(ns query1 ;;ns is namespace
  (:gen-class)
  (:require [clojure.java.io :as io]
            [clojure.string :as string]
		))

(defn reader []
	(io/reader "data/ca.csv"))

(defn parse-record [line]
	(let [y line
	      [city lat long country iso2 admin capital pop poppropper]
          (string/split y #",")]

	(into {}  [[:city city]
			   [:lat (read-string lat)]
			   [:long (read-string long)]
		       [:country country]
		       [:iso2 iso2]
		       [:admin admin]
		       [:capital capital]
		       [:pop (read-string pop)]
		       [:popproper poppropper]]
	)
))


(defn cities []
  (with-open [rdr (reader)]
	(vec
		(for [line (drop 1 (line-seq rdr))]
			(parse-record line)))))


(defn city ([name var]
   (->> var
        (filter #(= (:city %) name))
        first))
  ([name] (city name (cities))))

(println " ")
(println "City Toronto Hash Map")
(print (city "Toronto"))
(println " ")

(defn distance [record1 record2]
  (let [R 6371
        dlat (Math/toRadians (- (:lat record2) (:lat record1)))
        dlon (Math/toRadians (- (:lat record2) (:lat record1)))
        var1 (Math/toRadians (:lat record1))
        var2 (Math/toRadians (:lat record2))
        a (+ (* (Math/sin (/ dlat 2)) (Math/sin (/ dlat 2))) (* (Math/sin (/ dlon 2)) (Math/sin (/ dlon 2)) (Math/cos var1) (Math/cos var2)))]
    (* R 2 (Math/asin (Math/sqrt a)))))

(defn large [city-record]
  (let [newVec (:pop city-record)]
  (> newVec  0.5E6)))

(println " ")
(println "Large?")
(println (large (city "Toronto")))
(println " ")


; check if the two cities are no more than 600 km apart
(defn close [c1 c2]
  (let [dist (distance c1 c2)]
  (< dist 600))
  )

(println " ")
(println "Are Toronto and La Ronge Close?")
(println(close (city "Toronto") (city "La Ronge")))
(println " ")



; find distinct pairs of city names of *large* cities
; that are close.
(defn closest-city-pairs []
	(let [y ((cities) vec)
		 :when (large y)]
		(for [a (butlast y)
			  b (rest y)
			  :when (and (not= a b)
				(close a b))]
		[(:city a) (:city b) (distance a b)])))

(println " ")
(println "List of closest city pairs")
(print (closest-city-pairs))
(println " ")