import { IndexMetadata } from "../../metadata/IndexMetadata"
import { TableIndexOptions } from "../options/TableIndexOptions"

/**
 * Database's table index stored in this class.
 */
export class TableIndex {
    readonly "@instanceof" = Symbol.for("TableIndex")

    // -------------------------------------------------------------------------
    // Public Properties
    // -------------------------------------------------------------------------

    /**
     * Index name.
     */
    name?: string

    /**
     * Columns included in this index.
     */
    columnNames: string[] = []

    /**
     * Indicates if this index is unique.
     */
    isUnique: boolean

    /**
     * The SPATIAL modifier indexes the entire column and does not allow indexed columns to contain NULL values.
     * Works only in MySQL.
     */
    isSpatial: boolean

    /**
     * The FULLTEXT modifier indexes the entire column and does not allow prefixing.
     * Works only in MySQL.
     */
    isFulltext: boolean

    /**
     * NULL_FILTERED indexes are particularly useful for indexing sparse columns, where most rows contain a NULL value.
     * In these cases, the NULL_FILTERED index can be considerably smaller and more efficient to maintain than
     * a normal index that includes NULL values.
     *
     * Works only in Spanner.
     */
    isNullFiltered: boolean

    /**
     * Fulltext parser.
     * Works only in MySQL.
     */
    parser?: string

    /**
     * Index filter condition.
     */
    where: string

    // -------------------------------------------------------------------------
    // Constructor
    // -------------------------------------------------------------------------

    constructor(options: TableIndexOptions) {
        this.name = options.name
        this.columnNames = options.columnNames
        this.isUnique = !!options.isUnique
        this.isSpatial = !!options.isSpatial
        this.isFulltext = !!options.isFulltext
        this.isNullFiltered = !!options.isNullFiltered
        this.parser = options.parser
        this.where = options.where ? options.where : ""
    }

    // -------------------------------------------------------------------------
    // Public Methods
    // -------------------------------------------------------------------------

    /**
     * Creates a new copy of this index with exactly same properties.
     */
    clone(): TableIndex {
        return new TableIndex(<TableIndexOptions>{
            name: this.name,
            columnNames: [...this.columnNames],
            isUnique: this.isUnique,
            isSpatial: this.isSpatial,
            isFulltext: this.isFulltext,
            isNullFiltered: this.isNullFiltered,
            parser: this.parser,
            where: this.where,
        })
    }

    // -------------------------------------------------------------------------
    // Static Methods
    // -------------------------------------------------------------------------

    /**
     * Creates index from the index metadata object.
     */
    static create(indexMetadata: IndexMetadata): TableIndex {
        return new TableIndex(<TableIndexOptions>{
            name: indexMetadata.name,
            columnNames: indexMetadata.columns.map(
                (column) => column.databaseName,
            ),
            isUnique: indexMetadata.isUnique,
            isSpatial: indexMetadata.isSpatial,
            isFulltext: indexMetadata.isFulltext,
            isNullFiltered: indexMetadata.isNullFiltered,
            parser: indexMetadata.parser,
            where: indexMetadata.where,
        })
    }
}