better file handling

Don't download again if the final saved file exists (the preview)

Don't modify files in-place.

update_from_db.py

@@ -2,16 +2,36 @@
 from http.client import HTTPConnection
 import json
 import base64
+import sys
+
+def die(message,code=23):
+        print(message,file=sys.stderr)
+        raise SystemExit(code)
 
 server = "minetest.fensta.bplaced.net"
 skinsdir = "u_skins/textures/"
 metadir = "u_skins/meta/"
-i = 1
-pages = 1
+curskin = 0
+pages = None
+
+def replace(path,encoding=None):
+    mode = "wt" if encoding else "wb"
+    # an unpredictable temp name only needed for a+rwxt directories
+    tmp = '.'+path+'-tmp'
+    def deco(handle):
+        with open(tmp,mode,encoding=encoding) as out:
+            yield out
+        os.rename(tmp,path)
+    return deco
+
+def maybeReplace(path,encoding=None):
+    def deco(handle):
+        if os.path.exists(path): return
+        return replace(path,encoding)(handle)	
 
 c = HTTPConnection(server)
 def addpage(page):
-    global i, pages
+    global curskin, pages
     print("Page: " + str(page))
     r = 0
     try:
@@ -20,42 +40,52 @@ def addpage(page):
     except Exception:
         if r != 0:
             if r.status != 200:
-                print("Error", r.status)
-                exit(r.status)
+                die("Error", r.status)
         return
     
     data = r.read().decode()
     l = json.loads(data)
     if not l["success"]:
-        print("Success != True")
-        exit(1)
+        die("Success != True")
     r = 0
     pages = int(l["pages"])
+    foundOne = False
     for s in l["skins"]:
-        f = open(skinsdir + "character_" + str(i) + ".png", "wb")
-        f.write(base64.b64decode(bytes(s["img"], 'utf-8')))
-        f.close()
-        f = open(metadir + "character_" + str(i) + ".txt", "w")
-        f.write(str(s["name"]) + '\n')
-        f.write(str(s["author"]) + '\n')
-        f.write(str(s["license"]))
-        f.close()
+        # make sure to increment this, even if the preview exists!
+        curskin = curskin + 1
+        preview = skinsdir + "character_" + str(curskin) + "_preview.png"
+        if os.path.exists(preview): continue
+        foundOne = True
+        tmp = dest+'-tmp'
+        @maybeReplace(skinsdir + "character_" + str(curskin) + ".png")
+        def go(f):
+            f.write(base64.b64decode(bytes(s["img"], 'utf-8')))
+            f.close()
+            
+        @maybeReplace(metadir + "character_" + str(curskin) + ".txt",
+                      encoding='utf-8')
+        def go(f):
+            f.write(str(s["name"]) + '\n')
+            f.write(str(s["author"]) + '\n')
+            f.write(str(s["license"]))
         try:
             c.request("GET", "/skins/1/" + str(s["id"]) + ".png")
             r = c.getresponse()
-        except Exception:
-            if r != 0:
-                if r.status != 200:
-                    print("Error", r.status)
+        except HTTPException as e:
+            print(type(e),dir(e))
+            raise(e)
+        if r.status != 200:
+            print("Error", r.status)
             continue
-        
-        data = r.read()
-        f = open(skinsdir + "character_" + str(i) + "_preview.png", "wb")
-        f.write(data)
-        f.close()
-        i = i + 1
+        @replace(preview)
+        def go(f):
+            shutil.copyfileobj(r,f)
+    if not foundOne:
+        print("No skins updated on this page. Seems we're done?")
+        raise SystemExit
 addpage(1)
-if pages > 1:
-    for p in range(pages-1):
-        addpage(p+2)
+curpage = 1
+while pages > curpage:
+    curpage = curpage + 1
+    addpage(curpage)
 print("Skins have been updated!")