carlos / todomvc-bakeoff Public

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1	-- | The shapes the rest of the app talks in.
2	module Todo.Model
3	( ListId (..)
4	, TodoId (..)
5	, Todo (..)
6	, Filter (..)
7	, parseFilter
8	, filterName
9	, filterPath
10	, visible
11	, parseTodoId
12	, todoIdText
13	) where
14
15	import Data.Int (Int64)
16	import Data.Text (Text)
17	import Data.Text qualified as T
18	import Data.Text.Read qualified as T
19
20	-- | One visitor's list. Every query about todos is scoped by one.
21	newtype ListId = ListId Int64
22	deriving (Eq, Show)
23
24	newtype TodoId = TodoId Int64
25	deriving (Eq, Show)
26
27	data Todo = Todo
28	{ todoId :: !TodoId
29	, todoTitle :: !Text
30	, todoCompleted :: !Bool
31	}
32	deriving (Eq, Show)
33
34	data Filter = All | Active | Completed
35	deriving (Eq, Show, Enum, Bounded)
36
37	-- | The @filter@ form field. Anything missing or unknown means 'All'.
38	parseFilter :: Maybe Text -> Filter
39	parseFilter = \case
40	Just "active" -> Active
41	Just "completed" -> Completed
42	_ -> All
43
44	filterName :: Filter -> Text
45	filterName = \case
46	All -> "all"
47	Active -> "active"
48	Completed -> "completed"
49
50	filterPath :: Filter -> Text
51	filterPath = \case
52	All -> "/"
53	Active -> "/active"
54	Completed -> "/completed"
55
56	visible :: Filter -> Todo -> Bool
57	visible = \case
58	All -> const True
59	Active -> not . todoCompleted
60	Completed -> todoCompleted
61
62	-- | A todo id as it appears in a path or a query: plain decimal digits,
63	-- short enough to fit an 'Int64'.
64	parseTodoId :: Text -> Maybe TodoId
65	parseTodoId t
66	| T.null t || T.length t > 18 || not (T.all (\c -> c >= '0' && c <= '9') t) = Nothing
67	| otherwise = case T.decimal t of
68	Right (n, rest) | T.null rest -> Just (TodoId n)
69	_ -> Nothing
70
71	todoIdText :: TodoId -> Text
72	todoIdText (TodoId n) = T.pack (show n)
73