core.clj

(ns ^{:doc "Supporting macros for Reacl."}
  reacl2.core
  (:require [clojure.set :as set]
            [clojure.string :as string])
  (:refer-clojure :exclude [class]))

(def ^{:private true} special-tags
  (concat ['handle-message
           'component-will-mount
           'component-did-mount
           'component-will-receive-args
           'should-component-update?
           'component-will-update
           'component-did-update
           'component-will-unmount]))

(defn- split-symbol [stuff dflt]
  (if (symbol? (first stuff))
    [(first stuff) (rest stuff)]
    [dflt stuff]))

(defmacro class
  "Create a Reacl class.

  The syntax is

      (reacl.core/class <name> [<this-name> [<app-state-name>]] [<param> ...]
        render <renderer-exp>
        [local-state [<name> <initial-state-exp>]
        [local [<local-name> <local-expr>]]
        [handle-message <messager-handler-exp>]
        [<lifecycle-method-name> <lifecycle-method-exp> ...])

  `<name>` is a name for the class, for debugging purposes.

  A number of names are bound in the various expressions in the body
  of reacl.core/class:

  - `<this-name>` is bound to the component object itself
  - `<app-state-name>` is bound to the global application state
  - `<local-state-name>` is bound to the component-local state
  - the `<param>` ... names are the explicit arguments of instantiations

  A `local` clause allows binding additional local variables upon
  instantiation.  The syntax is analogous to `let`.

  `<renderer-exp>` is an expression that renders the component, and
  hence must return a virtual dom node.

  The `handle-message` function accepts a message sent to the
  component via [[reacl.core/send-message!]].  It's expected to
  return a value specifying a new application state and/or
  component-local state, via [[reacl.core/return]].

  A class can be invoked to yield a component as a function as follows:

  `(<class> <app-state> <reaction> <arg> ...)`

  In this invocation, the value of `<app-state>` will be the initial app
  state, `<reaction>` must evaluate to a *reaction* (see
  [[reacl.core.reaction]]) that gets invoked when the component's app
  state changes, and the `<arg>`s get evaluated to the `<param>`s.

  A lifecycle method can be one of:

    `component-will-mount` `component-did-mount`
    `component-will-receive-args` `should-component-update?`
    `component-will-update` `component-did-update` `component-will-unmount`

  These correspond to React's lifecycle methods, see
  here:

  http://facebook.github.io/react/docs/component-specs.html

  (`component-will-receive-args` is similar to `componentWillReceiveProps`.)

  Each right-hand-side `<lifecycle-method-exp>`s should evaluate to a
  function. The arguments, which slightly differ from the
  corresponding React methods, can be seen in the following list:

  `(component-will-mount)` The component can send itself messages in
  this method, or optionally return a new state
  via [[reacl.core/return]]. If that changes the state, the component
  will only render once.

  `(component-did-mount)` The component can update its DOM in this
  method.  It can also return a new state via [[reacl.core/return]].

  `(component-will-receive-args next-arg1 next-arg2 ...)` The
  component has the chance to update its local state in this method
  by sending itself a message or optionally return a new state
  via [[reacl.core/return]].

  `(should-component-update? next-app-state next-local-state next-arg1
  next-arg2 ...)` This method should return if the given new values
  should cause an update of the component (if render should be
  evaluated again). If it's not specified, a default implementation
  will do a (=) comparison with the current values. Implement this, if
  you want to prevent an update on every app-state change for example.

  `(component-will-update next-app-state next-local-state next-arg1 next-arg2 ...)`
  Called immediately before an update.
  
  `(component-did-update prev-app-state prev-local-state prev-arg1 prev-arg2 ...)`
  Called immediately after an update. The component can update its DOM here.
  
  `(component-will-unmount)`
  The component can cleanup it's DOM here for example.

  Example:

    (defrecord New-text [text])
    (defrecord Submit [])
    (defrecord Change [todo])

    (reacl/defclass to-do-app
      this app-state []

      local-state [local-state \"\"]

      render
      (dom/div
       (dom/h3 \"TODO\")
       (dom/div (map (fn [todo]
                       (dom/keyed (str (:id todo))
                                  (to-do-item
                                   todo
                                   (reacl/reaction this ->Change)
                                   this)))
                     (:todos app-state)))
       (dom/form
        {:onsubmit (fn [e _]
                     (.preventDefault e)
                     (reacl/send-message! this (Submit.)))}
        (dom/input {:onchange 
                    (fn [e]
                      (reacl/send-message!
                       this
                       (New-text. (.. e -target -value))))
                    :value local-state})
        (dom/button
         (str \"Add #\" (:next-id app-state)))))

      handle-message
      (fn [msg]
        (cond
         (instance? New-text msg)
         (reacl/return :local-state (:text msg))

         (instance? Submit msg)
         (let [next-id (:next-id app-state)]
           (reacl/return :local-state \"\"
                         :app-state
                         (assoc app-state
                           :todos
                           (concat (:todos app-state)
                                   [(Todo. next-id local-state false)])
                           :next-id (+ 1 next-id))))

         (instance? Delete msg)
         (let [id (:id (:todo msg))]
           (reacl/return :app-state
                         (assoc app-state
                           :todos 
                           (remove (fn [todo] (= id (:id todo)))
                                   (:todos app-state)))))

         (instance? Change msg)
         (let [changed-todo (:todo msg)
               changed-id (:id changed-todo)]
           (reacl/return :app-state
                         (assoc app-state
                           :todos (mapv (fn [todo]
                                          (if (= changed-id (:id todo) )
                                            changed-todo
                                            todo))
                                        (:todos app-state))))))))"
  [?name & ?stuff]

  (let [[?component ?stuff] (split-symbol ?stuff `component#)
        [has-app-state? ?app-state ?stuff] (if (symbol? (first ?stuff))
                                             [true (first ?stuff) (rest ?stuff)]
                                             [false `app-state# ?stuff])

        [?args & ?clauses] ?stuff

        ?clause-map (apply hash-map ?clauses)
        ?locals-clauses (get ?clause-map 'local [])
        ?locals-ids (map first (partition 2 ?locals-clauses))

        [?local-state ?initial-state-expr] (or (get ?clause-map 'local-state)
                                               [`local-state# nil])

        ?render-fn (when-let [?expr (get ?clause-map 'render)]
                     `(fn [] ~?expr))

        compat-v1? (get ?clause-map 'compat-v1?)

        ;; handle-message, lifecycle methods, and user-defined functions (v1 only)
        ?other-fns-map (dissoc ?clause-map 'local 'render 'mixins 'local-state 'compat-v1?)
        ;; user-defined functions
        ?misc-fns-map (apply dissoc ?other-fns-map special-tags)

        _ (when (and compat-v1? (not-empty ?misc-fns-map))
            (throw (Error. "invalid clauses in class definition: " (keys ?misc-fns-map))))
        

        ?wrap-std
        (fn [?f]
          (if ?f
            (let [?more `more#]
              `(fn [~?component ~?app-state ~?local-state [~@?locals-ids] [~@?args] & ~?more]
                 ;; every user misc fn is also visible; for v1 compat
                 (let [~@(mapcat (fn [[n f]] [n `(aget ~?component ~(str n))]) ?misc-fns-map)]
                   (apply ~?f ~?more))))
            'nil))

        ?std-fns-map (assoc ?other-fns-map
                       'render ?render-fn)

        ?wrapped-nlocals [['initial-state
                           (if (some? ?initial-state-expr)
                             `(fn [~?component ~?app-state [~@?locals-ids] [~@?args]]
                                ;; every user misc fn is also visible; for v1 compat
                                (let [~@(mapcat (fn [[n f]] [n `(aget ~?component ~(str n))]) ?misc-fns-map)]
                                  ~?initial-state-expr))
                             `nil)]]

        ?wrapped-std (map (fn [[?n ?f]] [?n (?wrap-std ?f)])
                          ?std-fns-map)

        ?fns
        (into {}
              (map (fn [[?n ?f]] [(keyword ?n) ?f])
                   (concat ?wrapped-nlocals ?wrapped-std)))

        ;; compile an argument to a mixin to a function of this
        compile-argument (fn [thing]
                           (if-let [index (first (filter identity (map-indexed (fn [i x] (if (= x thing) i nil)) ?args)))]
                             `(fn [this#]
                                (nth (reacl2.core/extract-args this#) ~index))
                             (throw (Error. (str "illegal mixin argument: " thing)))))

        ?mixins (if-let [mixins (get ?clause-map 'mixins)]
                  (map (fn [mix]
                         `(~(first mix) ~@(map compile-argument (rest mix))))
                       mixins)
                  nil)

        ?compute-locals
        `(fn [~?app-state [~@?args]]
           (let ~?locals-clauses
             [~@?locals-ids]))
        ]
    `(reacl2.core/create-class ~?name ~compat-v1? ~(if ?mixins `[~@?mixins] `nil) ~has-app-state? ~?compute-locals ~?fns)))

(defmacro defclass
  "Define a Reacl class, see [[class]] for documentation.

  The syntax is

      (reacl.core/defclass <name> [<this-name> [<app-state-name> [<local-state-name>]]] [<param> ...]
        render <renderer-exp>
        [initial-state <initial-state-exp>]
        [<lifecycle-method-name> <lifecycle-method-exp> ...]
        [handle-message <messager-handler-exp>]

        <event-handler-name> <event-handler-exp> ...)

  This expands to this:

      (def <name>
        (reacl.core/class <name> [<this-name> [<app-state-name> [<local-state-name>]]] [<param> ...]
          render <renderer-exp>
          [initial-state <initial-state-exp>]
          [<lifecycle-method-name> <lifecycle-method-exp> ...]
          [handle-message <messager-handler-exp>]

          <event-handler-name> <event-handler-exp> ...))"
  [?name & ?stuff]
  `(def ~?name (reacl2.core/class ~(str ?name) ~@?stuff)))

;; (mixin [<this-name> [<app-state-name> [<local-state-name>]]] [<param> ...])

;; FIXME: should really be restricted to lifecycle methods we know we support

(defmacro mixin
  "Define a mixin. Mixins let you provide additional lifecycle method expressions that
  you can mix into your components.
  
  The syntax is
  
      (reacl.core/mixin [<this> [<app-state> [<local-state>]]] [<param> ...]
        [<lifecycle-method-name> <lifecycle-method-exp> ...])
  
  In order to use the mixin you can use the `mixins` clause in `defclass`

      (reacl.core/defclass foo ...
        mixins [(<your-mixin-var> [<param> ...])]
        ...)

  The lifecycle method expressions in the mixins will be called in order. Only after all
  mixin lifecycle methods have been handled the component's own lifecycle method will be
  called."
  [& ?stuff]
  (let [[?component ?stuff] (split-symbol ?stuff `component#)
        [?app-state ?stuff] (split-symbol ?stuff `app-state#)
        [?local-state ?stuff] (split-symbol ?stuff `local-state#)
          
        [?args & ?clauses] ?stuff

        ?clause-map (apply hash-map ?clauses)
        ?wrap (fn [?f]
                (if ?f
                  (let [?more `more#]
                    `(fn [~?component ~?app-state ~?local-state [~@?args] & ~?more]
                       (apply ~?f ~?more)))
                  'nil))
        ?wrapped (into {}
                       (map (fn [[?n ?f]] [(keyword ?n) (?wrap ?f)])
                            ?clause-map))]
    `(reacl2.core/create-mixin ~?wrapped)))