feat: add AST for parsing JSON

Author: null-char

package.yaml

@@ -1,14 +1,14 @@
-name:                parser-combinators
-version:             0.1.0.0
-github:              "githubuser/parser-combinators"
-license:             BSD3
-author:              "Author name here"
-maintainer:          "[email protected]"
-copyright:           "2020 Author name here"
+name: parser-combinators
+version: 0.1.0.0
+github: "githubuser/parser-combinators"
+license: BSD3
+author: "Author name here"
+maintainer: "[email protected]"
+copyright: "2020 Author name here"
 
 extra-source-files:
-- README.md
-- ChangeLog.md
+  - README.md
+  - ChangeLog.md
 
 # Metadata used when publishing your package
 # synopsis:            Short description of your package
@@ -17,32 +17,34 @@ extra-source-files:
 # To avoid duplicated efforts in documentation and dealing with the
 # complications of embedding Haddock markup inside cabal files, it is
 # common to point users to the README.md file.
-description:         Please see the README on GitHub at <https://github.com/githubuser/parser-combinators#readme>
+description: Please see the README on GitHub at <https://github.com/githubuser/parser-combinators#readme>
 
 dependencies:
-- base >= 4.7 && < 5
+  - base >= 4.7 && < 5
+  - text
+  - containers
 
 library:
   source-dirs: src
 
 executables:
   parser-combinators-exe:
-    main:                Main.hs
-    source-dirs:         app
+    main: Main.hs
+    source-dirs: app
     ghc-options:
-    - -threaded
-    - -rtsopts
-    - -with-rtsopts=-N
+      - -threaded
+      - -rtsopts
+      - -with-rtsopts=-N
     dependencies:
-    - parser-combinators
+      - parser-combinators
 
 tests:
   parser-combinators-test:
-    main:                Spec.hs
-    source-dirs:         test
+    main: Spec.hs
+    source-dirs: test
     ghc-options:
-    - -threaded
-    - -rtsopts
-    - -with-rtsopts=-N
+      - -threaded
+      - -rtsopts
+      - -with-rtsopts=-N
     dependencies:
-    - parser-combinators
+      - parser-combinators

parser-combinators.cabal

@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 0330f6479464e5ffbbb1589d96011a9a3c47821ba74b14434ee6d16e3e138712
+-- hash: 431ab4fb1b73226f52fcb1b718332fbbedb7a2139aaf244e7c3dbeb952b40bc8
 
 name:           parser-combinators
 version:        0.1.0.0
@@ -35,6 +35,8 @@ library
       src
   build-depends:
       base >=4.7 && <5
+    , containers
+    , text
   default-language: Haskell2010
 
 executable parser-combinators-exe
@@ -46,7 +48,9 @@ executable parser-combinators-exe
   ghc-options: -threaded -rtsopts -with-rtsopts=-N
   build-depends:
       base >=4.7 && <5
+    , containers
     , parser-combinators
+    , text
   default-language: Haskell2010
 
 test-suite parser-combinators-test
@@ -59,5 +63,7 @@ test-suite parser-combinators-test
   ghc-options: -threaded -rtsopts -with-rtsopts=-N
   build-depends:
       base >=4.7 && <5
+    , containers
     , parser-combinators
+    , text
   default-language: Haskell2010

src/Parser.hs

@@ -1,24 +1,41 @@
+{-# LANGUAGE OverloadedStrings #-}
+
 module Parser
   (
   )
 where
 
+import qualified Data.Map as M
+import qualified Data.Text as T
 import Text.Read (readMaybe)
 
-newtype Parser a = Parser {runParser :: String -> Maybe (a, String)}
+data JsonVal
+  = -- Maybe indicates the fractional part of the number. This will obviously be `Nothing` if it's
+    -- just a plain integer.
+    JsonNumber Integer (Maybe Integer)
+  | JsonBool Bool
+  | JsonNull
+  | JsonString T.Text
+  | JsonArray [JsonVal]
+  | JsonObj (M.Map T.Text JsonVal)
+  deriving (Eq, Show)
+
+newtype Parser a = Parser {parse :: T.Text -> Maybe (a, T.Text)}
 
-parse :: Parser a -> String -> a
-parse m s =
-  case runParser m s of
-    Just (res, []) -> res
-    Just (_, rest) -> error "Parser did not consume entire stream"
+runParser :: Parser a -> T.Text -> a
+runParser m s =
+  case parse m s of
+    Just (res, "") -> res
+    Just (_, rest) -> error "Parser did not consume the entire stream"
     Nothing -> error "Parser did not manage to parse anything"
 
-item = Parser $ \s ->
+-- A test parser
+digit :: Parser Int
+digit = Parser $ \s ->
   case s of
-    [] -> Nothing
-    (c : cs) ->
-      let rc = readMaybe [c] :: Maybe Int
-       in case rc of
+    "" -> Nothing
+    t ->
+      let ch = T.head t; cs = T.tail t
+       in case readMaybe [ch] of
             Just x -> Just (x, cs)
             Nothing -> Nothing