From a5972febd232c4afd64499826c7faab85a10ee03 Mon Sep 17 00:00:00 2001
From: Javier Sancho <jsf@jsancho.org>
Date: Fri, 18 Mar 2016 17:39:32 +0100
Subject: [PATCH] Writing support

---
 src/bongodb.scm  | 49 ++++++++++++++++++++++++++++++++++++++----------
 tests/sample.scm | 10 +++++++---
 2 files changed, 46 insertions(+), 13 deletions(-)

diff --git a/src/bongodb.scm b/src/bongodb.scm
index 6fc16fe..3e5dc68 100644
--- a/src/bongodb.scm
+++ b/src/bongodb.scm
@@ -25,9 +25,12 @@
 	    count
 	    insert
 	    find
+	    update
 	    $eq
 	    $exists
-	    $not))
+	    $not
+	    $and
+	    $set))
 
 
 ;;; Collection Definition
@@ -78,26 +81,40 @@
 	       (apply insert (cons newcol (cdr documents)))
 	     (values rescol (cons docid docids)))))))
 
-(define (find col . filter)
+(define (find col filter)
+  "Query the collection and return the documents that match with filter"
+  (map vhash->alist (inner-find col filter)))
+
+(define (inner-find col filter)
   "Query the collection and return the documents that match with filter"
   (let ((table (get-table col)))
     (vhash-fold
      (lambda (key document result)
        (cond ((match-document? document filter)
-	      (cons (vhash->alist document) result))
+	      (cons document result))
 	     (else
 	      result)))
      '()
      table)))
 
 (define (match-document? document filter)
-  "Try to match the given document with a list of conditions"
-  (cond ((null? filter)
+  "Try to match the given document with a given filter"
+  (cond ((equal? filter #t)
 	 #t)
 	(else
-	 (and
-	  ((car filter) document)
-	  (match-document? document (cdr filter))))))
+	 (filter document))))
+
+(define (update col filter . changes)
+  "Update selected documents using the given filter"
+  (let ((documents (inner-find col filter)))
+    (apply insert (cons col (map (lambda (doc) (update-document doc changes)) documents)))))
+
+(define (update-document document changes)
+  "Update a document with the appropiate changes"
+  (cond ((null? changes)
+	 document)
+	(else
+	 (update-document ((car changes) document) (cdr changes)))))
 
 
 ;;; Queries
@@ -108,17 +125,29 @@
       (and stored
 	   (equal? (cdr stored) value)))))
 
-
 (define ($exists field)
   (lambda (document)
     (and (vhash-assoc field document)
 	 #t)))
 
-
 (define ($not expr)
   (lambda (document)
     (not (expr document))))
 
+(define-syntax $and
+  (syntax-rules ()
+    ((_ expr ...)
+     (lambda (document)
+       (and (expr document)
+	    ...)))))
+
+
+;;; Updates
+
+(define ($set field value)
+  (lambda (document)
+    (vhash-cons field value document)))
+
 	     
 ;;; Tools
 
diff --git a/tests/sample.scm b/tests/sample.scm
index 5054ffe..bd2cc6e 100644
--- a/tests/sample.scm
+++ b/tests/sample.scm
@@ -32,12 +32,16 @@
 (test-eqv 3 (count col))
 
 ; Search
-(test-eqv 3 (length (find col)))
+(test-eqv 3 (length (find col #t)))
 (test-eqv 2 (length (find col ($eq 'a 1))))
-(test-eqv 1 (length (find col ($eq 'a 1) ($eq 'b 2))))
-(test-eqv 0 (length (find col ($eq 'a "test"))))
+(test-eqv 1 (length (find col ($and ($eq 'a 1) ($eq 'b 2)))))
+(test-eqv 0 (length (find col ($eq 'c "test"))))
 
 (test-eqv 2 (length (find col ($exists 'b))))
 (test-eqv 2 (length (find col ($not ($exists 'c)))))
 
+; Update
+(set! col (update col ($exists 'c) ($set 'c "test")))
+(test-eqv 1 (length (find col ($eq 'c "test"))))
+
 (test-end "bongodb")
-- 
2.39.5