Add a --num option and default to 1 record

README.md

@@ -2,18 +2,34 @@
 
 [![Build status](https://dev.azure.com/mfussenegger/fake-json/_apis/build/status/fake-json-CI?branchName=master)](https://dev.azure.com/mfussenegger/fake-json/_build/latest?definitionId=2)
 
-`fake-json` is a CLI to generate random JSON records. If invoked it will
-generate and print 1 JSON object per line until cancelled:
+`fake-json` is a CLI to generate JSON records.
+
+
+Static JSON:
+
+```
+↪  fake-json x=10 y=20 foo=bar
+{"foo":"bar","x":10,"y":20}
+```
+
+Generated random data:
 
 ```
-↪  fake-json id=uuid4() x="randomInt(0, 10)" | head -n 3
+↪  fake-json --num 3 id="uuid4()" x="randomInt(0, 10)"
 {"id":"2c6ce42f-5f7d-4e65-a1a1-8b39f6cfce19","x":6}
 {"id":"d4c1af69-3cdd-417d-98e0-d3774f5fa1be","x":8}
 {"id":"8fc064c9-57ba-4d78-b205-57899776e757","x":6}
 ```
 
-It takes `fieldName=valueProvider()` pairs as argument. Each pair will result in
-a field within the JSON object.
+It takes `fieldName=value` or `fieldName=provider()` pairs as
+argument. Each pair will result in a field within the JSON object.
+
+To generate infinite records, use:
+
+```
+↪  fake-json --num Inf
+```
+
 
 ### Available providers
 

app/Main.hs

@@ -3,7 +3,7 @@
 module Main where
 
 import qualified Cli
-import           Control.Monad              (forever)
+import           Control.Monad              (forever, replicateM)
 import           Control.Monad.IO.Class     (liftIO)
 import           Data.Aeson                 (encode, object)
 import qualified Data.ByteString.Lazy.Char8 as BL
@@ -41,13 +41,15 @@ main = do
   if null errored
     then
       let
-        printRecords = forever $
+        printRecords = loop (Cli.num parsedArgs) $
           mapM runProvider providers >>= liftIO . BL.putStrLn . encode . object
       in
         runFakeT (Cli.seed parsedArgs) printRecords >> pure ()
     else
       mapM_ print errored
   where
+    loop Cli.Infinite  = forever
+    loop (Cli.Const n) = replicateM n
     unpackRight (x, Right y) = (x, y)
     unpackRight _            = error "Tuple must only contain Right eithers"
     runProvider (column, provider) = do

src/Cli.hs

@@ -1,14 +1,32 @@
 
 module Cli
   ( Args(..)
+  , Amount(..)
   , parseArgs
   ) where
 
 
-import Options.Applicative
+import           Options.Applicative hiding (Const)
+import           Text.Read           (readMaybe)
+
+
+data Args = Args
+  { seed :: !(Maybe Int)
+  , num :: !Amount }
+
+data Amount = Const Int
+            | Infinite
+            deriving (Show)
+
+
+parseNum :: ReadM Amount
+parseNum = eitherReader parseNum'
+  where
+    parseNum' "Inf" = Right Infinite
+    parseNum' s     = case readMaybe s of
+      (Just n) -> Right (Const n)
+      Nothing  -> Left "Expected a number or `Inf` for infinite records"
 
-newtype Args = Args
-  { seed :: Maybe Int }
 
 args :: Parser Args
 args = Args
@@ -17,6 +35,11 @@ args = Args
       ( long "seed"
       <> help "A seed for the random data generator"
       <> metavar "INT" ))
+  <*> option parseNum
+    ( long "num"
+    <> value (Const 1)
+    <> help "Number of records to generate. Use `Inf` for infinite records" )
+
 
 parseArgs :: [String] -> IO Args
 parseArgs cliArgs = handleParseResult $ execParserPure defaultPrefs opts cliArgs