using Microsoft.CodeAnalysis;
using PkmnLib.Plugin.Gen7.SourceGen.Emit;
using PkmnLib.Plugin.Gen7.SourceGen.Parsing;

namespace PkmnLib.Plugin.Gen7.SourceGen;

/// <summary>
/// Generates <c>public static readonly StringKey</c> constant classes (move names, type names,
/// move flags, etc.) from the Gen 7 data files, which are exposed to the generator as
/// <c>AdditionalFiles</c>.
/// </summary>
[Generator]
public sealed class DataConstantsGenerator : IIncrementalGenerator
{
    private static readonly DiagnosticDescriptor ParseFailure = new("PKMN7G000", "Data file parse failure", "{0}",
        "PkmnLib.SourceGen", DiagnosticSeverity.Error, true);

    private static readonly DiagnosticDescriptor DuplicateIdentifier = new("PKMN7G001", "Duplicate constant identifier",
        "{0}", "PkmnLib.SourceGen", DiagnosticSeverity.Error, true);

    private static readonly DiagnosticDescriptor UnusableName = new("PKMN7G002", "Unusable constant name", "{0}",
        "PkmnLib.SourceGen", DiagnosticSeverity.Error, true);

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        var results = context.AdditionalTextsProvider
            .Where(static text => DataExtractor.IsKnownFile(Path.GetFileName(text.Path))).Select(static (text, ct) =>
                DataExtractor.Extract(Path.GetFileName(text.Path), text.GetText(ct)?.ToString()));

        context.RegisterSourceOutput(results, static (context, result) =>
        {
            foreach (var diagnostic in result.Diagnostics)
            {
                Report(context, diagnostic);
            }
            foreach (var spec in result.Classes)
            {
                var diagnostics = new List<ExtractionDiagnostic>();
                var source = ConstantClassEmitter.Emit(spec, diagnostics);
                foreach (var diagnostic in diagnostics)
                {
                    Report(context, diagnostic);
                }
                context.AddSource($"{spec.ClassName}.g.cs", source);
            }
        });
    }

    private static void Report(SourceProductionContext context, ExtractionDiagnostic diagnostic)
    {
        var descriptor = diagnostic.Id switch
        {
            "PKMN7G001" => DuplicateIdentifier,
            "PKMN7G002" => UnusableName,
            _ => ParseFailure,
        };
        context.ReportDiagnostic(Diagnostic.Create(descriptor, Location.None, diagnostic.Message));
    }
}