;;;
;;; dbi - common database interface layer
;;;
;;;  Copyright (c) 2003-2005 Scheme Arts, L.L.C., All rights reserved.
;;;  Copyright (c) 2003-2005 Time Intermedia Corporation, All rights reserved.
;;;
;;;   Redistribution and use in source and binary forms, with or without
;;;   modification, are permitted provided that the following conditions
;;;   are met:
;;;
;;;   1. Redistributions of source code must retain the above copyright
;;;      notice, this list of conditions and the following disclaimer.
;;;
;;;   2. Redistributions in binary form must reproduce the above copyright
;;;      notice, this list of conditions and the following disclaimer in the
;;;      documentation and/or other materials provided with the distribution.
;;;
;;;   3. Neither the name of the authors nor the names of its contributors
;;;      may be used to endorse or promote products derived from this
;;;      software without specific prior written permission.
;;;
;;;   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;;   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;;   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;;   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;;   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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;;;   TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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;;;   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;;   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;;   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;

(define-module dbi
  (use text.sql)
  (use file.util)
  (use srfi-1)
  (use srfi-13)
  (use util.match)
  (extend util.relation)
  (export <dbi-error> <dbi-nonexistent-driver-error>
          <dbi-unsupported-error> <dbi-parameter-error>
          <dbi-driver> <dbi-connection> <dbi-query>
          dbi-connect dbi-close dbi-prepare dbi-execute dbi-do
          dbi-open? dbi-parse-dsn dbi-make-driver
          dbi-prepare-sql dbi-escape-sql dbi-list-drivers
          dbi-make-connection dbi-execute-using-connection
          ;; compatibility
          dbi-make-query dbi-execute-query dbi-get-value
          <dbi-exception> <dbi-result-set>))
(select-module dbi)

;;;==============================================================
;;; DBI conditions
;;;

;; Root of dbi-related errors
(define-condition-type <dbi-error> <error> #f)

;; Failed to load the specified driver
(define-condition-type <dbi-nonexistent-driver-error> <dbi-error> #f
  (driver-name))

;; Feature not supported
(define-condition-type <dbi-unsupported-error> <dbi-error> #f)

;; Parameter mismatch between a prepared query and its execution.
(define-condition-type <dbi-parameter-error> <dbi-error> #f)


;;;==============================================================
;;; DBI object definitions
;;;

;; <dbi-driver> is the base class of database drivers; a database
;; driver implements actual interface to a specific database system.
;; Each dbd.* module provides the concrete implementation.
;;
;; Usually the singleton instance of a concrete driver is created
;; implicitly by dbi-connect with the data-source string.  So the
;; user hardly need to see <dbi-driver> object.

(define-class <dbi-driver> ()
  ((driver-name :init-keyword :driver-name)  ; "mysql" "pg" etc.
   ))

;; <dbi-connection> : represents a connection to the database system.
;; All the transactions must be done while the connection is 'open'.
(define-class <dbi-connection> ()
  ((open :init-value #t) ;; this slot is for backward compatibility.
                         ;; do not count on this.  will be removed.
   ))

;; <dbi-query> : represents a prepared query.
(define-class <dbi-query> ()
  ((connection :init-keyword :connection)
   (prepared   :init-keyword :prepared)
   (open :init-value #t) ;; this slot is for backward compatibility.
                         ;; do not count on this.  will be removed.
   ))

;;;==============================================================
;;; User-level APIs
;;;

;; Establish a connection to the data source specified by DSN,
;; and returns a connection object.
;; DSN is the data source name, which can have the following syntax.
;;   "dbi:driver-type"
;;   "dbi:driver-type:connection-options"
;; Connection-options is like "name1=value1;name2=value2;...".
;;
(define (dbi-connect dsn . args)
  (receive (driver-name options option-alist) (dbi-parse-dsn dsn)
    (apply dbi-make-connection
           (dbi-make-driver driver-name) options option-alist args)))

;; Prepares SQL statement and returns a closure, which executes
;; the statement when called.  If the given SQL statement takes parameters,
;; the closure takes the same number of arguments as of the parameters.
;;
;; The default method uses text.sql to parse the SQL statement, and calls
;; legacy dbd API.  This will go away once the drivers switched to the
;; new dbd API.
(define-method dbi-prepare ((c <dbi-connection>) (sql <string>)
                            :key (pass-through #f))
  (let1 prepared (if pass-through
                   (^ args
                     (unless (null? args)
                       (error <dbi-parameter-error>
                              "parameter is given to the pass through sql:" sql))
                     sql)
                   (dbi-prepare-sql c sql))
    (make <dbi-query> :connection c :prepared prepared)))

(define-method dbi-execute ((q <dbi-query>) . params)
  (dbi-execute-using-connection (ref q 'connection) q params))

(define-method dbi-execute-using-connection ((c <dbi-connection>)
                                             (q <dbi-query>) params)
  (dbi-execute-query c (apply (ref q 'prepared) params)))

;; Does preparation and execution at once.  The driver may overload this.
(define-method dbi-do ((c <dbi-connection>) sql options . args)
  (unless (proper-list? options)
    (error "dbi-do: bad option list:" options))
  (apply dbi-execute (apply dbi-prepare c sql options) args))

(define-method dbi-do ((c <dbi-connection>) sql)
  (dbi-do c sql '()))

;; Returns a string safe to be embedded in SQL.
;;   (dbi-escape-sql c "Don't know") => "'Don''t know'"
;; What's "safe" depends on the underlying DBMS.  The default procedure
;; only escapes a single quote by repeating it.  If the DBMS has other
;; type of escaping mechanism, the driver should overload this with
;; a proper escaping method.
(define-method dbi-escape-sql ((c <dbi-connection>) str)
  (regexp-replace-all #/'/ str "''"))

;; Returns a list of available dbd.* backends.  Each entry is
;; a cons of a module name and its driver name.
(define (dbi-list-drivers)
  (library-map 'dbd.* (^[m p] m)))

;;;==============================================================
;;; DBD-level APIs
;;;

;; Subclass SHOULD implement this.
(define-method dbi-make-connection ((d <dbi-driver>)
                                    (options <string>)
                                    (option-alist <list>)
                                    :key (username "") (password ""))
  ;; The default method here is just a temporary one to use
  ;; older dbd drivers.  Will go away once the drivers catch up
  ;; the new interface.
  ;; Calls deprecated dbi-make-connection API.
  (dbi-make-connection d username password (or options "")))

;; Usually the subclass should define these for the connection
;; and result set objects.
(define-method dbi-open? (obj) #t)
(define-method dbi-close (obj) (undefined))

;;;===================================================================
;;; Low-level utilities
;;;

;; Parse data source name.  Returns
;;  (driver-name, option-string, option-alist)
;;
(define (dbi-parse-dsn data-source-name)
  (rxmatch-case data-source-name
    (#/^dbi:([\w-]+)(?::(.*))?$/ (#f driver options)
     (if (and options (not (string-null? options)))
       (let1 alist (map (^[nv] (receive (n v) (string-scan nv "=" 'both)
                                 (if n (cons n v) (cons nv #t))))
                        (string-split options #\;))
         (values driver options alist))
       (values driver "" '())))
    (else (error <dbi-error> "bad data source name spec:" data-source-name))))

;; Loads a concrete driver module, and returns an instance of
;; the driver.
(define (dbi-make-driver driver-name)
  (let* ([module (string->symbol #`"dbd.,driver-name")]
         [path   (module-name->path module)]
         [class-name  (string->symbol #`"<,|driver-name|-driver>")])
    (or (and-let* ([ (library-exists? path :strict? #t) ]
                   [driver-class
                    (begin (eval `(require ,(path-sans-extension path))
                                 (current-module))
                           (global-variable-ref module class-name #f))])
          (make driver-class :driver-name driver-name))
        (errorf <dbi-nonexistent-driver-error>
                :driver-name driver-name
                "couldn't load driver dbd.~a" driver-name))))

;; Default prepared-SQL handler
;; dbi-prepare-sql returns a procedure, which generates a complete sql
;; when called with binding values to the parameters.
(define (dbi-prepare-sql conn sql)
  (let* ([tokens (sql-tokenize sql)]
         [num-params (count (^[elt]
                              (match elt
                                [('parameter (? integer?)) #t]
                                [('parameter (? string? name))
                                 (errorf <dbi-unsupported-error>
                                         "Named parameter (:~a) isn't supported yet" name)]
                                [else #f]))
                            tokens)])
    (^ args
      (unless (= (length args) num-params)
        (error <dbi-parameter-error>
               "wrong number of parameters given to an SQL:" sql))
      (call-with-output-string
        (^p (with-port-locking p
              (cut generate-sql/parameters conn tokens args p sql)))))))

(define (generate-sql/parameters conn tokens args p sql)
  (let loop ([tokens tokens]
             [args   args]
             [delim  #t])
    (unless (null? tokens)
      (match (car tokens)
        [(? char? x)
         (display x p)
         (loop (cdr tokens) args #t)]
        [(? symbol? x)
         (unless delim (write-char #\space p))
         (display x p)
         (loop (cdr tokens) args #f)]
        [(? string? x)
         (unless delim (write-char #\space p))
         (display x p)
         (loop (cdr tokens) args #f)]
        [('delimited x)
         (unless delim (write-char #\space p))
         (format p "\"~a\"" (regexp-replace-all #/\"/ x "\"\""))
         (loop (cdr tokens) args #f)]
        [('string x)
         (unless delim (write-char #\space p))
         (format p "'~a'" (regexp-replace-all #/'/ x "''"))
         (loop (cdr tokens) args #f)]
        [('number x)
         (unless delim (write-char #\space p))
         (display x p)
         (loop (cdr tokens) args #f)]
        [('parameter n)
         (unless delim (write-char #\space p))
         (let* ([argval (car args)]
                [s (cond
                    [(not argval) "NULL"]
                    [(string? argval)
                     #`"',(dbi-escape-sql conn argval)'"]
                    [(symbol? argval)
                     #`"',(dbi-escape-sql conn (symbol->string argval))'"]
                    [(real? argval) (number->string argval)]
                    [else (error <dbi-parameter-error>
                                 "bad type of parameter for SQL:" argval)])])
           (display s p))
         (loop (cdr tokens) (cdr args) #f)]
        [('bitstring x)
         (unless delim (write-char #\space p))
         (format p "B'~a'" x)
         (loop (cdr tokens) args #f)]
        [('hexstring x)
         (unless delim (write-char #\space p))
         (format p "X'~a'" x)
         (loop (cdr tokens) args #f)]
        [else
         (errorf <dbi-unsupported-error>
                 "unsupported SQL token ~a in ~s" (car tokens) sql)]
        ))))


;;;==============================================================
;;; Backward compatibility stuff
;;;

;; These are provided for compatibility with dbi-0.1.5 and dbd-*
;; modules that depend on it.  The newly written code shouldn't use
;; these interface.  Will be gone in a few releases.

(define <dbi-exception> <dbi-error>)

(define-class <dbi-result-set> ()
  ((open :init-value #t)))

(define-method dbi-get-value ((r <sequence>) (n <integer>))
  (ref r n))

;; Older API
(define-method dbi-make-connection ((d <dbi-driver>)
                                    (user <string>)
                                    (pass <string>)
                                    (options <string>))
  (dbi-connect #`"dbi:,(slot-ref d 'driver-name):,options"
               :username user :password pass))
(define-method dbi-make-query ((c <dbi-connection>) . _)
  (make <dbi-query> :connection c))
(define-method dbi-execute-query ((q <dbi-query>) (s <string>))
  (dbi-do (ref q 'connection) s '(:pass-through #t)))

