Added search to: and keyword:

FAQ.md

@@ -1146,6 +1146,16 @@ This will result in searching like this:
 ("apple" AND "banana" AND NOT "cherry") OR "nuts"
 ```
 
+Since version 1.1979 it is possible to use these prefixes as a search expression:
+
+```
+from:<email address>
+to:<email address>
+keyword:<keyword>
+```
+
+There should be no space between the prefix and the search term, which will be applied as an AND-condition.
+
 Search expressions can be used for searching on the email server only, and not for searching on the device.
 
 Since version 1.1733 it is possible to save searches, which means that a named entry in the navigation menu will be created to repeat the same search later.

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

@@ -885,6 +885,8 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
         Long before = null;
 
         private static final String FROM = "from:";
+        private static final String TO = "to:";
+        private static final String KEYWORD = "keyword:";
 
         boolean onServer() {
             if (query == null)
@@ -899,6 +901,10 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                     return true;
                 else if (w.length() > FROM.length() && w.startsWith(FROM))
                     return true;
+                else if (w.length() > TO.length() && w.startsWith(TO))
+                    return true;
+                else if (w.length() > KEYWORD.length() && w.startsWith(KEYWORD))
+                    return true;
 
             return false;
         }
@@ -923,7 +929,9 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                 List<String> plus = new ArrayList<>();
                 List<String> minus = new ArrayList<>();
                 List<String> opt = new ArrayList<>();
-                List<String> from = new ArrayList<>();
+                List<String> andFrom = new ArrayList<>();
+                List<String> andTo = new ArrayList<>();
+                List<String> andKeyword = new ArrayList<>();
                 StringBuilder all = new StringBuilder();
                 for (String w : search.trim().split("\\s+")) {
                     if (all.length() > 0)
@@ -938,15 +946,20 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                     } else if (w.length() > 1 && w.startsWith("?")) {
                         opt.add(w.substring(1));
                         all.append(w.substring(1));
-                    } else if (w.length() > FROM.length() && w.startsWith(FROM)) {
-                        from.add(w.substring(FROM.length()));
-                    } else {
+                    } else if (w.length() > FROM.length() && w.startsWith(FROM))
+                        andFrom.add(w.substring(FROM.length()));
+                    else if (w.length() > TO.length() && w.startsWith(TO))
+                        andTo.add(w.substring(TO.length()));
+                    else if (w.length() > KEYWORD.length() && w.startsWith(KEYWORD))
+                        andKeyword.add(w.substring(KEYWORD.length()));
+                    else {
                         word.add(w);
                         all.append(w);
                     }
                 }
 
-                if (plus.size() + minus.size() + opt.size() + from.size() > 0)
+                if (plus.size() + minus.size() + opt.size() +
+                        andFrom.size() + andTo.size() + andKeyword.size() > 0)
                     search = all.toString();
 
                 // Yahoo! does not support keyword search, but uses the flags $Forwarded $Junk $NotJunk
@@ -957,21 +970,26 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                         break;
                     }
 
-                if (from.size() > 0) {
-                    for (String term : from)
+                if (andFrom.size() > 0) {
+                    for (String term : andFrom)
                         and.add(new FromStringTerm(term));
                 } else {
-                    if (in_senders)
+                    if (in_senders && !TextUtils.isEmpty(search))
                         or.add(new FromStringTerm(search));
                 }
 
-                if (in_recipients) {
+                if (andTo.size() > 0) {
+                    for (String term : andTo)
+                        and.add(new RecipientStringTerm(Message.RecipientType.TO, term));
+                } else {
+                    if (in_recipients && !TextUtils.isEmpty(search)) {
                         or.add(new RecipientStringTerm(Message.RecipientType.TO, search));
                         or.add(new RecipientStringTerm(Message.RecipientType.CC, search));
                         or.add(new RecipientStringTerm(Message.RecipientType.BCC, search));
                     }
+                }
 
-                if (in_subject)
+                if (in_subject && !TextUtils.isEmpty(search))
                     if (plus.size() + minus.size() + opt.size() == 0)
                         or.add(new SubjectTerm(search));
                     else
@@ -982,15 +1000,21 @@ public class BoundaryCallbackMessages extends PagedList.BoundaryCallback<TupleMe
                             or.add(new SubjectTerm(search));
                         }
 
-                if (in_keywords && hasKeywords) {
+                if (hasKeywords)
+                    if (andKeyword.size() > 0) {
+                        for (String term : andKeyword)
+                            and.add(new FlagTerm(new Flags(term), true));
+                    } else {
+                        if (in_keywords && !TextUtils.isEmpty(search)) {
                             String keyword = MessageHelper.sanitizeKeyword(search);
                             if (TextUtils.isEmpty(keyword))
                                 Log.w("Keyword empty=" + search);
                             else
                                 or.add(new FlagTerm(new Flags(keyword), true));
                         }
+                    }
 
-                if (in_message)
+                if (in_message && !TextUtils.isEmpty(search))
                     if (plus.size() + minus.size() + opt.size() == 0)
                         or.add(new BodyTerm(search));
                     else