Toml.Codec.Combinator.Map

Bidirectional codec for Map. It takes birectional converter for keys and values and produces bidirectional codec for Map. Currently it works only with array of tables, so you need to specify Maps in TOML files like this:

myMap =
    [ { name = "foo", payload = 42 }
    , { name = "bar", payload = 69 }
    ]

TomlCodec for such TOML field can look like this:

Toml.map (Toml.text "name") (Toml.int "payload") "myMap"

If there's no key with the name "myMap" then empty Map is returned.

This TomlCodec helps you to convert TOML key-value pairs directly to Map using TOML keys as Map keys. It can be convenient if your Map keys are types like Text or Int and you want to work with raw TOML keys directly.

For example, if you have TOML like this:

[colours]
yellow = "#FFFF00"
red    = { red = 255, green = 0, blue = 0 }
pink   = "#FFC0CB"

You want to convert such TOML configuration into the following Haskell types:

data Rgb = Rgb
    { rgbRed   :: Int
    , rgbGreen :: Int
    , rgbBlue  :: Int
    }

data Colour
    = Hex Text
    | RGB Rgb

colourCodec :: TomlCodec Colour
colourCodec = ...

data ColourConfig = ColourConfig
    { configColours :: Map Text Colour
    }

And you want in the result to have a Map like this:

fromList
    [ "yellow" -> Hex "#FFFF00"
    , "pink"   -> Hex "#FFC0CB"
    , "red"    -> Rgb 255 0 0
    ]

You can use tableMap to define TomlCodec in the following way:

colourConfigCodec :: TomlCodec ColourConfig
colourConfigCodec = ColourConfig
    <$> Toml.tableMap Toml._KeyText colourCodec "colours" .= configColours

Hint: You can use Toml.Codec.BiMap._KeyText or Toml.Codec.BiMap._KeyString to convert betwen TOML keys and Map keys (or you can write your custom TomlBiMap).

NOTE: Unlike the map codec, this codec is less flexible (i.e. it doesn't allow to have arbitrary structures as Keys, it works only for text-like keys), but can be helpful if you want to save a few keystrokes during TOML configuration. A similar TOML configuration, but suitable for the map codec will look like this:

colours =
    [ { key = "yellow", hex = "#FFFF00" }
    , { key = "pink",   hex = "#FFC0CB" }
    , { key = "red",    rgb = { red = 255, green = 0, blue = 0 } }
    ]

Bidirectional codec for HashMap. It takes birectional converter for keys and values and produces bidirectional codec for HashMap. It works with array of tables, so you need to specify HashMaps in TOML files like this:

myHashMap =
    [ { name = "foo", payload = 42 }
    , { name = "bar", payload = 69 }
    ]

TomlCodec for such TOML field can look like this:

Toml.hashMap (Toml.text "name") (Toml.int "payload") "myHashMap"

If there's no key with the name "myHashMap" then empty HashMap is returned.

This TomlCodec helps to convert TOML key-value pairs directly to HashMap using TOML keys as HashMap keys. It can be convenient if your HashMap keys are types like Text or Int and you want to work with raw TOML keys directly.

For example, if you can write your HashMap in TOML like this:

[myHashMap]
key1 = "value1"
key2 = "value2"

Bidirectional codec for IntMap. It takes birectional converter for keys and values and produces bidirectional codec for IntMap. It works with array of tables, so you need to specify IntMaps in TOML files like this:

myIntMap =
    [ { name = "foo", payload = 42 }
    , { name = "bar", payload = 69 }
    ]

TomlCodec for such TOML field can look like this:

Toml.intMap (Toml.text "name") (Toml.int "payload") "myIntMap"

If there's no key with the name "myIntMap" then empty IntMap is returned.

This TomlCodec helps to convert TOML key-value pairs directly to IntMap using TOML Int keys as IntMap keys.

For example, if you can write your IntMap in TOML like this:

[myIntMap]
1 = "value1"
2 = "value2"