(.using
  [library
   [lux {"-" Alias}
    ["@" target]
    ["[0]" meta]
    [abstract
     [monad {"+" do}]]
    [control
     ["[0]" io]
     ["[0]" maybe]
     ["<>" parser ("[1]#[0]" monad)
      ["<[0]>" code {"+" Parser}]]]
    [data
     ["[0]" product]
     ["[0]" text
      ["%" format {"+" format}]]
     [collection
      ["[0]" list ("[1]#[0]" functor)]]]
    [type
     abstract]
    [macro {"+" with_symbols}
     [syntax {"+" syntax:}]
     ["[0]" code]
     ["[0]" template]]]])

(abstract: .public (Object brand) Any)

(template [<name>]
  [(with_expansions [<brand> (template.symbol [<name> "'"])]
     (abstract: .public <brand> Any)
     (type: .public <name>
       (..Object <brand>)))]

  [Nil]
  [Function]
  )

(template [<name> <type>]
  [(type: .public <name>
     <type>)]

  [Boolean Bit]
  [Integer Int]
  [Float   Frac]
  [String  Text]
  )

(type: Nilable
  [Bit Code])

(def: nilable
  (Parser Nilable)
  (let [token (' "?")]
    (<| (<>.and (<>.parses? (<code>.this! token)))
        (<>.after (<>.not (<code>.this! token)))
        <code>.any)))

(type: Alias
  Text)

(def: alias
  (Parser Alias)
  (<>.after (<code>.this! (' "as")) <code>.local_symbol))

(type: Field
  [Bit Text (Maybe Alias) Nilable])

(def: static!
  (Parser Any)
  (<code>.this! (' "static")))

(def: field
  (Parser Field)
  (<code>.form ($_ <>.and
                   (<>.parses? ..static!)
                   <code>.local_symbol
                   (<>.maybe ..alias)
                   ..nilable)))

(def: constant
  (Parser Field)
  (<code>.form ($_ <>.and
                   (<>#in true)
                   <code>.local_symbol
                   (<>.maybe ..alias)
                   ..nilable)))

(type: Common_Method
  (Record
   [#name Text
    #alias (Maybe Alias)
    #inputs (List Nilable)
    #io? Bit
    #try? Bit
    #output Nilable]))

(def: common_method
  (Parser Common_Method)
  ($_ <>.and
      <code>.local_symbol
      (<>.maybe ..alias)
      (<code>.tuple (<>.some ..nilable))
      (<>.parses? (<code>.this! (' "io")))
      (<>.parses? (<code>.this! (' "try")))
      ..nilable))

(def: input_variables
  (-> (List Nilable) (List [Bit Code]))
  (|>> list.enumeration
       (list#each (function (_ [idx [nilable? type]])
                    [nilable? (|> idx %.nat code.local_symbol)]))))

(def: (nilable_type [nilable? type])
  (-> Nilable Code)
  (if nilable?
    (` (.Maybe (~ type)))
    type))

(def: (with_nil g!temp [nilable? input])
  (-> Code [Bit Code] Code)
  (if nilable?
    (` (case (~ input)
         {.#Some (~ g!temp)}
         (~ g!temp)

         {.#None}
         ("scheme object nil")))
    input))

(def: (without_nil g!temp [nilable? outputT] output)
  (-> Code Nilable Code Code)
  (if nilable?
    (` (let [(~ g!temp) (~ output)]
         (if ("scheme object nil?" (~ g!temp))
           {.#None}
           {.#Some (~ g!temp)})))
    (` (let [(~ g!temp) (~ output)]
         (if (not ("scheme object nil?" (~ g!temp)))
           (~ g!temp)
           (.panic! "Nil is an invalid value!"))))))

(type: Import
  (Variant
   {#Function Common_Method}
   {#Constant Field}))

(def: import
  (Parser Import)
  ($_ <>.or
      (<code>.form ..common_method)
      ..constant
      ))

(syntax: .public (try [expression <code>.any])
  ... {.#doc (example (case (try (risky_computation input))
  ...                   {.#Right success}
  ...                   (do_something success)

  ...                   {.#Left error}
  ...                   (recover_from_failure error)))}
  (in (list (` ("lux try" ((~! io.io) (~ expression)))))))

(def: (with_io with? without)
  (-> Bit Code Code)
  (if with?
    (` ((~! io.io) (~ without)))
    without))

(def: (io_type io? rawT)
  (-> Bit Code Code)
  (if io?
    (` ((~! io.IO) (~ rawT)))
    rawT))

(def: (with_try with? without_try)
  (-> Bit Code Code)
  (if with?
    (` (..try (~ without_try)))
    without_try))

(def: (try_type try? rawT)
  (-> Bit Code Code)
  (if try?
    (` (.Either .Text (~ rawT)))
    rawT))

(def: (make_function g!method g!temp source inputsT io? try? outputT)
  (-> Code Code Code (List Nilable) Bit Bit Nilable Code)
  (let [g!inputs (input_variables inputsT)]
    (` (def: ((~ g!method)
              [(~+ (list#each product.right g!inputs))])
         (-> [(~+ (list#each nilable_type inputsT))]
             (~ (|> (nilable_type outputT)
                    (try_type try?)
                    (io_type io?))))
         (:expected
          (~ (<| (with_io io?)
                 (with_try try?)
                 (without_nil g!temp outputT)
                 (` ("scheme apply"
                     (:as ..Function (~ source))
                     (~+ (list#each (with_nil g!temp) g!inputs)))))))))))

(syntax: .public (import: [import ..import])
  (with_symbols [g!temp]
    (case import
      {#Function [name alias inputsT io? try? outputT]}
      (let [imported (` ("scheme constant" (~ (code.text name))))]
        (in (list (..make_function (code.local_symbol (maybe.else name alias))
                                   g!temp
                                   imported
                                   inputsT
                                   io?
                                   try?
                                   outputT))))

      {#Constant [_ name alias fieldT]}
      (let [imported (` ("scheme constant" (~ (code.text name))))]
        (in (list (` ((~! syntax:) ((~ (code.local_symbol (maybe.else name alias))))
                      (# (~! meta.monad) (~' in)
                         (list (` (.:as (~ (nilable_type fieldT)) (~ imported))))))))))
      )))