server.clj

(ns fulcro.server
  (:require
    [com.stuartsierra.component :as component]
    [clojure.spec.alpha :as s]
    [clojure.java.io :as io]
    [clojure.edn :as edn]
    [clojure.walk :as walk]
    [cognitect.transit :as ct]
    [fulcro.transit :as transit]
    [fulcro.client.impl.parser :as parser]
    [fulcro.util :as util]
    [fulcro.logging :as log])
  (:import (clojure.lang ExceptionInfo)
           [java.io ByteArrayOutputStream]))

(defn parser
  "Create a parser. The argument is a map of two keys, :read and :mutate. Both
   functions should have the signature (Env -> Key -> Params -> ParseResult)."
  [opts]
  (parser/parser opts))

(defn dispatch
  "Helper function for implementing :read and :mutate as multimethods. Use this
   as the dispatch-fn."
  [_ key _] key)

(defn reader
  "Create a transit reader. This reader can handler the tempid type.
   Can pass transit reader customization opts map."
  ([in] (transit/reader in))
  ([in opts] (transit/reader in opts)))

(defn writer
  "Create a transit reader. This writer can handler the tempid type.
   Can pass transit writer customization opts map."
  ([out] (transit/writer out))
  ([out opts] (transit/writer out opts)))

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;; CONFIG
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(defn- get-system-prop [prop-name]
  (System/getProperty prop-name))

(defn load-edn
  "If given a relative path, looks on classpath (via class loader) for the file, reads the content as EDN, and returns it.
  If the path is an absolute path, it reads it as EDN and returns that.
  If the resource is not found, returns nil."
  [^String file-path]
  (let [?edn-file (io/file file-path)]
    (if-let [edn-file (and (.isAbsolute ?edn-file)
                        (.exists ?edn-file)
                        (io/file file-path))]
      (-> edn-file slurp edn/read-string)
      (some-> file-path io/resource .openStream slurp edn/read-string))))

(defn- open-config-file
  "Calls load-edn on `file-path`,
  and throws an ex-info if that failed."
  [file-path]
  (log/info "Reading configuration file at " file-path)
  (if-let [edn (some-> file-path load-edn)]
    edn
    (do
      (log/error "Unable to read configuration file " file-path)
      (throw (ex-info (str "Invalid config file at '" file-path "'")
               {:file-path file-path})))))

(def get-defaults open-config-file)
(def get-config open-config-file)

(defn- resolve-symbol [sym]
  {:pre  [(namespace sym)]
   :post [(not (nil? %))]}
  (or (resolve sym)
    (do (-> sym namespace symbol require)
        (resolve sym))))

(defn- get-system-env [var-name]
  (System/getenv var-name))

(defn load-config
  "Entry point for config loading, pass it a map with k-v pairs indicating where
  it should look for configuration in case things are not found.
  Eg:
  - config-path is the location of the config file in case there was no system property
  "
  ([] (load-config {}))
  ([{:keys [config-path]}]
   (let [defaults (get-defaults "config/defaults.edn")
         config   (get-config (or (get-system-prop "config") config-path))]
     (->> (util/deep-merge defaults config)
       (walk/prewalk #(cond-> % (symbol? %) resolve-symbol
                        (and (keyword? %) (namespace %)
                          (re-find #"^env.*" (namespace %)))
                        (-> name get-system-env
                          (cond-> (= "env.edn" (namespace %))
                            (edn/read-string)))))))))

(defrecord Config [value config-path]
  component/Lifecycle
  (start [this]
    (let [config (or value (load-config {:config-path config-path}))]
      (log/debug "Loaded configuration: " (pr-str config))
      (assoc this :value config)))
  (stop [this] this))

(defn raw-config
  "Creates a configuration component using the value passed in,
   it will NOT look for any config files."
  [value] (map->Config {:value value}))

(defn new-config
  "Create a new configuration component. It will load the application defaults from config/defaults.edn
   (using the classpath), then look for an override file in either:
   1) the file specified via the `config` system property
   2) the file at `config-path`
   and merge anything it finds there over top of the defaults.

   This function can override a number of the above defaults with the parameters:
   - `config-path`: The location of the disk-based configuration file.
   "
  [config-path]
  (map->Config {:config-path config-path}))

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;; TRANSIT
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(defn- write [x t opts]
  (let [baos (ByteArrayOutputStream.)
        w    (writer baos opts)
        _    (ct/write w x)
        ret  (.toString baos)]
    (.reset baos)
    ret))

(defn- get-content-type
  "Return the content-type of the request, or nil if no content-type is set. Defined here to limit the need for Ring."
  [request]
  (if-let [type (get-in request [:headers "content-type"])]
    (second (re-find #"^(.*?)(?:;|$)" type))))

(defn- transit-request? [request]
  (if-let [type (get-content-type request)]
    (let [mtch (re-find #"^application/transit\+(json|msgpack)" type)]
      [(not (empty? mtch)) (keyword (second mtch))])))

(defn- read-transit [request {:keys [opts]}]
  (let [[res _] (transit-request? request)]
    (if res
      (if-let [body (:body request)]
        (let [rdr (reader body opts)]
          (try
            [true (ct/read rdr)]
            (catch Exception ex
              [false nil])))))))

(def ^{:doc "The default response to return when a Transit request is malformed."}
default-malformed-response
  {:status  400
   :headers {"Content-Type" "text/plain"}
   :body    "Malformed Transit in request body."})

(defn wrap-transit-body
  "Middleware that parses the body of Transit request maps, and replaces the :body
  key with the parsed data structure. Requests without a Transit content type are
  unaffected.
  Accepts the following options:
  :keywords?          - true if the keys of maps should be turned into keywords
  :opts               - a map of options to be passed to the transit reader
  :malformed-response - a response map to return when the JSON is malformed"
  {:arglists '([handler] [handler options])}
  [handler & [{:keys [malformed-response]
               :or   {malformed-response default-malformed-response}
               :as   options}]]
  (fn [request]
    (if-let [[valid? transit] (read-transit request options)]
      (if valid?
        (handler (assoc request :body transit))
        malformed-response)
      (handler request))))

(defn- assoc-transit-params [request transit]
  (let [request (assoc request :transit-params transit)]
    (if (map? transit)
      (update-in request [:params] merge transit)
      request)))

(defn wrap-transit-params
  "Middleware that parses the body of Transit requests into a map of parameters,
  which are added to the request map on the :transit-params and :params keys.
  Accepts the following options:
  :malformed-response - a response map to return when the JSON is malformed
  :opts               - a map of options to be passed to the transit reader
  Use the standard Ring middleware, ring.middleware.keyword-params, to
  convert the parameters into keywords."
  {:arglists '([handler] [handler options])}
  [handler & [{:keys [malformed-response]
               :or   {malformed-response default-malformed-response}
               :as   options}]]
  (fn [request]
    (if-let [[valid? transit] (read-transit request options)]
      (if valid?
        (handler (assoc-transit-params request transit))
        malformed-response)
      (handler request))))

(defn- set-content-type
  "Returns an updated Ring response with the a Content-Type header corresponding
  to the given content-type. This is defined here so non-ring users do not need ring."
  [resp content-type]
  (assoc-in resp [:headers "Content-Type"] (str content-type)))

(defn wrap-transit-response
  "Middleware that converts responses with a map or a vector for a body into a
  Transit response.
  Accepts the following options:
  :encoding - one of #{:json :json-verbose :msgpack}
  :opts     - a map of options to be passed to the transit writer"
  {:arglists '([handler] [handler options])}
  [handler & [{:as options}]]
  (let [{:keys [encoding opts] :or {encoding :json}} options]
    (assert (#{:json :json-verbose :msgpack} encoding) "The encoding must be one of #{:json :json-verbose :msgpack}.")
    (fn [request]
      (let [response (handler request)]
        (if (coll? (:body response))
          (let [transit-response (update-in response [:body] write encoding opts)]
            (if (contains? (:headers response) "Content-Type")
              transit-response
              (set-content-type transit-response (format "application/transit+%s; charset=utf-8" (name encoding)))))
          response)))))

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;; HELPERS
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(defn arg-assertion [mutation & args]
  "The function will throw an assertion error if any args are nil."
  (assert (every? (comp not nil?) args) (str "All parameters to " mutation " mutation must be provided.")))

(defn assert-user [req]
  "Throws and AssertionError if the user credentials are missing from the request."
  (assert (:user req) "Request has no user credentials!"))

(defn transitive-join
  "Takes a map from a->b and a map from b->c and returns a map a->c."
  [a->b b->c]
  (reduce (fn [result k] (assoc result k (->> k (get a->b) (get b->c)))) {} (keys a->b)))

(defn augment-response
  "Augments the Ring response that's returned from the handler.

  Use this function when you need to add information into the handler response, for
  example when you need to add cookies or session data. Example:

      (defmethod my-mutate 'user/sign-in [_ _ _]
        {:action
         (fn []
           (augment-response
             {:uid 42} ; your regular response
             #(assoc-in % [:session :user-id] 42) ; a function resp -> resp
             ))})

  If your parser has multiple responses with `augment-response`, they will be applied
  in order, the first one will receive an empty map as input. Only top level values
  of your response will be checked for augmented response."
  [core-response ring-response-fn]
  (assert (instance? clojure.lang.IObj core-response) "Scalar values can't be augmented.")
  (with-meta core-response {::augment-response ring-response-fn}))

(defn serialize-exception
  "Convert exception data to string form for network transit."
  [^Throwable ex]
  (let [message         (.getMessage ex)
        type            (str (type ex))
        serialized-data {:type type :message message}]
    (if (instance? ExceptionInfo ex)
      (assoc serialized-data :data (ex-data ex))
      serialized-data)))

(defn unknow-error->response [error]
  (let [serialized-data (serialize-exception error)]
    {:status 500
     :body   serialized-data}))

(defn parser-read-error->response
  "Determines if ex-data from ExceptionInfo has headers matching the Fulcro Server API.
   Returns ex-map if the ex-data matches the API, otherwise returns the whole exception."
  [ex]
  (let [valid-response-keys #{:status :headers :body}
        ex-map              (ex-data ex)]
    (if (every? valid-response-keys (keys ex-map))
      ex-map
      (unknow-error->response ex))))

(defn parser-mutate-error->response
  [mutation-result]
  (let [raise-error-data (fn [item]
                           (if (and (map? item) (contains? item :fulcro.client.primitives/error))
                             (let [exception-data (serialize-exception (get-in item [:fulcro.client.primitives/error]))]
                               (assoc item :fulcro.client.primitives/error exception-data))
                             item))
        mutation-errors  (clojure.walk/prewalk raise-error-data mutation-result)]

    {:status 400 :body mutation-errors}))

(defn process-errors [error]
  (let [error-response (cond
                         (instance? ExceptionInfo error) (parser-read-error->response error)
                         (instance? Exception error) (unknow-error->response error)
                         :else (parser-mutate-error->response error))]
    (log/error error "Parser error:\n" error-response)
    error-response))

(defn valid-response? [result]
  (and
    (not (instance? Exception result))
    (not (some (fn [[_ {:keys [fulcro.client.primitives/error]}]] (some? error)) result))))

(defn raise-response
  "Mutations running through a parser all come back in a map like this {'my/mutation {:result {...}}}. This function
  converts that to {'my/mutation {...}}."
  [resp]
  (reduce (fn [acc [k v]]
            (if (and (symbol? k) (not (nil? (:result v))))
              (assoc acc k (:result v))
              (assoc acc k v)))
    {} resp))

(defn augment-map
  "Fulcro queries and mutations can wrap their responses with `augment-response` to indicate they need access to
   the raw Ring response. This function processes those into the response.

  IMPORTANT: This function expects that the parser results have already been raised via the raise-response function."
  [response]
  (->> (keep #(some-> (second %) meta :fulcro.server/augment-response) response)
    (reduce (fn [response f] (f response)) {})))

(defn generate-response
  "Generate a Fulcro-compatible response containing at least a status code, headers, and body. You should
  pre-populate at least the body of the input-response.
  The content type of the returned response will always be pegged to 'application/transit+json'."
  [{:keys [status body headers] :or {status 200} :as input-response}]
  (-> (assoc input-response :status status :body body)
    (update :headers assoc "Content-Type" "application/transit+json")))

(defn handle-api-request
  "Given a parser, a parser environment, and a query: Runs the parser on the query,
   and generates a standard Fulcro-compatible response."
  [parser env query]
  (generate-response
    (let [parse-result (try (raise-response (parser env query)) (catch Exception e
                                                                  (.printStackTrace e System/err)
                                                                  e))]
      (if (valid-response? parse-result)
        (merge {:status 200 :body parse-result} (augment-map parse-result))
        (process-errors parse-result)))))

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;; Pre-built parser support
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(defmulti server-mutate dispatch)


(s/def ::mutation-args (s/cat
                         :sym symbol?
                         :doc (s/? string?)
                         :arglist vector?
                         :action (s/? #(and (list? %) (= 'action (first %))))))

(defmacro ^{:doc      "Define a server-side Fulcro mutation.

                       The given symbol will be prefixed with the namespace of the current namespace UNLESS
                       it is fully qualified already. If you're using cljc files in order to get server-side rendering,
                       you can also include your server mutations in the same namespace as your client ones using
                       alternate namespace aliasing:

                       ```
                       #?(:clj (server/defmutation boo ...server...)
                          :cljs (m/defmutation boo ...client...))
                       ```

                       The client-side mutation is never needed for server-side rendering, so it is ok that the mutation
                       isn't installed when rendering on the server.

                       This macro expands just like the client defmutation (though it uses server multimethod and only
                       support `action`).

                       NOTE: It will only work if you're using the `fulcro-parser` as your server's parser.

                       There is special support for placing the action as a var in the namespace. This support
                       only work when using a plain symbol. Simple add `:intern` metadata to the symbol. If
                       the metadata is true, it will intern the symbol as-is. It it is a string, it will suffix
                       the symbol with that string. If it is a symbol, it will use that symbol. The interned
                       symbol will act like the action side of the mutation, and has the signature:
                       `(fn [env params])`. This is also useful in devcards for using mkdn-pprint-source on mutations,
                       and should give you docstring and navigation support from nREPL.
                       "
            :arglists '([sym docstring? arglist action])} defmutation
  [& args]
  (let [{:keys [sym doc arglist action remote]} (util/conform! ::mutation-args args)
        fqsym           (if (namespace sym)
                          sym
                          (symbol (name (ns-name *ns*)) (name sym)))
        intern?         (-> sym meta :intern)
        interned-symbol (cond
                          (string? intern?) (symbol (namespace fqsym) (str (name fqsym) intern?))
                          (symbol? intern?) intern?
                          :else fqsym)
        doc             (or doc "")
        {:keys [action-args action-body]} (if action
                                            (util/conform! ::action action)
                                            {:action-args ['env] :action-body []})
        env-symbol      (gensym "env")
        multimethod     `(defmethod fulcro.server/server-mutate '~fqsym [~env-symbol ~'_ ~(first arglist)]
                           (let [~(first action-args) ~env-symbol]
                             {:action (fn [] ~@action-body)}))]
    (if intern?
      `(def ~interned-symbol ~doc
         (do
           ~multimethod
           (fn [~(first action-args) ~(first arglist)]
             ~@action-body)))
      multimethod)))

(defmulti read-entity
  "The multimethod for Fulcro's built-in support for reading an entity."
  (fn [env entity-type id params] entity-type))
(defmulti read-root
  "The multimethod for Fulcro's built-in support for querying with a keyword "
  (fn [env keyword params] keyword))

(declare server-read)

(defn fulcro-parser
  "Builds and returns a parser that uses Fulcro's query and mutation handling. See `defquery-entity`, `defquery-root`,
  and `defmutation` in the `fulcro.server` namespace."
  []
  (parser {:read server-read :mutate server-mutate}))

(s/def ::action (s/cat
                  :action-name (fn [sym] (= sym 'action))
                  :action-args (fn [a] (and (vector? a) (= 1 (count a))))
                  :action-body (s/+ (constantly true))))

(s/def ::value (s/cat
                 :value-name (fn [sym] (= sym 'value))
                 :value-args (fn [a] (and (vector? a) (= 3 (count a))))
                 :value-body (s/+ (constantly true))))

(s/def ::query-entity-args (s/cat
                             :kw keyword?
                             :doc (s/? string?)
                             :value #(and (list? %) (= 'value (first %)) (vector? (second %)))))

(defmacro ^{:doc      "Define a server-side query handler for a given entity type.

(defentity-query :person/by-id
  \"Optional doc string\"
  (value [env id params] {:db/id id :person/name \"Joe\"}))

  The `env` argument will be the server parser environment, which will include all of your component injections, the AST for
  this query, along with the subquery. `id` will be the ID of the entity to load. `params` will be any additional
  params that were sent via the client `load` (i.e. `(load this [:person/by-id 1] Person {:params {:auth 1223555}})`).
"
            :arglists '([entity-type docstring? value])} defquery-entity
  [& args]
  (let [{:keys [kw doc value]} (util/conform! ::query-entity-args args)
        {:keys [value-args value-body]} (util/conform! ::value value)
        env-sym    (first value-args)
        id-sym     (second value-args)
        params-sym (nth value-args 2)]
    `(defmethod fulcro.server/read-entity ~kw [~env-sym ~'_ ~id-sym ~params-sym]
       (let [v# (do ~@value-body)]
         {:value v#}))))

(s/def ::root-value (s/cat
                      :value-name (fn [sym] (= sym 'value))
                      :value-args (fn [a] (and (vector? a) (= 2 (count a))))
                      :value-body (s/+ (constantly true))))

(s/def ::query-root-args (s/cat
                           :kw keyword?
                           :doc (s/? string?)
                           :value #(and (list? %) (= 'value (first %)) (vector? (second %)))))

(defmacro ^{:doc      "Define a server-side query handler for queries joined at the root.

The `value` method you define will receive the full Om parser environment (server-side, with your
component injections) as `env` and any params the server sent with the specific top-level query. Note that the subquery and
AST for the query will be available in `env`.

For example: `(load app :questions Question {:params {:list 1}})` on the client would result in params being set to `{:list 1}`
on the server.

The return value of `value` will be sent to the client.

(defquery-root :questions
  \"Optional doc string\"
  (value [{:keys [ast query] :as env} {:keys [list]}]
    [{:db/id 1 :question/value \"How are you?\"}
    {:db/id 2 :question/value \"What time is it?\"}
    {:db/id 3 :question/value \"How old are you?\"}]))
"
            :arglists '([root-kw docstring? value-method])} defquery-root
  [& args]
  (let [{:keys [kw doc value]} (util/conform! ::query-root-args args)
        {:keys [value-args value-body]} (util/conform! ::root-value value)
        env-sym    (first value-args)
        params-sym (second value-args)]
    `(defmethod fulcro.server/read-root ~kw [~env-sym ~'_ ~params-sym]
       (let [v# (do ~@value-body)]
         {:value v#}))))

(defn server-read
  "A built-in read method for Fulcro's built-in server parser."
  [env k params]
  (let [k (-> env :ast :key)]
    (if (util/ident? k)
      (read-entity env (first k) (second k) params)
      (read-root env k params))))

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;; Module-based composable server : DEPRECATED
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defprotocol Module
  (system-key [this]
    "Should return the key under which the module will be located in the system map.
     Unique-ness is checked and will be asserted.")
  (components [this]
    "Should return a map of components that this Module wants to build. Note that this does *not* cause
    them to be injected into this module. You still need to do that by wrapping an instance of the module
    in component/using! Unique-ness of the keywords is checked and will be asserted, so it pays to namespace them."))

(defprotocol APIHandler
  (api-read [this]
    "Returns a Fulcro read emitter for parsing read queries, ie: `(fn [env k params] ...)`.
     The emitter can return an untruthy value (`nil` or `false`),
     which tells the fulcro api-handler to try the next `Module` in the `:modules` chain.")
  (api-mutate [this]
    "Returns a Fulcro mutate emitter for parsing mutations, ie: `(fn [env k params] ...)`.
     The emitter can return an untruthy value (`nil` or `false`),
     which tells the fulcro api-handler to try the next `Module` in the `:modules` chain."))

(defn- chain
  "INTERNAL use only, use `fulcro-system` instead."
  [F api-fn module]
  (if-not (satisfies? APIHandler module) F
                                         (let [parser-fn (api-fn module)]
                                           (fn [env k p]
                                             (or (parser-fn (merge module env) k p)
                                               (F env k p))))))

(defn- comp-api-modules
  "INTERNAL use only, use `fulcro-system` instead."
  [{:as this :keys [modules]}]
  (reduce
    (fn [r+m module-key]
      (let [module (get this module-key)]
        (-> r+m
          (update :read chain api-read module)
          (update :mutate chain api-mutate module))))
    {:read   (constantly nil)
     :mutate (constantly nil)}
    (rseq modules)))

(defrecord FulcroApiHandler [app-name modules]
  component/Lifecycle
  (start [this]
    (let [api-url     (cond->> "/api" app-name (str "/" app-name))
          api-parser  (parser (comp-api-modules this))
          api-handler (partial handle-api-request api-parser)]
      (assoc this
        :handler api-handler
        :middleware
        (fn [h]
          (fn [req]
            (if-let [resp (and (= (:uri req) api-url)
                            (api-handler {:request req} (:transit-params req)))]
              resp (h req)))))))
  (stop [this] (dissoc this :middleware)))

(defn- api-handler
  "INTERNAL use only, use `fulcro-system` instead."
  [opts]
  (let [module-keys (mapv system-key (:modules opts))]
    (component/using
      (map->FulcroApiHandler
        (assoc opts :modules module-keys))
      module-keys)))

(defn- merge-with-no-duplicates!
  "INTERNAL use only, for checking that a merge doesn't override anything silently."
  [ctx & maps]
  (when (some identity maps)
    (let [merge-entry
          (fn [m e]
            (let [[k v] ((juxt key val) e)]
              (if-not (contains? m k) (assoc m k v)
                                      (throw (ex-info (str "Duplicate entries for key <" k "> found for " ctx ", see ex-data.")
                                               {:key k :prev-value (get m k) :new-value v})))))]
      (reduce (fn [m1 m2] (reduce merge-entry (or m1 {}) (seq m2))) maps))))

(defn fulcro-system
  "DEPRECATED. Do not use in new code. Library composition is better accomplished using the standard parser hooks.

  More powerful variant of `make-fulcro-server` that allows for libraries to provide
   components and api methods (by implementing `components` and `APIHandler` respectively).
   However note that `fulcro-system` does not include any components for you,
   so you'll have to include things like a web-server (eg: `make-web-server`), middleware,
   config, etc...

   Takes a map with keys:
   * `:api-handler-key` - OPTIONAL, Where to place the generated (composed from modules) api-handler in the system-map. The
                          generated component will be injectable, and will contain the key `:middleware` whose value
                          is a (fn [h] (fn [req] resp)) that handles `/api` requests.
                          Defaults to `:fulcro.server/api-handler`.
   * `:app-name` - OPTIONAL, a string that will turn \"/api\" into \"/<app-name>/api\".
   * `:components` - A `com.stuartsierra.component/system-map` of components that this module wants to ADD to the overall system. Libraries should namespace their components.
   * `:modules` - A vector of implementations of Module (& optionally APIHandler),
                  that will be composed in the order they were passed in.
                  Eg: [mod1 mod2 ...] => mod1 will be tried first, mod2 next, etc...
                  This should be used to compose libraries api methods with your own,
                  with full control over execution order.

   NOTE: Stores the key api-handler is located in the meta data under `::api-handler-key`.
         Currently used by protocol support to test your api methods without needing networking."
  [{:keys [api-handler-key modules] :as opts}]
  (-> (apply component/system-map
        (apply concat
          (merge-with-no-duplicates! "fulcro-system"
            (:components opts)
            (apply merge-with-no-duplicates! "Module/system-key"
              (map (comp (partial apply hash-map) (juxt system-key identity)) modules))
            (apply merge-with-no-duplicates! "Module/components"
              (map components modules))
            {(or api-handler-key ::api-handler)
             (api-handler opts)})))
    (vary-meta assoc ::api-handler-key (or api-handler-key ::api-handler))))