;;; -*- lexical-binding: t -*-
;;
;; this file:
;;   https://dataswamp.org/~incal/emacs-init/frame-size.el
;;
;; frame size = top of seat tube to center of bottom bracket
;;
;; source MTB:
;;   https://www.evanscycles.com/help/bike-sizing-mountain

(require 'cl-lib)

(defun in-interval (a min max &optional exclusive)
  (let ((op (if exclusive #'< #'<=)))
    (and (apply op (list min a))
         (apply op (list a max)) )))

(defun frame-size (h &optional mtb)
  (pcase-let*((table (if mtb '(((148 158) (33 37))
                               ((158 168) (38 42))
                               ((168 178) (43 47))
                               ((178 185) (48 52))
                               ((185 193) (53 57))
                               ((193 198) (58 61)) )
                       '(((168 175) (54 55)) ; data source lost
                         ((175 183) (56 58))
                         ((183 191) (58 60)) )))
              (`((,h-min ,h-max) (,f-min ,f-max))
               (cl-find-if (lambda (e)
                             (in-interval h (caar e) (cadar e)) )
                           table) )
              (f-cm (+ (* (/ (- h     h-min)
                             (- h-max h-min)
                             1.0)
                          (- f-max f-min) )
                       f-min) )
              (f-cm-round (round f-cm))
              (f-inches   (round (/ f-cm 2.54))) )
    (message "%d cm (%d\")" f-cm-round f-inches) ))

;;   (insert " ; " (frame-size 180 t)) ; 49 cm (19")
;;   (insert " ; " (frame-size 181 t)) ; 50 cm (20")
;;   (insert "  ; " (frame-size 180))  ; 57 cm (23")
;;   (insert "  ; " (frame-size 190))  ; 60 cm (24")

(provide 'frame-size)