashAfter, StringComparison.Ordinal))
        {
            File.Delete(temporary);
            throw new InvalidOperationException("LEGACY_SETTINGS_CHANGED_DURING_ACQUISITION");
        }
        var final = Path.Combine(snapshots, copiedHash + ".xml");
        if (File.Exists(final)) File.Delete(temporary); else File.Move(temporary, final);
        if (!string.Equals(Hash(final), copiedHash, StringComparison.Ordinal)) throw new InvalidOperationException("LEGACY_SETTINGS_SNAPSHOT_HASH_MISMATCH");
        return new(endpoint, Fingerprint(endpoint, copiedHash), copiedHash, first.Length, new DateTimeOffset(first.LastWriteTimeUtc), DateTimeOffset.UtcNow, final, false);
    }

    private static LegacySettingsSnapshot OfflineSnapshot(string endpoint, string localRoot)
    {
        var snapshots = Path.Combine(Path.GetFullPath(localRoot), "configuration-snapshots");
        if (!Directory.Exists(snapshots)) throw new InvalidOperationException("LEGACY_SETTINGS_NETWORK_UNAVAILABLE");
        var candidate = Directory.GetFiles(snapshots, "*.xml").OrderByDescending(File.GetLastWriteTimeUtc).FirstOrDefault();
        if (candidate is null) throw new InvalidOperationException("LEGACY_SETTINGS_NETWORK_UNAVAILABLE");
        var info = new FileInfo(candidate);
        var hash = Hash(candidate);
        return new(endpoint, Fingerprint(endpoint, hash), hash, info.Length, new DateTimeOffset(info.LastWriteTimeUtc), DateTimeOffset.UtcNow, candidate, true);
    }

    private static string Hash(string path) { using var stream = File.OpenRead(path); return Convert.ToHexString(SHA256.HashData(stream)); }
    private static string Fingerprint(string endpoint, string hash) => Convert.ToHexString(SHA256.HashData(System.Text.Encoding.UTF8.GetBytes(endpoint + "|" + hash)));
}