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70 lines
1.2 KiB
Elm
70 lines
1.2 KiB
Elm
port module IO
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exposing
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( IO(..)
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, writeLine
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, readLine
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, readFile
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, input
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, decodeIO
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)
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import Json.Decode exposing (..)
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{-| Output a string to stdout
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-}
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port writeLine : String -> Cmd msg
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{-| Read a line from the stdin
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-}
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port readLine : String -> Cmd msg
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{-| Read the contents of a file
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-}
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port readFile : String -> Cmd msg
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{-| Received a response for a command.
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-}
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port input : (Value -> msg) -> Sub msg
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type IO
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= LineRead (Maybe String)
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| LineWritten
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| FileRead String
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| Exception String
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decodeIO : Decoder IO
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decodeIO =
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field "tag" string
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|> andThen decodeTag
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decodeTag : String -> Decoder IO
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decodeTag tag =
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case tag of
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"lineRead" ->
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field "line" (nullable string)
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|> map LineRead
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"lineWritten" ->
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succeed LineWritten
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"fileRead" ->
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field "contents" string
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|> map FileRead
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"exception" ->
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field "message" string
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|> map Exception
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_ ->
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fail <|
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"Trying to decode IO, but tag "
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++ tag
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++ " is not supported."
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