namespace MycroForge.CLI.CodeGen;

public class DbEnvInitializer
{
    private readonly Source _source;
    private SourceMatch? _alembicImport;
    private SourceMatch? _targetMetaDataAssignment;
    private SourceMatch? _urlAssignmentContext;
    private SourceMatch? _connectableAssignmentContext;

    public DbEnvInitializer(string source)
    {
        _source = new Source(source);
    }

    public string Rewrite()
    {
        InsertDefaultDbImports();

        InsertTargetMetadata();

        InsertConnectionstringFromDbSettings();

        InsertSqlAlchemyConfigUpdate();

        return _source.Text;
    }

    private void InsertSqlAlchemyConfigUpdate()
    {
        _connectableAssignmentContext = _source.Find(@"connectable\s*=\s*.+\(\s*");

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

        const string indent = "    ";
        _source.InsertMultiLine(_connectableAssignmentContext.StartIndex, [
            $"url = DbSettings.get_connectionstring()",
            $"{indent}context.config.set_main_option('sqlalchemy.url', url)\n{indent}",
        ]);
    }

    private void InsertConnectionstringFromDbSettings()
    {
        _urlAssignmentContext = _source.Find("""url\s*=\s*config\s*.+\s*get_main_option\(\s*"sqlalchemy.url"\s*\)""");

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

        _source.Replace(_urlAssignmentContext, "url = DbSettings.get_connectionstring()");
    }

    private void InsertTargetMetadata()
    {
        _targetMetaDataAssignment = _source.Find(@"target_metadata\s*=\s*None");

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

        _source.Replace(_targetMetaDataAssignment, "target_metadata = EntityBase.metadata");
    }

    private void InsertDefaultDbImports()
    {
        _alembicImport = _source.Find(@"from\s+alembic\s+import\s+context");

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

        _source.InsertMultiLine(_alembicImport.EndIndex, [
            $"\nfrom {Features.Db.FeatureName}.settings import DbSettings",
            $"from {Features.Db.FeatureName}.entities.entity_base import EntityBase\n"
        ]);
    }
}