make nav cope with missing wallets

core/views/wallets.py

@@ -309,8 +309,47 @@ def walletedit(request, path=None):
         wallet = f"{year}:{wnumber:02d}"
         return (None, wallet)
         
+    def identify_most_recent_wallet(wallet, y):
+        """ Need to find the last wallet of the previous year
+        Has to cope with years when there are no wallets
+        Has to cope with weirdly named imported wallets from 1999 & earlier
+        Has to cope if the 'current' wallet is one that happens to 'not exist' too.
+        
+        Frankly this has just become too bizarre and we should devise a quite different
+        navigation system.
+        """
+        current_name = wallet.replace(":","#")
+           
+        try:
+            allwallets = Wallet.objects.all().order_by('walletname')
+            previous_wallet = allwallets.first()
+            for w in allwallets:
+                if len(w.walletname) < 5:
+                    continue
+                if w.walletname[4] != "#":
+                        continue
+   
+                if w.walletname == current_name:
+                    break
+                if int(w.walletyear.year) >= int(y):
+                    break
+                previous_wallet = w
+            name = previous_wallet.walletname
+           
+            y = name[:4]
+            prevy = f"{int(y)-1}"
+            n = name[5:]
+            prev = f"{int(n):02d}"
+            
+        except:
+            raise
+            prev = f"{int(n):02d}"  
+              
+        print(prev, prevy, y)
+        return prev, prevy, y
+                
     def create_nav_links(wallet):
-        print(f"--- {wallet} now current")
+        """Find the previous wallet and next wallet and create navigation shortcuts"""
         y = wallet[:4]
         n = wallet[5:]
         nexty = f"{int(y)+1}"
@@ -318,9 +357,9 @@ def walletedit(request, path=None):
         next = f"{int(n)+1:02d}"
         prev = f"{int(n)-1:02d}"
 
-        if int(n) == 0:
-            prev = f"{int(n):02d}"
-            
+        if int(n) == 0: 
+            prev, prevy, y = identify_most_recent_wallet(wallet, y)
+ 
         return next, nexty, prev, prevy, y
 
     def read_json():
@@ -339,7 +378,7 @@ def walletedit(request, path=None):
                     DataIssue.objects.create(parser="scans", message=message, url=wurl)  # set URL to this wallet folder
                     raise
         else:  # no JSON file exists
-            print("--- No JSON exists, so creating blank copy")
+            print("--- No JSON exists, so using default copy")
             waldata = WALLET_BLANK_JSON.copy()
         if not waldata["survex file"]:
             try:
@@ -366,7 +405,7 @@ def walletedit(request, path=None):
         """We need a wallet Object so that the django template stuff can find the files"""
         try:
             w, created = Wallet.objects.get_or_create(walletname=walletname)
-            print(f"--- Wallet string {walletname}, wallet object {w} created new?: {created}")
+            # print(f"--- Wallet string {walletname}, wallet object {w} created new?: {created}")
             if created:
                 w.fpath = Path(settings.SCANS_ROOT, walletname[0:4], walletname)
                 w.save()
@@ -755,7 +794,7 @@ def walletedit(request, path=None):
             caveifywallet(thiswallet)
             thiswallet.ticks = thiswallet.get_ticks()  # the complaints in colour form
             # fixsurvextick(thiswallet, thiswallet.ticks)
-            print(f"--- {wallet}  {thiswallet} walletdate={thiswallet.walletdate} immediately before form render")
+            # print(f"--- {wallet}  {thiswallet} walletdate={thiswallet.walletdate} immediately before form render")
         except:
             thiswallet = None
         context = {