(ns bank
  (:use [account] :reload-all))

(defn add-random-account
  [bank]
  {:accounts (conj (:accounts bank) (create-random-account)) :overdraft-fund (:overdraft-fund bank)})


;; assuming this interpretation of the overdraft conditions:
(defn overdraft-allowed
  [bank account transaction]
  (cond (< (- (balance account) (:amount transaction)) -1000) false
        (zero? (:overdraft-fund bank)) false
        :else true))

(defn apply-simple-transaction
  [bank account transaction]
  (let [updated-transaction (assoc transaction :balance (+ (balance account) (:amount transaction)))
        updated-account (assoc account
                     :transaction-history (conj (:transaction-history account) updated-transaction))]
    (assoc-in bank [:accounts (.indexOf (bank :accounts) account)] updated-account)))

(defn apply-overdraft
  [bank account transaction]
  (let [overdraft-amount (- (:amount transaction) (balance account))
        charge (* overdraft-amount (overdraft-charge (:type account)))
        updated-transaction (assoc transaction :balance (- (+ overdraft-amount charge)))
        updated-account (assoc account
                     :transaction-history (conj (:transaction-history account) updated-transaction))
        updated-overdraft-fund (- (:overdraft-fund bank) overdraft-amount)]
    (assoc-in bank [:accounts (.indexOf (bank :accounts) account)] updated-account)
    (assoc bank :overdraft-fund updated-overdraft-fund)))

(def failed-overdraft-charge 10)

(defn apply-failed-overdraft
  [bank account transaction]
  (let [updated-transaction (assoc transaction :balance (- (balance account) failed-overdraft-charge))
        updated-account (assoc account
                     :transaction-history (conj (:transaction-history account) updated-transaction))]
    (assoc-in bank [:accounts (.indexOf (bank :accounts) account)] updated-account)))

;; current balance of account is defined by the balance field of the last transaction.
;; apply-bonus and apply-interest are not considered transactions themselves.

(defn apply-extras
  [bank account amount]
  (let [transaction (last (:transaction-history account))
        updated-transaction (assoc transaction :balance (+ (:balance transaction) amount))
        updated-account (assoc-in account [:transaction-history (.indexOf (account :transaction-history) transaction)] updated-transaction)]
    (assoc-in bank [:accounts (.indexOf (bank :accounts) account)] updated-account)))

(defn apply-interest
  [bank account]
  (apply-extras bank account (interest-amount account)))

(defn apply-bonus
  [bank account]
  (apply-extras bank account (bonus-amount account)))

(defn extra-applies?
  [transaction-number interval]
  (cond
    (zero? transaction-number) false
    (zero? (mod transaction-number interval)) true
    :else false))

(defn apply-transaction
  [bank account transaction]
  (let [account-index (.indexOf (bank :accounts) account)
        bank (cond (>= (:amount transaction) 0) (apply-simple-transaction bank account transaction)
                   (>= (- (balance account) (:amount transaction)) 0) (apply-simple-transaction bank account transaction)
                   (true? (overdraft-allowed bank account transaction)) (apply-overdraft bank account transaction))
        transaction-number (.size (:transaction-history account))
        updated-account ((bank :accounts) account-index)
        bank (if (extra-applies? transaction-number bonus-interval) (apply-bonus bank updated-account) bank)
        updated-account ((bank :accounts) account-index)
        bank (if (extra-applies? transaction-number interest-interval) (apply-interest bank updated-account) bank)]
    bank))