(ns clj-hl7-fhir.core
  (:import (java.util Date)
           (clojure.lang ExceptionInfo))
  (:require [clojure.string :as str])
  (:use [camel-snake-kebab]
        [clj-hl7-fhir.util]))

(defn- ->fhir-resource-name [x]
  (name (->CamelCase x)))

(defn- fhir-get-request [base-url resource-url & [params]]
  (let [query (map->query-string params)]
    (http-get-json (build-url base-url resource-url query))))

(defn- ->search-param-name [parameter & [modifier]]
  (keyword
    (str
      (if (vector? parameter)
        (->> parameter
             (map name)
             (str/join ".")
             )
        (name parameter))
      (if modifier
        (str ":" (name modifier))))))

(defn- ->search-param-descriptor [parameter value operator {:keys [modifier]}]
  {:name (->search-param-name parameter modifier)
   :operator operator
   :value value})

(defmacro ^:private single-search-op [name operator]
  `(defn ~name [parameter# value# & options#]
     [(->search-param-descriptor parameter# value# ~operator (apply hash-map options#))]))

(defmacro ^:private double-search-op [name operator1 operator2]
  `(defn ~name [parameter# value1# value2# & options#]
     [(->search-param-descriptor parameter# value1# ~operator1 (apply hash-map options#))
      (->search-param-descriptor parameter# value2# ~operator2 (apply hash-map options#))]))

(defn- escape-parameter [value]
  (-> value
      (.replace "\\" "\\\\")
      (.replace "$" "\\$")
      (.replace "," "\\,")
      (.replace "|" "\\|")))

(defn- format-search-value [value]
  (cond
    (sequential? value)
    (->> value
         (map format-search-value)
         (str/join ","))

    (map? value)
    (str (:namespace value) "|" (format-search-value (:value value)))

    (instance? Date value)
    (->timestamp value)

    :else
    (-> value str escape-parameter)))

(defn- search-params->query-map [params]
  (->> params
       (apply concat)
       (map
         (fn [{:keys [name operator value]}]
           [name
            (str
              (if-not (= "=" operator) operator)
              (format-search-value value))]))
       (reduce
         (fn [m [name value]]
           (if (contains? m name)
             (update-in m [name] #(conj (if (vector? %) % [%]) value))
             (assoc m name value)))
         {})))

(defn- get-bundle-next-page-url [bundle]
  (->> (:link bundle)
       (filter #(= "next" (:rel %)))
       (first)
       :href))

(single-search-op eq "=")
(single-search-op lt "<")
(single-search-op lte "<=")
(single-search-op gt ">")
(single-search-op gte ">=")
(double-search-op between ">" "<")

(defn namespaced
  ([value]
   (namespaced nil value))
  ([namespace value]
   {:namespace namespace
    :value value}))

(defn collect-resources
  "returns a sequence containing all of the resources contained in the given bundle

  reference:
  bundles: http://hl7.org/implement/standards/fhir/extras.html#bundle"
  [bundle]
  (->> bundle
       :entry
       (map :content)))

(defn fetch-next-page
  "for resources that are returned over more then one page, this will fetch the
   next page of resources as indicated by the link information contained in the
   passed bundle. the return value is another bundle that can be passed again
   to this function to get subsequent pages. if this function is passed the
   bundle for the last page of resources, nil is returned

   reference:
   bundles: http://hl7.org/implement/standards/fhir/extras.html#bundle
   paging: http://hl7.org/implement/standards/fhir/http.html#paging"
  [bundle]
  (if-let [next-url (get-bundle-next-page-url bundle)]
    (http-get-json next-url)))

(defn- concat-bundle-entries [bundle other-bundle]
  (if (nil? bundle)
    other-bundle
    (update-in
      bundle [:entry]
      (fn [existing-entries]
        (->> (:entry other-bundle)
             (concat existing-entries)
             (vec))))))

(defn- strip-bundle-page-links [bundle]
  (if bundle
    (assoc bundle
      :link
      (->> (:link bundle)
           (remove
             (fn [{:keys [rel]}]
               (or (= rel "first")
                   (= rel "last")
                   (= rel "next")
                   (= rel "previous"))))
           (vec)))))

(defn fetch-all
  "for resources that are returned over more then one page, this will automatically
   fetch all pages of resources and them into a single bundle that contains all of
   the resources.

   reference:
   bundles: http://hl7.org/implement/standards/fhir/extras.html#bundle
   paging: http://hl7.org/implement/standards/fhir/http.html#paging"
  [bundle]
  (loop [current-page   bundle
         working-bundle nil]
    (let [merged    (concat-bundle-entries working-bundle current-page)
          next-page (fetch-next-page current-page)]
      (if next-page
        (recur next-page merged)
        (strip-bundle-page-links merged)))))

(defn get-resource
  "gets a single resource from a FHIR server. can optionally get a specific version of a resource.
   the raw resource itself is returned (that is, it is not contained in a bundle). if the
   resource could not be found, nil is returned.

   reference:
   read: http://hl7.org/implement/standards/fhir/http.html#read
   vread: http://hl7.org/implement/standards/fhir/http.html#vread"
  [base-url type id & {:keys [version]}]
  (let [resource-name  (->fhir-resource-name type)
        url-components (if version
                         ["/" resource-name id "_history" version]
                         ["/" resource-name id])]
    (try
      (fhir-get-request
        base-url
        (apply join-paths url-components))
      (catch ExceptionInfo ex
        (if (not= 404 (get-in (ex-data ex) [:object :status]))
          (throw ex))))))

(defn get-resource-bundle
  "gets a single resource from a FHIR server. the returned resource will be contained in a
   bundle. if the resource could not be found, a bundle containing zero resources is returned.

  reference:
  bundles: http://hl7.org/implement/standards/fhir/extras.html#bundle"
  [base-url type id]
  (let [resource-name (->fhir-resource-name type)
        url-components ["/" resource-name]]
    (fhir-get-request
      base-url
      (apply join-paths url-components)
      {:_id id})))

(defn search
  "searches for resources on a FHIR server. multiple parameters are ANDed together. use of the search
   operator helper functions is encouraged to ensure proper escaping/encoding of search parameters.
   the results of this function can be passed to fetch-next-page or fetch-all to collect resources
   returned in paged search results easier

   reference:
   search: http://hl7.org/implement/standards/fhir/http.html#search"
  [base-url type where & params]
  (let [resource-name  (->fhir-resource-name type)
        url-components ["/" resource-name]]
    (fhir-get-request
      base-url
      (apply join-paths url-components)
      (merge
        (search-params->query-map where)
        (apply hash-map (if (and (seq? params)
                                 (= 1 (count params)))
                          (first params)
                          params))))))

(defn search-and-fetch
  "same as search, but automatically fetches all pages of resources returning a single bundle
   that contains all search results."
  [base-url type where & params]
  (fetch-all
    (search base-url type where params)))

;(def server-url "http://fhir.healthintersections.com.au/open")
;(def server-url "http://spark.furore.com/fhir")
(def server-url "http://uhnvesb01d.uhn.on.ca:25180/hapi-fhir-jpaserver/base")

;(get-resource server-url :patient 1)

;(get-resource server-url :patient 181)

;(search server-url :patient [(lt :birthdate "1984-12-13")])

;(search server-url :patient [(eq :birthdate "1985-01-01")])

;(search server-url :patient [(eq :birthdate "1925-08-27T00:00:00")])
;(search server-url :patient [(eq :birthdate (new Date 25 7 27))])
;(search server-url :patient [(eq :birthdate (new Date 90 0 1))])

;(search server-url :patient [(eq :name "king") (eq :age 1337)])

;(search-params->query-kvs [(eq :name "king") (eq :age 1337)])