Proof of concept: clean with Adguard filter files

ATTRIBUTION.md

@@ -52,3 +52,4 @@ FairEmail uses parts or all of:
 * [Jayway JsonPath](https://github.com/json-path/JsonPath). Copyright 2011 the original author or authors. [Apache License 2.0](https://github.com/json-path/JsonPath/blob/master/LICENSE).
 * [tinylog 2](https://github.com/tinylog-org/tinylog). Copyright 2016-2023 Martin Winandy. [Apache License 2.0](https://github.com/tinylog-org/tinylog/blob/v2.7/license.txt).
 * [Brave Lists](https://github.com/brave/adblock-lists). [Mozilla Public License Version 2.0](https://github.com/brave/adblock-lists/blob/master/LICENSE).
+* [AG Filters Registry](https://github.com/AdguardTeam/FiltersRegistry). [GNU Lesser General Public License Version 3](https://github.com/AdguardTeam/FiltersRegistry/blob/master/LICENSE).

app/src/main/assets/ATTRIBUTION.md

@@ -52,3 +52,4 @@ FairEmail uses parts or all of:
 * [Jayway JsonPath](https://github.com/json-path/JsonPath). Copyright 2011 the original author or authors. [Apache License 2.0](https://github.com/json-path/JsonPath/blob/master/LICENSE).
 * [tinylog 2](https://github.com/tinylog-org/tinylog). Copyright 2016-2023 Martin Winandy. [Apache License 2.0](https://github.com/tinylog-org/tinylog/blob/v2.7/license.txt).
 * [Brave Lists](https://github.com/brave/adblock-lists). [Mozilla Public License Version 2.0](https://github.com/brave/adblock-lists/blob/master/LICENSE).
+* [AG Filters Registry](https://github.com/AdguardTeam/FiltersRegistry). [GNU Lesser General Public License Version 3](https://github.com/AdguardTeam/FiltersRegistry/blob/master/LICENSE).

app/src/main/java/eu/faircode/email/UriHelper.java

@@ -401,6 +401,14 @@ public class UriHelper {
         if (url.isOpaque() || !isHyperLink(url))
             return uri;
 
+        if (BuildConfig.DEBUG) {
+            Uri result = filterAdguard(context, url);
+            if (result != null) {
+                changed = true;
+                url = result;
+            }
+        }
+
         Uri.Builder builder = url.buildUpon();
 
         builder.clearQuery();
@@ -445,6 +453,180 @@ public class UriHelper {
         return (changed ? builder.build() : null);
     }
 
+    @Nullable
+    private static Uri filterAdguard(Context context, Uri uri) {
+        if (uri.isOpaque())
+            return null;
+        String host = uri.getHost();
+        if (TextUtils.isEmpty(host))
+            return null;
+
+        List<String> removes = new ArrayList<>();
+
+        // https://github.com/AdguardTeam/FiltersRegistry/blob/master/filters/filter_17_TrackParam/filter.txt
+        try (BufferedReader br = new BufferedReader(
+                new InputStreamReader(context.getAssets().open("adguard_filter.txt")))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                if (TextUtils.isEmpty(line) || line.startsWith("!"))
+                    continue;
+
+                int dollar = line.indexOf('$');
+                while (dollar > 0 && line.charAt(dollar - 1) == '\\')
+                    dollar = line.indexOf('$', dollar + 1);
+                if (dollar < 0)
+                    continue;
+
+                String expr = line.substring(0, dollar).replace("\\$", "$");
+                String rest = line.substring(dollar + 1);
+
+                List<String> commands = new ArrayList<>();
+                int start = 0;
+                while (start < rest.length()) {
+                    int comma = rest.indexOf(',', start);
+                    while (comma > 0 && rest.charAt(comma - 1) == '\\')
+                        comma = rest.indexOf(',', comma + 1);
+                    int end = (comma < 0 ? rest.length() : comma);
+                    commands.add(rest.substring(start, end).replace("\\,", ","));
+                    start = (comma < 0 ? end : end + 1);
+                }
+
+                String remove = null;
+                boolean matches = true;
+                for (String command : commands) {
+                    int equal = command.indexOf('=');
+                    String c = (equal < 0 ? command : command.substring(0, equal));
+                    String e = (equal < 0 ? "" : command.substring(equal + 1));
+                    if ("removeparam".equals(c))
+                        remove = e;
+                    else if ("domain".equals(c)) {
+                        // https://adguard.com/kb/general/ad-filtering/create-own-filters/#domain-modifier
+                        matches = false;
+
+                        List<String> domains = new ArrayList<>();
+                        start = 0;
+                        while (start < c.length()) {
+                            int pipe = e.indexOf('|', start);
+                            while (pipe > 0 && e.charAt(pipe - 1) == '\\')
+                                pipe = e.indexOf('|', pipe + 1);
+                            int end = (pipe < 0 ? e.length() : pipe);
+                            domains.add(e.substring(start, end).replace("\\|", "|"));
+                            start = (pipe < 0 ? end : end + 1);
+                        }
+
+                        for (String domain : domains) {
+                            boolean not = domain.startsWith("~");
+                            String d = (not ? domain.substring(1) : domain);
+                            if (d.contains("*") && !d.endsWith("*"))
+                                Log.w("Adguard unexpected domain=" + domain);
+
+                            if (d.endsWith("*"))
+                                matches = d.substring(0, d.length() - 1).startsWith(host);
+                            else
+                                matches = d.equals(host);
+                            if (matches)
+                                Log.w("Adguard domain=" + domain + " host=" + host);
+                            if (not)
+                                matches = !matches;
+                            if (matches)
+                                break;
+                        }
+                    }
+                }
+
+                if (remove == null /* no removeparam */ || !matches)
+                    continue;
+
+                boolean except = false;
+                matches = TextUtils.isEmpty(expr);
+                if (!matches) {
+                    if (expr.startsWith("@@")) {
+                        except = true;
+                        expr = expr.substring(2);
+                    }
+
+                    String u = uri.toString();
+                    if (expr.startsWith("||")) {
+                        int ss = u.indexOf("//");
+                        if (ss > 0)
+                            u = u.substring(ss + 2);
+                        expr = expr.substring(2);
+                    }
+
+                    // https://adguard.com/kb/general/ad-filtering/create-own-filters/#basic-rules-special-characters
+                    StringBuilder b = new StringBuilder();
+                    b.append(".*");
+                    for (char c : expr.toCharArray())
+                        if (c == '*')
+                            b.append(".*");
+                        else if (c == '^')
+                            b.append("[^0-9a-zA-Z\\_\\-\\.\\%]");
+                        else if (c == '|')
+                            Log.w("Adguard unexpected expr=" + expr);
+                        else {
+                            if ("\\.?![]{}()<>*+-=^$|".indexOf(c) >= 0)
+                                b.append("\\");
+                            b.append(c);
+                        }
+                    if (!expr.endsWith("*"))
+                        b.append(".*");
+                    matches = Pattern.compile(b.toString()).matcher(u).matches();
+                    if (matches)
+                        Log.w("Adguard expr=" + b + " remove=" + remove);
+                }
+
+                if (matches)
+                    if (except)
+                        removes.clear();
+                    else if (!removes.contains(remove))
+                        removes.add(remove);
+            }
+        } catch (Throwable ex) {
+            Log.e(ex);
+        }
+
+        try {
+            boolean changed = false;
+            Uri.Builder builder = uri.buildUpon();
+            builder.clearQuery();
+            if (removes.contains("") /* all */)
+                changed = true;
+            else
+                for (String key : uri.getQueryParameterNames()) {
+                    boolean omit = false;
+                    for (String remove : removes)
+                        if (remove.startsWith("/")) {
+                            int end = remove.indexOf('/', 1);
+                            if (end > 0) {
+                                String regex = remove.substring(1, end);
+                                String rest = remove.substring(end + 1);
+                                if (!TextUtils.isEmpty(rest))
+                                    Log.w("Adguard unexpected remove=" + remove);
+                                if (Pattern.compile(regex).matcher(key).matches()) {
+                                    omit = true;
+                                    Log.w("Adguard omit regex=" + regex);
+                                    break;
+                                }
+                            }
+                        } else if (remove.equals(key)) {
+                            omit = true;
+                            Log.w("Adguard omit key=" + key);
+                            break;
+                        }
+                    if (omit)
+                        changed = true;
+                    else
+                        for (String value : uri.getQueryParameters(key))
+                            builder.appendQueryParameter(key, value);
+                }
+
+            return (changed ? builder.build() : null);
+        } catch (Throwable ex) {
+            Log.e(ex);
+            return null;
+        }
+    }
+
     @Nullable
     private static List<String> getBraveClean(Context context, Uri uri) {
         // https://github.com/brave/adblock-lists/blob/master/brave-lists/clean-urls.json