GenerateUniquePostcode Class — drizzle-orm Architecture

Source Code

drizzle-seed/src/services/Generators.ts lines 2468–2551

export class GenerateUniquePostcode extends AbstractGenerator<{ isUnique?: boolean }> {
	static override readonly entityKind: string = 'GenerateUniquePostcode';

	private state: {
		rng: prand.RandomGenerator;
		templates: {
			template: string;
			indicesGen: GenerateUniqueInt;
			placeholdersCount: number;
			count: number;
			maxUniquePostcodeNumber: number;
		}[];
	} | undefined;
	public override isUnique = true;

	override init({ count, seed }: { count: number; seed: number }) {
		const maxUniquePostcodeNumber = Math.pow(10, 5) + Math.pow(10, 9);
		if (count > maxUniquePostcodeNumber) {
			throw new RangeError(
				`count exceeds max number of unique postcodes(${maxUniquePostcodeNumber}).`,
			);
		}

		const rng = prand.xoroshiro128plus(seed);
		const templates = [
			{
				template: '#####',
				indicesGen: new GenerateUniqueInt({ minValue: 0, maxValue: Math.pow(10, 5) - 1 }),
				placeholdersCount: 5,
				count: 0,
				maxUniquePostcodeNumber: Math.pow(10, 5),
			},
			{
				template: '#####-####',
				indicesGen: new GenerateUniqueInt({ minValue: 0, maxValue: Math.pow(10, 9) - 1 }),
				placeholdersCount: 9,
				count: 0,
				maxUniquePostcodeNumber: Math.pow(10, 9),
			},
		];

		const maxPostcodeLength = Math.max(...templates.map((template) => template.template.length));
		if (this.stringLength !== undefined && this.stringLength < maxPostcodeLength) {
			throw new Error(
				`You can't use postcode generator with a db column length restriction of ${this.stringLength}. Set the maximum string length to at least ${maxPostcodeLength}.`,
			);
		}

		for (const templateObj of templates) {
			templateObj.indicesGen.skipCheck = true;
			templateObj.indicesGen.init({ count, seed });
		}

		this.state = { rng, templates };
	}

	generate() {
		if (this.state === undefined) {
			throw new Error('state is not defined.');
		}

		let idx: number;

		[idx, this.state.rng] = prand.uniformIntDistribution(0, this.state.templates.length - 1, this.state.rng);
		const templateObj = this.state.templates[idx]!;

		const postcodeNumber = templateObj.indicesGen.generate() as number;

		templateObj.count += 1;
		if (templateObj.count === templateObj.maxUniquePostcodeNumber) {
			this.state.templates[idx] = this.state.templates.at(-1)!;
			this.state.templates.pop();
		}

		const postcode = fillTemplate({
			template: templateObj.template,
			placeholdersCount: templateObj.placeholdersCount,
			values: [...String(postcodeNumber)],
			defaultValue: '0',
		});