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import { COLUMN_TYPES } from "../constants.ts";import type { DatabaseDialect } from "../connect.ts";import { quote } from "../utils/dialect.ts";
/** * Represents a table column for Schema */export class ColumnBuilder {  private isPrimaryKey: boolean = false;  private isNotNull: boolean = false;  private isUnique: boolean = false;  private isUnsigned: boolean = false;  private defaultValue: any;  private isDefaultValueAnExpression = false;
  constructor(    /** The column name */    private name: string,    /** The column type */    private type: keyof typeof COLUMN_TYPES,    /** The column length (varchar only) */    private length?: number,  ) {}
  /** Make this integer column unsigned */  public unsigned() {    this.isUnsigned = true;    return this;  }
  /** Set this column to be the PRIMARY KEY */  public primary(): ColumnBuilder {    this.isPrimaryKey = true;    return this;  }
  /** Add the NOT NULL constraint */  public notNull(): ColumnBuilder {    this.isNotNull = true;    return this;  }
  /** Add the UNIQUE constraint */  public unique(): ColumnBuilder {    this.isUnique = true;    return this;  }
  /**   * Set the default value of this column   *    * @param value the default value of the column   * @param isExpression wether the value is an SQL expression or not (default false)   */  public default(value: any, isExpression: boolean = false) {    this.defaultValue = value;    this.isDefaultValueAnExpression = isExpression;    return this;  }
  /**   * Generate the SQL column definition   *    * @param dialect the database dialect which you currently using   */  public toSQL(dialect: DatabaseDialect): string {    // If the type is VARCHAR, set the length
    let columnType = COLUMN_TYPES[this.type][dialect].toUpperCase();
    if (      (this.type === "integer" ||        this.type === "bigInteger" ||        this.type === "smallInteger") &&      this.isUnsigned    ) {      columnType = "UNSIGNED " + columnType;    }
    if (this.type === "varchar") {      columnType += typeof this.length === "number"        ? `(${this.length})`        : "(255)";    }
    // Set the column name and its type (for a specific database dialect)    const query = [`${quote(this.name, dialect)} ${columnType}`];
    // Add the PRIMARY KEY    if (this.isPrimaryKey) {      query.push("PRIMARY KEY");    }
    // Add the NOT NULL constraint if exists    if (this.isNotNull) {      query.push("NOT NULL");    }
    // Add the UNIQUE constraint if exists    if (this.isUnique) {      query.push("UNIQUE");    }
    // Check if the type is auto increment    const isIncrement = this.type === "increments" ||      this.type === "smallIncrements" || this.type === "bigIncrements";
    // In sqlite and mysql, we need to explicitly call AUTO_INCREMENT or AUTOINCREMENT    // to enable the auto increment feature. Unlike postgres which only uses SERIAL type.    if (      isIncrement &&      (dialect === "mysql" || dialect === "sqlite")    ) {      // Get database specific column type for auto increment      query.push(        dialect === "mysql" ? "AUTO_INCREMENT" : "AUTOINCREMENT",      );    }
    // Add the default value    const defaultValue = this.getDefaultValueSQL(dialect);    if (defaultValue) {      query.push(defaultValue);    }
    return query.join(" ");  }
  /**   * Get the default value text of the column   */  private getDefaultValueSQL(dialect: DatabaseDialect): string | null {    if (this.defaultValue === null) {      return "DEFAULT NULL";    } else if (typeof this.defaultValue === "boolean") {      if (dialect === "sqlite" || dialect === "mysql") {        return `DEFAULT ${this.defaultValue ? 1 : 0}`;      } else {        return `DEFAULT ${this.defaultValue ? "true" : "false"}`;      }    } else if (typeof this.defaultValue === "number") {      return `DEFAULT ${this.defaultValue}`;    } else if (typeof this.defaultValue === "string") {      const value = this.isDefaultValueAnExpression        ? this.defaultValue        : `'${this.defaultValue}'`;      return `DEFAULT ${value}`;    } else {      return null;    }  }}