Implement a simplified grep with extensible flags

## Problem Implement a simplified version of `grep` that searches a text file and returns the lines that match a given query string. You should focus on **clean, readable, extensible design** (e.g., parsing flags/options in a way that makes it easy to add new flags later), not on advanced algorithms. ## Requirements - Input: - `pattern`: a non-empty string to search for. - `lines`: an array/list of strings representing the file content, one element per line. - `flags/options`: a set of optional flags (you may choose the interface, e.g., CLI args, a struct/object, or a map). - Output: - The matching lines, in original order. ## Supported flags (minimum) Define at least a few flags and implement them, such as: - Case-insensitive match (e.g., `-i`) - Print line numbers along with matched lines (e.g., `-n`) - Invert match (return non-matching lines) (e.g., `-v`) ## Notes - Assume a simple **substring match** (not full regex). - Be explicit about edge cases (empty file, empty lines, pattern casing, etc.). - The interviewer will evaluate: - Code organization (separation of concerns: parsing, matching, formatting) - Extensibility (how easy it is to add a new flag) - Correctness and testability ## Example Given: - `pattern = "error"` - `lines = ["ok", "Error: disk full", "no issue", "error again"]` - flags: case-insensitive Output: - `"Error: disk full"` - `"error again"`