FileUtilities.swift

// This sucks. I'm probably doing it wrong. Please flame me.

import Foundation

enum FileSearchError: Error {
    case fileNotFound
    case readError(String)
}

/// Searches a file for lines containing a specific string and prints matching lines
/// - Parameters:
///   - searchString: The string to search for in each line
///   - filePath: The path to the file to search
/// - Throws: `FileSearchError` if the file cannot be opened or read
func searchFile(for searchString: String, in filePath: String) throws {
    guard let fileHandle = FileHandle(forReadingAtPath: filePath) else {
        throw FileSearchError.fileNotFound
    }
    
    defer {
        if #available(macOS 15.0, *) {
            try? fileHandle.close()
        } else {
            fileHandle.closeFile()
        }
    }
    
    // I can use let here because the data isn't modified after assignment.
    let fileData: Data

    do {
        // Get the file data
        if #available(macOS 15.0, *) {
            fileData = try fileHandle.readToEnd() ?? Data()
        } else {
            // Otherwise
            fileData = fileHandle.readDataToEndOfFile()
        }
        
        // Convert to string
        guard let fileContents = String(data: fileData, encoding: .utf8) else {
            throw FileSearchError.readError("Could not decode file contents as UTF-8")
        }
        
        // Split into lines and search
        let lines = fileContents.components(separatedBy: .newlines)
        
        // Track if we found any matches
        var matchFound = false
        
        // Check each line for the search string
        for (index, line) in lines.enumerated() {
            if line.contains(searchString) {
                print("Line \(index + 1): \(line)")
                matchFound = true
            }
        }
        
        if !matchFound {
            print("No matches found for '\(searchString)' in \(filePath)")
        }
    } catch {
        throw FileSearchError.readError(error.localizedDescription)
    }
}

// Use like so:
// do {
//     try searchFile(for: "Apple", in: "/Users/jake/.config/oui/manuf")
// } catch FileSearchError.fileNotFound {
//     print("Error: The specified file could not be found.")
// } catch FileSearchError.readError(let errorMessage) {
//     print("Error reading file: \(errorMessage)")
// } catch {
//     print("An unexpected error occurred: \(error)")
// }