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d04f74a | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | /**
* Merge an authoritative baseline without moving identities already visible to
* the client. Baseline-only identities are inserted relative to the nearest
* following known identity; identities absent from the baseline are removed.
*
* @param current - the established client order.
* @param baseline - the latest authoritative rows.
* @param keyOf - stable identity selector.
* @returns baseline-valued rows with the established relative order retained.
*/
export function mergeOrderedBaseline<T>(
current: readonly T[],
baseline: readonly T[],
keyOf: (value: T) => unknown,
): T[] {
const baselineByKey = new Map<unknown, T>()
for (const value of baseline) baselineByKey.set(keyOf(value), value)
const merged = current
.map(value => baselineByKey.get(keyOf(value)))
.filter((value): value is T => value !== undefined)
const mergedKeys = new Set(merged.map(keyOf))
for (let index = 0; index < baseline.length; index++) {
const value = baseline[index]
/* v8 ignore next -- dense-array guard: index is bounded by baseline.length. */
if (value === undefined || mergedKeys.has(keyOf(value))) continue
let insertion = merged.length
for (let following = index + 1; following < baseline.length; following++) {
const candidate = baseline[following]
/* v8 ignore next -- dense-array guard: following is bounded by baseline.length. */
if (candidate === undefined) continue
const known = merged.findIndex(item => keyOf(item) === keyOf(candidate))
if (known !== -1) {
insertion = known
break
}
}
merged.splice(insertion, 0, value)
mergedKeys.add(keyOf(value))
}
return merged
}
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