#lang racket/base
(require "readability.rkt")
(require racket/contract racket/match)
(require (only-in racket/path filename-extension))
(require (only-in racket/format ~a))
(require (only-in racket/list empty empty? second filter-not splitf-at takef dropf))
(require (only-in racket/string string-join))
(require (only-in xml xexpr?))
(provide (all-defined-out) (all-from-out "readability.rkt"))

;; setup for test cases
(module+ test
  (require rackunit)
  (define foo-path-strings '("foo" "foo.txt" "foo.bar" "foo.bar.txt"))
  (define-values (foo-path foo.txt-path foo.bar-path foo.bar.txt-path) (apply values (map string->path foo-path-strings)))
  ;; test the sample paths before using them for other tests
  (define foo-paths (list foo-path foo.txt-path foo.bar-path foo.bar.txt-path))
  (for-each check-equal? (map path->string foo-paths) foo-path-strings))


;; does path have a certain extension
(define/contract (has-ext? path ext)
  (path? symbol? . -> . boolean?)
  (define ext-of-path (filename-extension path))
  (and ext-of-path (equal? (bytes->string/utf-8 ext-of-path) (as-string ext))))

(module+ test
  (check-false (has-ext? foo-path 'txt)) 
  (check-true (has-ext? foo.txt-path 'txt))
  (check-true (has-ext? foo.bar.txt-path 'txt))
  (check-false (has-ext? foo.bar.txt-path 'doc))) ; wrong extension


;; take one extension off path
(define/contract (remove-ext path)
  (path? . -> . path?)
  (path-replace-suffix path ""))

(module+ test  
  (check-equal? (remove-ext foo-path) foo-path)
  (check-equal? (remove-ext foo.txt-path) foo-path)
  (check-equal? (remove-ext foo.bar.txt-path) foo.bar-path)
  (check-not-equal? (remove-ext foo.bar.txt-path) foo-path)) ; does not remove all extensions


;; take all extensions off path
(define/contract (remove-all-ext path)
  (path? . -> . path?)
  (define path-with-removed-ext (remove-ext path))
  (if (equal? path path-with-removed-ext)
      path
      (remove-all-ext path-with-removed-ext)))

(module+ test  
  (check-equal? (remove-all-ext foo-path) foo-path)
  (check-equal? (remove-all-ext foo.txt-path) foo-path)
  (check-not-equal? (remove-all-ext foo.bar.txt-path) foo.bar-path) ; removes more than one ext
  (check-equal? (remove-all-ext foo.bar.txt-path) foo-path))


;; is it an xexpr attributes?
(define/contract (xexpr-attr? x)
  (any/c . -> . boolean?)
  (match x
    ; list of symbol + string pairs
    [(list (list (? symbol? key) (? string? value)) ...) #t]
    [else #f]))

(module+ test  
  (check-true (xexpr-attr? '((key "value"))))
  (check-true (xexpr-attr? '((key "value") (foo "bar"))))
  (check-false (xexpr-attr? '((key "value") "foo" "bar"))) ; content, not attr
  (check-false (xexpr-attr? '(key "value"))) ; not a nested list
  (check-false (xexpr-attr? '(("key" "value")))) ; two strings
  (check-false (xexpr-attr? '((key value))))) ; two symbols


;; is it xexpr content?
(define/contract (xexpr-content? x)
  (any/c . -> . boolean?)
  (match x
    ;; this is more strict than xexpr definition in xml module
    ;; don't allow symbols or numbers to be part of content
    [(list elem ...) (andmap (λ(i) (or (string? i) (named-xexpr? i))) elem)]
    [else #f]))

(module+ test  
  (check-true (xexpr-content? '("p" "foo" "123")))
  (check-false (xexpr-content? "foo")) ; not a list
  (check-false (xexpr-content? '("p" "foo" 123))) ; includes number
  (check-false (xexpr-content? '(p "foo" "123"))) ; includes symbol
  (check-false (xexpr-content? '(((key "value")) "foo" "bar"))) ; includes attr
  (check-false (xexpr-content? '("foo" "bar" ((key "value")))))) ; malformed


;; is it a named x-expression?
;; todo: rewrite this recurively so errors can be pinpointed (for debugging)
(define/contract (named-xexpr? x)
  (any/c . -> . boolean?)
  (and (xexpr? x) ; meets basic xexpr contract
       (match x
         [(list (? symbol? name) rest ...) ; is a list starting with a symbol
          (or (xexpr-content? rest) ; the rest is content or ...
              (and (xexpr-attr? (car rest)) (xexpr-content? (cdr rest))))] ; attr + content 
         [else #f])))

(module+ test  
  (check-true (named-xexpr? '(p "foo" "bar")))
  (check-true (named-xexpr? '(p ((key "value")) "foo" "bar")))
  (check-false (named-xexpr? "foo")) ; not a list with symbol
  (check-false (named-xexpr? '(p "foo" "bar" ((key "value"))))) ; malformed
  (check-false (named-xexpr? '("p" "foo" "bar"))) ; no name
  (check-false (named-xexpr? '(p 123)))) ; content is a number

;; helper for comparison of values
;; normal function won't work for this. Has to be syntax-rule
(define-syntax-rule (values->list vs)
  (call-with-values (λ() vs) list))


;; create named-xexpr from parts (opposite of break-named-xexpr)
(define/contract (make-named-xexpr name [attr empty] [content empty])
  ((symbol?) (xexpr-attr? xexpr-content?) . ->* . named-xexpr?)
  (filter-not empty? `(,name ,attr ,@content)))

(module+ test
  (check-equal? (make-named-xexpr 'p) '(p))
  (check-equal? (make-named-xexpr 'p '((key "value"))) '(p ((key "value"))))
  (check-equal? (make-named-xexpr 'p empty '("foo" "bar")) '(p "foo" "bar"))
  (check-equal? (make-named-xexpr 'p '((key "value")) (list "foo" "bar")) 
                '(p ((key "value")) "foo" "bar")))


;; decompose named-xexpr into parts (opposite of make-named-xexpr)
(define/contract (break-named-xexpr nx)
  (named-xexpr? . -> . (values symbol? xexpr-attr? xexpr-content?))
  (match 
      ; named-xexpr may or may not have attr
      ; if not, add empty attr so that decomposition only handles one case
      (match nx
        [(list _ (? xexpr-attr?) _ ...) nx]
        [else `(,(car nx) ,empty ,@(cdr nx))])
    [(list name attr content ...) (values name attr content)]))

(module+ test
  (check-equal? (values->list (break-named-xexpr '(p))) 
                (values->list (values 'p empty empty)))
  (check-equal? (values->list (break-named-xexpr '(p "foo"))) 
                (values->list (values 'p empty '("foo"))))
  (check-equal? (values->list (break-named-xexpr '(p ((key "value"))))) 
                (values->list (values 'p '((key "value")) empty)))
  (check-equal? (values->list (break-named-xexpr '(p ((key "value")) "foo"))) 
                (values->list (values 'p '((key "value")) '("foo")))))


;; apply filter proc recursively
(define/contract (filter-tree proc tree)
  (procedure? list? . -> . list?)
  (define (remove-empty x)
    (cond
      [(list? x) (map remove-empty (filter-not empty? x))]
      [else x]))
  
  (define (filter-tree-inner proc tree)
    (cond
      [(list? tree) (map (λ(i) (filter-tree-inner proc i)) tree)]
      [else (if (proc tree) tree empty)]))
  
  (remove-empty (filter-tree-inner proc tree)))

(module+ test
  (check-equal? (filter-tree string? '(p)) empty)
  (check-equal? (filter-tree string? '(p "foo" "bar")) '("foo" "bar"))
  (check-equal? (filter-tree string? '(p "foo" (p "bar"))) '("foo" ("bar"))))

;; apply filter-not proc recursively
(define/contract (filter-not-tree proc tree)
  (procedure? list? . -> . list?)
  (filter-tree (λ(i) (not (proc i))) tree))

(module+ test
  (check-equal? (filter-not-tree string? '(p)) '(p))
  (check-equal? (filter-not-tree string? '(p "foo" "bar")) '(p))
  (check-equal? (filter-not-tree string? '(p "foo" (p "bar"))) '(p (p))))


;; Find adjacent newline characters in a list and merge them into one item
;; Scribble, by default, makes each newline a separate list item
;; In practice, this is worthless.
(define/contract (merge-newlines x)
  (list? . -> . list?)
  (define (newline? x)
    (and (string? x) (equal? "\n" x)))
  (define (not-newline? x)
    (not (newline? x)))
  
  (define (really-merge-newlines xs [acc '()])
    (if (empty? xs)
        acc
        ;; Try to peel the newlines off the front.
        (let-values ([(leading-newlines remainder) (splitf-at xs newline?)])
          (if (not (empty? leading-newlines)) ; if you got newlines ...
              ;; combine them into a string and append them to the accumulator, 
              ;; and recurse on the rest
              (really-merge-newlines remainder (append acc (list (string-join leading-newlines ""))))
              ;; otherwise peel off elements up to the next newline, append them to accumulator,
              ;; and recurse on the rest
              (really-merge-newlines (dropf remainder not-newline?) 
                               (append acc (takef remainder not-newline?)))))))
  
  (cond
    [(list? x) (really-merge-newlines (map merge-newlines x))]
    [else x]))

(module+ test
  (check-equal? (merge-newlines '(p "\n" "foo" "\n" "\n" "bar" (em "\n" "\n" "\n"))) 
                '(p "\n" "foo" "\n\n" "bar" (em "\n\n\n"))))