#lang debug racket/base
(require racket/contract racket/function rackunit racket/list "pass.rkt" "drawing.rkt" "quad.rkt")
(provide quad-compile)

(define/contract (posn-add p0 p1)
  ($point? $size? . -> . $point?)
  ($point (+ ($point-x p0) ($size-width p1)) (+ ($point-y p0) ($size-height p1))))

(define/contract (size char)
  ($quad? . -> . $size?)
  ($size 1 1))

(define/contract (advance char)
  ($quad? . -> . $size?)
  ($size 1 0))

(define/contract (quadify str)
  (string? . -> . (listof $quad?))
  (for/list ([c (in-string str)])
            ($quad #f c)))

(define/contract (make-compiler . passes)
  (() #:rest (listof pass/c)
      . ->* . (any/c . -> . (listof any/c)))
  (apply compose1 (reverse (cons quadify passes))))

(define (min-x rect) ($point-x ($rect-origin rect)))
(define (width rect) ($size-width ($rect-size rect)))
(define (max-x rect) (+ (min-x rect) (width rect)))
(define (min-y rect) ($point-y ($rect-origin rect)))
(define (height rect) ($size-height ($rect-size rect)))
(define (max-y rect) (+ (min-y rect) (height rect)))

(define/contract (rect-contains-point? rect pt)
  ($rect? $point? . -> . boolean?)
  (and (<= (min-x rect) ($point-x pt) (max-x rect))
       (<= (min-y rect) ($point-y pt) (max-y rect))))

(define/contract (rect-contains-rect? outer inner)
  ($rect? $rect? . -> . boolean?)
  (and (rect-contains-point? outer ($rect-origin inner))
       (rect-contains-point? outer ($point (max-x inner) (max-y inner)))))
  
(define (has-position? q) (not (eq? ($quad-posn q) #false)))
(define-pass (layout qs)
  #:precondition (λ (qs) (and (list? qs) (andmap (λ (q) (not (has-position? q))) qs)))
  #:postcondition (λ (qs) (and (list? qs) (andmap has-position? qs)))
  (define frame ($rect ($point 0 0) ($size (current-wrap-width) 30)))
  (define (quad-fits? q posn)
    (define q-size (size q))
    (define quad-rect ($rect posn q-size))
    (and (rect-contains-rect? frame quad-rect) posn))
  (for/fold ([posn ($point 0 0)]
             #:result qs)
            ([q (in-list qs)])
    (define first-posn-on-next-line ($point 0 (add1 ($point-y posn))))
    (define winning-posn (or (ormap (λ (posn) (quad-fits? q posn)) (list posn first-posn-on-next-line)) (error 'no-posn-that-fits)))
    (set-$quad-posn! q winning-posn)
    (posn-add winning-posn (advance q))))

(define-pass (make-drawing-insts qs)
  #:precondition (λ (qs) (andmap has-position? qs))
  #:postcondition (λ (qs) (andmap $drawing-inst? qs))
  (flatten
   (list ($doc 'start) ($page 'start)
         (for/list ([q (in-list qs)])
                   (cond
                     [($quad? q)
                      (list ($move ($quad-posn q)) ($text ($quad-char q)))]
                     [else (error 'render-unknown-thing)]))
         ($page 'end) ($doc 'end))))
  
(define quad-compile (make-compiler layout make-drawing-insts))
#;(check-equal? 
   (list
    ($quad ($point 0 0) #\H)
    ($quad ($point 1 0) #\e)
    ($quad ($point 2 0) #\l)
    ($quad ($point 3 0) #\l)
    ($quad ($point 4 0) #\o)
    ($quad ($point 0 1) #\space)
    ($quad ($point 1 1) #\w)
    ($quad ($point 2 1) #\o)
    ($quad ($point 3 1) #\r)
    ($quad ($point 4 1) #\l)
    ($quad ($point 0 2) #\d)))