(require 'company)
(eval-when-compile (require 'cl))

(defconst company-css-property-alist
  ;; see http://www.w3.org/TR/CSS21/propidx.html
  '(("azimuth" angle "left-side" "far-left" "left" "center-left" "center"
     "center-right" "right" "far-right" "right-side" "behind" "leftwards"
     "rightwards")
    ("background" background-color background-image background-repeat
     background-attachment background-position)
    ("background-attachment" "scroll" "fixed")
    ("background-color" color "transparent")
    ("background-image" uri "none")
    ("background-position" percentage length "left" "center" "right" percentage
     length "top" "center" "bottom" "left" "center" "right" "top" "center"
     "bottom")
    ("background-repeat" "repeat" "repeat-x" "repeat-y" "no-repeat")
    ("border" border-width border-style border-color)
    ("border-bottom" border)
    ("border-bottom-color" border-color)
    ("border-bottom-style" border-style)
    ("border-bottom-width" border-width)
    ("border-collapse" "collapse" "separate")
    ("border-color" color "transparent")
    ("border-left" border)
    ("border-left-color" border-color)
    ("border-left-style" border-style)
    ("border-left-width" border-width)
    ("border-right" border)
    ("border-right-color" border-color)
    ("border-right-style" border-style)
    ("border-right-width" border-width)
    ("border-spacing" length length)
    ("border-style" border-style)
    ("border-top" border)
    ("border-top-color" border-color)
    ("border-top-style" border-style)
    ("border-top-width" border-width)
    ("border-width" border-width)
    ("bottom" length percentage "auto")
    ("caption-side" "top" "bottom")
    ("clear" "none" "left" "right" "both")
    ("clip" shape "auto")
    ("color" color)
    ("content" "normal" "none" string uri counter "attr()" "open-quote"
     "close-quote" "no-open-quote" "no-close-quote")
    ("counter-increment" identifier integer "none")
    ("counter-reset" identifier integer "none")
    ("cue" cue-before cue-after)
    ("cue-after" uri "none")
    ("cue-before" uri "none")
    ("cursor" uri "*" "auto" "crosshair" "default" "pointer" "move" "e-resize"
     "ne-resize" "nw-resize" "n-resize" "se-resize" "sw-resize" "s-resize"
     "w-resize" "text" "wait" "help" "progress")
    ("direction" "ltr" "rtl")
    ("display" "inline" "block" "list-item" "run-in" "inline-block" "table"
     "inline-table" "table-row-group" "table-header-group" "table-footer-group"
     "table-row" "table-column-group" "table-column" "table-cell"
     "table-caption" "none")
    ("elevation" angle "below" "level" "above" "higher" "lower")
    ("empty-cells" "show" "hide")
    ("float" "left" "right" "none")
    ("font" font-style font-variant font-weight font-size "/" line-height
     font-family "caption" "icon" "menu" "message-box" "small-caption"
     "status-bar")
    ("font-family" family-name generic-family)
    ("font-size" absolute-size relative-size length percentage)
    ("font-style" "normal" "italic" "oblique")
    ("font-variant" "normal" "small-caps")
    ("font-weight" "normal" "bold" "bolder" "lighter" "100" "200" "300" "400"
     "500" "600" "700" "800" "900")
    ("height" length percentage "auto")
    ("left" length percentage "auto")
    ("letter-spacing" "normal" length)
    ("line-height" "normal" number length percentage)
    ("list-style" list-style-type list-style-position list-style-image)
    ("list-style-image" uri "none")
    ("list-style-position" "inside" "outside")
    ("list-style-type" "disc" "circle" "square" "decimal" "decimal-leading-zero"
     "lower-roman" "upper-roman" "lower-greek" "lower-latin" "upper-latin"
     "armenian" "georgian" "lower-alpha" "upper-alpha" "none")
    ("margin" margin-width)
    ("margin-bottom" margin-width)
    ("margin-left" margin-width)
    ("margin-right" margin-width)
    ("margin-top" margin-width)
    ("max-height" length percentage "none")
    ("max-width" length percentage "none")
    ("min-height" length percentage)
    ("min-width" length percentage)
    ("orphans" integer)
    ("outline" outline-color outline-style outline-width)
    ("outline-color" color "invert")
    ("outline-style" border-style)
    ("outline-width" border-width)
    ("overflow" "visible" "hidden" "scroll" "auto")
    ("padding" padding-width)
    ("padding-bottom" padding-width)
    ("padding-left" padding-width)
    ("padding-right" padding-width)
    ("padding-top" padding-width)
    ("page-break-after" "auto" "always" "avoid" "left" "right")
    ("page-break-before" "auto" "always" "avoid" "left" "right")
    ("page-break-inside" "avoid" "auto")
    ("pause" time percentage)
    ("pause-after" time percentage)
    ("pause-before" time percentage)
    ("pitch" frequency "x-low" "low" "medium" "high" "x-high")
    ("pitch-range" number)
    ("play-during" uri "mix" "repeat" "auto" "none")
    ("position" "static" "relative" "absolute" "fixed")
    ("quotes" string string "none")
    ("richness" number)
    ("right" length percentage "auto")
    ("speak" "normal" "none" "spell-out")
    ("speak-header" "once" "always")
    ("speak-numeral" "digits" "continuous")
    ("speak-punctuation" "code" "none")
    ("speech-rate" number "x-slow" "slow" "medium" "fast" "x-fast" "faster"
     "slower")
    ("stress" number)
    ("table-layout" "auto" "fixed")
    ("text-align" "left" "right" "center" "justify")
    ("text-decoration" "none" "underline" "overline" "line-through" "blink")
    ("text-indent" length percentage)
    ("text-transform" "capitalize" "uppercase" "lowercase" "none")
    ("top" length percentage "auto")
    ("unicode-bidi" "normal" "embed" "bidi-override")
    ("vertical-align" "baseline" "sub" "super" "top" "text-top" "middle"
     "bottom" "text-bottom" percentage length)
    ("visibility" "visible" "hidden" "collapse")
    ("voice-family" specific-voice generic-voice "*" specific-voice
     generic-voice)
    ("volume" number percentage "silent" "x-soft" "soft" "medium" "loud"
     "x-loud")
    ("white-space" "normal" "pre" "nowrap" "pre-wrap" "pre-line")
    ("widows" integer)
    ("width" length percentage "auto")
    ("word-spacing" "normal" length)
    ("z-index" "auto" integer))
  "A list of CSS properties and their possible values.")

(defconst company-css-value-classes
  '((absolute-size "xx-small" "x-small" "small" "medium" "large" "x-large"
                   "xx-large")
    (border-style "none" "hidden" "dotted" "dashed" "solid" "double" "groove"
                  "ridge" "inset" "outset")
    (color "aqua" "black" "blue" "fuchsia" "gray" "green" "lime" "maroon" "navy"
           "olive" "orange" "purple" "red" "silver" "teal" "white" "yellow")
    (counter "counter(,)")
    (family-name "Courier" "Helvetica" "Times")
    (generic-family "serif" "sans-serif" "cursive" "fantasy" "monospace")
    (generic-voice "male" "female" "child")
    (margin-width "auto") ;; length percentage
    (relative-size "larger" "smaller")
    (shape "rect(,,,)")
    (uri "url()"))
  "A list of CSS property value classes and their contents.")
;; missing, because not completable
;; <angle><frequency><identifier><integer><length><number><padding-width>
;; <percentage><specific-voice><string><time><uri>

(defconst company-css-html-tags
  '("a" "abbr" "acronym" "address" "applet" "area" "b" "base" "basefont" "bdo"
    "big" "blockquote" "body" "br" "button" "caption" "center" "cite" "code"
    "col" "colgroup" "dd" "del" "dfn" "dir" "div" "dl" "dt" "em" "fieldset"
    "font" "form" "frame" "frameset" "h1" "h2" "h3" "h4" "h5" "h6" "head" "hr"
    "html" "i" "iframe" "img" "input" "ins" "isindex" "kbd" "label" "legend"
    "li" "link" "map" "menu" "meta" "noframes" "noscript" "object" "ol"
    "optgroup" "option" "p" "param" "pre" "q" "s" "samp" "script" "select"
    "small" "span" "strike" "strong" "style" "sub" "sup" "table" "tbody" "td"
    "textarea" "tfoot" "th" "thead" "title" "tr" "tt" "u" "ul" "var")
  "A list of HTML tags for use in CSS completion.")

(defconst company-css-pseudo-classes
  '("active" "after" "before" "first" "first-child" "first-letter" "first-line"
    "focus" "hover" "lang" "left" "link" "right" "visited")
  "Identifiers for CSS pseudo-elements and pseudo-classes.")

(defconst company-css-property-cache (make-hash-table :size 115 :test 'equal))

(defun company-css-property-values (attribute)
  "Access the `company-css-property-alist' cached and flattened."
  (or (gethash attribute company-css-property-cache)
      (let (results)
        (dolist (value (cdr (assoc attribute company-css-property-alist)))
          (if (symbolp value)
              (dolist (child (or (cdr (assoc value company-css-value-classes))
                                 (company-css-property-values
                                  (symbol-name value))))
                (add-to-list 'results child))
            (add-to-list 'results value)))
        (setq results (sort results 'string<))
        (puthash attribute results company-css-property-cache)
        results)))

;;; bracket detection

(defconst company-css-braces-syntax-table
  (let ((table (make-syntax-table)))
    (setf (aref table ?{) '(4 . 125))
    (setf (aref table ?}) '(5 . 123))
    table)
  "A syntax table giving { and } paren syntax.")

(defun company-css-inside-braces-p ()
  "Return non-nil, if point is within matched { and }."
  (ignore-errors
    (with-syntax-table company-css-braces-syntax-table
      (let ((parse-sexp-ignore-comments t))
        (scan-lists (point) -1 1)))))

;;; tags
(defconst company-css-tag-regexp
  (concat "\\(?:\\`\\|}\\)[[:space:]]*"
          ;; multiple
          "\\(?:"
          ;; previous tags:
          "\\(?:#\\|\\_<[[:alpha:]]\\)[[:alnum:]-#]*\\(?:\\[[^]]*\\]\\)?"
          ;; space or selectors
          "\\(?:[[:space:]]+\\|[[:space:]]*[+,>][[:space:]]*\\)"
          "\\)*"
          "\\(\\(?:#\\|\\_<[[:alpha:]]\\)\\(?:[[:alnum:]-#]*\\_>\\)?\\_>\\|\\)"
          "\\=")
  "A regular expression matching CSS tags")

;;; pseudo id
(defconst company-css-pseudo-regexp
  (concat "\\(?:\\`\\|}\\)[[:space:]]*"
          ;; multiple
          "\\(?:"
          ;; previous tags:
          "\\(?:#\\|\\_<[[:alpha:]]\\)[[:alnum:]-#]*\\(?:\\[[^]]*\\]\\)?"
          ;; space or delimiters
          "\\(?:[[:space:]]+\\|[[:space:]]*[+,>][[:space:]]*\\)"
          "\\)*"
          "\\(?:\\(?:\\#\\|\\_<[[:alpha:]]\\)[[:alnum:]-#]*\\):"
          "\\([[:alpha:]-]+\\_>\\|\\)\\_>\\=")
  "A regular expression matching CSS pseudo classes")

;;; properties

(defun company-css-grab-property ()
  "Return the CSS property before point, if any.
Returns \"\" if no property found, but feasible at this position."
  (when (company-css-inside-braces-p)
    (or (company-grab "\\_<[[:alpha:]-]+\\_>\\=")
        (company-grab "{\\|[[:space:]]" 1))))

;;; values
(defconst company-css-property-value-regexp
  "\\_<\\([[:alpha:]-]+\\):\\(?:[^};]*[[:space:]]+\\)?\\([^};]*\\_>\\|\\)\\="
  "A regular expression matching CSS tags")

(defun company-css (command &optional arg &rest ignored)
  (case command
    ('prefix (and (eq major-mode 'css-mode)
                  (or (company-grab company-css-tag-regexp 1)
                      (company-grab company-css-pseudo-regexp 1)
                      (company-grab company-css-property-value-regexp 2)
                      (company-css-grab-property))))
    ('candidates
     (cond
      ((company-grab company-css-tag-regexp 1)
       (all-completions arg company-css-html-tags))
      ((company-grab company-css-pseudo-regexp 1)
       (all-completions arg company-css-pseudo-classes))
      ((company-grab company-css-property-value-regexp 2)
       (all-completions arg
                        (company-css-property-values
                         (company-grab company-css-property-value-regexp 1))))
      ((company-css-grab-property)
       (all-completions arg company-css-property-alist))))
    ('sorted t)))

(provide 'company-css)
;;; company-css.el ends here