// Copyright Epic Games, Inc. All Rights Reserved.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using EpicGames.Core;
using Microsoft.Extensions.Logging;
using UnrealBuildBase;

namespace UnrealBuildTool
{
	/// <summary>
	/// Queries information about the targets supported by a project
	/// </summary>
	[ToolMode("QueryTargets", ToolModeOptions.XmlConfig | ToolModeOptions.BuildPlatformsHostOnly | ToolModeOptions.SingleInstance)]
	class QueryTargetsMode : ToolMode
	{
		/// <summary>
		/// Path to the project file to query
		/// </summary>
		[CommandLine("-Project=")]
		FileReference? ProjectFile = null;

		/// <summary>
		/// Path to the output file to receive information about the targets
		/// </summary>
		[CommandLine("-Output=")]
		FileReference? OutputFile = null;

		/// <summary>
		/// Write out all targets, even if a default is specified in the BuildSettings section of the Default*.ini files. 
		/// </summary>
		[CommandLine("-IncludeAllTargets")]
		bool bIncludeAllTargets = false;

		/// <summary>
		/// Write all targets from parent assemblies (useful for EngineRules which can be chained)
		/// </summary>
		[CommandLine("-IncludeParentAssembly", Value ="true")]
		[CommandLine("-DontIncludeParentAssembly", Value = "false")]
		bool bIncludeParentAssembly = true;

		/// <summary>
		/// Execute the mode
		/// </summary>
		/// <param name="Arguments">Command line arguments</param>
		/// <returns></returns>
		/// <param name="Logger"></param>
		public override Task<int> ExecuteAsync(CommandLineArguments Arguments, ILogger Logger)
		{
			Arguments.ApplyTo(this);

			// Create the build configuration object, and read the settings
			BuildConfiguration BuildConfiguration = new BuildConfiguration();
			XmlConfig.ApplyTo(BuildConfiguration);
			Arguments.ApplyTo(BuildConfiguration);

			// Ensure the path to the output file is valid
			if (OutputFile == null)
			{
				OutputFile = GetDefaultOutputFile(ProjectFile);
			}

			// Create the rules assembly
			RulesAssembly Assembly;
			if (ProjectFile != null)
			{
				Assembly = RulesCompiler.CreateProjectRulesAssembly(ProjectFile, BuildConfiguration.bUsePrecompiled, BuildConfiguration.bSkipRulesCompile, BuildConfiguration.bForceRulesCompile, Logger);
			}
			else
			{
				Assembly = RulesCompiler.CreateEngineRulesAssembly(BuildConfiguration.bUsePrecompiled, BuildConfiguration.bSkipRulesCompile, BuildConfiguration.bForceRulesCompile, Logger);
			}

			// Write information about these targets
			WriteTargetInfo(ProjectFile, Assembly, OutputFile, Arguments, Logger, bIncludeAllTargets, bIncludeParentAssembly);
			Logger.LogInformation("Written {OutputFile}", OutputFile);
			return Task.FromResult(0);
		}

		/// <summary>
		/// Gets the path to the target info output file
		/// </summary>
		/// <param name="ProjectFile">Project file being queried</param>
		/// <returns>Path to the output file</returns>
		public static FileReference GetDefaultOutputFile(FileReference? ProjectFile)
		{
			if (ProjectFile == null)
			{
				return FileReference.Combine(Unreal.EngineDirectory, "Intermediate", "TargetInfo.json");
			}
			else
			{
				return FileReference.Combine(ProjectFile.Directory, "Intermediate", "TargetInfo.json");
			}
		}

		/// <summary>
		/// Writes information about the targets in an assembly to a file
		/// </summary>
		/// <param name="ProjectFile">The project file for the targets being built</param>
		/// <param name="Assembly">The rules assembly for this target</param>
		/// <param name="OutputFile">Output file to write to</param>
		/// <param name="Arguments"></param>
		/// <param name="Logger">Logger for output</param>
		/// <param name="bIncludeAllTargets">Include all targets even if a default target is specified for a given target type.</param>
		/// <param name="bIncludeParentAssembly">Include all targets from parent assemblies (useful for EngineRules which can be chained)</param>
		public static void WriteTargetInfo(FileReference? ProjectFile, RulesAssembly Assembly, FileReference OutputFile, CommandLineArguments Arguments, ILogger Logger, bool bIncludeAllTargets = true, bool bIncludeParentAssembly = false)
		{
			// Construct all the targets in this assembly
			List<string> TargetNames = new List<string>();
			Assembly.GetAllTargetNames(TargetNames, bIncludeParentAssembly);

			// Generate json
			using System.IO.StringWriter StringWriter = new();
			using (JsonWriter Writer = new(StringWriter))
			{
				Writer.WriteObjectStart();
				Writer.WriteArrayStart("Targets");
				foreach (string TargetName in TargetNames)
				{
					// skip target rules that are platform extension or platform group specializations
					string[] TargetPathSplit = TargetName.Split(new char[] { '_' }, StringSplitOptions.RemoveEmptyEntries);
					if (TargetPathSplit.Length > 1 && (UnrealTargetPlatform.IsValidName(TargetPathSplit.Last()) || UnrealPlatformGroup.IsValidName(TargetPathSplit.Last())))
					{
						continue;
					}

					// Construct the rules object
					TargetRules TargetRules;
					try
					{
						UnrealArchitectures Architectures = UnrealArchitectureConfig.ForPlatform(BuildHostPlatform.Current.Platform).ActiveArchitectures(ProjectFile, TargetName);
						TargetRules = Assembly.CreateTargetRules(TargetName, BuildHostPlatform.Current.Platform, UnrealTargetConfiguration.Development, Architectures, ProjectFile, Arguments, Logger, ValidationOptions: TargetRulesValidationOptions.ValidateNothing);
					}
					catch (Exception Ex)
					{
						Logger.LogWarning("Unable to construct target rules for {TargetName}", TargetName);
						Logger.LogDebug("{Ex}", ExceptionUtils.FormatException(Ex));
						continue;
					}

					// Is this a default target?
					bool? bIsDefaultTarget = null;
					if (ProjectFile != null)
					{
						string? DefaultTargetName = ProjectFileGenerator.GetProjectDefaultTargetNameForType(ProjectFile.Directory, TargetRules.Type);

						// GetProjectDefaultTargetNameForType returns
						if (DefaultTargetName != null)
						{
							bIsDefaultTarget = DefaultTargetName == TargetName;
						}
					}

					// If we don't want all targets, skip over non-defaults.
					if (!bIncludeAllTargets && bIsDefaultTarget.HasValue && !bIsDefaultTarget.Value)
					{
						continue;
					}

					// Get the path to the target
					FileReference? path = Assembly.GetTargetFileName(TargetName);

					// Write the target info
					Writer.WriteObjectStart();
					Writer.WriteValue("Name", TargetName);
					if (path != null)
					{
						Writer.WriteValue("Path", path.MakeRelativeTo(OutputFile.Directory));
					}
					Writer.WriteValue("Type", TargetRules.Type.ToString());

					if (bIncludeAllTargets && bIsDefaultTarget.HasValue)
					{
						Writer.WriteValue("DefaultTarget", bIsDefaultTarget.Value);
					}
					Writer.WriteObjectEnd();
				}
				Writer.WriteArrayEnd();
				Writer.WriteObjectEnd();
			}

			// Write the output file
			DirectoryReference.CreateDirectory(OutputFile.Directory);
			FileReference.WriteAllTextIfDifferent(OutputFile, StringWriter.ToString());
			// even if the contents don't change, we need to update the last write time (this is safer to do in parallel, unlike WriteAllText)
			FileReference.SetLastWriteTimeUtc(OutputFile, DateTime.UtcNow);
		}
	}
}