using MycroForge.Parsing;

namespace MycroForge.CLI.CodeGen;

public class DbEnvInitializer : PythonSourceModifier
{
    private PythonParser.Import_fromContext? _alembicImport;
    private PythonParser.AssignmentContext? _targetMetaDataAssignment;
    private PythonParser.AssignmentContext? _urlAssignmentContext;
    private PythonParser.AssignmentContext? _connectableAssignmentContext;

    public DbEnvInitializer(string source) : base(source)
    {
    }

    public override string Rewrite()
    {
        var tree = Parser.file_input();
        Visit(tree);
        
        if (_alembicImport is null)
            throw new Exception("Could not find import insertion point.");

        if (_targetMetaDataAssignment is null)
            throw new Exception("Could not find metadata insertion point.");

        if (_urlAssignmentContext is null)
            throw new Exception("Could not find url insertion point.");

        if (_connectableAssignmentContext is null)
            throw new Exception("Could not find connectable insertion point.");

        Rewrite(_alembicImport, [
            GetOriginalText(_alembicImport),
            $"from {Features.Db.FeatureName}.settings import DbSettings",
            $"from {Features.Db.FeatureName}.entities.entity_base import EntityBase"
        ]);

        Rewrite(_targetMetaDataAssignment, "target_metadata = EntityBase.metadata");

        Rewrite(_urlAssignmentContext, "url = DbSettings.get_connectionstring()");

        const string indent = "    ";
        Rewrite(_connectableAssignmentContext, [
            "url = DbSettings.get_connectionstring()",
            $"{indent}context.config.set_main_option('sqlalchemy.url', url)",
            $"{indent}{GetOriginalText(_connectableAssignmentContext)}"
        ]);

        return Rewriter.GetText();
    }

    public override object? VisitImport_from(PythonParser.Import_fromContext context)
    {
        var text = GetOriginalText(context);

        if (text == "from alembic import context")
            _alembicImport = context;

        return base.VisitImport_from(context);
    }

    public override object? VisitAssignment(PythonParser.AssignmentContext context)
    {
        var text = GetOriginalText(context);

        if (text == "target_metadata = None")
            _targetMetaDataAssignment = context;
        
        else if (text == "url = config.get_main_option(\"sqlalchemy.url\")")
            _urlAssignmentContext = context;

        else if (text.StartsWith("connectable ="))
            _connectableAssignmentContext = context;

        return base.VisitAssignment(context);
    }
}