// Holder counts, and the one rule that decides whether a count is "low".
//
// The block explorer's holders_count is optional: it is absent on a token it
// has only just indexed, and it goes missing on a degraded or changed API.
// Absent means the count is unknown.  It does not mean the token has no
// holders, and collapsing the two hides a token the user really holds as if
// it were spam.  Every call site reads the count through here so the
// distinction cannot be lost again in one place while holding in the others.

const LOW_HOLDER_THRESHOLD = 1000;

// Parse an explorer-supplied holders_count into a number, or null when it is
// not one.  Only a whole number of zero or more, or a string made of nothing
// but the digits 0-9, is a count.  Anything else is null, never read in part:
// "1,000", "0x10" and "1e3" are unknown, not 1, 0 and 1, because a count we
// cannot read is not a low count.  A count above Number.MAX_SAFE_INTEGER is
// null too: a number cannot hold it exactly, so it would come back rounded,
// or as Infinity.
function parseHoldersCount(raw) {
    if (typeof raw === "number") {
        return Number.isSafeInteger(raw) && raw >= 0 ? raw : null;
    }
    if (typeof raw === "string" && /^[0-9]+$/.test(raw)) {
        const count = Number(raw);
        return Number.isSafeInteger(count) ? count : null;
    }
    return null;
}

// True only for a token the explorer reported as having fewer holders than
// the threshold.  An unknown count is never low: showing a spam token the
// user can see is unusual costs less than hiding an asset they own.
function isLowHolderCount(holders) {
    return holders != null && holders < LOW_HOLDER_THRESHOLD;
}

module.exports = {
    LOW_HOLDER_THRESHOLD,
    parseHoldersCount,
    isLowHolderCount,
};