What Firebase Security rules should I use to read the messages? -

i want users read messages uid equal either or both to or from fields of message or if 'to' section of message set all.
this database:

{ "intents" : {   "intentfields" : "",   "intentname" : "",   "to" : "" }, "messages" : {   "-kvivgc7zg051emxp0-5" : {     "from" : "ed",     "name" : "ed",     "photourl" : "https://cdn1.iconfinder.com/data/icons/user-pictures/100/male3-512.png",     "text" : "hello, i'm ed",     "timestamp" : "1476880306",     "to" : "all",     "type" : "text"   },   "-kwmsuvm0ujif01ehfyn" : {     "from" : "capyv3mxqsuun2w1npogcj0ex9t2",     "name" : "aakash bansal",     "photourl" : "https://lh5.googleusercontent.com/-oqya4hxvycc/aaaaaaaaaai/aaaaaaaahko/ov0a0p0ljiy/s96-c/photo.jpg",     "text" : "ho",     "timestamp" : "1479396273",     "to" : "ed",     "type" : "text"   } } } 

i tries several rules, , read firebase documentation too. none of rules helped me achieve result.

an example of rules tried :

{ "rules": {   "intents" : {     ".read" : "auth.uid === data.child('to').val()",     ".write" : true   },   "messages" : {     "$message": {            ".read":  "auth.uid !== null",            ".write": true     }   } } } 

whereas following set of rules works fine, although don't achieve desired result display messages in app.

{ "rules": {   "intents" : {     ".read" : "auth.uid === data.child('to').val()",     ".write" : true   },   "messages" : {     ".read":  "auth.uid !== null",     "$message": {            ".write": true     }   } } } 

inform, i'm using firebaseui in android app read data. please tell me if wrong in understanding of 'firebase security rules'.

edit : following set of rules not working:

{ "rules": {   "intents" : {     ".read" : "auth.uid === data.child('to').val()",     ".write" : true   },   "messages": {     "$message": {       ".read" : true,       ".write": true     }   } } } 

android code use read data is:

mfirebaseadapter = new messageadapter(friendlymessage.class,        r.layout.message_my,        recyclerview.viewholder.class,        mfirebasedatabasereference.child("/messages")); 

{   "rules": {     "messages": {       "$message": {         ".read": "auth.uid === data.child('to').val() || auth.uid === data.child('from').val() || data.child('to').val() === 'all' ",         ".write": true       }     }   } }