import { sha256Text } from "../indexing/hash.ts";
import { normalizeVector } from "./vector.ts";
import type {
	EmbeddingService,
	EmbeddingStatusValue,
} from "./EmbeddingService.ts";

export class MockEmbeddingService implements EmbeddingService {
	readonly kind = "local" as const;
	readonly provider = "transformers" as const;
	readonly modelId = "mock-local-hash-embedding";
	readonly dimensions: number;
	status: EmbeddingStatusValue = "ready";

	constructor(dimensions = 64) {
		this.dimensions = dimensions;
	}

	async ensureReady(): Promise<void> {}

	async embedTexts(texts: string[]): Promise<number[][]> {
		return texts.map((text) => deterministicEmbedding(text, this.dimensions));
	}
}

export function deterministicEmbedding(
	text: string,
	dimensions = 64,
): number[] {
	const vector = new Array<number>(dimensions).fill(0);
	const tokens = text.toLowerCase().match(/[a-z0-9_]+/g) ?? [];
	for (const token of tokens) {
		const hash = sha256Text(token);
		const index = Number.parseInt(hash.slice(0, 8), 16) % dimensions;
		const sign = Number.parseInt(hash.slice(8, 10), 16) % 2 === 0 ? 1 : -1;
		vector[index] += sign;
	}
	return normalizeVector(vector);
}