;;; Copyright (c) 2017, Sudhir Shenoy.  All rights reserved.

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;;;; Calendar.lisp - Holiday calendar class and associated methods to
;;;; classify dates as business days / holidays / weekends

(in-package :cl-dates)

(defparameter +default-weekend+ '(:saturday :sunday))

(defparameter +known-centres+
  ;;    Centre              Hol function     discriminant
  (list :Eurex       (list #'german-holidays :Eurex)
	:Frankfurt   (list #'german-holidays :Eurex)
	:Euwax       (list #'german-holidays :Euwax)
	:Stuttgart   (list #'german-holidays :Euwax)
	:Germany     (list #'german-holidays :settlement)
	:DEM         (list #'german-holidays :settlement) ; Deutsche Mark doesn't exist but still ...
	:Tokyo       (list #'japan-holidays  :settlement)
	:Japan       (list #'japan-holidays  :settlement)
	:JPY         (list #'japan-holidays  :settlement)
	:Zurich      (list #'swiss-holidays  :settlement)
	:Switzerland (list #'swiss-holidays  :settlement)
	:CHF         (list #'swiss-holidays  :settlement)
	:TARGET      (list #'target-holidays :settlement)
	:EUR         (list #'target-holidays :settlement)
	:London      (list #'uk-holidays     :settlement)
	:UK          (list #'uk-holidays     :settlement)
	:GBP         (list #'uk-holidays     :settlement)
	:US          (list #'us-holidays     :settlement)
	:USD         (list #'us-holidays     :settlement)
	:NYSE        (list #'us-holidays     :NYSE)
	:NY          (list #'us-holidays     :NYSE)
	:UST         (list #'us-holidays     :bonds)
	:US-Bond     (list #'us-holidays     :bonds)))

;; base class - no functionality (null calendar)
(defclass calendar ()
  ((name :initarg :name :accessor name)
   (weekend :initarg :weekend :accessor weekend)))

(defclass calendar-single (calendar)
  ((centre :initarg :centre :accessor centre)
   (holidays :initarg :holidays :accessor holidays)
   (holidays-min-year :accessor holidays-min-year)
   (holidays-max-year :accessor holidays-max-year)))

(defclass calendar-union (calendar)
  ((calendars :initarg :calendars :accessor calendars))) ; list of calendars

(defun make-calendar (centres &key (name nil) (weekend (copy-list +default-weekend+))
				   (holidays nil) (base-year 0))
  (typecase centres
    (keyword (multiple-value-bind (hols from-year to-year) (get-holiday-hash centres base-year)
		(let ((cal (make-instance 'calendar-single :name name :centre :centres
							   :weekend weekend :holidays hols)))
		  (setf (holidays-min-year cal) from-year
			(holidays-max-year cal) to-year)
		  (unless name
		    (setf (name cal) (string centres)))
		  (when holidays
		    (dolist (hol holidays)
		      (add-holiday cal hol)))
		  cal)))
    ((and list (not null)) (let ((cal (make-instance 'calendar-union :name name
								     :calendars nil)))
			     (unless name
			       (setf (name cal) (format nil "~{~a~^+~}" centres)))
			     (dolist (centre centres)
			       (push (make-calendar centre :name nil :weekend weekend
							   :holidays holidays
							   :base-year base-year)
				     (calendars cal)))
			     cal))
    (t (when (null name)
	 (setf name "Null Calendar"))
     (make-instance 'calendar :name name :weekend weekend))))

(defun known-centres ()
  "Return centres for which holiday auto-generation is supported"
  (loop for x on +known-centres+ by #'cddr
	collect (car x)))

(defun get-holidays-for-centre (centre year)
  (let ((spec (getf +known-centres+ centre)))
    (if spec
	(funcall (first spec) year :which (second spec))
	nil)))

(defun get-holiday-hash (centre base-year)
  (when (or (not (integerp base-year)) (<= base-year 1950))
    (setf base-year (date->ymd (todays-date))))
  (let* ((from-year (- base-year 2))
	 (to-year (+ base-year 3))
	 (hols (loop for yy from from-year upto to-year
		     collect (get-holidays-for-centre centre yy)))
	 (hash (make-hash-table :test 'equal)))
    (dolist (hols-for-year hols)
      (dolist (hol hols-for-year)
	(setf (gethash hol hash) 1)))
    (values hash from-year to-year)))

(defmethod has-holidays-for-year ((cal calendar) (year integer))
  t)

(defmethod has-holidays-for-year ((cal calendar-single) (year integer))
  (<= (holidays-min-year cal) year (holidays-max-year cal)))

(defmethod has-holidays-for-year ((cal calendar-union) (year integer))
  (every #'identity (mapcar (lambda(x) (has-holidays-for-year x year)) (calendars cal))))

(defmethod update-calendar ((cal calendar) (year integer))
  cal)

(defmethod update-calendar ((cal calendar-single) (year integer))
  (let ((from-year (min (- year 2) (1+ (holidays-max-year cal))))
	(to-year (max (+ year 3) (1- (holidays-min-year cal)))))
    (loop for yy from from-year upto to-year
	  when (or (< yy (holidays-min-year cal))
		   (> yy (holidays-max-year cal)))
	    do (let ((hols (get-holidays-for-centre (centre cal) yy)))
		 (dolist (hol hols)
		   (setf (gethash hol (holidays cal)) 1))))
    (setf (holidays-min-year cal) (min (holidays-min-year cal) from-year)
	  (holidays-max-year cal) (max (holidays-max-year cal) to-year)))
  cal)

(defmethod update-calendar ((cal calendar-union) (year integer))
  (dolist (c (calendars cal))
    (update-calendar c year))
  cal)

(defmethod weekend-p (date (weekend-days list))
  (member (day-of-week date) weekend-days))

(defmethod weekend-p (date (cal calendar))
  (weekend-p date (weekend cal)))

(defmethod weekday-p (date (weekend-days list))
  (not (weekend-p date weekend-days)))

(defmethod weekday-p (date (cal calendar))
  (weekday-p date (weekend cal)))

(defmethod holiday-p (date (cal calendar))
  (declare (ignore date cal))
  nil)

(defmethod holiday-p (date (cal calendar-single))
  (let ((year (date->ymd date)))
    (unless (has-holidays-for-year cal year)
      (update-calendar cal year)))
  (not (null (gethash (jday-number date) (holidays cal)))))

(defmethod holiday-p (date (cal calendar-union))
  (some #'identity (lambda (cal) (holiday-p date cal)) (calendars cal)))

(defmethod business-day-p (date (cal calendar))
  (and (weekday-p date cal)
       (not (holiday-p date cal))))

(defmethod add-holiday ((cal calendar-single) date)
  (let ((year (date->ymd date)))
    (unless (<= (holidays-min-year cal) year (holidays-max-year cal))
      (update-calendar cal year)))
  (setf (gethash (jday-number date) (holidays cal)) 2))

(defmethod remove-holiday ((cal calendar-single) date)
  (remhash (jday-number date) (holidays cal)))