MFlow-0.2.0.7: src/MFlow/Forms.hs
{-# OPTIONS -XDeriveDataTypeable
-XUndecidableInstances
-XExistentialQuantification
-XMultiParamTypeClasses
-XTypeSynonymInstances
-XFlexibleInstances
-XScopedTypeVariables
-XFunctionalDependencies
-XFlexibleContexts
-XRecordWildCards
-XIncoherentInstances
-XTypeFamilies
-XTypeOperators
-XOverloadedStrings
#-}
{- | This module implement stateful processes (flows) that are optionally persistent.
This means that they automatically store and recover his execution state. They are executed by the MFlow app server.
defined in the "MFlow" module.
These processses interact with the user trough user interfaces made of widgets (see below) that return back statically typed responses to
the calling process. Because flows are stateful, not request-response, the code is more understandable, because
all the flow of request and responses is coded by the programmer in a single function. Allthoug
single request-response flows and callbacks are possible.
This module is abstract with respect to the formatting (here referred with the type variable @view@) . For an
instantiation for "Text.XHtml" import "MFlow.Forms.XHtml", "MFlow.Hack.XHtml.All" or "MFlow.Wai.XHtml.All" .
To use Haskell Server Pages import "MFlow.Forms.HSP". However the functionalities are documented here.
`ask` is the only method for user interaction. It run in the @MFlow view m@ monad, with @m@ the monad chosen by the user, usually IO.
It send user interfaces (in the @View view m@ monad) and return statically
typed responses. The user interface definitions are based on a extension of
formLets (<http://www.haskell.org/haskellwiki/Formlets>) with the addition of caching, links, formatting, attributes,
extra combinators, callbaks and modifiers.
The interaction with the user is stateful. In the same computation there may be many
request-response interactions, in the same way than in the case of a console applications.
* APPLICATION SERVER
Therefore, session and state management is simple and transparent: it is in the haskell
structures in the scope of the computation. `transient` (normal) procedures have no persistent session state
and `stateless` procedures accept a single request and return a single response.
`MFlow.Forms.step` is a lifting monad transformer that permit persistent server procedures that
remember the execution state even after system shutdowns by using the package workflow (<http://hackage.haskell.org/package/Workflow>) internally.
This state management is transparent. There is no programer interface for session management.
The programmer set the process timeout and the session timeout with `setTimeouts`.
If the procedure has been stopped due to the process timeout or due to a system shutdowm,
the procedure restart in the last state when a request for this procedure arrives
(if the procedure uses the `step` monad transformer)
* WIDGETS
The correctness of the web responses is assured by the use of formLets.
But unlike formLets in its current form, it permits the definition of widgets.
/A widget is a combination of formLets and links within its own formatting template/, all in
the same definition in the same source file, in plain declarative Haskell style.
The formatting is abstract. It has to implement the 'FormInput' class.
There are instances for Text.XHtml ("MFlow.Forms.XHtml"), Haskell Server Pages ("MFlow.Forms.HSP")
and ByteString. So widgets
can use any formatting that is instance of `FormInput`.
It is possible to use more than one format in the same widget.
Links defined with `wlink` are treated the same way than forms. They are type safe and return values
to the same flow of execution.
It is posssible to combine links and forms in the same widget by using applicative combinators but also
additional applicative combinators like \<+> !*> , |*|. Widgets are also monoids, so they can
be combined as such.
* NEW IN THIS RELEASE
[@WAI interface@] Now MFlow works with Snap and other WAI developments. Include "MFlow.Wai" or "MFlow.Wai.Blaze.Html.All" to use it.
[@blaze-html support@] see <http://hackage.haskell.org/package/blaze-html> import "MFlow.Forms.Blaze.Html" or "MFlow.Wai.Blaze.Html.All" to use Blaze-Html
[@AJAX@] Now an ajax procedures (defined with 'ajax' can perform many interactions with the browser widgets, instead
of a single request-response (see 'ajaxSend').
[@Active widgets@] "MFlow.Forms.Widgets" contains active widgets that interact with the
server via Ajax and dynamically control other widgets: 'wEditList', 'autocomplete' 'autocompleteEdit' and others.
[@Requirements@] a widget can specify javaScript files, JavasScript online scipts, CSS files, online CSS and server processes
and any other instance of the 'Requrement' class. See 'requires' and 'WebRequirements'
[@content-management@] for templating and online edition of the content template. See 'tFieldEd' 'tFieldGen' and 'tField'
[@multilanguage@] see 'mField' and 'mFieldEd'
[@URLs to internal states@] if the web navigation is trough GET forms or links,
an URL can express a direct path to the n-th step of a flow, So this URL can be shared with other users.
Just like in the case of an ordinary stateless application.
* NEW IN PREVIOUS RELEASE:
[@Back Button@] This is probably the first implementation in any language where the navigation
can be expressed procedurally and still it works well with the back button, thanks
to monad magic. (See <http://haskell-web.blogspot.com.es/2012/03//failback-monad.html>)
[@Cached widgets@] with `cachedWidget` it is possible to cache the rendering of a widget as a ByteString (maintaining type safety)
, the caching can be permanent or for a certain time. this is very useful for complex widgets that present information. Specially if
the widget content comes from a database and it is shared by all users.
[@Callbacks@] `waction` add a callback to a widget. It is executed when its input is validated.
The callback may initate a flow of interactions with the user or simply executes an internal computation.
Callbacks are necessary for the creation of abstract container
widgets that may not know the behaviour of its content. with callbacks, the widget manages its content as black boxes.
[@Modifiers@] `wmodify` change the visualization and result returned by the widget. For example it may hide a
login form and substitute it by the username if already logged.
Example:
@ ask $ wform userloginform \``validate`\` valdateProc \``waction`\` loginProc \``wmodify`\` hideIfLogged@
[@attributes for formLet elements@] to add atributes to widgets. See the '<!' opèrator
[@ByteString normalization and hetereogeneous formatting@] For caching the rendering of widgets at the
ByteString level, and to permit many formatring styles
in the same page, there are operators that combine different formats which are converted to ByteStrings.
For example the header and footer may be coded in XML, while the formlets may be formatted using Text.XHtml.
[@File Server@] With file caching. See "MFlow.FileServer"
-}
module MFlow.Forms(
-- * Basic definitions
-- FormLet(..),
FlowM, View(..), FormElm(..), FormInput(..)
-- * Users
,userRegister, userValidate, isLogged, setAdminUser, getAdminName
,getCurrentUser,getUserSimple, getUser, userFormLine, userLogin,logout, userWidget,getLang, login,
userName,
-- * User interaction
ask, askt, clearEnv, wstateless, transfer,
-- * formLets
-- | They usually produce the HTML form elements (depending on the FormInput instance used)
-- It is possible to modify their attributes with the `<!` operator.
-- They are combined with applicative ombinators and some additional ones
-- formatting can be added with the formatting combinators.
-- modifiers change their presentation and behaviour
getString,getInt,getInteger, getTextBox
,getMultilineText,getBool,getSelect, setOption,setSelectedOption, getPassword,
getRadio, setRadio, setRadioActive, getCheckBoxes, genCheckBoxes, setCheckBox,
submitButton,resetButton, whidden, wlink, returning, wform, firstOf, manyOf, wraw, wrender
-- * FormLet modifiers
,validate, noWidget, waction, wmodify,
-- * Caching widgets
cachedWidget, wcached, wfreeze,
-- * Widget combinators
(<+>),(|*>),(|+|), (**>),(<**),(<|>),(<*),(<$>),(<*>),(>:>)
-- * Normalized (convert to ByteString) widget combinators
-- | These dot operators are indentical to the non dot operators, with the addition of the conversion of the arguments to lazy byteStrings
--
-- The purpose is to combine heterogeneous formats into byteString-formatted widgets that
-- can be cached with `cachedWidget`
,(.<+>.), (.|*>.), (.|+|.), (.**>.),(.<**.), (.<|>.),
-- * Formatting combinators
(<<<),(<++),(++>),(<!),
-- * Normalized (convert to ByteString) formatting combinators
-- | Some combinators that convert the formatting of their arguments to lazy byteString
(.<<.),(.<++.),(.++>.)
-- * ByteString tags
,btag,bhtml,bbody
-- * Normalization
, flatten, normalize
-- * Running the flow monad
,runFlow,runFlowOnce,runFlowIn,MFlow.Forms.Internals.step, goingBack,breturn, preventGoingBack
-- * Setting parameters
,setHeader
,setSessionData
,getSessionData
,getHeader
,setTimeouts
-- * Cookies
,setCookie
-- * Ajax
,ajax
,ajaxSend
,ajaxSend_
-- * Requirements
,Requirements(..)
,WebRequirement(..)
,requires
-- * Utility
,genNewId
,changeMonad
,FailBack
,fromFailBack
,toFailBack
-- * The monster of the deep
,MFlowState
)
where
import Data.RefSerialize hiding ((<|>))
import Data.TCache
import Data.TCache.Memoization
import MFlow
import MFlow.Forms.Internals
import MFlow.Cookies
import Data.ByteString.Lazy.Char8 as B(ByteString,cons,pack,unpack,append,empty,fromChunks)
import Data.List
--import qualified Data.CaseInsensitive as CI
import Data.Typeable
import Data.Monoid
import Control.Monad.State.Strict
import Data.Maybe
import Control.Applicative
import Control.Exception
import Control.Concurrent
import Control.Workflow as WF
import Control.Monad.Identity
import Unsafe.Coerce
import Data.List(intersperse)
import Data.IORef
import qualified Data.Map as M
import System.IO.Unsafe
import Data.Char(isNumber)
import Network.HTTP.Types.Header
import Debug.Trace
(!>)= flip trace
-- | Validates a form or widget result against a validating procedure
--
-- @getOdd= getInt Nothing `validate` (\x -> return $ if mod x 2==0 then Nothing else Just "only odd numbers, please")@
validate
:: (FormInput view, Monad m) =>
View view m a
-> (a -> WState view m (Maybe view))
-> View view m a
validate formt val= View $ do
FormElm form mx <- (runView formt)
case mx of
Just x -> do
me <- val x
modify (\s -> s{inSync= True})
case me of
Just str ->
return $ FormElm ( form ++ [inred str]) Nothing
Nothing -> return $ FormElm [] mx
_ -> return $ FormElm form mx
-- | Actions are callbacks that are executed when a widget is validated.
-- It is useful when the widget is inside widget containers that know nothing about his content.
--
-- It returns a result that can be significative or, else, be ignored with '<**' and '**>'.
-- An action may or may not initiate his own dialog with the user via `ask`
waction
:: (FormInput view, Monad m)
=> View view m a
-> (a -> FlowM view m b)
-> View view m b
waction f ac = do
x <- f
s <- get
let env = mfEnv s
let seq = mfSequence s
put s{mfSequence=mfSequence s+ 100,mfEnv=[]}
r <- flowToView $ ac x
modify $ \s-> s{mfSequence= seq, mfEnv= env}
return r
where
flowToView x=
View $ do
r <- runBackT $ runFlowM x
case r of
NoBack x ->
return (FormElm [] $ Just x)
BackPoint x->
return (FormElm [] $ Just x)
GoBack-> do
modify $ \s ->s{notSyncInAction= True}
return (FormElm [] Nothing)
wmodify :: (Monad m, FormInput v)
=> View v m a
-> ([v] -> Maybe a -> WState v m ([v], Maybe b))
-> View v m b
wmodify formt act = View $ do
FormElm f mx <- runView formt
(f',mx') <- act f mx
return $ FormElm f' mx'
--
--instance (FormInput view, FormLet a m view , FormLet b m view )
-- => FormLet (a,b) m view where
-- digest mxy = do
-- let (x,y)= case mxy of Nothing -> (Nothing, Nothing); Just (x,y)-> (Just x, Just y)
-- (,) <$> digest x <*> digest y
--
--instance (FormInput view, FormLet a m view , FormLet b m view,FormLet c m view )
-- => FormLet (a,b,c) m view where
-- digest mxy = do
-- let (x,y,z)= case mxy of Nothing -> (Nothing, Nothing, Nothing); Just (x,y,z)-> (Just x, Just y,Just z)
-- (,,) <$> digest x <*> digest y <*> digest z
-- | Display a text box and return a String
getString :: (FormInput view,Monad m) =>
Maybe String -> View view m String
getString = getTextBox
-- | Display a text box and return an Integer (if the value entered is not an Integer, fails the validation)
getInteger :: (FormInput view, MonadIO m) =>
Maybe Integer -> View view m Integer
getInteger = getTextBox
-- | Display a text box and return a Int (if the value entered is not an Int, fails the validation)
getInt :: (FormInput view, MonadIO m) =>
Maybe Int -> View view m Int
getInt = getTextBox
-- | Display a password box
getPassword :: (FormInput view,
Monad m) =>
View view m String
getPassword = getParam Nothing "password" Nothing
data Radio= Radio String
-- | Implement a radio button that perform a submit when pressed.
-- the parameter is the name of the radio group
setRadioActive :: (FormInput view, MonadIO m) =>
String -> String -> View view m Radio
setRadioActive v n = View $ do
st <- get
put st{needForm= True}
let env = mfEnv st
FormElm form mn <- getParam1 n env []
return $ FormElm [finput n "radio" v
( isJust mn && v== fromJust mn) (Just "this.form.submit()")]
(fmap Radio mn)
-- | Implement a radio button
-- the parameter is the name of the radio group
setRadio :: (FormInput view, MonadIO m) =>
String -> String -> View view m Radio
setRadio v n= View $ do
st <- get
put st{needForm= True}
let env = mfEnv st
FormElm f mn <- getParam1 n env []
return $ FormElm
(f++[finput n "radio" v
( isJust mn && v== fromJust mn) Nothing])
(fmap Radio mn)
getRadio
:: (Monad m, Functor m, FormInput view) =>
[String -> View view m Radio] -> View view m String
getRadio rs= do
id <- genNewId
Radio r <- firstOf $ map (\r -> r id) rs
return r
data CheckBoxes = CheckBoxes [String]
instance Monoid CheckBoxes where
mappend (CheckBoxes xs) (CheckBoxes ys)= CheckBoxes $ xs ++ ys
mempty= CheckBoxes []
--instance (Monad m, Functor m) => Monoid (View v m CheckBoxes) where
-- mappend x y= mappend <$> x <*> y
-- mempty= return (CheckBoxes [])
instance (Monad m, Functor m, Monoid a) => Monoid (View v m a) where
mappend x y = mappend <$> x <*> y -- beware that both operands must validate to generate a sum
mempty= return mempty
-- | Display a text box and return the value entered if it is readable( Otherwise, fail the validation)
setCheckBox :: (FormInput view, MonadIO m) =>
Bool -> String -> View view m CheckBoxes
setCheckBox checked v= View $ do
n <- genNewId
st <- get
put st{needForm= True}
let env = mfEnv st
strs= map snd $ filter ((==) n . fst) env
mn= if null strs then Nothing else Just $ head strs
val <- gets inSync
let ret= case val of
True -> Just $ CheckBoxes strs
False -> Nothing
return $ FormElm
( [ finput n "checkbox" v
( checked || (isJust mn && v== fromJust mn)) Nothing])
ret
-- | Read the checkboxes dinamically created by JavaScript within the view parameter
-- see for example `selectAutocomplete` in "MFlow.Forms.Widgets"
genCheckBoxes :: (Monad m, FormInput view) => view -> View view m CheckBoxes
genCheckBoxes v= View $ do
n <- genNewId
st <- get
put st{needForm= True}
let env = mfEnv st
strs= map snd $ filter ((==) n . fst) env
mn= if null strs then Nothing else Just $ head strs
val <- gets inSync
let ret= case val of
True -> Just $ CheckBoxes strs
False -> Nothing
return $ FormElm [ftag "span" v `attrs`[("id",n)]] ret
whidden :: (Monad m, FormInput v,Read a, Show a, Typeable a) => a -> View v m a
whidden x= View $ do
n <- genNewId
env <- gets mfEnv
let showx= case cast x of
Just x' -> x'
Nothing -> show x
getParam1 n env [finput n "hidden" showx False Nothing]
getCheckBoxes ::(FormInput view, Monad m)=> View view m CheckBoxes -> View view m [String]
getCheckBoxes boxes = View $ do
n <- genNewId
env <- gets mfEnv
FormElm form (mr :: Maybe String) <- getParam1 n env [finput n "hidden" "" False Nothing]
st <- get
let env = mfEnv st
put st{needForm= True}
FormElm form2 mr2 <- runView boxes
return $ FormElm (form ++ form2) $
case (mr,mr2) of
(Nothing,_) -> Nothing
(Just _,Nothing) -> Just []
(Just _, Just (CheckBoxes rs)) -> Just rs
getTextBox
:: (FormInput view,
Monad m,
Typeable a,
Show a,
Read a) =>
Maybe a -> View view m a
getTextBox ms = getParam Nothing "text" ms
getParam
:: (FormInput view,
Monad m,
Typeable a,
Show a,
Read a) =>
Maybe String -> String -> Maybe a -> View view m a
getParam look type1 mvalue = View $ do
tolook <- case look of
Nothing -> genNewId
Just n -> return n
let nvalue= case mvalue of
Nothing -> ""
Just v ->
case cast v of
Just v' -> v'
Nothing -> show v
-- let typev= typeOf v
-- in if typev==typeOf (undefined :: String) then unsafeCoerce v
-- else if typev==typeOf (undefined :: String) then unsafeCoerce v
-- else if typev==typeOf (undefined :: ByteString) then unsafeCoerce v
-- else show v
form= [finput tolook type1 nvalue False Nothing]
st <- get
let env = mfEnv st
put st{needForm= True}
getParam1 tolook env form
-- | Generate a new string. Useful for creating tag identifiers and other attributes
genNewId :: MonadState (MFlowState view) m => m String
genNewId= do
st <- get
case mfCached st of
False -> do
let n= mfSequence st
put $ st{mfSequence= n+1}
return $ 'p':(show n)
True -> do
let n = mfSeqCache st
put $ st{mfSeqCache=n+1}
return $ 'c' : (show n)
getCurrentName :: MonadState (MFlowState view) m => m String
getCurrentName= do
st <- get
let parm = mfSequence st
return $ "p"++show parm
-- | Display a multiline text box and return its content
getMultilineText :: (FormInput view,
Monad m) =>
String -> View view m String
getMultilineText nvalue = View $ do
tolook <- genNewId
env <- gets mfEnv
let form= [ftextarea tolook nvalue]
getParam1 tolook env form
--instance (MonadIO m, Functor m, FormInput view) => FormLet Bool m view where
-- digest mv = getBool b "True" "False"
-- where
-- b= case mv of
-- Nothing -> Nothing
-- Just bool -> Just $ case bool of
-- True -> "True"
-- False -> "False"
-- | Display a dropdown box with the two values (second (true) and third parameter(false))
-- . With the value of the first parameter selected.
getBool :: (FormInput view,
Monad m) =>
Bool -> String -> String -> View view m Bool
getBool mv truestr falsestr= View $ do
tolook <- genNewId
st <- get
let env = mfEnv st
put st{needForm= True}
r <- getParam1 tolook env $ [fselect tolook(foption1 truestr mv `mappend` foption1 falsestr (not mv))]
return $ fmap fromstr r
-- case mx of
-- Nothing -> return $ FormElm f Nothing
-- Just x -> return . FormElm f $ fromstr x
where
fromstr x= if x== truestr then True else False
-- | Display a dropdown box with the options in the first parameter is optionally selected
-- . It returns the selected option.
getSelect :: (FormInput view,
Monad m,Typeable a, Read a) =>
View view m (MFOption a) -> View view m a
getSelect opts = View $ do
tolook <- genNewId
st <- get
let env = mfEnv st
put st{needForm= True}
FormElm form mr <- (runView opts)
getParam1 tolook env [fselect tolook $ mconcat form]
data MFOption a= MFOption
instance (Monad m, Functor m) => Monoid (View view m (MFOption a)) where
mappend = (<|>)
mempty = Control.Applicative.empty
-- | Set the option for getSelect. Options are concatenated with `<|>`
setOption n v = setOption1 n v False
-- | Set the selected option for getSelect. Options are concatenated with `<|>`
setSelectedOption n v= setOption1 n v True
setOption1 :: (FormInput view,
Monad m, Typeable a, Show a) =>
a -> view -> Bool -> View view m (MFOption a)
setOption1 nam val check= View $ do
st <- get
let env = mfEnv st
put st{needForm= True}
let n= if typeOf nam== typeOf(undefined :: String) then unsafeCoerce nam else show nam
return . FormElm [foption n val check] $ Just MFOption
-- | Enclose Widgets within some formating.
-- @view@ is intended to be instantiated to a particular format
--
-- This is a widget, which is a table with some links. it returns an Int
--
-- it has a infix priority : @infixr 5@ less than '++>' so use parenthesis when appropriate
--
-- > import MFlow.Forms.Blaze.Html
-- >
-- > tableLinks :: View Html Int
-- > table ! At.style "border:1;width:20%;margin-left:auto;margin-right:auto"
-- > <<< caption << text "choose an item"
-- > ++> thead << tr << ( th << b << text "item" <> th << b << text "times chosen")
-- > ++> (tbody
-- > <<< tr ! rowspan "2" << td << linkHome
-- > ++> (tr <<< td <<< wlink IPhone (b << text "iphone") <++ td << ( b << text (fromString $ show ( cart V.! 0)))
-- > <|> tr <<< td <<< wlink IPod (b << text "ipad") <++ td << ( b << text (fromString $ show ( cart V.! 1)))
-- > <|> tr <<< td <<< wlink IPad (b << text "ipod") <++ td << ( b << text (fromString $ show ( cart V.! 2))))
-- > )
(<<<) :: (Monad m, Monoid view)
=> (view ->view)
-> View view m a
-> View view m a
(<<<) v form= View $ do
FormElm f mx <- runView form
return $ FormElm [v $ mconcat f] mx
infixr 5 <<<
-- | Useful for the creation of pages using two or more views.
-- For example 'HSP' and 'Html'.
-- Because both have ConvertTo instances to ByteString, then it is possible
-- to mix them via 'normalize':
--
-- > normalize widget <+> normalize widget'
--
-- is equivalent to
--
-- > widget .<+>. widget'
-- | Append formatting code to a widget
--
-- @ getString "hi" <++ H1 << "hi there"@
--
-- It has a infix prority: @infixr 6@ higuer that '<<<' and most other operators
(<++) :: (Monad m)
=> View v m a
-> v
-> View v m a
(<++) form v= View $ do
FormElm f mx <- runView form
return $ FormElm ( f ++ [ v]) mx
infixr 6 <++ , .<++. , ++> , .++>.
-- | Prepend formatting code to a widget
--
-- @bold << "enter name" ++> getString Nothing @
--
-- It has a infix prority: @infixr 6@ higuer that '<<<' and most other operators
(++>) :: (Monad m, Monoid view)
=> view -> View view m a -> View view m a
html ++> digest = (html `mappend`) <<< digest
-- | Add attributes to the topmost tag of a widget
--
-- it has a fixity @infix 8@
infix 8 <!
widget <! attribs= View $ do
FormElm fs mx <- runView widget
return $ FormElm (head fs `attrs` attribs:tail fs) mx
-- case fs of
-- [hfs] -> return $ FormElm [hfs `attrs` attribs] mx
-- _ -> error $ "operator <! : malformed widget: "++ concatMap (unpack. toByteString) fs
-- | Is an example of login\/register validation form needed by 'userWidget'. In this case
-- the form field appears in a single line. it shows, in sequence, entries for the username,
-- password, a button for loging, a entry to repeat password necesary for registering
-- and a button for registering.
-- The user can build its own user login\/validation forms by modifying this example
--
-- @ userFormLine=
-- (User \<\$\> getString (Just \"enter user\") \<\*\> getPassword \<\+\> submitButton \"login\")
-- \<\+\> fromStr \" password again\" \+\> getPassword \<\* submitButton \"register\"
-- @
userFormLine :: (FormInput view, Functor m, Monad m)
=> View view m (Maybe (UserStr,PasswdStr), Maybe PasswdStr)
userFormLine=
((,) <$> getString (Just "enter user") <! [("size","5")]
<*> getPassword <! [("size","5")]
<** submitButton "login")
<+> (fromStr " password again" ++> getPassword <! [("size","5")]
<* submitButton "register")
-- | Example of user\/password form (no validation) to be used with 'userWidget'
userLogin :: (FormInput view, Functor m, Monad m)
=> View view m (Maybe (UserStr,PasswdStr), Maybe String)
userLogin=
((,) <$> fromStr "Enter User: " ++> getString Nothing <! [("size","4")]
<*> fromStr " Enter Pass: " ++> getPassword <! [("size","4")]
<** submitButton "login")
<+> (noWidget
<* noWidget)
-- | Empty widget that return Nothing. May be used as \"empty boxes\" inside larger widgets
noWidget :: (FormInput view,
Monad m) =>
View view m a
noWidget= View . return $ FormElm [] Nothing
-- | Render a Show-able value and return it
wrender
:: (Monad m, Functor m, Show a, FormInput view) =>
a -> View view m a
wrender x = (fromStr $ show x) ++> return x
-- | Render raw view formatting. It is useful for displaying information
wraw :: Monad m => view -> View view m ()
wraw x= View . return . FormElm [x] $ Just ()
-- | Wether the user is logged or is anonymous
isLogged :: MonadState (MFlowState v) m => m Bool
isLogged= do
rus <- return . tuser =<< gets mfToken
return . not $ rus == anonymous
-- | It creates a widget for user login\/registering. If a user name is specified
-- in the first parameter, it is forced to login\/password as this specific user.
-- If this user was already logged, the widget return the user without asking.
-- If the user press the register button, the new user-password is registered and the
-- user logged.
userWidget :: ( MonadIO m, Functor m
, FormInput view)
=> Maybe String
-> View view m (Maybe (UserStr,PasswdStr), Maybe String)
-> View view m String
userWidget muser formuser= do
user <- getCurrentUser
if muser== Just user || isNothing muser && user/= anonymous
then return user
else formuser `validate` val muser `waction` login1
where
val _ (Nothing,_) = return . Just $ fromStr "Plese fill in the user/passwd to login, or user/passwd/passwd to register"
val mu (Just us, Nothing)=
if isNothing mu || isJust mu && fromJust mu == fst us
then userValidate us
else return . Just $ fromStr "wrong user for the operation"
val mu (Just us, Just p)=
if isNothing mu || isJust mu && fromJust mu == fst us
then if length p > 0 && snd us== p
then return Nothing
else return . Just $ fromStr "The passwords do not match"
else return . Just $ fromStr "wrong user for the operation"
-- val _ _ = return . Just $ fromStr "Please fill in the fields for login or register"
login1
:: (MonadIO m, MonadState (MFlowState view) m) =>
(Maybe (String, String), Maybe String) -> m String
login1 (Just (uname,_), Nothing)= login uname >> return uname
login1 (Just us@(u,p), Just _)= do -- register button pressed
userRegister u p
login u
return u
-- | change the user
--
-- It is supposed that the user has been validated
login uname= do
st <- get
let t = mfToken st
u = tuser t
if u== uname then return () else do
let t'= t{tuser= uname}
moveState (twfname t) t t'
put st{mfToken= t'}
liftIO $ deleteTokenInList t
liftIO $ addTokenToList t'
setCookie cookieuser uname "/" (Just $ 365*24*60*60)
return ()
-- | logout. The user is resetted to the `anonymous` user
logout :: (MonadIO m, MonadState (MFlowState view) m) => m ()
logout= do
st <- get
let t = mfToken st
t'= t{tuser= anonymous}
moveState (twfname t) t t'
put st{mfToken= t'}
liftIO $ deleteTokenInList t
liftIO $ addTokenToList t'
setCookie cookieuser anonymous "/" (Just $ -1000)
-- | If not logged, perform login. otherwise return the user
--
-- @getUserSimple= getUser Nothing userFormLine@
getUserSimple :: ( FormInput view, Typeable view)
=> FlowM view IO String
getUserSimple= getUser Nothing userFormLine
-- | Very basic user authentication. The user is stored in a cookie.
-- it looks for the cookie. If no cookie, it ask to the user for a `userRegister`ed
-- user-password combination.
-- The user-password combination is only asked if the user has not logged already
-- otherwise, the stored username is returned.
--
-- @getUser mu form= ask $ userWidget mu form@
getUser :: ( FormInput view, Typeable view)
=> Maybe String
-> View view IO (Maybe (UserStr,PasswdStr), Maybe String)
-> FlowM view IO String
getUser mu form= ask $ userWidget mu form
-- | Join two widgets in the same page
-- the resulting widget, when `ask`ed with it, return a 2 tuple of their validation results
-- if both return Noting, the widget return @Nothing@ (invalid).
--
-- it has a low infix priority: @infixr 2@
--
-- > r <- ask widget1 <+> widget2
-- > case r of (Just x, Nothing) -> ..
(<+>) , mix :: Monad m
=> View view m a
-> View view m b
-> View view m (Maybe a, Maybe b)
mix digest1 digest2= View $ do
FormElm f1 mx' <- runView digest1
FormElm f2 my' <- runView digest2
return $ FormElm (f1++f2)
$ case (mx',my') of
(Nothing, Nothing) -> Nothing
other -> Just other
infixr 2 <+>, .<+>.
(<+>) = mix
-- | The first elem result (even if it is not validated) is discarded, and the secod is returned
-- . This contrast with the applicative operator '*>' which fails the whole validation if
-- the validation of the first elem fails.
--
-- The first element is displayed however, as happens in the case of '*>' .
--
-- Here @w\'s@ are widgets and @r\'s@ are returned values
--
-- @(w1 <* w2)@ will return @Just r1@ only if w1 and w2 are validated
--
-- @(w1 <** w2)@ will return @Just r1@ even if w2 is not validated
--
-- it has a low infix priority: @infixr 1@
(**>) :: (Functor m, Monad m)
=> View view m a -> View view m b -> View view m b
(**>) form1 form2 = valid form1 *> form2
infixr 1 **> , .**>. , <** , .<**.
-- | The second elem result (even if it is not validated) is discarded, and the first is returned
-- . This contrast with the applicative operator '*>' which fails the whole validation if
-- the validation of the second elem fails.
-- The second element is displayed however, as in the case of '<*'.
-- see the `<**` examples
--
-- it has a low infix priority: @infixr 1@
(<**)
:: (Functor m, Monad m) =>
View view m a -> View view m b -> View view m a
(<**) form1 form2 = form1 <* valid form2
valid form= View $ do
FormElm form mx <- runView form
return $ FormElm form $ Just undefined
-- | for compatibility with the same procedure in 'MFLow.Forms.Text.askt'.
-- This is the non testing version
--
-- > askt v w= ask w
--
-- hide one or the other
askt :: FormInput v => (Int -> a) -> View v IO a -> FlowM v IO a
askt v w = ask w
-- | It is the way to interact with the user.
-- It takes a widget and return the user result.
--
-- If the widget is not validated (return @Nothing@), the page is presented again
--
-- If the environment has the parameters being looked at, as a result of a previous interaction,
-- it will not ask to the user.
-- To force asking in any case, put an `clearEnv` statement before
ask
:: (FormInput view) =>
View view IO a -> FlowM view IO a
ask w = do
st1 <- get
let env= mfEnv st1
let mv1= lookup "ajax" env
let majax1= mfAjax st1
case (majax1,mv1,M.lookup (fromJust mv1)(fromJust majax1), lookup "val" env) of
(Just ajaxl,Just v1,Just f, Just v2) -> do
FlowM . lift $ (unsafeCoerce f) v2
FlowM $ lift receiveWithTimeouts
ask w
_ -> do
let st= st1{needForm= False, inSync= False, mfRequirements= []}
put st
FormElm forms mx <- FlowM . lift $ runView w
st' <- get
if notSyncInAction st' then put st'{notSyncInAction=False}>> ask w else
case mx of
Just x -> do
put st'{prevSeq= mfSequence st: prevSeq st',onInit= True ,mfEnv=[]}
breturn x -- !> "just x"
Nothing ->
if not (inSync st') && not (onInit st') && hasParams (mfSequence st') (mfSeqCache st') ( mfEnv st') -- !> (show $ inSync st') !> (show $ onInit st')
then do
put st'{ mfSequence= head1 $ prevSeq st',
prevSeq= tail1 $ prevSeq st' }
fail ""
else do
reqs <- FlowM $ lift installAllRequirements
let header= mfHeader st'
t= mfToken st'
cont = case (needForm st') of
True -> header $ reqs <> (formAction (twfname t ) $ mconcat forms)
_ -> header $ reqs <> mconcat forms
HttpData ctype c s= toHttpData cont
liftIO . sendFlush t $ HttpData (ctype++mfHttpHeaders st') (mfCookies st' ++ c) s
put st{mfCookies=[],mfHttpHeaders=[], onInit= False, mfToken= t, mfAjax= mfAjax st', mfSeqCache= mfSeqCache st' } -- !> ("after "++show ( mfSequence st'))
FlowM $ lift receiveWithTimeouts
ask w
where
head1 []=0
head1 xs= head xs
tail1 []=[]
tail1 xs= tail xs
hasParams seq cseq= not . null . filter (\(p,_) ->
let tailp = tail p
in and (map isNumber tailp) &&
let rt= read tailp
in case head p of
'p' -> rt <= seq
'c' -> rt <= cseq
_ -> False)
-- (head p== 'p' || head p == 'c')
-- && and (map isNumber tailp)
-- && read tailp <= seq)
-- | True if the flow is going back (as a result of the back button pressed in the web browser).
-- Usually this chech is nos necessary unless conditional code make it necessary
--
-- @menu= do
-- mop <- getGoStraighTo
-- case mop of
-- Just goop -> goop
-- Nothing -> do
-- r \<- `ask` option1 \<|> option2
-- case r of
-- op1 -> setGoStraighTo (Just goop1) >> goop1
-- op2 -> setGoStraighTo (Just goop2) >> goop2@
--
-- This pseudocode below would execute the ask of the menu once. But the user will never have
-- the possibility to see the menu again. To let him choose other option, the code
-- has to be change to
--
-- @menu= do
-- mop <- getGoStraighTo
-- back <- `goingBack`
-- case (mop,back) of
-- (Just goop,False) -> goop
-- _ -> do
-- r \<- `ask` option1 \<|> option2
-- case r of
-- op1 -> setGoStraighTo (Just goop1) >> goop1
-- op2 -> setGoStraighTo (Just goop2) >> goop2@
--
-- However this is very specialized. Normally the back button detection is not necessary.
-- In a persistent flow (with step) even this default entry option would be completely automatic,
-- since the process would restar at the last page visited. No setting is necessary.
goingBack :: MonadState (MFlowState view) m => m Bool
goingBack = do
st <- get
return $ not (inSync st) && not (onInit st)
-- | Will prevent the backtrack beyond the point where 'preventGoingBack' is located.
-- If the user press the back button beyond that point, the flow parameter is executed, usually
-- it is an ask statement with a message. If the flow is not going back, it does nothing. It is a cut in backtracking
--
-- It is useful when an undoable transaction has been commited. For example, after a payment.
--
-- This example show a message when the user go back and press again to pay
--
-- > ask $ wlink () << b << "press here to pay 100000 $ "
-- > payIt
-- > preventGoingBack . ask $ b << "You paid 10000 $ one time"
-- > ++> wlink () << b << " Please press here to complete the proccess"
-- > ask $ wlink () << b << "OK, press here to go to the menu or press the back button to verify that you can not pay again"
-- > where
-- > payIt= liftIO $ print "paying"
preventGoingBack
:: (Functor m, MonadIO m, FormInput v) => FlowM v m () -> FlowM v m ()
preventGoingBack msg= do
back <- goingBack
if not back then breturn() else do
clearEnv
msg
breturn()
receiveWithTimeouts :: MonadIO m => WState view m ()
receiveWithTimeouts= do
st <- get
let t= mfToken st
t1= mfkillTime st
t2= mfSessionTime st
req <- return . getParams =<< liftIO ( receiveReqTimeout t1 t2 t)
put st{mfEnv= req}
-- | Creates a stateless flow (see `stateless`) whose behaviour is defined as a widget. It is a
-- higuer level form of the latter
wstateless
:: (Typeable view, FormInput view) =>
View view IO a -> Flow
wstateless w = transient $ runFlow loop
where
loop= do
ask w
env <- get
put $ env{ mfSequence= 0,prevSeq=[]}
loop
---- This version writes a log with all the values returned by ask
--wstatelessLog
-- :: (Typeable view, ToHttpData view, FormInput view,Serialize a,Typeable a) =>
-- View view IO a -> (Token -> Workflow IO ())
--wstatelessLog w = runFlow loop
-- where
-- loop= do
-- MFlow.Forms.step $ do
-- r <- ask w
-- env <- get
-- put $ env{ mfSequence= 0,prevSeq=[]}
-- return r
-- loop
-- | transfer control to another flow.
transfer :: MonadIO m => String -> FlowM v m ()
transfer flowname =do
t <- gets mfToken
let t'= t{twfname= flowname}
liftIO $ do
(r,_) <- msgScheduler t'
sendFlush t r
-- | Wrap a widget of form element within a form-action element.
---- Usually this is not necessary since this wrapping is done automatically by the @Wiew@ monad.
wform :: (Monad m, FormInput view)
=> View view m b -> View view m b
wform x = View $ do
FormElm form mr <- (runView $ x )
st <- get
let t = mfToken st
anchor <- genNewId
put st{needForm=False}
let anchorf= (ftag "a") mempty `attrs` [("name",anchor)]
let form1= formAction (twfname t {-++"#"++anchor-}) $ mconcat ( anchorf:form) -- !> anchor
return $ FormElm [form1] mr
resetButton :: (FormInput view, Monad m) => String -> View view m ()
resetButton label= View $ return $ FormElm [finput "reset" "reset" label False Nothing] $ Just ()
submitButton :: (FormInput view, Monad m) => String -> View view m String
submitButton label= getParam Nothing "submit" $ Just label
newtype AjaxSessionId= AjaxSessionId String deriving Typeable
-- | Install the server code and return the client code for an AJAX interaction.
--
-- This example increases the value of a text box each time the box is clicked
--
-- > ask $ do
-- > let elemval= "document.getElementById('text1').value"
-- > ajaxc <- ajax $ \n -> return $ elemval <> "='" <> B.pack(show(read n +1)) <> "'"
-- > b << text "click the box"
-- > ++> getInt (Just 0) <! [("id","text1"),("onclick", ajaxc elemval)]
ajax :: (MonadIO m)
=> (String -> View v m ByteString) -- ^ user defined procedure, executed in the server.Receives the value of the javascript expression and must return another javascript expression that will be executed in the web browser
-> View v m (String -> String) -- ^ returns a function that accept a javascript expression and return a javascript event handler expression that invoques the ajax server procedure
ajax f = do
requires[JScript ajaxScript]
t <- gets mfToken
id <- genNewId
installServerControl id $ \x-> do
setSessionData $ AjaxSessionId id
r <- f x
liftIO $ sendFlush t (HttpData [("Content-Type", "text/plain")][] r )
return ()
installServerControl :: MonadIO m => String -> (String -> View v m ()) -> View v m (String -> String)
installServerControl id f= do
t <- gets mfToken
st <- get
let ajxl = fromMaybe M.empty $ mfAjax st
let ajxl'= M.insert id (unsafeCoerce f ) ajxl
put st{mfAjax=Just ajxl'}
return $ \param -> "doServer("++"'" ++ twfname t ++"','"++id++"',"++ param++")"
-- | Send the javascript expression, generated by the procedure parameter as a ByteString, execute it in the browser and the result is returned back
--
-- The @ajaxSend@ invocation must be inside a ajax procedure or else a /No ajax session set/ error will be produced
ajaxSend
:: (Read a,MonadIO m) => View v m ByteString -> View v m a
ajaxSend cmd= View $ do
AjaxSessionId id <- getSessionData `onNothing` error "no AjaxSessionId set"
env <- getEnv
t <- getToken
case (lookup "ajax" $ env, lookup "val" env) of
(Nothing,_) -> return $ FormElm [] Nothing
(Just id, Just _) -> do
FormElm __ (Just str) <- runView cmd
liftIO $ sendFlush t $ HttpData [("Content-Type", "text/plain")][] $ str <> readEvalLoop t id "''"
receiveWithTimeouts
env <- getEnv
case (lookup "ajax" $ env,lookup "val" env) of
(Nothing,_) -> return $ FormElm [] Nothing
(Just id, Just v2) -> do
return $ FormElm [] . Just $ read v2
where
readEvalLoop t id v = "doServer('"<> pack (twfname t)<>"','"<> pack id<>"',"<>v<>");" :: ByteString
-- | Like @ajaxSend@ but the result is ignored
ajaxSend_
:: MonadIO m => View v m ByteString -> View v m ()
ajaxSend_ = ajaxSend
-- | Creates a link wiget. A link can be composed with other widget elements,
wlink :: (Typeable a, Read a, Show a, MonadIO m, Functor m, FormInput view)
=> a -> view -> View view m a
wlink x v= View $ do
verb <- getWFName
name <- genNewId
env <- gets mfEnv
let
showx= if typeOf x== typeOf (undefined :: String) then unsafeCoerce x else show x
toSend = flink (verb ++ "?" ++ name ++ "=" ++ showx) v
getParam1 name env [toSend]
-- | When some user interface int return some response to the server, but it is not produced by
-- a form or a link, but for example by an script, @returning@ notify the type checker.
--
-- At runtime the parameter is read from the environment and validated.
--
-- . The parameter is the visualization code, that accept a serialization function that generate
-- the server invocation string, used by the visualization to return the value by means
-- of a link or a @window.location@ statement in javasCript
returning ::(Typeable a, Read a, Show a,Monad m, FormInput view)
=> ((a->String) ->view) -> View view m a
returning expr=View $ do
verb <- getWFName
name <- genNewId
env <- gets mfEnv
let string x=
let showx= case cast x of
Just x' -> x'
_ -> show x
in (verb ++ "?" ++ name ++ "=" ++ showx)
toSend= expr string
getParam1 name env [toSend]
--instance (Widget a b m view, Monoid view) => Widget [a] b m view where
-- widget xs = View $ do
-- forms <- mapM(\x -> (runView $ widget x )) xs
-- let vs = concatMap (\(FormElm v _) -> v) forms
-- res = filter isJust $ map (\(FormElm _ r) -> r) forms
-- res1= if null res then Nothing else head res
-- return $ FormElm [mconcat vs] res1
-- | Concat a list of widgets of the same type, return a the first validated result
firstOf :: (Monoid view, Monad m, Functor m)=> [View view m a] -> View view m a
firstOf xs= View $ do
forms <- mapM runView xs
let vs = concatMap (\(FormElm v _) -> [mconcat v]) forms
res = filter isJust $ map (\(FormElm _ r) -> r) forms
res1= if null res then Nothing else head res
return $ FormElm vs res1
-- | from a list of widgets, it return the validated ones.
manyOf :: (FormInput view, MonadIO m, Functor m)=> [View view m a] -> View view m [a]
manyOf xs= whidden () *> (View $ do
forms <- mapM runView xs
let vs = concatMap (\(FormElm v _) -> [mconcat v]) forms
res1= catMaybes $ map (\(FormElm _ r) -> r) forms
return $ FormElm vs $ Just res1)
(>:>) ::(Monad m)=> View v m a -> View v m [a] -> View v m [a]
(>:>) w ws= View $ do
FormElm fs mxs <- runView $ ws
FormElm f1 mx <- runView w
return $ FormElm (f1++ fs)
$ case( mx,mxs) of
(Just x, Just xs) -> Just $ x:xs
(Nothing, mxs) -> mxs
(Just x, _) -> Just [x]
-- | Intersperse a widget in a list of widgets. the results is a 2-tuple of both types.
--
-- it has a infix priority @infixr 5@
(|*>) :: (MonadIO m, Functor m,Monoid view)
=> View view m r
-> [View view m r']
-> View view m (Maybe r,Maybe r')
(|*>) x xs= View $ do
FormElm fxs rxs <- runView $ firstOf xs
FormElm fx rx <- runView $ x
return $ FormElm (fx ++ intersperse (mconcat fx) fxs ++ fx)
$ case (rx,rxs) of
(Nothing, Nothing) -> Nothing
other -> Just other
infixr 5 |*>, .|*>.
-- | Put a widget before and after other. Useful for navigation links in a page that appears at toAdd
-- and at the bottom of a page.
-- It has a low infix priority: @infixr 1@
(|+|) :: (Functor m, Monoid view, MonadIO m)
=> View view m r
-> View view m r'
-> View view m (Maybe r, Maybe r')
(|+|) w w'= w |*> [w']
infixr 1 |+|, .|+|.
-- | Flatten a binary tree of tuples of Maybe results produced by the \<+> operator
-- into a single tuple with the same elements in the same order.
-- This is useful for easing matching. For example:
--
-- @ res \<- ask $ wlink1 \<+> wlink2 wform \<+> wlink3 \<+> wlink4@
--
-- @res@ has type:
--
-- @Maybe (Maybe (Maybe (Maybe (Maybe a,Maybe b),Maybe c),Maybe d),Maybe e)@
--
-- but @flatten res@ has type:
--
-- @ (Maybe a, Maybe b, Maybe c, Maybe d, Maybe e)@
flatten :: Flatten (Maybe tree) list => tree -> list
flatten res= doflat $ Just res
class Flatten tree list where
doflat :: tree -> list
type Tuple2 a b= Maybe (Maybe a, Maybe b)
type Tuple3 a b c= Maybe ( (Tuple2 a b), Maybe c)
type Tuple4 a b c d= Maybe ( (Tuple3 a b c), Maybe d)
type Tuple5 a b c d e= Maybe ( (Tuple4 a b c d), Maybe e)
type Tuple6 a b c d e f= Maybe ( (Tuple5 a b c d e), Maybe f)
instance Flatten (Tuple2 a b) (Maybe a, Maybe b) where
doflat (Just(ma,mb))= (ma,mb)
doflat Nothing= (Nothing,Nothing)
instance Flatten (Tuple3 a b c) (Maybe a, Maybe b,Maybe c) where
doflat (Just(mx,mc))= let(ma,mb)= doflat mx in (ma,mb,mc)
doflat Nothing= (Nothing,Nothing,Nothing)
instance Flatten (Tuple4 a b c d) (Maybe a, Maybe b,Maybe c,Maybe d) where
doflat (Just(mx,mc))= let(ma,mb,md)= doflat mx in (ma,mb,md,mc)
doflat Nothing= (Nothing,Nothing,Nothing,Nothing)
instance Flatten (Tuple5 a b c d e) (Maybe a, Maybe b,Maybe c,Maybe d,Maybe e) where
doflat (Just(mx,mc))= let(ma,mb,md,me)= doflat mx in (ma,mb,md,me,mc)
doflat Nothing= (Nothing,Nothing,Nothing,Nothing,Nothing)
instance Flatten (Tuple6 a b c d e f) (Maybe a, Maybe b,Maybe c,Maybe d,Maybe e,Maybe f) where
doflat (Just(mx,mc))= let(ma,mb,md,me,mf)= doflat mx in (ma,mb,md,me,mf,mc)
doflat Nothing= (Nothing,Nothing,Nothing,Nothing,Nothing,Nothing)
infixr 7 .<<.
-- | > (.<<.) w x = w $ toByteString x
(.<<.) :: (FormInput view) => (ByteString -> ByteString) -> view -> ByteString
(.<<.) w x = w ( toByteString x)
-- | > (.<+>.) x y = normalize x <+> normalize y
(.<+>.)
:: (Monad m, FormInput v, FormInput v1) =>
View v m a -> View v1 m b -> View ByteString m (Maybe a, Maybe b)
(.<+>.) x y = normalize x <+> normalize y
-- | > (.|*>.) x y = normalize x |*> map normalize y
(.|*>.)
:: (Functor m, MonadIO m, FormInput v, FormInput v1) =>
View v m r
-> [View v1 m r'] -> View ByteString m (Maybe r, Maybe r')
(.|*>.) x y = normalize x |*> map normalize y
-- | > (.|+|.) x y = normalize x |+| normalize y
(.|+|.)
:: (Functor m, MonadIO m, FormInput v, FormInput v1) =>
View v m r -> View v1 m r' -> View ByteString m (Maybe r, Maybe r')
(.|+|.) x y = normalize x |+| normalize y
-- | > (.**>.) x y = normalize x **> normalize y
(.**>.)
:: (Monad m, Functor m, FormInput v, FormInput v1) =>
View v m a -> View v1 m b -> View ByteString m b
(.**>.) x y = normalize x **> normalize y
-- | > (.<**.) x y = normalize x <** normalize y
(.<**.)
:: (Monad m, Functor m, FormInput v, FormInput v1) =>
View v m a -> View v1 m b -> View ByteString m a
(.<**.) x y = normalize x <** normalize y
-- | > (.<|>.) x y= normalize x <|> normalize y
(.<|>.)
:: (Monad m, Functor m, FormInput v, FormInput v1) =>
View v m a -> View v1 m a -> View ByteString m a
(.<|>.) x y= normalize x <|> normalize y
-- | > (.<++.) x v= normalize x <++ toByteString v
(.<++.) :: (Monad m, FormInput v, FormInput v') => View v m a -> v' -> View ByteString m a
(.<++.) x v= normalize x <++ toByteString v
-- | > (.++>.) v x= toByteString v ++> normalize x
(.++>.) :: (Monad m, FormInput v, FormInput v') => v -> View v' m a -> View ByteString m a
(.++>.) v x= toByteString v ++> normalize x
instance FormInput ByteString where
toByteString= id
toHttpData = HttpData [contentHtml ] []
ftag x= btag x []
inred = btag "b" [("style", "color:red")]
finput n t v f c= btag "input" ([("type", t) ,("name", n),("value", v)] ++ if f then [("checked","true")] else []
++ case c of Just s ->[( "onclick", s)]; _ -> [] ) ""
ftextarea name text= btag "textarea" [("name", name)] $ pack text
fselect name options= btag "select" [("name", name)] options
foption value content msel= btag "option" ([("value", value)] ++ selected msel) content
where
selected msel = if msel then [("selected","true")] else []
attrs = addAttrs
formAction action form = btag "form" [("action", action),("method", "post")] form
fromStr = pack
fromStrNoEncode= pack
flink v str = btag "a" [("href", v)] str