From fd25dc987d3ff030c72a999dbe6df3b27eda64fb Mon Sep 17 00:00:00 2001
From: Laurent Monin <github@norz.org>
Date: Wed, 19 Feb 2020 00:47:50 +0100
Subject: [PATCH] PICARD-1748: limit number of countries displayed to 10

---
 picard/releasegroup.py  | 10 +++++++---
 picard/util/__init__.py | 37 +++++++++++++++++++++++++++++++++++++
 test/test_utils.py      | 26 ++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/picard/releasegroup.py b/picard/releasegroup.py
index 5256df2d9..d95444135 100644
--- a/picard/releasegroup.py
+++ b/picard/releasegroup.py
@@ -2,6 +2,7 @@
 #
 # Picard, the next-generation MusicBrainz tagger
 # Copyright (C) 2012 Michael Wiencek
+# Copyright (C) 2020 Laurent Monin
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -30,7 +31,10 @@ from picard.mbjson import (
     media_formats_from_node,
 )
 from picard.metadata import Metadata
-from picard.util import uniqify
+from picard.util import (
+    limited_join,
+    uniqify,
+)
 
 
 class ReleaseGroup(DataObject):
@@ -86,8 +90,8 @@ class ReleaseGroup(DataObject):
             release = {
                 "id":      node['id'],
                 "year":    node['date'][:4] if "date" in node else "????",
-                "country": "+".join(countries) if countries
-                           else node.get('country', '') or "??",
+                "country": limited_join(countries, 10, '+', '…') if countries
+                else node.get('country', '') or "??",
                 "format":  media_formats_from_node(node['media']),
                 "label":  ", ".join([' '.join(x.split(' ')[:2]) for x in set(labels)]),
                 "catnum": ", ".join(set(catnums)),
diff --git a/picard/util/__init__.py b/picard/util/__init__.py
index 3e26d206f..8d6b9ec51 100644
--- a/picard/util/__init__.py
+++ b/picard/util/__init__.py
@@ -3,6 +3,7 @@
 # Picard, the next-generation MusicBrainz tagger
 # Copyright (C) 2004 Robert Kaye
 # Copyright (C) 2006 Lukáš Lalinský
+# Copyright (C) 2020 Laurent Monin
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -593,3 +594,39 @@ def get_qt_enum(cls, enum):
         if isinstance(value, enum):
             values.append(key)
     return values
+
+
+def limited_join(a_list, limit, join_string='+', middle_string='…'):
+    """Join elements of a list with `join_string`
+    If list is longer than `limit`, middle elements will be dropped,
+    and replaced by `middle_string`.
+
+    Args:
+        a_list: list of strings to join
+        limit: maximum number of elements to join before limiting
+        join_string: string used to join elements
+        middle_string: string to insert in the middle if limited
+
+    Returns:
+        A string
+
+    Example:
+        >>> limited_join(['a', 'b', 'c', 'd', 'e', 'f'], 2)
+        'a+…+f'
+        >>> limited_join(['a', 'b', 'c', 'd', 'e', 'f'], 3)
+        'a+…+f'
+        >>> limited_join(['a', 'b', 'c', 'd', 'e', 'f'], 4)
+        'a+b+…+e+f'
+        >>> limited_join(['a', 'b', 'c', 'd', 'e', 'f'], 6)
+        'a+b+c+d+e+f'
+        >>> limited_join(['a', 'b', 'c', 'd', 'e', 'f'], 2, ',', '?')
+        'a,?,f'
+    """
+    length = len(a_list)
+    if limit <= 1 or limit >= length:
+        return join_string.join(a_list)
+
+    half = limit // 2
+    start = a_list[:half]
+    end = a_list[-half:]
+    return join_string.join(start + [middle_string] + end)
diff --git a/test/test_utils.py b/test/test_utils.py
index 2889fde32..a3f7de329 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -12,6 +12,7 @@ from picard.const.sys import IS_WIN
 from picard.util import (
     find_best_match,
     imageinfo,
+    limited_join,
     sort_by_similarity,
 )
 
@@ -342,3 +343,28 @@ class GetQtEnum(PicardTestCase):
         self.assertIn('LocateFile', values)
         self.assertIn('LocateDirectory', values)
         self.assertNotIn('DesktopLocation', values)
+
+
+class LimitedJoin(PicardTestCase):
+
+    def setUp(self):
+        self.list = [str(x) for x in range(0, 10)]
+
+    def test_1(self):
+        expected = '0+1+...+8+9'
+        result = limited_join(self.list, 5, '+', '...')
+        self.assertEqual(result, expected)
+
+    def test_2(self):
+        expected = '0+1+2+3+4+5+6+7+8+9'
+        result = limited_join(self.list, -1)
+        self.assertEqual(result, expected)
+        result = limited_join(self.list, len(self.list))
+        self.assertEqual(result, expected)
+        result = limited_join(self.list, len(self.list) + 1)
+        self.assertEqual(result, expected)
+
+    def test_3(self):
+        expected = '0,1,2,3,…,6,7,8,9'
+        result = limited_join(self.list, len(self.list) - 1, ',')
+        self.assertEqual(result, expected)