using System.Linq;
using Semmle.Util;
using Semmle.Util.Logging;
using Semmle.Autobuild.Shared;
using Semmle.Extraction.CSharp;

namespace Semmle.Autobuild.CSharp
{
    /// <summary>
    /// Encapsulates C# build options.
    /// </summary>
    public class CSharpAutobuildOptions : AutobuildOptionsShared
    {
        private const string extractorOptionPrefix = "CODEQL_EXTRACTOR_CSHARP_OPTION_";

        public bool Buildless { get; }

        public override Language Language => Language.CSharp;


        /// <summary>
        /// Reads options from environment variables.
        /// Throws ArgumentOutOfRangeException for invalid arguments.
        /// </summary>
        public CSharpAutobuildOptions(IBuildActions actions) : base(actions)
        {
            Buildless = actions.GetEnvironmentVariable(lgtmPrefix + "BUILDLESS").AsBool("buildless", false) ||
                actions.GetEnvironmentVariable(extractorOptionPrefix + "BUILDLESS").AsBool("buildless", false);
        }
    }

    public class CSharpAutobuilder : Autobuilder<CSharpAutobuildOptions>
    {
        private const string buildCommandDocsUrl =
            "https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/configuring-the-codeql-workflow-for-compiled-languages";

        private readonly AutoBuildRule autoBuildRule;

        public CSharpAutobuilder(IBuildActions actions, CSharpAutobuildOptions options) : base(actions, options, new CSharpDiagnosticClassifier()) =>
            this.autoBuildRule = new AutoBuildRule(this);

        public override BuildScript GetBuildScript()
        {
            var attempt = BuildScript.Failure;
            switch (GetCSharpBuildStrategy())
            {
                case CSharpBuildStrategy.CustomBuildCommand:
                    attempt = new BuildCommandRule(DotNetRule.WithDotNet).Analyse(this, false) & CheckExtractorRun(true);
                    break;
                case CSharpBuildStrategy.Buildless:
                    attempt = DotNetRule.WithDotNet(this, (dotNetPath, env) =>
                        {
                            // No need to check that the extractor has been executed in buildless mode
                            return new StandaloneBuildRule(dotNetPath).Analyse(this, false);
                        });
                    break;
                case CSharpBuildStrategy.MSBuild:
                    attempt = new MsBuildRule().Analyse(this, false) & CheckExtractorRun(true);
                    break;
                case CSharpBuildStrategy.DotNet:
                    attempt = new DotNetRule().Analyse(this, false) & CheckExtractorRun(true);
                    break;
                case CSharpBuildStrategy.Auto:
                    attempt =
                        // Attempt a few different build strategies to see if one works
                        this.autoBuildRule.Analyse(this, true) |
                        // All attempts failed: print message
                        AutobuildFailure();
                    break;
            }

            return attempt;
        }

        /// <summary>
        /// A script that checks that the C# extractor has been executed.
        /// </summary>
        public BuildScript CheckExtractorRun(bool warnOnFailure) =>
            BuildScript.Create(actions =>
            {
                if (actions.FileExists(Extractor.GetCSharpLogPath()))
                    return 0;

                if (warnOnFailure)
                    Log(Severity.Error, "No C# code detected during build.");

                return 1;
            });

        protected override void AutobuildFailureDiagnostic()
        {
            // if `ScriptPath` is not null here, the `BuildCommandAuto` rule was
            // run and found at least one script to execute
            if (this.autoBuildRule.BuildCommandAutoRule.ScriptPath is not null)
            {
                var relScriptPath = this.MakeRelative(autoBuildRule.BuildCommandAutoRule.ScriptPath);

                // if we found multiple build scripts in the project directory, then we can say
                // as much to indicate that we may have picked the wrong one;
                // otherwise, we just report that the one script we found didn't work
                DiagnosticMessage message =
                    this.autoBuildRule.BuildCommandAutoRule.CandidatePaths.Count() > 1 ?
                    new(
                        this.Options.Language,
                        "multiple-build-scripts",
                        "There are multiple potential build scripts",
                        markdownMessage:
                            "CodeQL found multiple potential build scripts for your project and " +
                            $"attempted to run `{relScriptPath}`, which failed. " +
                            "This may not be the right build script for your project.\n\n" +
                            $"Set up a [manual build command]({buildCommandDocsUrl})."
                    ) :
                    new(
                        this.Options.Language,
                        "script-failure",
                        "Unable to build project using build script",
                        markdownMessage:
                            "CodeQL attempted to build your project using a script located at " +
                            $"`{relScriptPath}`, which failed.\n\n" +
                            $"Set up a [manual build command]({buildCommandDocsUrl})."
                    );

                AddDiagnostic(message);
            }

            // project files which don't exist get marked as not .NET core projects, but we don't want
            // to show an error for this if the files don't exist
            var foundNotDotNetProjects = autoBuildRule.DotNetRule.NotDotNetProjects.Where(
                proj => this.Actions.FileExists(proj.FullPath)
            );

            // both dotnet and msbuild builds require project or solution files; if we haven't found any
            // then neither of those rules would've worked
            if (this.ProjectsOrSolutionsToBuild.Count == 0)
            {
                this.AddDiagnostic(new(
                    this.Options.Language,
                    "no-projects-or-solutions",
                    "No project or solutions files found",
                    markdownMessage:
                        "CodeQL could not find any project or solution files in your repository.\n\n" +
                        $"Set up a [manual build command]({buildCommandDocsUrl})."
                ));
            }
            // show a warning if there are projects which are not compatible with .NET Core, in case that is unintentional
            else if (foundNotDotNetProjects.Any())
            {
                this.AddDiagnostic(new(
                    this.Options.Language,
                    "dotnet-incompatible-projects",
                    "Some projects are incompatible with .NET Core",
                    severity: DiagnosticMessage.TspSeverity.Warning,
                    markdownMessage: $"""
                    CodeQL found some projects which cannot be built with .NET Core:

                    {autoBuildRule.DotNetRule.NotDotNetProjects.Select(p => this.MakeRelative(p.FullPath)).ToMarkdownList(MarkdownUtil.CodeFormatter, 5)}
                    """
                ));
            }

            // report any projects that failed to build with .NET Core
            if (autoBuildRule.DotNetRule.FailedProjectsOrSolutions.Any())
            {
                this.AddDiagnostic(new(
                    this.Options.Language,
                    "dotnet-build-failure",
                    "Some projects or solutions failed to build using .NET Core",
                    markdownMessage: $"""
                    CodeQL was unable to build the following projects using .NET Core:

                    {autoBuildRule.DotNetRule.FailedProjectsOrSolutions.Select(p => this.MakeRelative(p.FullPath)).ToMarkdownList(MarkdownUtil.CodeFormatter, 10)}

                    Set up a [manual build command]({buildCommandDocsUrl}).
                    """
                ));
            }

            // report any projects that failed to build with MSBuild
            if (autoBuildRule.MsBuildRule.FailedProjectsOrSolutions.Any())
            {
                this.AddDiagnostic(new(
                    this.Options.Language,
                    "msbuild-build-failure",
                    "Some projects or solutions failed to build using MSBuild",
                    markdownMessage: $"""
                    CodeQL was unable to build the following projects using MSBuild:

                    {autoBuildRule.MsBuildRule.FailedProjectsOrSolutions.Select(p => this.MakeRelative(p.FullPath)).ToMarkdownList(MarkdownUtil.CodeFormatter, 10)}

                    Set up a [manual build command]({buildCommandDocsUrl}).
                    """
                ));
            }
        }

        /// <summary>
        /// Gets the build strategy that the autobuilder should apply, based on the
        /// options in the `lgtm.yml` file.
        /// </summary>
        private CSharpBuildStrategy GetCSharpBuildStrategy()
        {
            if (Options.BuildCommand is not null)
                return CSharpBuildStrategy.CustomBuildCommand;

            if (Options.Buildless)
                return CSharpBuildStrategy.Buildless;

            if (Options.MsBuildArguments is not null
                || Options.MsBuildConfiguration is not null
                || Options.MsBuildPlatform is not null
                || Options.MsBuildTarget is not null)
            {
                return CSharpBuildStrategy.MSBuild;
            }

            if (Options.DotNetArguments is not null || Options.DotNetVersion is not null)
                return CSharpBuildStrategy.DotNet;

            return CSharpBuildStrategy.Auto;
        }

        private enum CSharpBuildStrategy
        {
            CustomBuildCommand,
            Buildless,
            MSBuild,
            DotNet,
            Auto
        }
    }
}