Add parsers for test tables (#45)

* Create base for customers parser

* Define types for Customer

* Write parser for Customer table

* Add parser for invoices table

a-deeper-dive-into-relational-algebra-by-way-of-adjunctions.cabal

@@ -27,7 +27,9 @@ library
         Data.PointedSet,
         Data.Key,
         Database.Bag,
-        Database.IndexedTable
+        Database.IndexedTable,
+        Text.Parser.Customers,
+        Text.Parser.Invoices
 
     -- Modules included in this library but not exported.
     other-modules: 
@@ -39,7 +41,8 @@ library
         FlexibleInstances
     build-depends:
         base >=4.16.4.0,
-        array >= 0.5.4.0
+        array >= 0.5.4.0,
+        parsec >= 0.3.1.15
     hs-source-dirs:   src
     default-language: Haskell2010
 
@@ -70,10 +73,13 @@ test-suite spec
         Data.PointedSetSpec,
         Data.KeySpec,
         Database.BagSpec,
-        Database.IndexedTableSpec
+        Database.IndexedTableSpec,
+        Text.Parser.CustomersSpec,
+        Text.Parser.InvoicesSpec
     build-depends:
         base >=4.16.4.0,
         hspec ^>=2.10,
         a-deeper-dive-into-relational-algebra-by-way-of-adjunctions,
-        array >= 0.5.4.0
+        array >= 0.5.4.0,
+        parsec >= 0.3.1.15
     build-tool-depends: hspec-discover:hspec-discover == 2.*

src/Text/Parser/Customers.hs

@@ -0,0 +1,39 @@
+module Text.Parser.Customers where
+
+import Text.ParserCombinators.Parsec
+import Data.Bag
+
+type Identifier = Int
+type Name = String
+data Customer = C { cid :: Identifier, name :: Name } deriving (Show, Eq)
+
+csvFile :: GenParser Char st (Bag Customer)
+csvFile = do
+  result <- many record
+  eof
+  return (Bag result)
+
+record :: GenParser Char st Customer
+record = do
+  id <- cidCell
+  separator
+  name <- nameCell
+  eol
+  return (C id name)
+
+cidCell :: GenParser Char st Identifier
+cidCell = do
+  id <- many digit
+  return (read id)
+
+nameCell :: GenParser Char st Name
+nameCell = many (noneOf ",\n")
+
+separator :: GenParser Char st Char
+separator = char ','
+
+eol :: GenParser Char st Char
+eol = char '\n'
+
+parseCSV :: String -> Either ParseError (Bag Customer)
+parseCSV input = parse csvFile "(unknown)" input

src/Text/Parser/Invoices.hs

@@ -0,0 +1,56 @@
+module Text.Parser.Invoices where
+
+import Text.ParserCombinators.Parsec
+import Data.Bag
+
+type Identifier = Int
+type Date = Int
+type Amount = Int
+
+data Invoice = I 
+  { iid :: Identifier
+  , cust :: Identifier
+  , due :: Date
+  , amount :: Amount} deriving (Show, Eq)
+
+csvFile :: GenParser Char st (Bag Invoice)
+csvFile = do
+  result <- many invoiceRecord
+  eof
+  return (Bag result)
+
+invoiceRecord :: GenParser Char st Invoice
+invoiceRecord = do
+  iidCell <- identifier 
+  separator
+  custIdCell <- identifier
+  separator
+  dueCell <- date
+  separator
+  amountCell <- price
+  eol
+  return (I iidCell custIdCell dueCell amountCell)
+
+identifier :: GenParser Char st Identifier
+identifier = do
+  id <- many digit
+  return (read id)
+
+price :: GenParser Char st Amount
+price = do
+  id <- many digit
+  return (read id)
+
+date :: GenParser Char st Date
+date = do
+  id <- many digit
+  return (read id)
+
+separator :: GenParser Char st Char
+separator = char ','
+
+eol :: GenParser Char st Char
+eol = char '\n'
+
+parseCSV :: String -> Either ParseError (Bag Invoice)
+parseCSV input = parse csvFile "(unknown)" input

test/Text/Parser/CustomersSpec.hs

@@ -0,0 +1,16 @@
+module Text.Parser.CustomersSpec where
+
+import Test.Hspec 
+import Text.Parser.Customers
+import Data.Bag as Bag
+import Text.ParserCombinators.Parsec
+import Data.Either
+
+expectedOutput = Bag [C 1 "John", C 2 "Kayla"]
+
+spec :: Spec
+spec = do
+  describe "parseCSV" $ do
+    it "can correctly parse the example" $ do
+      testFile <- readFile "test/Text/Parser/customertest.csv"
+      fromRight Bag.empty (parseCSV testFile) `shouldBe` expectedOutput

test/Text/Parser/InvoicesSpec.hs

@@ -0,0 +1,16 @@
+module Text.Parser.InvoicesSpec where
+
+import Test.Hspec 
+import Text.Parser.Invoices
+import Data.Bag as Bag
+import Text.ParserCombinators.Parsec
+import Data.Either
+
+expectedOutput = Bag [I 10 1 20160101 10, I 11 1 20160102 83, I 12 2 20160103 15]
+
+spec :: Spec
+spec = do
+  describe "parseCSV" $ do
+    it "can correctly parse the example" $ do
+      testFile <- readFile "test/Text/Parser/invoicestest.csv"
+      fromRight Bag.empty (parseCSV testFile) `shouldBe` expectedOutput

test/Text/Parser/customertest.csv

@@ -0,0 +1,2 @@
+1,John
+2,Kayla

test/Text/Parser/invoicestest.csv

@@ -0,0 +1,3 @@
+10,1,20160101,10
+11,1,20160102,83
+12,2,20160103,15