Search a Unix-Like File Tree with Composable Filters

## Problem Search an in-memory Unix-like file tree from a given directory. Return every physical file whose name contains a query string and whose size is greater than a supplied minimum. The caller chooses `"AND"` or `"OR"` combination. Symbolic links may point to files or directories and may form cycles. Each node has stable identity, `name`, and `type` (`file`, `directory`, or `symlink`). Files have `size` and a canonical path. Directories have child nodes. A symlink has a target node or a broken null target. ### Function Contract Implement `searchFiles(startDirectory, nameQuery, minSize, mode, followSymlinks)`. - Return canonical paths sorted lexicographically. - Return each physical file identity at most once, even if several links reach it. - When `followSymlinks` is false, ignore links. - When true, follow valid targets without looping; broken links contribute nothing. ### Constraints & Assumptions - At most `300,000` distinct node identities are reachable. - `mode` is `"AND"` or `"OR"`. - Name matching is case-sensitive substring matching. - `minSize >= 0`. - The start node is a directory. ### Clarifying Questions to Ask - Does size equality pass? No, the comparison is strictly greater than the minimum. - Are results logical link paths or physical files? Return each physical file's canonical path once. - Can links create cycles? Yes. - Does an empty name query match every file name? Yes. ```hint Track identities, not paths Maintain visited directory identities to stop symlink cycles and emitted file identities to deduplicate aliases. ``` ```hint Isolate the predicate Compute `nameMatches` and `sizeMatches`, then combine them according to the requested mode; traversal logic should not duplicate filter logic. ``` ### Example ```text nameQuery = "report" minSize = 100 mode = "AND" ``` Only files whose names contain `report` and whose sizes are greater than `100` are returned, regardless of whether reached directly or through a symlink. ### Evaluation Focus - Traverses arbitrary depth without recursion overflow. - Handles broken links, directory-link cycles, and duplicate aliases. - Applies AND/OR predicates exactly. - Runs in `O(v + e + r log r)` time for reachable nodes/edges and `r` results. ### Extensions to Discuss 1. What changes if results must preserve every logical link path? 2. How would permissions and mount boundaries affect traversal? 3. How could file-system events keep a search index current?