33 lines
1.5 KiB
TypeScript
33 lines
1.5 KiB
TypeScript
// Head/tail height-cap arithmetic shared by the block primitives (TerminalBlock,
|
||
// SearchBlock), so long results use consistent head and tail slices. The split is
|
||
// `ceil(maxLines / 2)` head rows and the remainder as tail rows; a result within
|
||
// the cap shows every row and hides none.
|
||
|
||
/** The head/tail split metrics for a capped list. */
|
||
export interface HeadTailCap {
|
||
/** Rows beyond the cap (list length − maxLines); ≤ 0 means nothing is hidden. */
|
||
hidden: number
|
||
/** Whether the list is over the cap and not expanded, so it shows a head/tail slice. */
|
||
capped: boolean
|
||
/** Head-slice row count: `ceil(maxLines / 2)`. */
|
||
headLines: number
|
||
/** Tail-slice row count: the remainder after the head. */
|
||
tailLines: number
|
||
}
|
||
|
||
/**
|
||
* Compute the head/tail cap metrics for a list of `total` rows against `maxLines`,
|
||
* given whether the surface is expanded. Pure arithmetic; the caller slices its
|
||
* own rows with `headLines`/`tailLines` so a block can layer its own concerns
|
||
* (SearchBlock restores a tail file header) on top.
|
||
* @param total - the list's row count.
|
||
* @param maxLines - the collapsed-height cap in rows.
|
||
* @param expanded - whether the surface is expanded (uncaps the list).
|
||
* @returns the split metrics.
|
||
*/
|
||
export function headTailCap(total: number, maxLines: number, expanded: boolean): HeadTailCap {
|
||
const hidden = total - maxLines
|
||
const headLines = Math.ceil(maxLines / 2)
|
||
return { hidden, capped: hidden > 0 && !expanded, headLines, tailLines: maxLines - headLines }
|
||
}
|