Add the support for multiple formats.

Some people does not use the common YYYYMMDDXX format and/or does not
want to use the "; serial" comment right after the serial number. This
commit allow multiple formats to be defined, hense more users can use
the plugin. A huge consequence of this is that user can also define
additional custom formats depending on their needs.

autoload/dnsserial.vim

@@ -12,28 +12,59 @@
 " See the License for the specific language governing permissions and
 " limitations under the License.
 
-function! s:IncrementSerial(old_date, old_nb)
-    let curr_date = strftime("%Y%m%d")
-    if a:old_date ==? curr_date
-        let curr_nb = a:old_nb + 1
-        if curr_nb < 10
-            let curr_nb = "0".curr_nb
+
+function! s:HasDateChanged(pattern, old_matchlist)
+    let i = 0
+    for matching in a:pattern.matching
+        if matching.type ==? 'date'
+            let old_date = a:old_matchlist[i]
+            let new_date = strftime(matching.fmt)
+            if old_date !=? new_date
+                return 1
+            endif
         endif
-    else
-        let curr_nb = "01"
+        let i += 1
+    endfor
+    return 0
+endfunction
+
+function! s:GetNewValue(matching, old_value, date_changed)
+    if a:matching.type ==? 'date'
+        return strftime(a:matching.fmt)
+    elseif a:matching.type ==? 'integer'
+        let nb = a:old_value + get(a:matching, 'offset', 1)
+        if a:date_changed && get(a:matching, 'date_reset', 0)
+            let nb = 0
+        endif
+        return printf('%0' . get(a:matching, 'padding', 1) . 'd', nb)
     endif
-    return curr_date.curr_nb
+    return a:old_value
+endfunction
+
+function! s:GetNewSerial(pattern, old_matchlist)
+    let date_changed = s:HasDateChanged(a:pattern, a:old_matchlist)
+    let new_serial = []
+    let i = 0
+    for matching in a:pattern.matching
+        let new_value = s:GetNewValue(matching, a:old_matchlist[i], date_changed)
+        call add(new_serial, new_value)
+        let i += 1
+    endfor
+    return join(new_serial, '')
 endfunction
 
 function! dnsserial#DNSSerialUpdate()
-    let pattern = '\(\d\{8}\)\(\d\+\)\s*;\s*\cserial'
-    if search(pattern) == 0
-        echom "No serial found."
-        return 0
-    endif
-    let old_pattern = matchlist(getline('.'), pattern)
-    let old_serial = old_pattern[1].old_pattern[2]
-    let new_serial = s:IncrementSerial(old_pattern[1], old_pattern[2])
-    execute "s/".old_serial."/".new_serial."/"
-    echom "Serial updated to ".new_serial."."
+    let patterns = g:dnsserial_custom_patterns + g:dnsserial_patterns
+    for pattern in patterns
+        if search(pattern.regex) != 0
+            let offset = len(pattern.matching)
+            let old_matchlist = matchlist(getline('.'), pattern.regex)[1:offset]
+            let old_serial = join(old_matchlist, '')
+            let new_serial = s:GetNewSerial(pattern, old_matchlist)
+            execute "s/" . old_serial . "/" . new_serial . "/"
+            echom "Serial updated to " . new_serial . "."
+            return 0
+        endif
+    endfor
+    echom "No serial found."
 endfunction