package postgressqlstore

import (
	"context"

	"github.com/uptrace/bun"
)

type dialect struct {
}

func (dialect *dialect) MigrateIntToTimestamp(ctx context.Context, bun bun.IDB, table string, column string) error {
	columnType, err := dialect.GetColumnType(ctx, bun, table, column)
	if err != nil {
		return err
	}

	// bigint for postgres and INTEGER for sqlite
	if columnType != "bigint" {
		return nil
	}

	// if the columns is integer then do this
	if _, err := bun.
		ExecContext(ctx, `ALTER TABLE `+table+` RENAME COLUMN `+column+` TO `+column+`_old`); err != nil {
		return err
	}

	// add new timestamp column
	if _, err := bun.
		NewAddColumn().
		Table(table).
		ColumnExpr(column + " TIMESTAMP").
		Exec(ctx); err != nil {
		return err
	}

	if _, err := bun.
		NewUpdate().
		Table(table).
		Set(column + " = to_timestamp(cast(" + column + "_old as INTEGER))").
		Where("1=1").
		Exec(ctx); err != nil {
		return err
	}

	// drop old column
	if _, err := bun.
		NewDropColumn().
		Table(table).
		Column(column + "_old").
		Exec(ctx); err != nil {
		return err
	}

	return nil
}

func (dialect *dialect) MigrateIntToBoolean(ctx context.Context, bun bun.IDB, table string, column string) error {
	columnType, err := dialect.GetColumnType(ctx, bun, table, column)
	if err != nil {
		return err
	}

	if columnType != "bigint" {
		return nil
	}

	if _, err := bun.
		ExecContext(ctx, `ALTER TABLE `+table+` RENAME COLUMN `+column+` TO `+column+`_old`); err != nil {
		return err
	}

	// add new boolean column
	if _, err := bun.
		NewAddColumn().
		Table(table).
		ColumnExpr(column + " BOOLEAN").
		Exec(ctx); err != nil {
		return err
	}

	// copy data from old column to new column, converting from int to boolean
	if _, err := bun.NewUpdate().
		Table(table).
		Set(column + " = CASE WHEN " + column + "_old = 1 THEN true ELSE false END").
		Where("1=1").
		Exec(ctx); err != nil {
		return err
	}

	// drop old column
	if _, err := bun.NewDropColumn().Table(table).Column(column + "_old").Exec(ctx); err != nil {
		return err
	}

	return nil
}

func (dialect *dialect) GetColumnType(ctx context.Context, bun bun.IDB, table string, column string) (string, error) {
	var columnType string

	err := bun.NewSelect().
		ColumnExpr("data_type").
		TableExpr("information_schema.columns").
		Where("table_name = ?", table).
		Where("column_name = ?", column).
		Scan(ctx, &columnType)
	if err != nil {
		return "", err
	}

	return columnType, nil
}

func (dialect *dialect) ColumnExists(ctx context.Context, bun bun.IDB, table string, column string) (bool, error) {
	var count int
	err := bun.NewSelect().
		ColumnExpr("COUNT(*)").
		TableExpr("information_schema.columns").
		Where("table_name = ?", table).
		Where("column_name = ?", column).
		Scan(ctx, &count)

	if err != nil {
		return false, err
	}

	return count > 0, nil
}

func (dialect *dialect) RenameColumn(ctx context.Context, bun bun.IDB, table string, oldColumnName string, newColumnName string) (bool, error) {
	oldColumnExists, err := dialect.ColumnExists(ctx, bun, table, oldColumnName)
	if err != nil {
		return false, err
	}

	newColumnExists, err := dialect.ColumnExists(ctx, bun, table, newColumnName)
	if err != nil {
		return false, err
	}

	if !oldColumnExists && newColumnExists {
		return true, nil
	}

	_, err = bun.
		ExecContext(ctx, "ALTER TABLE "+table+" RENAME COLUMN "+oldColumnName+" TO "+newColumnName)
	if err != nil {
		return false, err
	}
	return true, nil
}