43 lines
2.0 KiB
TypeScript
43 lines
2.0 KiB
TypeScript
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/**
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* Fail-safe consistency check for inline (ghost-text) suggestions.
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*
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* Ghost text renders `suggestion.substring(trackedInput.length)` after the
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* cursor, where `trackedInput` is what the client thinks the user has typed.
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* On hosts with non-standard echo (hardware bastion hosts / network OS such as
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* `ecOS#`, issue #1013, previously #756 / #906) that tracked value drifts out
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* of sync with what is actually on the terminal line, and the ghost ends up
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* painted over characters the user already typed (`int` + ghost `terface` →
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* `intterface`).
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*
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* This detects the one direction that produces visible corruption: the real
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* line being AHEAD of the tracked input (it contains the tracked input
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* followed by more, untracked characters). SSH echo latency is the opposite
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* case — the line is a prefix-behind of the tracked input — and is
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* intentionally NOT flagged, so the ghost stays responsive on slow links.
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*
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* Returns true when the caller should hide the ghost.
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*/
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export function lineHasUntrackedTrailingInput(
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trackedInput: string,
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lineBeforeCursor: string,
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): boolean {
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// Single chars match too loosely to judge reliably; let them through.
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if (trackedInput.length < 2) return false;
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// Column↔string mapping is only unambiguous for narrow (ASCII) input, so the
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// existing wide-char (CJK / emoji) handling is left untouched.
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if (!/^[\x20-\x7e]+$/.test(trackedInput)) return false;
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// Use the last occurrence so a prompt or command that repeats the same token
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// earlier on the line doesn't shadow the freshly-typed input.
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const idx = lineBeforeCursor.lastIndexOf(trackedInput);
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if (idx < 0) {
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// Tracked input isn't on screen yet — the echo is still catching up
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// (latency). Keep the ghost; reality being behind never corrupts.
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return false;
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}
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// Non-whitespace characters between the tracked input and the cursor mean the
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// device echoed input we never tracked → the ghost would overlap real text.
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return lineBeforeCursor.slice(idx + trackedInput.length).trimEnd().length > 0;
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}
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