(namespace core)

(docs "the simplest way to conditionally execute code."
      tags [ conditional flow-control ]
      example (ternary (< 50 100)
         "fifty is less than 100"
         "fifty is more than 100"))

(macro ternary (cond if-true if-false)
       ["(" (transpile cond) ") ? "
            (transpile if-true) " : "
            (transpile if-false)])


(docs "evaluates statements in `body` if `condition` is true. `body`
      is `scoped` in a self-evaluating function to support having a
      return value from the if statement."
      tags [ conditional flow-control language ]
      example: (when (< 3 i) (console.log i) (get arr i)))

(macro when (condition ...body)
       (^*scoped-without-return
         "if (" @condition ") {"
         (indent `(do ...@body))
         "}"))

(docs "evaluates statements in `body` if `condition` is falsy. `body`
      is `scoped` in a self-evaluating function to support having a
      return value from the if statement."
      tags [conditional flow-control]
      example: (unless (< 3 i) (console.log i) (get arr i)))

(macro unless (condition ...body)
       ["(function() {"
        (indent ["if (" '(not @condition) ") {"
                        (indent '(do ...@body))
                        "}"])
        "}).call(this)"])

(docs "tests any number of `alternating-conditions-and-branches`.  If
      an odd number of branches are supplied, the final branch is a
      default else clause.  To evaluate more than one expression as a
      branch, use the `do` macro, as shown in the examples:"
      tags [conditional flow-control]
      examples [ (if true (console.log 'here))
                 (if (= 1 arguments.length) (console.log "one argument")
                     (= 'blue favorite-color) (console.log "blue")
                     (assign examples 'difficult))
                 (if (foo?) (do (a b)
                                (c))
                     (bar?) (do (baz)
                                (wibble))
                     (do (d e)
                         (console.log 'default))) ])



(macro if (...alternating-conditions-and-branches)
       ["(function() {"
        (indent
         (interleave " else "
               (bulk-map alternating-conditions-and-branches
                         (#(cond val)
                           (if (!= (typeof val) 'undefined)
                                 ["if (" (transpile cond) ") {"
                                   (indent '(do @val))
                                   "}"]
                                 ["{" (indent '(do @cond)) "}"])))))
        "}).call(this)"])