new.hs

module Main where

import Lib

import Data.Text 
import Data.List

data Patient   = Patient Text
data Disease   = Dis Text
type Diagnosis = (Patient,Disease)

data PatientError = NoDiagnosis | NoPatientWithSuchDisease 

getPatientByDisease :: [Diagnosis] -> Disease -> Either PatientError Patient
getPatientByDisease [] _ = Left NoDiagnosis
getPatientByDisease diagnosis disease  = 
    let maybeDiagnosis = Data.List.find predicate diagnosis
    in case maybeDiagnosis of
        Nothing           -> Left NoPatientWithSuchDisease 
        Just (patient, _) -> Right patient
  where
    predicate :: Diagnosis -> Bool 
    predicate (_,patientDisease Text) = diseaseName == patientDiseaseName
      where
        (Dis diseaseName)        = disease
        (Dis patientDiseaseName) = patientDisease
    
main :: IO ()
main = print $ getPatientByDisease [(Patient "Иван", Diesease "Простуда")] (Disease "Простуда")