;;; nnweb.el --- retrieving articles via web search engines
;; Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
;;        Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: news

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; Note: You need to have `w3' installed for some functions to work.

;;; Code:

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

(require 'nnoo)
(require 'message)
(require 'gnus-util)
(require 'gnus)
(require 'nnmail)
(require 'mm-util)
(require 'mm-url)
(eval-and-compile
  (ignore-errors
    (require 'url)))
(autoload 'w3-parse-buffer "w3-parse")

(nnoo-declare nnweb)

(defvoo nnweb-directory (nnheader-concat gnus-directory "nnweb/")
  "Where nnweb will save its files.")

(defvoo nnweb-type 'google
  "What search engine type is being used.
Valid types include `google', `dejanews', and `gmane'.")

(defvar nnweb-type-definition
  '((google
     (article . ignore)
     (id . "http://groups.google.com/groups?selm=%s&output=gplain")
     (reference . identity)
     (map . nnweb-google-create-mapping)
     (search . nnweb-google-search)
     (address . "http://groups.google.com/groups")
     (identifier . nnweb-google-identity))
    (dejanews ;; alias of google
     (article . ignore)
     (id . "http://groups.google.com/groups?selm=%s&output=gplain")
     (reference . identity)
     (map . nnweb-google-create-mapping)
     (search . nnweb-google-search)
     (address . "http://groups.google.com/groups")
     (identifier . nnweb-google-identity))
    (gmane
     (article . nnweb-gmane-wash-article)
     (id . "http://gmane.org/view.php?group=%s")
     (reference . identity)
     (map . nnweb-gmane-create-mapping)
     (search . nnweb-gmane-search)
     (address . "http://gmane.org/")
     (identifier . nnweb-gmane-identity)))
  "Type-definition alist.")

(defvoo nnweb-search nil
  "Search string to feed to Google.")

(defvoo nnweb-max-hits 999
  "Maximum number of hits to display.")

(defvoo nnweb-ephemeral-p nil
  "Whether this nnweb server is ephemeral.")

;;; Internal variables

(defvoo nnweb-articles nil)
(defvoo nnweb-buffer nil)
(defvoo nnweb-group-alist nil)
(defvoo nnweb-group nil)
(defvoo nnweb-hashtb nil)

;;; Interface functions

(nnoo-define-basics nnweb)

(deffoo nnweb-retrieve-headers (articles &optional group server fetch-old)
  (nnweb-possibly-change-server group server)
  (save-excursion
    (set-buffer nntp-server-buffer)
    (erase-buffer)
    (let (article header)
      (mm-with-unibyte-current-buffer
	(while (setq article (pop articles))
	  (when (setq header (cadr (assq article nnweb-articles)))
	    (nnheader-insert-nov header))))
      'nov)))

(deffoo nnweb-request-scan (&optional group server)
  (nnweb-possibly-change-server group server)
  (if nnweb-ephemeral-p
      (setq nnweb-hashtb (gnus-make-hashtable 4095)))
  (funcall (nnweb-definition 'map))
  (unless nnweb-ephemeral-p
    (nnweb-write-active)
    (nnweb-write-overview group)))

(deffoo nnweb-request-group (group &optional server dont-check)
  (nnweb-possibly-change-server nil server)
  (when (and group
	     (not (equal group nnweb-group))
	     (not nnweb-ephemeral-p))
    (setq nnweb-group group
	  nnweb-articles nil)
    (let ((info (assoc group nnweb-group-alist)))
      (when info
	(setq nnweb-type (nth 2 info))
	(setq nnweb-search (nth 3 info))
	(unless dont-check
	  (nnweb-read-overview group)))))
  (cond
   ((not nnweb-articles)
    (nnheader-report 'nnweb "No matching articles"))
   (t
    (let ((active (if nnweb-ephemeral-p
		      (cons (caar nnweb-articles)
			    (caar (last nnweb-articles)))
		    (cadr (assoc group nnweb-group-alist)))))
      (nnheader-report 'nnweb "Opened group %s" group)
      (nnheader-insert
       "211 %d %d %d %s\n" (length nnweb-articles)
       (car active) (cdr active) group)))))

(deffoo nnweb-close-group (group &optional server)
  (nnweb-possibly-change-server group server)
  (when (gnus-buffer-live-p nnweb-buffer)
    (save-excursion
      (set-buffer nnweb-buffer)
      (set-buffer-modified-p nil)
      (kill-buffer nnweb-buffer)))
  t)

(deffoo nnweb-request-article (article &optional group server buffer)
  (nnweb-possibly-change-server group server)
  (save-excursion
    (set-buffer (or buffer nntp-server-buffer))
    (let* ((header (cadr (assq article nnweb-articles)))
	   (url (and header (mail-header-xref header))))
      (when (or (and url
		     (mm-with-unibyte-current-buffer
		       (mm-url-insert url)))
		(and (stringp article)
		     (nnweb-definition 'id t)
		     (let ((fetch (nnweb-definition 'id))
			   art active)
		       (when (string-match "^<\\(.*\\)>$" article)
			 (setq art (match-string 1 article)))
		       (when (and fetch art)
			 (setq url (format fetch art))
			 (mm-with-unibyte-current-buffer
			   (mm-url-insert url))
			 (if (nnweb-definition 'reference t)
			     (setq article
				   (funcall (nnweb-definition
					     'reference) article)))))))
	(unless nnheader-callback-function
	  (funcall (nnweb-definition 'article)))
	(nnheader-report 'nnweb "Fetched article %s" article)
	(cons group (and (numberp article) article))))))

(deffoo nnweb-close-server (&optional server)
  (when (and (nnweb-server-opened server)
	     (gnus-buffer-live-p nnweb-buffer))
    (save-excursion
      (set-buffer nnweb-buffer)
      (set-buffer-modified-p nil)
      (kill-buffer nnweb-buffer)))
  (nnoo-close-server 'nnweb server))

(deffoo nnweb-request-list (&optional server)
  (nnweb-possibly-change-server nil server)
  (save-excursion
    (set-buffer nntp-server-buffer)
    (nnmail-generate-active nnweb-group-alist)
    t))

(deffoo nnweb-request-update-info (group info &optional server)
  (nnweb-possibly-change-server group server))

(deffoo nnweb-asynchronous-p ()
  nil)

(deffoo nnweb-request-create-group (group &optional server args)
  (nnweb-possibly-change-server nil server)
  (nnweb-request-delete-group group)
  (push `(,group ,(cons 1 0) ,@args) nnweb-group-alist)
  (nnweb-write-active)
  t)

(deffoo nnweb-request-delete-group (group &optional force server)
  (nnweb-possibly-change-server group server)
  (gnus-pull group nnweb-group-alist t)
  (nnweb-write-active)
  (gnus-delete-file (nnweb-overview-file group))
  t)

(nnoo-define-skeleton nnweb)

;;; Internal functions

(defun nnweb-read-overview (group)
  "Read the overview of GROUP and build the map."
  (when (file-exists-p (nnweb-overview-file group))
    (mm-with-unibyte-buffer
      (nnheader-insert-file-contents (nnweb-overview-file group))
      (goto-char (point-min))
      (let (header)
	(while (not (eobp))
	  (setq header (nnheader-parse-nov))
	  (forward-line 1)
	  (push (list (mail-header-number header)
		      header (mail-header-xref header))
		nnweb-articles)
	  (nnweb-set-hashtb header (car nnweb-articles)))))))

(defun nnweb-write-overview (group)
  "Write the overview file for GROUP."
  (with-temp-file (nnweb-overview-file group)
    (let ((articles nnweb-articles))
      (while articles
	(nnheader-insert-nov (cadr (pop articles)))))))

(defun nnweb-set-hashtb (header data)
  (gnus-sethash (nnweb-identifier (mail-header-xref header))
		data nnweb-hashtb))

(defun nnweb-get-hashtb (url)
  (gnus-gethash (nnweb-identifier url) nnweb-hashtb))

(defun nnweb-identifier (ident)
  (funcall (nnweb-definition 'identifier) ident))

(defun nnweb-overview-file (group)
  "Return the name of the overview file of GROUP."
  (nnheader-concat nnweb-directory group ".overview"))

(defun nnweb-write-active ()
  "Save the active file."
  (gnus-make-directory nnweb-directory)
  (with-temp-file (nnheader-concat nnweb-directory "active")
    (prin1 `(setq nnweb-group-alist ',nnweb-group-alist) (current-buffer))))

(defun nnweb-read-active ()
  "Read the active file."
  (load (nnheader-concat nnweb-directory "active") t t t))

(defun nnweb-definition (type &optional noerror)
  "Return the definition of TYPE."
  (let ((def (cdr (assq type (assq nnweb-type nnweb-type-definition)))))
    (when (and (not def)
	       (not noerror))
      (error "Undefined definition %s" type))
    def))

(defun nnweb-possibly-change-server (&optional group server)
  (nnweb-init server)
  (when server
    (unless (nnweb-server-opened server)
      (nnweb-open-server server)))
  (unless nnweb-group-alist
    (nnweb-read-active))
  (unless nnweb-hashtb
    (setq nnweb-hashtb (gnus-make-hashtable 4095)))
  (when group
    (when (and (not nnweb-ephemeral-p)
	       (equal group nnweb-group))
      (nnweb-request-group group nil t))))

(defun nnweb-init (server)
  "Initialize buffers and such."
  (unless (gnus-buffer-live-p nnweb-buffer)
    (setq nnweb-buffer
	  (save-excursion
	    (mm-with-unibyte
	      (nnheader-set-temp-buffer
	       (format " *nnweb %s %s %s*"
		       nnweb-type nnweb-search server))
	      (current-buffer))))))

;;;
;;; Deja bought by google.com
;;;

(defun nnweb-google-wash-article ()
  (let ((case-fold-search t) url)
    (goto-char (point-min))
    (re-search-forward "^<pre>" nil t)
    (narrow-to-region (point-min) (point))
    (search-backward "<table " nil t 2)
    (delete-region (point-min) (point))
    (if (re-search-forward "Search Result [0-9]+" nil t)
	(replace-match ""))
    (if (re-search-forward "View complete thread ([0-9]+ articles?)" nil t)
	(replace-match ""))
    (goto-char (point-min))
    (while (search-forward "<br>" nil t)
      (replace-match "\n"))
    (mm-url-remove-markup)
    (goto-char (point-min))
    (while (re-search-forward "^[ \t]*\n" nil t)
      (replace-match ""))
    (goto-char (point-max))
    (insert "\n")
    (widen)
    (narrow-to-region (point) (point-max))
    (search-forward "</pre>" nil t)
    (delete-region (point) (point-max))
    (mm-url-remove-markup)
    (widen)))

(defun nnweb-google-parse-1 (&optional Message-ID)
  (let ((i 0)
	(case-fold-search t)
	(active (cadr (assoc nnweb-group nnweb-group-alist)))
	Subject Score Date Newsgroups From
	map url mid)
    (unless active
      (push (list nnweb-group (setq active (cons 1 0))
		  nnweb-type nnweb-search)
	    nnweb-group-alist))
    ;; Go through all the article hits on this page.
    (goto-char (point-min))
    (while (re-search-forward
	    "a href=/groups\\(\\?[^ \">]*selm=\\([^ &\">]+\\)\\)" nil t)
      (setq mid (match-string 2)
	    url (format
		 "http://groups.google.com/groups?selm=%s&output=gplain" mid))
      (narrow-to-region (search-forward ">" nil t)
			(search-forward "</a>" nil t))
      (mm-url-remove-markup)
      (mm-url-decode-entities)
      (setq Subject (buffer-string))
      (goto-char (point-max))
      (widen)
      (forward-line 2)
      (when (looking-at "<br><font[^>]+>")
	(goto-char (match-end 0)))
      (if (not (looking-at "<a[^>]+>"))
	  (skip-chars-forward " \t")
	(narrow-to-region (point)
			  (search-forward "</a>" nil t))
	(mm-url-remove-markup)
	(mm-url-decode-entities)
	(setq Newsgroups (buffer-string))
	(goto-char (point-max))
	(widen)
	(skip-chars-forward "- \t"))
      (when (looking-at
	     "\\([0-9]+\\)[/ ]\\([A-Za-z]+\\)[/ ]\\([0-9]+\\)[ \t]*by[ \t]*\\([^<]*\\) - <a")
	(setq From (match-string 4)
	      Date (format "%s %s 00:00:00 %s"
			   (match-string 2) (match-string 1)
			   (match-string 3))))
      (forward-line 1)
      (incf i)
      (unless (nnweb-get-hashtb url)
	(push
	 (list
	  (incf (cdr active))
	  (make-full-mail-header
	   (cdr active) (if Newsgroups
			    (concat  "(" Newsgroups ") " Subject)
			  Subject)
	   From Date (or Message-ID mid)
	   nil 0 0 url))
	 map)
	(nnweb-set-hashtb (cadar map) (car map))))
    map))

(defun nnweb-google-reference (id)
  (let ((map (nnweb-google-parse-1 id)) header)
    (setq nnweb-articles
	  (nconc nnweb-articles map))
    (when (setq header (cadar map))
      (mm-with-unibyte-current-buffer
	(mm-url-insert (mail-header-xref header)))
      (caar map))))

(defun nnweb-google-create-mapping ()
  "Perform the search and create a number-to-url alist."
  (save-excursion
    (set-buffer nnweb-buffer)
    (erase-buffer)
    (when (funcall (nnweb-definition 'search) nnweb-search)
	(let ((more t)
	      (i 0))
	  (while more
	    (setq nnweb-articles
		  (nconc nnweb-articles (nnweb-google-parse-1)))
	    ;; Check if there are more articles to fetch
	    (goto-char (point-min))
	    (incf i 100)
	    (if (or (not (re-search-forward
			  "<td nowrap><a href=\\([^>]+\\).*<span class=b>Next</span>" nil t))
		    (>= i nnweb-max-hits))
		(setq more nil)
	      ;; Yup, there are more articles
	      (setq more (concat "http://groups.google.com" (match-string 1)))
	    (when more
	      (erase-buffer)
	      (mm-url-insert more))))
	  ;; Return the articles in the right order.
	  (setq nnweb-articles
		(sort nnweb-articles 'car-less-than-car))))))

(defun nnweb-google-search (search)
  (mm-url-insert
   (concat
    (nnweb-definition 'address)
    "?"
    (mm-url-encode-www-form-urlencoded
     `(("q" . ,search)
       ("num". "100")
       ("hq" . "")
       ("hl" . "")
       ("lr" . "")
       ("safe" . "off")
       ("sites" . "groups")))))
  t)

(defun nnweb-google-identity (url)
  "Return an unique identifier based on URL."
  (if (string-match "selm=\\([^ &>]+\\)" url)
      (match-string 1 url)
    url))

;;;
;;; gmane.org
;;;
(defun nnweb-gmane-create-mapping ()
  "Perform the search and create a number-to-url alist."
  (save-excursion
    (set-buffer nnweb-buffer)
    (erase-buffer)
    (when (funcall (nnweb-definition 'search) nnweb-search)
      (let ((more t)
	    (case-fold-search t)
	    (active (or (cadr (assoc nnweb-group nnweb-group-alist))
			(cons 1 0)))
	    subject group url
	    map)
	  ;; Remove stuff from the beginning of results
	(goto-char (point-min))
	(search-forward "Search Results</h1><ul>" nil t)
	(delete-region (point-min) (point))
	(goto-char (point-min))
	;; Iterate over the actual hits
	(while (re-search-forward ".*href=\"\\([^\"]+\\)\">\\(.*\\)" nil t)
	    (setq url (concat "http://gmane.org/" (match-string 1)))
	    (setq subject (match-string 2))
	  (unless (nnweb-get-hashtb url)
	    (push
	     (list
	      (incf (cdr active))
	      (make-full-mail-header
	       (cdr active) (concat  "(" group ") " subject) nil nil
	       nil nil 0 0 url))
	     map)
	    (nnweb-set-hashtb (cadar map) (car map))))
	;; Return the articles in the right order.
	(setq nnweb-articles
	      (sort (nconc nnweb-articles map) 'car-less-than-car))))))

(defun nnweb-gmane-wash-article ()
  (let ((case-fold-search t))
    (goto-char (point-min))
    (re-search-forward "<!--X-Head-of-Message-->" nil t)
    (delete-region (point-min) (point))
    (goto-char (point-min))
    (while (looking-at "^<li><em>\\([^ ]+\\)</em>.*</li>")
      (replace-match "\\1\\2" t)
      (forward-line 1))
    (mm-url-remove-markup)))

(defun nnweb-gmane-search (search)
  (mm-url-insert
   (concat
    (nnweb-definition 'address)
    "?"
    (mm-url-encode-www-form-urlencoded
     `(("query" . ,search)))))
  (setq buffer-file-name nil)
  t)


(defun nnweb-gmane-identity (url)
  "Return a unique identifier based on URL."
  (if (string-match "group=\\(.+\\)" url)
      (match-string 1 url)
    url))

;;;
;;; General web/w3 interface utility functions
;;;

(defun nnweb-insert-html (parse)
  "Insert HTML based on a w3 parse tree."
  (if (stringp parse)
      (insert (nnheader-string-as-multibyte parse))
    (insert "<" (symbol-name (car parse)) " ")
    (insert (mapconcat
	     (lambda (param)
	       (concat (symbol-name (car param)) "="
		       (prin1-to-string
			(if (consp (cdr param))
			    (cadr param)
			  (cdr param)))))
	     (nth 1 parse)
	     " "))
    (insert ">\n")
    (mapc 'nnweb-insert-html (nth 2 parse))
    (insert "</" (symbol-name (car parse)) ">\n")))

(defun nnweb-parse-find (type parse &optional maxdepth)
  "Find the element of TYPE in PARSE."
  (catch 'found
    (nnweb-parse-find-1 type parse maxdepth)))

(defun nnweb-parse-find-1 (type contents maxdepth)
  (when (or (null maxdepth)
	    (not (zerop maxdepth)))
    (when (consp contents)
      (when (eq (car contents) type)
	(throw 'found contents))
      (when (listp (cdr contents))
	(dolist (element contents)
	  (when (consp element)
	    (nnweb-parse-find-1 type element
				(and maxdepth (1- maxdepth)))))))))

(defun nnweb-parse-find-all (type parse)
  "Find all elements of TYPE in PARSE."
  (catch 'found
    (nnweb-parse-find-all-1 type parse)))

(defun nnweb-parse-find-all-1 (type contents)
  (let (result)
    (when (consp contents)
      (if (eq (car contents) type)
	  (push contents result)
	(when (listp (cdr contents))
	  (dolist (element contents)
	    (when (consp element)
	      (setq result
		    (nconc result (nnweb-parse-find-all-1 type element))))))))
    result))

(defvar nnweb-text)
(defun nnweb-text (parse)
  "Return a list of text contents in PARSE."
  (let ((nnweb-text nil))
    (nnweb-text-1 parse)
    (nreverse nnweb-text)))

(defun nnweb-text-1 (contents)
  (dolist (element contents)
    (if (stringp element)
	(push element nnweb-text)
      (when (and (consp element)
		 (listp (cdr element)))
	(nnweb-text-1 element)))))

(provide 'nnweb)

;;; nnweb.el ends here