# Feed Flow GO

1. Fetcher
2. Pusher
3. Differ

## FETCHER

### /api/v1/feed (GetUserFeed)

#### Request structure

{
"userId" int required
"feedId" int required
"languageId" int required
"nextToken" int
"mixed" bool
"config" json {"ratio" map[int]int}
}
#### Flow

st=>start: Receive API
e=>end: Retention Tracking
op1=>operation: getUserMetadata(cursor and top)
cond1=>condition: Metadata found
cond2=>condition: nextToken>0
cond3=>condition: top-cursor<30
cond4=>condition: isFirstFeedCallOfTheDay
op2=>operation: Paginate from nextToken
op3=>operation: Return trails,nextToken and cursor
op5=>operation: Handle Missing Metadata
(Look in mongodb if not found push data)
op6=>operation: Get content above cursor (paginate from cursor)
op8=>operation: fetch from bottom(paginate from 0)
op9=>operation: Call Pusher
st->op1->cond1
cond1(yes)->cond4
cond4(yes)->op9
cond4(no)->cond2
cond2(yes)->op2
cond2(no)->op6
op6->cond3
cond3(no)->op3
cond3(yes)->op9
cond1(no)->op5
op2->op3
op8->op3
op5->cond2

### /api/v1/feed/detailed (GetUserFeedDetailed)

Call Trail service /api/v1/trail/mobile/mini for detailed user feed

### /api/v1/feed/reset (ResetUserFeed)

Deletes cursor and user feed from both redis and mongo

## PUSHER

{
"userId" int required
"categoruId" int required
"languageId" int required
"count" int required
"userStackKey" string required
"mixed" bool
"config" json {"ratio" map[int]int}
}

st=>start: Start
op1=>operation: get User feed stack key 
                 (uf:u:f:l)
op2=>operation: Call diff service
op3=>operation: Add result to user stack
(redis and mongo)
en=>end: Return no of items in user stack

st->op1->op2->op3->en

## DIFFER

st=>start: Start
op1=>operation: get userstack from redis
op2=>operation: get (count) pinned trails from content stack 
that are not already in user stack
cond1=>condition: If len (pinned )<count
op3=>operation: Get popular content
(old new and blog merged)
cond2=>condition: If len(UserStack)>300
op4=>operation: get served but not seen content
op5=>operation: merge in ratio
en=>end: Return merged content (trailIds array)

st->op1->op2->cond1
op3->cond2
op4->op5->en
cond1(no)->en
cond2(yes)->op4
cond2(no)->op5
cond1(yes)->op3

## Cron Job for populating stacks

st=>start: Start
op1=>operation: get active feed categories
op2=>operation: get content for each afc
op3=>operation: clear and add into content stack

st->op1->op2->op3->op1

## Cron Job for populating Hot-start content stacks

st=>start: Start
op1=>operation: get active ad campaigns
op2=>operation: get content for each active campaign    
op3=>operation: clear and add into content stack

st->op1->op2->op3->op1