(ns auto-ap.ledger
  (:require [datomic.api :as d]
            [auto-ap.datomic.accounts :as a]
            [auto-ap.datomic :refer [uri remove-nils]]))


(defn datums->impacted-entity [db [e changes]]
  (let [entity (d/pull db '[* {:invoice/_expense-accounts [:db/id] :transaction/_accounts [:db/id]}] e)
        namespaces (->> changes
                        (map :a)
                        (map namespace)
                        set)]
    (cond (namespaces "invoice" )   [[:invoice e]]
          (namespaces "invoice-expense-account" ) [[:invoice (:db/id (:invoice/_expense-accounts entity))]]
          (namespaces "transaction-account" ) [[:transaction (:db/id (:transaction/_accounts entity))]]
          (namespaces "transaction" )   [[:transaction e]]
          :else nil)))



(defn infer-entity [_ [_ changes]]
  (let [namespaces (->> changes
                        (map :a)
                        (map namespace)
                        set)]
    (cond (namespaces "invoice" )   :invoice
          (namespaces "invoice-expense-account" )   :invoice-expense-account
          (namespaces "transaction-account" )   :transaction-account
          :else nil)))

(defmulti entity-change->ledger (fn [_ [type]]
                                  type))

(defmethod entity-change->ledger :invoice
  [db [type id]]
  (let [entity (d/pull db ['* {:invoice/vendor '[*] :invoice/payment '[*]}] id)]
    (remove-nils 
     {:journal-entry/source "invoice"
      :journal-entry/client (:db/id (:invoice/client entity))
      :journal-entry/date (:invoice/date entity)
      :journal-entry/original-entity (:db/id entity)
      :journal-entry/vendor (:db/id (:invoice/vendor entity))
      :journal-entry/amount (:invoice/total entity)

      :journal-entry/line-items (into [{:journal-entry-line/account (a/get-account-by-numeric-code-and-sets 2110 ["default"]) 
                                        :journal-entry-line/location "A"
                                        :journal-entry-line/credit (:invoice/total entity)}]
                                      (map (fn [ea]
                                             (remove-nils {:journal-entry-line/account (:db/id (:invoice-expense-account/account ea)) 
                                                           :journal-entry-line/location (or (:invoice-expense-account/location ea) "HQ") ;; TODO?
                                                           :journal-entry-line/debit (:invoice-expense-account/amount ea)}))
                                              (:invoice/expense-accounts entity)))
      :journal-entry/cleared (and (< (:invoice/outstanding-balance entity) 0.01)
                                  (every? #(= :payment-status/cleared (:payment/status %)) (:invoice/payments entity))
                                  )})))

(defmethod entity-change->ledger :transaction
  [db [type id]]
  (let [entity (d/pull db ['* {:transaction/vendor '[*]
                               :transaction/client '[*]
                               :transaction/bank-account '[* {:bank-account/type [:db/ident]}]
                               :transaction/accounts '[*
                                                       {:transaction-account/account [*]}] }] id)
        bank-account-type (-> entity :transaction/bank-account :bank-account/type :db/ident)
        decreasing? (< (:transaction/amount entity) 0.0)
        credit-from-bank? decreasing?
        debit-from-bank? (not decreasing?)]
    (when-not (:transaction/exclude-from-ledger entity)
      (remove-nils 
       {:journal-entry/source "transaction"
        :journal-entry/client (:db/id (:transaction/client entity))
        :journal-entry/date (:transaction/date entity)
        :journal-entry/original-entity (:db/id entity)
        :journal-entry/vendor (:db/id (:transaction/vendor entity))
        :journal-entry/amount (Math/abs (:transaction/amount entity))

        :journal-entry/line-items (into [(remove-nils {:journal-entry-line/account (:db/id (:transaction/bank-account entity))
                                                       :journal-entry-line/location "A"
                                                       :journal-entry-line/credit (when credit-from-bank?
                                                                                    (Math/abs (:transaction/amount entity)))
                                                       :journal-entry-line/debit (when debit-from-bank?
                                                                                   (Math/abs (:transaction/amount entity)))})
                                         ]
                                        (map
                                         (fn [a]
                                           (remove-nils{:journal-entry-line/account (:db/id (:transaction-account/account a))
                                                        :journal-entry-line/location (:transaction-account/location a)
                                                        :journal-entry-line/debit (when credit-from-bank?
                                                                                    (Math/abs (:transaction-account/amount a)))
                                                        :journal-entry-line/credit (when debit-from-bank?
                                                                                     (Math/abs (:transaction-account/amount a)))}))
                                         (if (seq (:transaction/accounts entity))
                                           (:transaction/accounts entity)
                                           [{:transaction-account/amount (:transaction/amount entity)}])))
        
        :journal-entry/cleared true}))))

(defmethod entity-change->ledger :invoice-expense-account
  [db [entity changes]]
  nil
  )

(defmethod entity-change->ledger nil
  [db [entity changes]]
  nil)

#_(defn entity-change->ledger [[entity-id changes]]
  [entity-id (infer-entity changes)])

(defn ledger-entries->transaction [entries]
  (into [[:replace-general-ledger (:journal-entry/original-entity (first entries))]]
        entries))

(defn process-one [report-queue]
  
  (let [transaction (.take report-queue)
        _ (println "processing transaction" transaction)
        db (:db-after transaction)
        affected-entities (->> (:tx-data transaction)
                               (map (fn [^datomic.db.Datum x]
                                      {:e (:e x)
                                       :a (d/ident db (:a x))
                                       :v (:v x)
                                       :added (:added x)}))
                               (group-by :e)
                               (mapcat #(datums->impacted-entity db %))
                               (set)) 
        d-txs (->> affected-entities
                   (map #(entity-change->ledger db %))
                   (filter seq))
        retractions (map (fn [[_ e]] [:db/retractEntity [:journal-entry/original-entity e]]) affected-entities)]

    (when (seq retractions)
      (println "Retracting " retractions)
      @(d/transact (d/connect uri) retractions))
    
    
    (doseq [d-tx d-txs]
      (clojure.pprint/pprint d-tx)
      #_(println "updating general-ledger " d-tx)
      @(d/transact (d/connect uri) [d-tx]))))

(defn process-all []
  (while (not (Thread/interrupted))
    (process-one (d/tx-report-queue (d/connect uri) ))))


#_(process-one (d/tx-report-queue (d/connect uri) ))

#_(process-all)