// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using Microsoft.DotNet.ProjectModel.Graph;
using Microsoft.DotNet.ProjectModel.Resolution;
using Microsoft.Extensions.Internal;
using Microsoft.Extensions.PlatformAbstractions;
using NuGet.Frameworks;

namespace Microsoft.DotNet.ProjectModel
{
    public class ProjectContextBuilder
    {
        private Project Project { get; set; }

        private LockFile LockFile { get; set; }

        private GlobalSettings GlobalSettings { get; set; }

        private NuGetFramework TargetFramework { get; set; }

        private IEnumerable<string> RuntimeIdentifiers { get; set; } = Enumerable.Empty<string>();

        private string RootDirectory { get; set; }

        private string ProjectDirectory { get; set; }

        private string PackagesDirectory { get; set; }

        private string ReferenceAssembliesPath { get; set; }

        private bool IsDesignTime { get; set; }

        private Func<string, Project> ProjectResolver { get; set; }

        private Func<string, LockFile> LockFileResolver { get; set; }

        private ProjectReaderSettings Settings { get; set; } = ProjectReaderSettings.ReadFromEnvironment();

        public ProjectContextBuilder()
        {
            ProjectResolver = ResolveProject;
            LockFileResolver = ResolveLockFile;
        }

        public ProjectContextBuilder WithLockFile(LockFile lockFile)
        {
            LockFile = lockFile;
            return this;
        }

        public ProjectContextBuilder WithProject(Project project)
        {
            Project = project;
            return this;
        }

        public ProjectContextBuilder WithProjectDirectory(string projectDirectory)
        {
            ProjectDirectory = projectDirectory;
            return this;
        }

        public ProjectContextBuilder WithTargetFramework(NuGetFramework targetFramework)
        {
            TargetFramework = targetFramework;
            return this;
        }

        public ProjectContextBuilder WithTargetFramework(string targetFramework)
        {
            TargetFramework = NuGetFramework.Parse(targetFramework);
            return this;
        }

        public ProjectContextBuilder WithRuntimeIdentifiers(IEnumerable<string> runtimeIdentifiers)
        {
            RuntimeIdentifiers = runtimeIdentifiers;
            return this;
        }

        public ProjectContextBuilder WithReferenceAssembliesPath(string referenceAssembliesPath)
        {
            ReferenceAssembliesPath = referenceAssembliesPath;
            return this;
        }

        public ProjectContextBuilder WithPackagesDirectory(string packagesDirectory)
        {
            PackagesDirectory = packagesDirectory;
            return this;
        }

        public ProjectContextBuilder WithRootDirectory(string rootDirectory)
        {
            RootDirectory = rootDirectory;
            return this;
        }

        public ProjectContextBuilder WithProjectResolver(Func<string, Project> projectResolver)
        {
            ProjectResolver = projectResolver;
            return this;
        }

        public ProjectContextBuilder WithLockFileResolver(Func<string, LockFile> lockFileResolver)
        {
            LockFileResolver = lockFileResolver;
            return this;
        }

        public ProjectContextBuilder WithReaderSettings(ProjectReaderSettings settings)
        {
            Settings = settings;
            return this;
        }

        public ProjectContextBuilder AsDesignTime()
        {
            IsDesignTime = true;
            return this;
        }

        public IEnumerable<ProjectContext> BuildAllTargets()
        {
            ProjectDirectory = Project?.ProjectDirectory ?? ProjectDirectory;
            EnsureProjectLoaded();
            LockFile = LockFile ?? LockFileResolver(ProjectDirectory);

            if (LockFile != null)
            {
                foreach (var target in LockFile.Targets)
                {
                    yield return new ProjectContextBuilder()
                    .WithProject(Project)
                    .WithLockFile(LockFile)
                    .WithTargetFramework(target.TargetFramework)
                    .WithRuntimeIdentifiers(new[] { target.RuntimeIdentifier })
                    .Build();
                }
            }
        }

        public ProjectContext Build()
        {
            var diagnostics = new List<DiagnosticMessage>();

            ProjectDirectory = Project?.ProjectDirectory ?? ProjectDirectory;

            if (GlobalSettings == null && ProjectDirectory != null)
            {
                RootDirectory = ProjectRootResolver.ResolveRootDirectory(ProjectDirectory);

                GlobalSettings globalSettings;
                if (GlobalSettings.TryGetGlobalSettings(RootDirectory, out globalSettings))
                {
                    GlobalSettings = globalSettings;
                }
            }

            RootDirectory = GlobalSettings?.DirectoryPath ?? RootDirectory;
            PackagesDirectory = PackagesDirectory ?? PackageDependencyProvider.ResolvePackagesPath(RootDirectory, GlobalSettings);
            ReferenceAssembliesPath = ReferenceAssembliesPath ?? FrameworkReferenceResolver.GetDefaultReferenceAssembliesPath();
            var frameworkReferenceResolver = new FrameworkReferenceResolver(ReferenceAssembliesPath);

            LockFileLookup lockFileLookup = null;
            EnsureProjectLoaded();

            ReadLockFile(diagnostics);

            var validLockFile = true;
            string lockFileValidationMessage = null;

            if (LockFile != null)
            {
                if (Project != null)
                {
                    validLockFile = LockFile.IsValidForProject(Project, out lockFileValidationMessage);
                }

                lockFileLookup = new LockFileLookup(LockFile);
            }

            var libraries = new Dictionary<LibraryKey, LibraryDescription>();
            var projectResolver = new ProjectDependencyProvider(ProjectResolver);

            ProjectDescription mainProject = null;
            if (Project != null)
            {
                mainProject = projectResolver.GetDescription(TargetFramework, Project, targetLibrary: null);

                // Add the main project
                libraries.Add(new LibraryKey(mainProject.Identity.Name), mainProject);
            }

            LibraryRange? platformDependency = null;
            if (mainProject != null)
            {
                platformDependency = mainProject.Dependencies
                    .Where(d =>  d.Type.Equals(LibraryDependencyType.Platform))
                    .Cast<LibraryRange?>()
                    .FirstOrDefault();
            }
            bool isPortable = platformDependency != null || TargetFramework.IsDesktop();

            LockFileTarget target = null;
            LibraryDescription platformLibrary = null;

            if (lockFileLookup != null)
            {
                target = SelectTarget(LockFile, isPortable);
                if (target != null)
                {
                    var nugetPackageResolver = new PackageDependencyProvider(PackagesDirectory, frameworkReferenceResolver);
                    var msbuildProjectResolver = new MSBuildDependencyProvider(Project, ProjectResolver);
                    ScanLibraries(target, lockFileLookup, libraries, msbuildProjectResolver, nugetPackageResolver, projectResolver);

                    if (platformDependency != null)
                    {
                        platformLibrary = libraries[new LibraryKey(platformDependency.Value.Name)];
                    }
                }
            }

            string runtime;
            if (TargetFramework.IsDesktop())
            {
                var legacyRuntime = PlatformServices.Default.Runtime.GetLegacyRestoreRuntimeIdentifier();
                if (RuntimeIdentifiers.Contains(legacyRuntime))
                {
                    runtime = legacyRuntime;
                }
                else
                {
                    runtime = RuntimeIdentifiers.FirstOrDefault();
                }
            }
            else
            {
                runtime = target?.RuntimeIdentifier;
            }

            var referenceAssemblyDependencyResolver = new ReferenceAssemblyDependencyResolver(frameworkReferenceResolver);
            bool requiresFrameworkAssemblies;

            // Resolve the dependencies
            ResolveDependencies(libraries, referenceAssemblyDependencyResolver, out requiresFrameworkAssemblies);

            // REVIEW: Should this be in NuGet (possibly stored in the lock file?)
            if (LockFile == null)
            {
                diagnostics.Add(new DiagnosticMessage(
                    ErrorCodes.NU1009,
                    $"The expected lock file doesn't exist. Please run \"dotnet restore\" to generate a new lock file.",
                    Path.Combine(Project.ProjectDirectory, LockFile.FileName),
                    DiagnosticMessageSeverity.Error));
            }

            if (!validLockFile)
            {
                diagnostics.Add(new DiagnosticMessage(
                    ErrorCodes.NU1006,
                    $"{lockFileValidationMessage}. Please run \"dotnet restore\" to generate a new lock file.",
                    Path.Combine(Project.ProjectDirectory, LockFile.FileName),
                    DiagnosticMessageSeverity.Warning));
            }

            if (requiresFrameworkAssemblies)
            {
                var frameworkInfo = Project.GetTargetFramework(TargetFramework);

                if (string.IsNullOrEmpty(ReferenceAssembliesPath))
                {
                    // If there was an attempt to use reference assemblies but they were not installed
                    // report an error
                    diagnostics.Add(new DiagnosticMessage(
                        ErrorCodes.DOTNET1012,
                        $"The reference assemblies directory was not specified. You can set the location using the DOTNET_REFERENCE_ASSEMBLIES_PATH environment variable.",
                        filePath: Project.ProjectFilePath,
                        severity: DiagnosticMessageSeverity.Error,
                        startLine: frameworkInfo.Line,
                        startColumn: frameworkInfo.Column
                    ));
                }
                else if (!frameworkReferenceResolver.IsInstalled(TargetFramework))
                {
                    // If there was an attempt to use reference assemblies but they were not installed
                    // report an error
                    diagnostics.Add(new DiagnosticMessage(
                        ErrorCodes.DOTNET1011,
                        $"Framework not installed: {TargetFramework.DotNetFrameworkName} in {ReferenceAssembliesPath}",
                        filePath: Project.ProjectFilePath,
                        severity: DiagnosticMessageSeverity.Error,
                        startLine: frameworkInfo.Line,
                        startColumn: frameworkInfo.Column
                    ));
                }
            }

            // Create a library manager
            var libraryManager = new LibraryManager(libraries.Values.ToList(), diagnostics, Project?.ProjectFilePath);

            return new ProjectContext(
                GlobalSettings,
                mainProject,
                platformLibrary,
                TargetFramework,
                isPortable,
                runtime,
                PackagesDirectory,
                libraryManager,
                LockFile);
        }

        private void ReadLockFile(ICollection<DiagnosticMessage> diagnostics)
        {
            try
            {
                LockFile = LockFile ?? LockFileResolver(ProjectDirectory);
            }
            catch (FileFormatException e)
            {
                var lockFilePath = "";
                if (LockFile != null)
                {
                    lockFilePath = LockFile.LockFilePath;
                }
                else if (Project != null)
                {
                    lockFilePath = Path.Combine(Project.ProjectDirectory, LockFile.FileName);
                }

                diagnostics.Add(new DiagnosticMessage(
                    ErrorCodes.DOTNET1014,
                    ComposeMessageFromInnerExceptions(e),
                    lockFilePath,
                    DiagnosticMessageSeverity.Error));
            }
        }

        private static string ComposeMessageFromInnerExceptions(Exception exception)
        {
            var sb = new StringBuilder();
            var messages = new HashSet<string>();

            while (exception != null)
            {
                messages.Add(exception.Message);
                exception = exception.InnerException;
            }

            foreach (var message in messages)
            {
                sb.AppendLine(message);
            }

            return sb.ToString();
        }

        private void ResolveDependencies(Dictionary<LibraryKey, LibraryDescription> libraries,
                                         ReferenceAssemblyDependencyResolver referenceAssemblyDependencyResolver,
                                         out bool requiresFrameworkAssemblies)
        {
            // Remark: the LibraryType in the key of the given dictionary are all "Unspecified" at the beginning.
            requiresFrameworkAssemblies = false;

            foreach (var pair in libraries.ToList())
            {
                var library = pair.Value;

                // The System.* packages provide placeholders on any non netstandard platform 
                // To make them work seamlessly on those platforms, we fill the gap with a reference
                // assembly (if available)
                var package = library as PackageDescription;
                if (package != null && package.Resolved && !package.CompileTimeAssemblies.Any())
                {
                    var replacement = referenceAssemblyDependencyResolver.GetDescription(new LibraryRange(library.Identity.Name, LibraryType.ReferenceAssembly), TargetFramework);
                    if (replacement?.Resolved == true)
                    {
                        requiresFrameworkAssemblies = true;

                        // Remove the original package reference
                        libraries.Remove(pair.Key);

                        // Insert a reference assembly key if there isn't one
                        var key = new LibraryKey(replacement.Identity.Name, LibraryType.ReferenceAssembly);
                        if (!libraries.ContainsKey(key))
                        {
                            libraries[key] = replacement;
                        }
                    }
                }
            }

            foreach (var pair in libraries.ToList())
            {
                var library = pair.Value;
                library.Framework = library.Framework ?? TargetFramework;
                foreach (var dependency in library.Dependencies)
                {
                    var keyType = dependency.Target == LibraryType.ReferenceAssembly ?
                                  LibraryType.ReferenceAssembly :
                                  LibraryType.Unspecified;

                    var key = new LibraryKey(dependency.Name, keyType);

                    LibraryDescription dependencyDescription;
                    if (!libraries.TryGetValue(key, out dependencyDescription))
                    {
                        if (keyType == LibraryType.ReferenceAssembly)
                        {
                            // a dependency is specified to be reference assembly but fail to match
                            // then add a unresolved dependency
                            dependencyDescription = referenceAssemblyDependencyResolver.GetDescription(dependency, TargetFramework) ??
                                                    UnresolvedDependencyProvider.GetDescription(dependency, TargetFramework);
                            libraries[key] = dependencyDescription;
                        }
                        else if (!libraries.TryGetValue(new LibraryKey(dependency.Name, LibraryType.ReferenceAssembly), out dependencyDescription))
                        {
                            // a dependency which type is unspecified fails to match, then try to find a 
                            // reference assembly type dependency
                            dependencyDescription = UnresolvedDependencyProvider.GetDescription(dependency, TargetFramework);
                            libraries[key] = dependencyDescription;
                        }
                    }

                    dependencyDescription.RequestedRanges.Add(dependency);
                    dependencyDescription.Parents.Add(library);
                }
            }
        }

        private void ScanLibraries(LockFileTarget target,
                                   LockFileLookup lockFileLookup,
                                   Dictionary<LibraryKey, LibraryDescription> libraries,
                                   MSBuildDependencyProvider msbuildResolver,
                                   PackageDependencyProvider packageResolver,
                                   ProjectDependencyProvider projectResolver)
        {
            foreach (var library in target.Libraries)
            {
                LibraryDescription description = null;
                var type = LibraryType.Unspecified;

                if (string.Equals(library.Type, "project"))
                {
                    var projectLibrary = lockFileLookup.GetProject(library.Name);

                    if (projectLibrary != null)
                    {
                        if (MSBuildDependencyProvider.IsMSBuildProjectLibrary(projectLibrary))
                        {
                            description = msbuildResolver.GetDescription(TargetFramework, projectLibrary, library, IsDesignTime);
                            type = LibraryType.MSBuildProject;
                        }
                        else
                        {
                            var path = Path.GetFullPath(Path.Combine(ProjectDirectory, projectLibrary.Path));
                            description = projectResolver.GetDescription(library.Name, path, library, ProjectResolver);
                            type = LibraryType.Project;
                        }
                    }
                }
                else
                {
                    var packageEntry = lockFileLookup.GetPackage(library.Name, library.Version);

                    if (packageEntry != null)
                    {
                        description = packageResolver.GetDescription(TargetFramework, packageEntry, library);
                    }

                    type = LibraryType.Package;
                }

                description = description ?? UnresolvedDependencyProvider.GetDescription(new LibraryRange(library.Name, type), target.TargetFramework);

                libraries.Add(new LibraryKey(library.Name), description);
            }
        }

        private void EnsureProjectLoaded()
        {
            if (Project == null && ProjectDirectory != null)
            {
                Project = ProjectResolver(ProjectDirectory);
            }
        }

        private LockFileTarget SelectTarget(LockFile lockFile, bool isPortable)
        {
            if (!isPortable)
            {
                foreach (var runtimeIdentifier in RuntimeIdentifiers)
                {
                    foreach (var scanTarget in lockFile.Targets)
                    {
                        if (Equals(scanTarget.TargetFramework, TargetFramework) && string.Equals(scanTarget.RuntimeIdentifier, runtimeIdentifier, StringComparison.Ordinal))
                        {
                            return scanTarget;
                        }
                    }
                }
            }

            foreach (var scanTarget in lockFile.Targets)
            {
                if (Equals(scanTarget.TargetFramework, TargetFramework) && string.IsNullOrEmpty(scanTarget.RuntimeIdentifier))
                {
                    return scanTarget;
                }
            }

            return null;
        }

        private Project ResolveProject(string projectDirectory)
        {
            // TODO: Handle diagnostics
            Project project;
            if (ProjectReader.TryGetProject(projectDirectory, out project, diagnostics: null, settings: Settings))
            {
                return project;
            }
            else
            {
                return null;
            }
        }

        private static LockFile ResolveLockFile(string projectDir)
        {
            var projectLockJsonPath = Path.Combine(projectDir, LockFile.FileName);
            return File.Exists(projectLockJsonPath) ?
                        LockFileReader.Read(Path.Combine(projectDir, LockFile.FileName), designTime: false) :
                        null;
        }

        private struct LibraryKey
        {
            public LibraryKey(string name) : this(name, LibraryType.Unspecified)
            {
            }

            public LibraryKey(string name, LibraryType libraryType)
            {
                Name = name;
                LibraryType = libraryType;
            }

            public string Name { get; }
            public LibraryType LibraryType { get; }

            public override bool Equals(object obj)
            {
                var otherKey = (LibraryKey)obj;

                return string.Equals(otherKey.Name, Name, StringComparison.Ordinal) &&
                    otherKey.LibraryType.Equals(LibraryType);
            }

            public override int GetHashCode()
            {
                var combiner = new HashCodeCombiner();
                combiner.Add(Name);
                combiner.Add(LibraryType);

                return combiner.CombinedHash;
            }
            
            public override string ToString()
            {
                return Name + " " + LibraryType;
            }
        }
    }
}