//
// Copyright (c) 2022-present, Trail of Bits, Inc.
// All rights reserved.
//
// This source code is licensed in accordance with the terms specified in
// the LICENSE file found in the root directory of this source tree.
//
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;

namespace RpcInvestigator
{
    using static TraceLogger;

    public class Settings
    {
        public static readonly string m_WorkingDir = Environment.GetFolderPath(
            Environment.SpecialFolder.ApplicationData) + "\\RpcInvestigator";
        public static readonly string m_LogDir = Path.Combine(m_WorkingDir, "Logs");
        private static string m_DefaultPath = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
                "RpcInvestigator");
        private static string m_DefaultSettingsFileName = "settings.json";
        public string m_DbghelpPath;
        public string m_SymbolPath;
        public SourceLevels m_TraceLevel;
        public List<string> m_SnifferColumns;

        public Settings()
        {
            m_TraceLevel = SourceLevels.Information;
            m_SnifferColumns = new List<string>();
            if (!Directory.Exists(m_DefaultPath))
            {
                try
                {
                    Directory.CreateDirectory(m_DefaultPath);
                }
                catch (Exception ex) // swallow
                {
                    Trace(TraceLoggerType.Settings,
                        TraceEventType.Warning,
                        "Unable to create settings directory '" +
                        m_DefaultPath + "': " + ex.Message);
                }
            }

            if (!Directory.Exists(m_LogDir))
            {
                try
                {
                    Directory.CreateDirectory(m_LogDir);
                }
                catch (Exception ex) // swallow
                {
                    Trace(TraceLoggerType.Settings,
                        TraceEventType.Warning,
                        "Unable to create log directory '" +
                        m_LogDir + "': " + ex.Message);
                }
            }

            m_SymbolPath = @"srv*c:\symbols*https://msdl.microsoft.com/download/symbols";
            m_DbghelpPath = FindDbghelpDll();
        }

        public static void Validate (Settings Object)
        {
            return;
        }

        static public void Save(Settings Object, string Target)
        {
            string target = Target;

            if (string.IsNullOrEmpty(target))
            {
                target = Path.Combine(m_DefaultPath, m_DefaultSettingsFileName);
            }

            string json;
            try
            {
                json = JsonConvert.SerializeObject(Object, Formatting.Indented);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (var sw = new StreamWriter(ms))
                    {
                        sw.Write(json);
                        sw.Flush();
                    }
                }
                File.WriteAllText(target, json);
            }
            catch (Exception ex)
            {
                throw new Exception("Could not serialize the Settings object " +
                    "to JSON:  " +
                    ex.Message);
            }
        }

        static public Settings Load(string Location)
        {
            if (!File.Exists(Location))
            {
                throw new Exception("File does not exist");
            }

            Settings settings;

            try
            {
                var json = File.ReadAllText(Location);
                settings = (Settings)JsonConvert.DeserializeObject(json, typeof(Settings));
                Validate(settings);
            }
            catch (Exception ex)
            {
                throw new Exception("Could not deserialize settings: " + ex.Message);
            }
            return settings;
        }

        static public Settings LoadDefault()
        {
            var target = Path.Combine(m_DefaultPath, m_DefaultSettingsFileName);
            if (!File.Exists(target))
            {
                return new Settings();
            }
            return Load(target);
        }

        private string FindDbghelpDll()
        {
            //
            // First try to get the dbghelp.dll from the Windows debugging tools.
            //
            Trace(TraceLoggerType.Settings,
                TraceEventType.Information,
                "Searching for dbghelp.dll");

            var debuggingToolsPath =
                @"C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\dbghelp.dll";
            if (File.Exists(debuggingToolsPath))
            {
                Trace(TraceLoggerType.Settings,
                    TraceEventType.Information,
                    "Found dbghelp.dll in Debugging Tools for Windows: " +
                    debuggingToolsPath);
                return debuggingToolsPath;
            }

            //
            // If that fails, try to get dbghelp.dll from any of the installed Windows
            // SDKs and prefer the most recent version of the SDK.
            //
            var baseDir = @"C:\Program Files (x86)\Windows Kits\10\bin";
            var potentialKits = new List<string>();
            foreach (string dirname in Directory.GetDirectories(baseDir))
            {
                if (Path.GetFileName(dirname).StartsWith("10."))
                {
                    potentialKits.Add(dirname);
                }
            }

            //
            // Sort and then reverse potential kits so that we look at the most recent
            // kit first
            //
            potentialKits.Sort();
            potentialKits.Reverse();
            foreach (string dirname in potentialKits)
            {
                var dll = Path.Combine(dirname, "x64", "dbghelp.dll");
                if (File.Exists(dll))
                {
                    Trace(TraceLoggerType.Settings,
                        TraceEventType.Information,
                        $"Found dbghelp.dll in SDK: {dll}");
                    return dll;
                }
            }

            Trace(TraceLoggerType.Settings,
                TraceEventType.Warning,
                "unable to find dbghelp.dll, symbols may not be available");

            return null;
        }
    }
}