(module util mzscheme
  
  (require "config.ss"
           "planet-archives.ss"
           
           "private/planet-shared.ss"
           "private/linkage.ss"
           "resolver.ss"
           (lib "url.ss" "net")
           (lib "pack.ss" "setup")
           (lib "contract.ss")
           (lib "file.ss")
           (lib "list.ss")
           (lib "plt-single-installer.ss" "setup"))

  #| The util collection provides a number of useful functions for interacting with the PLaneT system. |#
  
  (provide 
   
   current-cache-contents
   current-linkage
   make-planet-archive
   get-installed-planet-archives
   get-hard-linked-packages
   remove-pkg
   unlink-all
   
   resolve-planet-path)
  
  (provide/contract
   [download/install-pkg
    (-> string? string? natural-number/c natural-number/c (union pkg? false/c))]
   [add-hard-link 
    (-> string? string? natural-number/c natural-number/c path? void?)]
   [remove-hard-link 
    (-> string? string? natural-number/c natural-number/c void?)]
   [erase-pkg
    (-> string? string? natural-number/c natural-number/c boolean?)])

  ;; download/install-pkg : string string nat nat -> pkg | #f
  (define (download/install-pkg owner name maj min)
    (let* ([pspec (pkg-spec->full-pkg-spec (list owner name maj min) #f)]
           [upkg (get-package-from-server pspec)])
      (cond
        [(uninstalled-pkg? upkg)
         (pkg-promise->pkg upkg)]
        [else #f])))
  
  ;; current-cache-contents : -> ((string ((string ((nat (nat ...)) ...)) ...)) ...)
  ;; returns the packages installed in the local PLaneT cache
  (define (current-cache-contents)
    (cdr (tree->list (repository-tree))))
  
  ;; just so it will be provided
  (define unlink-all remove-all-linkage!)
  
  ;; to remove:
  ;;   -- setup-plt -c the package
  ;;   -- remove relevant infodomain cache entries
  ;;   -- delete files from cache directory
  ;;   -- remove any existing linkage for package
  ;; returns #t if the removal worked; #f if no package existed.
  (define (remove-pkg owner name maj min)
    (let ((p (get-installed-package owner name maj min)))
      (and p
           (let ((path (pkg-path p)))
             (with-logging 
              (LOG-FILE)
              (lambda () 
                (printf "\n============= Removing ~a =============\n" (list owner name maj min))
                (clean-planet-package path (list owner name '() maj min))))
             (erase-metadata p)
             (delete-directory/files path)
             (trim-directory (CACHE-DIR) path)
             #t))))
  
  ;; erase-metadata : pkg -> void
  ;; clears out any references to the given package in planet's metadata files
  ;; (i.e., linkage and info.ss cache; not hard links which are not considered metadata)
  (define (erase-metadata p)
    (remove-infodomain-entries (pkg-path p))
    (remove-linkage-to! p))
    
  ;; this really should go somewhere else. But what should setup's behavior be
  ;; when a package is cleaned? should it clear info-domain entries out? I think
  ;; no; an uncompiled package isn't necessarily not to be indexed and so on.
  ;; remove-infodomain-entries : path -> void
  (define (remove-infodomain-entries path)
    (let* ([pathbytes (path->bytes path)]
           [cache-file (build-path (PLANET-DIR) "cache.ss")])
      (when (file-exists? cache-file)
        (let ([cache-lines (with-input-from-file cache-file read)])
          (with-output-to-file cache-file
            (lambda ()
              (if (pair? cache-lines)
                  (write (filter (lambda (line) (not (and (pair? line) (equal? (car line) pathbytes)))) cache-lines))
                  (printf "\n")))
            'truncate/replace)))))
  
  (define (erase-pkg owner name maj min)
    (let* ([uninstalled-pkg-dir
            (build-path (UNINSTALLED-PACKAGE-CACHE) owner name (number->string maj) (number->string min))]
           [uninstalled-pkg-file (build-path uninstalled-pkg-dir name)])
      (let ([removed-something? (remove-pkg owner name maj min)]
            [erased-something?
             (if (file-exists? uninstalled-pkg-file)
                 (begin
                   (delete-file uninstalled-pkg-file)
                   (trim-directory (UNINSTALLED-PACKAGE-CACHE) uninstalled-pkg-dir)
                   #t)
                 #f)])
        (or removed-something? erased-something?))))

  ;; listof X * listof X -> nonempty listof X
  ;; returns de-prefixed version of l2 if l1 is a proper prefix of l2; 
  ;; signals an error otherwise.
  (define (drop-common-base list1 list2)
    (let loop ((l1 list1) (l2 list2))
      (cond
        [(null? l2)
         (error 'drop-common-base "root ~s is not a prefix of stem ~s" list1 list2)]
        [(null? l1) l2]
        [(not (equal? (car l1) (car l2)))
         (error 'drop-common-base "root ~s is not a prefix of stem ~s" list1 list2)]
        [else (loop (cdr l1) (cdr l2))])))
  
  ;; pathify-list : path (listof path) -> listof path
  ;; given a base and a list of names, interprets each name as a subdirectory
  ;; of the previous, starting with base, and returns a list. (This list
  ;; is in reverse order, so the deepest subdirectory is returned first)
  (define (pathify-list root dirs)
    (let loop ((base root) (dirs dirs) (acc '()))
      (cond
        [(null? dirs) acc]
        [else
         (let ((new (build-path base (car dirs))))
           (loop new (cdr dirs) (cons new acc)))])))
  
  ;; directory-empty? path -> bool
  ;; #t iff the given directory contains no subdirectories of files
  (define (directory-empty? dir)
    (null? (directory-list dir)))
  
  ;; trim-directory path path -> void
  ;; deletes nonempty directories starting with stem and working down to root
  (define (trim-directory root stem)
    (let* ([rootl (explode-path root)]
           [steml (explode-path stem)]
           [extras (cdr (pathify-list root (drop-common-base rootl steml)))])
      (let loop ((dirs extras))
        (cond
          [(null? dirs) (void)]
          [(directory-empty? (car dirs))
           (delete-directory (car dirs))
           (loop (cdr dirs))]
          [else (void)]))))

  ;; current-linkage : -> ((symbol (package-name nat nat) ...) ...)
  ;; gives the current "linkage table"; a table that links modules to particular versions
  ;; of planet requires that satisfy those linkages
  (define (current-linkage)
    (let* ((links 
            (if (file-exists? (LINKAGE-FILE))
                (with-input-from-file (LINKAGE-FILE) read-all)
                '()))
           (buckets (categorize caar links)))
      (map
       (lambda (x) (cons (car x) (map (lambda (y) (drop-last (cadr y))) (cdr x))))
       buckets)))
  
  ;; make-planet-archive: directory [file] -> file
  ;; Makes a .plt archive file suitable for PLaneT whose contents are
  ;; all files in the given directory and returns that file's name.
  ;; If the optional filename argument is provided, that filename will 
  ;; be used as the output file's name.
  (define make-planet-archive
    (case-lambda
      [(dir) 
       (let-values ([(path name must-be-dir?) (split-path dir)])
         (make-planet-archive 
          dir 
          (build-path (normalize-path (current-directory))
                      (string-append (path->string name) ".plt"))))]
      [(dir archive-name)
       (parameterize ((current-directory dir))
         (pack archive-name
               "archive" 
               (list ".")
               null
               std-filter
               #t
               'file
               #f
               #f))
       (normalize-path archive-name)]))
  
  ;; ============================================================
  ;; HARD LINKS (aka development links)
  
  ;; add-hard-link : string string num num path -> void
  ;; adds an entry in the hard-links table associating the given
  ;; require spec to the given path
  (define (add-hard-link owner pkg-name maj min path)
    (unless (directory-exists? path)
      (if (file-exists? path)
          (error 'add-hard-link "Hard links must point to directories, not files")
          (fprintf (current-error-port) 
                   "Warning: directory ~a does not exist\n"
                   (path->string path))))
    (add-hard-link! pkg-name (list owner) maj min path))
  
  ;; remove-hard-link : string string num num -> void
  ;; removes any development association from the given package spec
  (define (remove-hard-link owner pkg-name maj min)
    (filter-link-table!
     (lambda (row) 
       (not (points-to? row pkg-name (list owner) maj min)))
     (lambda (row) 
       (let ([p (row->package row)])
         (when p
           (erase-metadata p)))))))