#nullable enable
// Copyright (c) Nate McMaster.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Text.Json;
using BTCPayServer.Plugins.Dotnet.Internal;

namespace BTCPayServer.Plugins.Dotnet.Loader
{
    /// <summary>
    /// Extensions for creating a load context using settings from a runtimeconfig.json file
    /// </summary>
    public static class RuntimeConfigExtensions
    {
        private const string JsonExt = ".json";
        private static readonly JsonSerializerOptions s_serializerOptions = new()
        {
            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
        };

        /// <summary>
        /// Adds additional probing paths to a managed load context using settings found in the runtimeconfig.json
        /// and runtimeconfig.dev.json files.
        /// </summary>
        /// <param name="builder">The context builder</param>
        /// <param name="runtimeConfigPath">The path to the runtimeconfig.json file</param>
        /// <param name="includeDevConfig">Also read runtimeconfig.dev.json file, if present.</param>
        /// <param name="error">The error, if one occurs while parsing runtimeconfig.json</param>
        /// <returns>The builder.</returns>
        public static AssemblyLoadContextBuilder TryAddAdditionalProbingPathFromRuntimeConfig(
            this AssemblyLoadContextBuilder builder,
            string runtimeConfigPath,
            bool includeDevConfig,
            out Exception? error)
        {
            error = null;
            try
            {
                var config = TryReadConfig(runtimeConfigPath);
                if (config == null)
                {
                    return builder;
                }

                RuntimeConfig? devConfig = null;
                if (includeDevConfig)
                {
                    var configDevPath = runtimeConfigPath.Substring(0, runtimeConfigPath.Length - JsonExt.Length) + ".dev.json";
                    devConfig = TryReadConfig(configDevPath);
                }

                var tfm = config.runtimeOptions?.Tfm ?? devConfig?.runtimeOptions?.Tfm;

                if (config.runtimeOptions != null)
                {
                    AddProbingPaths(builder, config.runtimeOptions, tfm);
                }

                if (devConfig?.runtimeOptions != null)
                {
                    AddProbingPaths(builder, devConfig.runtimeOptions, tfm);
                }

                if (tfm != null)
                {
                    var dotnet = Process.GetCurrentProcess().MainModule?.FileName;
                    if (dotnet != null && string.Equals(Path.GetFileNameWithoutExtension(dotnet), "dotnet", StringComparison.OrdinalIgnoreCase))
                    {
                        var dotnetHome = Path.GetDirectoryName(dotnet);
                        if (dotnetHome != null)
                        {
                            builder.AddProbingPath(Path.Combine(dotnetHome, "store", RuntimeInformation.OSArchitecture.ToString().ToLowerInvariant(), tfm));
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                error = ex;
            }
            return builder;
        }

        private static void AddProbingPaths(AssemblyLoadContextBuilder builder, RuntimeOptions options, string? tfm)
        {
            if (options.AdditionalProbingPaths == null)
            {
                return;
            }

            foreach (var item in options.AdditionalProbingPaths)
            {
                var path = item;
                if (path.Contains("|arch|"))
                {
                    path = path.Replace("|arch|", RuntimeInformation.OSArchitecture.ToString().ToLowerInvariant());
                }

                if (path.Contains("|tfm|"))
                {
                    if (tfm == null)
                    {
                        // We don't have enough information to parse this
                        continue;
                    }

                    path = path.Replace("|tfm|", tfm);
                }

                builder.AddProbingPath(path);
            }
        }

        private static RuntimeConfig? TryReadConfig(string path)
        {
            try
            {
                var file = File.ReadAllBytes(path);
                return JsonSerializer.Deserialize<RuntimeConfig>(file, s_serializerOptions);
            }
            catch
            {
                return null;
            }
        }
    }
}