;; Previously in core.rs
; Logic

; Just to keep them if someone uses them
(def! true t)
(def! false nil)

; Identity function
(def! I (fn* [x] x))

(def! not (fn* [x]
    (if x nil t)))

(def! and (fn* [a b]
    (if a
        b)))

(def! or (fn* [a b]
    (if a
        a
        b)))

(def! xor (fn* [a b]
    (if a
        (not b)
        b)))

; Arithmetic
(def! > (fn* [a b]
    (< b a)))

(def! >= (fn* [a b]
    (not (< a b))))

(def! <= (fn* [a b]
    (>= b a)))

; Other functions in core.rs
(def! num? (fn* [a]
    (= (type a) :number)))

(def! sym? (fn* [a]
    (= (type a) :symbol)))

(def! list? (fn* [a]
    (= (type a) :list)))

(def! atom? (fn* [a]
    (= (type a) :atom)))

(def! empty? (fn* [l]
    (= (count l) 0)))

(def! mod (fn* [a b]
    (- a (* (floor (/ a b)) b))))

(def! ceil (fn* [n]
    (if (= (num n) 1)
        n
        (+ (floor n) 1))))

; Other functions
(def! assert-msg (fn* [e m]
    (if (not e)
        (raise m))))

(def! assert (fn* [e] (assert-msg e "Assertion failed")))

(def! assert-eq (fn* [a b]
    "returns an error if arguments are not equals, NIL otherwise"
    (assert-msg (= a b) (str "Expected " b (type b) ", found " a (type a)))))

(def! assert-fail (fn* [x]
    "returns NIL if evaluation of argument fails, error otherwise"
    (assert-msg (not (ok? (eval x))) (str "Expected failure, but " x " is correct"))))

;; Since thread safety is not required, I will leave it like this,
;;   to make thread safe just guard the function
(def! swap! (fn* [a f]
    (reset! a (f @a))))

;; File-interaction functions
(def! load-file (fn* [f]
    "open a mal file and evaluate its content"
    (eval (read-string (str "(do " (slurp f) "\nnil)")))))

(def! module (fn* [f]
    "load a file from the library path"
    (load-file (str MAL_HOME "/libs/" f ".mal"))))

(def! conf-reload (fn* []
    "reload mal config file"
    (load-file (str MAL_HOME "/" "config.mal"))))

;; Shorthand
(def! quit (fn* []
    "Quit the program with status '0'"
    (exit 0)))

;; variables
(def! MAL_HISTORY (str MAL_HOME "/" ".mal-history"))

;; helper functions
;   these functions are never called, their symbols should always resolve
;   in a special form, they are here only to provide informations through
;   the "find" and "help" functions
(def! def! (fn* [symbol value] "==SPECIAL FORM=="
    "<symbol>: Sym"
    "assign <value> to <symbol> in the current environment"
    "#returns: <value>"))

(def! let* (fn* [binding statement...] "==SPECIAL FORM=="
    "<bindings>: Vec"
    "create a new environment and assign values to symbols according"
    "to the <binding> vector then evaluate each <statement>"
    "#returns: result of the last evaluation"))

(def! do (fn* [statement...] "==SPECIAL FORM=="
    "evaluate each <statement> in the current environment"
    "#returns: result of the last evalutaion"))

(def! if (fn* [condition if-true if-false] "==SPECIAL FORM=="
    "first evaluate <condition>, based on the result of evaluation"
    "evaluates one of the two conditional branches, a missing branch"
    "evaluates to NIL"
    "#returns: result of the last evaluation"))

(def! fn* (fn* [arguments statement...] "==SPECIAL FORM=="
    "arguments: Vec"
    "#alias: λ"                                             ; >:3
    "#returns: new lambda that accepts <arguments>, evaluates each"
    "        : <statement> and returns the last evaluation's result"))

(def! help (fn* [symbol] "==SPECIAL FORM=="
    "symbol: Sym"
    "display an helper f or the specified symbol"
    "#returns: NIL"))

(def! find (fn* [substring...] "==SPECIAL FORM=="
    "print all the known symbols partially matching <substring> in"
    "the current environment"
    "#returns: NIL"))

(def! quote (fn* [statement] "==SPECIAL FORM=="
    "prevents <statement> from being evaluated, it's possible to use"
    "the ' symbol: 'sym is equivalent to (quote sym)"))

(def! ok? (fn* [statement] "==SPECIAL FORM=="
    "evaluate <statement>"
    "#returns: true if  evaluation succeeds, NIL otherwise"))

(def! eval (fn* [statement] "==SPECIAL FORM=="
    "evaluate <statement>"
    "#returns: the result of the evaluation"))

(def! BANNER
    (str 
        "; rust-mal: a toy lisp interpreter written in rust\n"
        "; $ mal [filename [args ...]] : run mal script with arguments, loaded in \"*ARGV*\"\n"
        "; (load-file <name>)          : load specified file while mal is running\n"
        "; (find [pattern...])         : list symbols matching all patterns\n"
        "; (help <symbol>)             : print information about a symbol\n"
        ";\n"
        "; enjoy ^.^\n"))

(def! reverse (fn* [x]
    "Reverses order of elements in the arg"
    (def! reverse-r (fn* [x e]
        (if (empty? x)
            e
            (reverse-r (cdr x) (cons (car x) e)))))
    (reverse-r x '())))

(def! map (fn* [f l]
    "Apply function f to all elements of l"
    (def! map-r (fn* [l p]
        (if (empty? l)
            p
            (map-r (cdr l) (cons (f (car l)) p)))))
    (reverse (map-r l '()))))

(def! filter (fn* [f l]
    "Remove all elements of l that don't satisfy f"
    (def! filter-r (fn* [l p]
        (if (empty? l)
            p
            (if (f (def! e (car l)))
                (filter-r (cdr l) (cons e p))
                (filter-r (cdr l) p)))))
    (reverse (filter-r l '()))))

(def! map-if (fn* [c f l]
    "Apply function f to all elements of l that satisfy c"
    (map (fn* [x] (if (c x) (f x) x)) l)))

(def! collect (fn* [f i l]
    "Apply collector function f to list l"
    "Collector function must accept two parameters:"
    "collector and current element, result is the collector in the next iteration"
    "Collector is initialized as i"
    (def! collect-r (fn* [c l]
        (if (empty? l)
            c
            (collect-r (f c (car l)) (cdr l)))))
    (collect-r i l)))

(conf-reload)