(local insert table.insert)
(local _unpack (or table.unpack unpack))
(import-macros {: fn*} :macros.fn)

(fn seq [tbl]
  "Create sequential table.
Transforms original table to sequential table of key value pairs
stored as sequential tables in linear time.  If `tbl' is an
associative table, returns `[[key1 value1] ... [keyN valueN]]' table.
If `tbl' is sequential table, leaves it unchanged."
  (var assoc? false)
  (let [res []]
    (each [k v (pairs tbl)]
      (if (and (not assoc?)
               (not (= (type k) "number")))
          (set assoc? true))
      (insert res [k v]))
    (if assoc? res tbl)))

(fn first [itbl]
  "Return first element of an indexed table."
  (. (seq itbl) 1))


(fn rest [itbl]
  "Returns table of all elements of indexed table but the first one."
  [(_unpack (seq itbl) 2)])


(fn* conj
  "Insert `x' as a last element of indexed table `itbl'. Modifies `itbl'"
  ([] [])
  ([itbl] itbl)
  ([itbl x] (doto itbl (insert x)))
  ([itbl x & xs]
   (if (> (length xs) 0)
       (let [[y & xs] xs] (conj (conj itbl x) y (_unpack xs)))
       (conj itbl x))))


(fn* consj
  "Like conj but joins at the front. Modifies `itbl'."
  ([] [])
  ([itbl] itbl)
  ([itbl x] (doto itbl (insert 1 x)))
  ([itbl x & xs]
   (if (> (length xs) 0)
       (let [[y & xs] xs] (consj (consj itbl x) y (_unpack xs)))
       (consj itbl x))))


(fn cons [x itbl]
  "Insert `x' to `itbl' at the front. Modifies `itbl'."
  (doto (or itbl [])
    (insert 1 x)))


(fn* reduce
  "Reduce indexed table using function `f' and optional initial value `val'.

([f table])
([f val table])

`f' should be a function of 2 arguments.  If val is not supplied,
returns the result of applying f to the first 2 items in coll, then
applying f to that result and the 3rd item, etc.  If coll contains no
items, f must accept no arguments as well, and reduce returns the
result of calling f with no arguments.  If coll has only 1 item, it is
returned and f is not called.  If val is supplied, returns the result
of applying f to val and the first item in coll, then applying f to
that result and the 2nd item, etc.  If coll contains no items, returns
val and f is not called."
  ([f itbl]
   (let [itbl (seq itbl)]
     (match (length itbl)
       0 (f)
       1 (. itbl 1)
       2 (f (. itbl 1) (. itbl 2))
       _ (let [[a b & rest] itbl]
           (reduce f (f a b) rest)))))
  ([f val [x & xs]]
   (if (not (= x nil))
       (reduce f (f val x) xs)
      val)))

(fn* reduce-kv
  "Reduces an associative table using function `f' and initial value `val'.

([f val table])

`f' should be a function of 3 arguments.  Returns the result of
applying `f' to `val', the first key and the first value in coll, then
applying `f' to that result and the 2nd key and value, etc.  If coll
contains no entries, returns `val' and `f' is not called.  Note that
reduce-kv is supported on vectors, where the keys will be the
ordinals."  [f val kvtbl]
  (var res val)
  (each [_ [k v] (pairs (seq kvtbl))]
    (set res (f res k v)))
  res)

(fn* mapv
  "Maps function `f' over one or more tables.

Accepts arbitrary amount of tables, calls `seq' on each of it.
Function `f' must take the same amount of parameters as the amount of
tables passed to `mapv'. Applies `f' over first value of each
table. Then applies `f' to second value of each table. Continues until
any of the tables is exhausted. All remaining values are
ignored. Returns a table of results."
  ([f itbl]
   (local res [])
   (each [_ v (ipairs (seq itbl))]
     (insert res (f v)))
   res)
  ([f t1 t2]
   (let [res []
         t1 (seq t1)
         t2 (seq t2)]
     (var (i1 v1) (next t1))
     (var (i2 v2) (next t2))
     (while (and i1 i2)
       (insert res (f v1 v2))
       (set (i1 v1) (next t1 i1))
       (set (i2 v2) (next t2 i2)))
     res))
  ([f t1 t2 t3]
   (let [res []
         t1 (seq t1)
         t2 (seq t2)
         t3 (seq t3)]
     (var (i1 v1) (next t1))
     (var (i2 v2) (next t2))
     (var (i3 v3) (next t3))
     (while (and i1 i2 i3)
       (insert res (f v1 v2 v3))
       (set (i1 v1) (next t1 i1))
       (set (i2 v2) (next t2 i2))
       (set (i3 v3) (next t3 i3)))
     res))
  ([f t1 t2 t3 & tbls]
   (let [step (fn step [tbls]
                (when (->> tbls
                           (mapv #(~= (next $) nil))
                           (reduce #(and $1 $2)))
                  (cons (mapv #(first (seq $)) tbls) (step (mapv rest tbls)))))
         res []]
     (each [_ v (ipairs (step (consj tbls t3 t2 t1)))]
       (insert res (f (_unpack v))))
     res)))

(fn kvseq [kvtbl]
  (let [res []]
    (each [k v (pairs kvtbl)]
      (insert res [k v]))
    res))

(fn* eq?
  "Deep compare values."
  ([x] true)
  ([x y]
   (if (and (= (type x) "table") (= (type y) "table"))
       (and (reduce #(and $1 $2) true (mapv (fn [[k v]] (eq? (. y k) v)) (kvseq x)))
            (reduce #(and $1 $2) true (mapv (fn [[k v]] (eq? (. x k) v)) (kvseq y))))
       (= x y)))
  ([x y & xs]
   (reduce #(and $1 $2) (eq? x y) (mapv #(eq? x $) xs))))

;;;;;;;;;; fn stuff ;;;;;;;;
(fn identity [x] x)

(fn* comp
  ([] identity)
  ([f] f)
  ([f g]
   (fn*
     ([] (f (g)))
     ([x] (f (g x)))
     ([x y] (f (g x y)))
     ([x y z] (f (g x y z)))
     ([x y z & args] (f g x y z (_unpack args)))))
  ([f g & fs]
   (reduce comp (conj [f g] (_unpack fs)))))

(fn* every?
  [pred itbl]
  (if (= 0 (length itbl)) true
      (pred (first itbl)) (every? pred (rest itbl))
      false))

;; (fn* some
;;   [pred itbl]
;;   (if (> (length itbl) 0)
;;       ))

(fn* range
  "return range of of numbers from `lower' to `upper' with optional `step'."
  ([upper] (range 0 upper 1))
  ([lower upper] (range lower upper 1))
  ([lower upper step]
   (let [res []]
     (for [i lower (- upper step) step]
       (table.insert res i))
     res)))

{: seq
 : mapv
 : reduce
 : reduce-kv
 : conj
 : cons
 : first
 : rest
 : eq?
 : identity
 : comp
 : every?
 : range}