55 lines
2.6 KiB
TypeScript
55 lines
2.6 KiB
TypeScript
// Local-only files displaced by `FileOperations.ensureClearPath` are named
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// `conflict-<uuid>-<originalName>`. The UUID is a full RFC-4122 v4 value so
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// a user-authored filename that happens to start with `conflict-` doesn't
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// get misclassified. The leading `(?:^|\/)` and trailing `[^/]*$` anchor the
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// match to the final path segment so intermediate directories named after
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// old conflict files (if a user renames one into a directory) don't ignore
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// everything beneath them.
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export const CONFLICT_PATH_REGEX =
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/(?:^|\/)conflict-[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}-[^/]*$/u;
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// Safe segment length for common filesystems (ext4 / NTFS / APFS all cap
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// at 255 bytes). `conflict-<36-char-uuid>-` adds 46 bytes; reserve a few
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// extra bytes for a future prefix bump and leave room for multi-byte UTF-8
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// characters in the original name.
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const CONFLICT_PREFIX_LEN = "conflict-".length + 36 + 1;
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const MAX_SEGMENT_BYTES = 255;
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const MAX_ORIGINAL_BYTES = MAX_SEGMENT_BYTES - CONFLICT_PREFIX_LEN - 4;
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export function buildConflictFileName(fileName: string): string {
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// Truncate the original name if keeping it whole would bust the
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// filesystem's segment-length cap. Preserve the trailing extension
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// so the file is still recognizable / openable.
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const safeName = truncateFileNameToByteLimit(fileName, MAX_ORIGINAL_BYTES);
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return `conflict-${crypto.randomUUID()}-${safeName}`;
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}
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function truncateFileNameToByteLimit(
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fileName: string,
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maxBytes: number
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): string {
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const encoder = new TextEncoder();
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if (encoder.encode(fileName).byteLength <= maxBytes) return fileName;
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const dotIndex = fileName.lastIndexOf(".");
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// Dotfile (starts with "." and nothing else) → no extension to preserve.
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const hasExtension = dotIndex > 0;
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const extension = hasExtension ? fileName.slice(dotIndex) : "";
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const stem = hasExtension ? fileName.slice(0, dotIndex) : fileName;
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const extensionBytes = encoder.encode(extension).byteLength;
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const stemBudget = Math.max(0, maxBytes - extensionBytes);
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// Walk the stem by grapheme cluster so we never split an emoji sequence
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// (e.g. ZWJ families, skin-tone modifiers) or a base+combining-mark pair.
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const segmenter = new Intl.Segmenter(undefined, { granularity: "grapheme" });
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let truncatedStem = "";
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let usedBytes = 0;
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for (const { segment } of segmenter.segment(stem)) {
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const segmentBytes = encoder.encode(segment).byteLength;
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if (usedBytes + segmentBytes > stemBudget) break;
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truncatedStem += segment;
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usedBytes += segmentBytes;
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}
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return truncatedStem + extension;
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}
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