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// ┃ ██████ ██████ ██████       █      █      █      █      █ █▄  ▀███ █       ┃
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// ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
// ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
// ┃ This file is part of the Perspective library, distributed under the terms ┃
// ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

/**
 * Numeric extent — used by series + candlestick build pipelines for
 * value / category axis domains.
 */
export interface Domain {
    min: number;
    max: number;
}

/**
 * Union `next` (a freshly-computed extent) with `prev` (the prior
 * accumulator) IN PLACE on `next`, then return a fresh copy to store
 * back as the new accumulator. Idempotent when `prev` is null — `next`
 * is left untouched.
 *
 * Used by the `domain_mode: "expand"` mirror-back step in the series /
 * candlestick / cartesian build pipelines: mutating `next` in place
 * means every downstream assignment that reads from the pipeline
 * result struct automatically picks up the grown extent.
 */
export function expandDomainInPlace(prev: Domain | null, next: Domain): Domain {
    if (prev) {
        next.min = Math.min(prev.min, next.min);
        next.max = Math.max(prev.max, next.max);
    }

    return { min: next.min, max: next.max };
}