import { HIBP_CODES } from "../error-codes.js";
import { HibpError } from "../errors/hibp-error.js";

/** Strict-mode framing: uppercase hex, single colon, decimal count. */
const STRICT_LINE_RE = /^[0-9A-F]{35}:[0-9]+$/;

/**
 * One parsed line from a range response: the 35-char hex suffix plus its
 * documented breach count.
 */
export interface RangeLine {
    readonly suffix: string;
    readonly count: number;
}

/**
 * Validate and split a raw line. In strict mode, malformed lines throw
 * `HIBP.MALFORMED_RESPONSE` with the offending zero-based line index. In
 * off-mode, lowercase hex is accepted (uppercased on the way out), and an
 * unparseable count defaults to `0`.
 */
export function parseRangeLine(
    raw: string,
    lineIndex: number,
    strict: boolean
): RangeLine {
    if (strict) {
        if (!STRICT_LINE_RE.test(raw)) {
            throw new HibpError(
                HIBP_CODES.MALFORMED_RESPONSE,
                `malformed range line at index ${lineIndex}`,
                { context: { lineIndex } }
            );
        }
        const idx = raw.indexOf(":");
        return {
            suffix: raw.slice(0, idx),
            count: Number.parseInt(raw.slice(idx + 1), 10),
        };
    }
    const idx = raw.indexOf(":");
    if (idx === -1) {
        throw new HibpError(
            HIBP_CODES.MALFORMED_RESPONSE,
            `malformed range line at index ${lineIndex}`,
            { context: { lineIndex } }
        );
    }
    const suffix = raw.slice(0, idx).toUpperCase();
    if (suffix.length !== 35 || !/^[0-9A-F]{35}$/.test(suffix)) {
        throw new HibpError(
            HIBP_CODES.MALFORMED_RESPONSE,
            `malformed range line at index ${lineIndex}`,
            { context: { lineIndex } }
        );
    }
    const tail = raw.slice(idx + 1);
    const parsed = Number.parseInt(tail, 10);
    const count = Number.isFinite(parsed) && parsed >= 0 ? parsed : 0;
    return { suffix, count };
}