{- Checks system configuration and generates SysConfig.hs. -}

import System.IO
import System.Cmd
import System.Exit
import System.Directory

type ConfigKey = String
data ConfigValue = BoolConfig Bool | StringConfig String
data Config = Config ConfigKey ConfigValue

type Test = IO Config
type TestName = String
data TestCase = TestCase TestName Test

instance Show Config where
        show (Config key value) = unlines [
			  key ++ " :: " ++ valuetype value
			, key ++ " = " ++ showvalue value
		]
		where
			valuetype (BoolConfig _) = "Bool"
			valuetype (StringConfig _) = "String"
			showvalue (BoolConfig b) = show b
			showvalue (StringConfig s) = show s

tests :: [TestCase]
tests = [
	  TestCase "cp -a" $ testCp "cp_a" "-a"
	, TestCase "cp -p" $ testCp "cp_p" "-p"
	, TestCase "cp --reflink=auto" $ testCp "cp_reflink_auto" "--reflink=auto"
	, TestCase "uuid" $ selectCmd "uuid" ["uuid", "uuidgen"]
	, TestCase "xargs -0" $ requireCmd "xargs_0" "xargs -0" "xargs -0 </dev/null"
	, TestCase "rsync" $ requireCmd "rsync" "rsync" "rsync --version >/dev/null"
	]

tmpDir :: String
tmpDir = "tmp"

testFile :: String
testFile = tmpDir ++ "/testfile"

requireCmd :: ConfigKey -> String -> String -> Test
requireCmd k c cmdline = do
	ret <- testCmd k cmdline
	handle ret
	where
		handle r@(Config _ (BoolConfig True)) = return r
		handle r = do
			testEnd r
			error $ "** the " ++ c ++ " command is required to use git-annex"

testCp :: ConfigKey -> String -> Test
testCp k option = testCmd k $
	"cp " ++ option ++ " " ++ testFile ++ " " ++ testFile ++ ".new"

testCmd :: ConfigKey -> String -> Test
testCmd k c = do
	ret <- system $ quiet c
	return $ Config k (BoolConfig $ ret == ExitSuccess)

selectCmd :: ConfigKey -> [String] -> Test
selectCmd k cmds = search cmds
	where
		search [] = do
			testEnd $ Config k (BoolConfig False)
			error $ "* need one of these commands, but none are available: " ++ show cmds
		search (c:cs) = do
			ret <- system $ quiet c
			if (ret == ExitSuccess)
				then return $ Config k (StringConfig c)
				else search cs

quiet :: String -> String
quiet s = s ++ " >/dev/null 2>&1"

testStart :: TestName -> IO ()
testStart s = do
	putStr $ "  checking " ++ s ++ "..."
	hFlush stdout

testEnd :: Config -> IO ()
testEnd (Config _ (BoolConfig True)) = putStrLn $ " yes"
testEnd (Config _ (BoolConfig False)) = putStrLn $ " no"
testEnd (Config _ (StringConfig s)) = putStrLn $ " " ++ s

writeSysConfig :: [Config] -> IO ()
writeSysConfig config = writeFile "SysConfig.hs" body
	where
		body = unlines $ header ++ map show config ++ footer
		header = [
			  "{- Automatically generated by configure. -}"
			, "module SysConfig where"
			, ""
			]
		footer = []

runTests :: [TestCase] -> IO [Config]
runTests [] = return []
runTests ((TestCase tname t):ts) = do
	testStart tname
	c <- t
	testEnd c
	rest <- runTests ts
	return $ c:rest

setup :: IO ()
setup = do
	createDirectoryIfMissing True tmpDir
	writeFile testFile "test file contents"

cleanup :: IO ()
cleanup = do
	removeDirectoryRecursive tmpDir

main :: IO ()
main = do
	setup
	config <- runTests tests
	writeSysConfig config
	cleanup