MarkdownParse.java

// File reading code from https://howtodoinjava.com/java/io/java-read-file-to-string-examples/
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;

public class MarkdownParse {
    public static ArrayList<String> getLinks(String markdown) {
        ArrayList<String> toReturn = new ArrayList<>();
        // find the next [, then find the ], then find the (, then take up to
        // the next )
        int currentIndex = 0;
        while(currentIndex < markdown.length()) {
            int nextOpenBracket = markdown.indexOf("[", currentIndex);

            if(nextOpenBracket < 0) break;

            // Check if this is actually an image
            if(nextOpenBracket > 0 && markdown.charAt(nextOpenBracket-1) == '!'){
                currentIndex = nextOpenBracket+1;
                continue;
            }

            int nextCloseBracket = markdown.indexOf("]", nextOpenBracket);
            int openParen = markdown.indexOf("(", nextCloseBracket);

            // Check if open paren is immediately after close bracket
            if(openParen != nextCloseBracket+1){
                currentIndex++;
                continue;
            }

            int closeParen = markdown.indexOf(")", openParen);

            // Check if any brackets or parens were not found
            if(nextCloseBracket == -1 || openParen == -1 || closeParen == -1){
                break;
            }

            int nextNextOpenBracket = markdown.indexOf("[", currentIndex+1);

            if(nextNextOpenBracket < closeParen && nextNextOpenBracket > -1){
                currentIndex = nextNextOpenBracket;
                continue;
            }

            toReturn.add(markdown.substring(openParen + 1, closeParen));
            currentIndex = closeParen + 1;
        }
        return toReturn;
    }
    public static void main(String[] args) throws IOException {
		Path fileName = Path.of(args[0]);
	    String contents = Files.readString(fileName);
        ArrayList<String> links = getLinks(contents);
        System.out.println(links);
    }

    // file has changed
}