using System.IO;
using System.Diagnostics;
using System.Text;
using Microsoft.Data.Sqlite;

namespace DorkNet.Launcher.Backend;

/// <summary>Spawns + manages the downloaded server binary as a child
/// process. Each running launcher owns one server at a time — the
/// previous one is killed before starting a new one.</summary>
public sealed class ServerProcess : IAsyncDisposable
{
    public const int DefaultLocalPort = 5005;
    public const int LanPort = 80;

    private Process? _process;
    private readonly StringBuilder _stderrBuffer = new();
    public string? StdoutLogPath { get; private set; }
    public bool IsRunning => _process is not null && !_process.HasExited;

    /// <summary>Boot the server in <paramref name="serverDir"/>.
    /// Passes the user's Photon AppIds + apex domain via environment
    /// so we don't need to write a per-launch appsettings.Local.json.</summary>
    public Task StartAsync(
        string serverDir,
        AppState state,
        string apex,
        HostingMode hostingMode,
        CancellationToken ct = default)
    {
        if (IsRunning)
            throw new InvalidOperationException("A server is already running; stop it first.");

        var exe = FindServerExecutable(serverDir);
        // db lives under %APPDATA%\DorkNet so it survives reinstalls of
        // the server cache dir (which sits under %LOCALAPPDATA%).
        var dbPath = Path.Combine(AppPaths.RoamingRoot, "dorknet.db");
        MigrateLegacyDbIfPresent(serverDir, dbPath);
        ApplySqliteCompatibilityPatches(dbPath);
        StdoutLogPath = Path.Combine(AppPaths.LogsRoot, $"server-{DateTime.UtcNow:yyyyMMdd-HHmmss}.log");

        var psi = new ProcessStartInfo
        {
            FileName = exe,
            WorkingDirectory = serverDir,
            UseShellExecute = false,
            CreateNoWindow = true,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
        };
        psi.Environment["ASPNETCORE_ENVIRONMENT"] = "Development";
        var singleOriginMode = hostingMode == HostingMode.SingleOriginTunnel;
        var directMode = hostingMode is HostingMode.LocalNetwork or HostingMode.Internet;
        psi.Environment["ASPNETCORE_URLS"] = directMode
            ? $"http://0.0.0.0:{LanPort}"
            : $"http://127.0.0.1:{DefaultLocalPort}";
        psi.Environment["Database__Provider"] = "sqlite";
        psi.Environment["Database__SqlitePath"] = dbPath;
        psi.Environment["Jwt__Secret"] = EnsureJwtSecret();
        psi.Environment["Photon__AppId"] = state.PhotonAppId;
        psi.Environment["Photon__VoiceAppId"] =
            string.IsNullOrEmpty(state.PhotonVoiceAppId) ? state.PhotonAppId : state.PhotonVoiceAppId;
        psi.Environment["Photon__CloudRegion"] = state.PhotonRegion;
        psi.Environment["Domain__Apex"] = apex;
        psi.Environment["Domain__Scheme"] = directMode ? "http" : "https";
        psi.Environment["Domain__Port"] = "";
        if (singleOriginMode)
            psi.Environment["Domain__SingleOriginBaseUrl"] = $"https://{apex}";

        AppendLog($"[launcher] serverDir={serverDir}");
        AppendLog($"[launcher] exe={exe}");
        AppendLog($"[launcher] urls={psi.Environment["ASPNETCORE_URLS"]}");
        AppendLog($"[launcher] domain apex={apex}, scheme={psi.Environment["Domain__Scheme"]}, port={psi.Environment["Domain__Port"]}");
        if (singleOriginMode)
            AppendLog($"[launcher] single origin={psi.Environment["Domain__SingleOriginBaseUrl"]}");

        _process = new Process { StartInfo = psi, EnableRaisingEvents = true };
        _process.OutputDataReceived += (_, e) => AppendLog(e.Data);
        _process.ErrorDataReceived += (_, e) => { AppendLog(e.Data); if (e.Data is not null) _stderrBuffer.AppendLine(e.Data); };
        _process.Start();
        _process.BeginOutputReadLine();
        _process.BeginErrorReadLine();
        return Task.CompletedTask;
    }

    private void AppendLog(string? line)
    {
        if (line is null || StdoutLogPath is null) return;
        try { File.AppendAllText(StdoutLogPath, line + Environment.NewLine); }
        catch { /* disk full / locked / can't help here */ }
    }

    public async Task StopAsync()
    {
        if (_process is null || _process.HasExited) return;
        try
        {
            _process.CloseMainWindow();
            if (!_process.WaitForExit(2000))
            {
                _process.Kill(entireProcessTree: true);
            }
            await _process.WaitForExitAsync();
        }
        catch { /* already gone */ }
    }

    public string TailStderr(int lines = 30)
    {
        var all = _stderrBuffer.ToString().Split('\n');
        return string.Join('\n', all[Math.Max(0, all.Length - lines)..]);
    }

    private static string FindServerExecutable(string serverDir)
    {
        // Self-contained .NET publish drops a per-RID binary; on Windows
        // it's DorkNet.Server.exe, on Linux/Mac it's DorkNet.Server
        // (no extension). Try both, then scan as a last resort.
        var ext = OperatingSystem.IsWindows() ? ".exe" : "";
        var canonical = Path.Combine(serverDir, $"DorkNet.Server{ext}");
        if (File.Exists(canonical)) return canonical;

        // Windows scan picks any .exe; on Unix, scan for files that are
        // executable + match the expected name pattern.
        if (OperatingSystem.IsWindows())
        {
            var any = Directory.GetFiles(serverDir, "*.exe").FirstOrDefault();
            if (any is not null) return any;
        }
        else
        {
            var any = Directory.GetFiles(serverDir, "DorkNet.Server*")
                .Where(p => !p.EndsWith(".dll") && !p.EndsWith(".pdb") && !p.EndsWith(".json"))
                .FirstOrDefault();
            if (any is not null) return any;
        }

        throw new FileNotFoundException(
            $"No server binary found in {serverDir}. The release artifact may be corrupt.");
    }

    private static void ApplySqliteCompatibilityPatches(string dbPath)
    {
        if (!File.Exists(dbPath)) return;

        using var conn = new SqliteConnection($"Data Source={dbPath}");
        conn.Open();
        AddSqliteColumnIfMissing(conn, "Rooms", "HiddenFromBrowse",
            @"""HiddenFromBrowse"" INTEGER NOT NULL DEFAULT 0");
    }

    /// <summary>If an older launcher build left the SQLite db under
    /// <c>&lt;serverDir&gt;\data\dorknet.db</c> (where the server defaulted
    /// before <see cref="Database__SqlitePath"/> took over), copy it to
    /// the new <see cref="AppPaths.RoamingRoot"/> location so existing
    /// players, rooms, and dorms survive the move. Best-effort — never
    /// throws, never overwrites a db that's already at the new path.</summary>
    private static void MigrateLegacyDbIfPresent(string serverDir, string newDbPath)
    {
        try
        {
            if (File.Exists(newDbPath)) return;
            var legacy = Path.Combine(serverDir, "data", "dorknet.db");
            if (!File.Exists(legacy)) return;

            var destDir = Path.GetDirectoryName(newDbPath);
            if (!string.IsNullOrEmpty(destDir)) Directory.CreateDirectory(destDir);
            File.Copy(legacy, newDbPath);
            // SQLite WAL/SHM sidecars live next to the .db — copy them
            // too so the move doesn't drop in-flight wal frames.
            foreach (var suffix in new[] { "-wal", "-shm" })
            {
                var src = legacy + suffix;
                if (File.Exists(src)) File.Copy(src, newDbPath + suffix, overwrite: true);
            }
        }
        catch { /* best-effort — fresh db will be created on first server boot */ }
    }

    private static void AddSqliteColumnIfMissing(
        SqliteConnection conn,
        string table,
        string column,
        string definition)
    {
        var tableSql = table.Replace("\"", "\"\"");
        using (var check = conn.CreateCommand())
        {
            check.CommandText = $"PRAGMA table_info(\"{tableSql}\");";
            using var reader = check.ExecuteReader();
            while (reader.Read())
            {
                if (string.Equals(reader.GetString(1), column, StringComparison.OrdinalIgnoreCase))
                    return;
            }
        }

        using var alter = conn.CreateCommand();
        alter.CommandText = $"ALTER TABLE \"{tableSql}\" ADD COLUMN {definition};";
        alter.ExecuteNonQuery();
    }

    /// <summary>JWT signing key — random per-machine, persisted under
    /// LocalAppData so re-launches keep the same key (so existing
    /// tokens stay valid).</summary>
    private static string EnsureJwtSecret()
    {
        var path = Path.Combine(AppPaths.LocalRoot, "jwt.secret");
        if (File.Exists(path))
        {
            var existing = File.ReadAllText(path).Trim();
            if (existing.Length >= 64) return existing;
        }
        var bytes = new byte[64];
        System.Security.Cryptography.RandomNumberGenerator.Fill(bytes);
        var secret = Convert.ToBase64String(bytes);
        File.WriteAllText(path, secret);
        return secret;
    }

    public async ValueTask DisposeAsync()
    {
        await StopAsync();
        _process?.Dispose();
    }
}