From 5a8e75112f7cc59358e85699caa6836b2f3a4451 Mon Sep 17 00:00:00 2001
From: Daniel Quinn <code@danielquinn.org>
Date: Sun, 28 Feb 2016 00:41:03 +0000
Subject: [PATCH] Added a custom manager for groupped logs

---
 src/documents/managers.py | 70 +++++++++++++++++++++++++++++++++++++++
 src/documents/models.py   |  4 +++
 2 files changed, 74 insertions(+)
 create mode 100644 src/documents/managers.py

diff --git a/src/documents/managers.py b/src/documents/managers.py
new file mode 100644
index 000000000..d7e7225eb
--- /dev/null
+++ b/src/documents/managers.py
@@ -0,0 +1,70 @@
+from django.conf import settings
+
+from django.db import models
+from django.db.models.aggregates import Max
+
+
+class Concat(models.Aggregate):
+    """
+    Theoretically, this should work in Sqlite, PostgreSQL, and MySQL, but I've
+    only ever tested it in Sqlite.
+    """
+
+    ENGINE_SQLITE = 1
+    ENGINE_POSTGRESQL = 2
+    ENGINE_MYSQL = 3
+    ENGINES = {
+        "django.db.backends.sqlite3": ENGINE_SQLITE,
+        "django.db.backends.postgresql_psycopg2": ENGINE_POSTGRESQL,
+        "django.db.backends.postgresql": ENGINE_POSTGRESQL,
+        "django.db.backends.mysql": ENGINE_MYSQL
+    }
+
+    def __init__(self, expression, separator="\n", **extra):
+
+        self.engine = self._get_engine()
+        self.function = self._get_function()
+        self.template = self._get_template(separator)
+
+        models.Aggregate.__init__(
+            self,
+            expression,
+            output_field=models.CharField(),
+            **extra
+        )
+
+    def _get_engine(self):
+        engine = settings.DATABASES["default"]["ENGINE"]
+        try:
+            return self.ENGINES[engine]
+        except KeyError:
+            raise NotImplementedError(
+                "There's currently no support for {} when it comes to group "
+                "concatenation in Paperless".format(engine)
+            )
+
+    def _get_function(self):
+        if self.engine == self.ENGINE_POSTGRESQL:
+            return "STRING_AGG"
+        return "GROUP_CONCAT"
+
+    def _get_template(self, separator):
+        if self.engine == self.ENGINE_MYSQL:
+            return "%(function)s(%(expressions)s, SEPARATOR '{}')".format(
+                separator)
+        return "%(function)s(%(expressions)s, '{}')".format(separator)
+
+
+class LogQuerySet(models.query.QuerySet):
+
+    def by_group(self):
+        return self.values("group").annotate(
+            time=Max("modified"),
+            messages=Concat("message"),
+        ).order_by("-time")
+
+
+class LogManager(models.Manager):
+
+    def get_queryset(self):
+        return LogQuerySet(self.model, using=self._db)
diff --git a/src/documents/models.py b/src/documents/models.py
index 91dd458ea..e5556534a 100644
--- a/src/documents/models.py
+++ b/src/documents/models.py
@@ -8,6 +8,8 @@ from django.db import models
 from django.template.defaultfilters import slugify
 from django.utils import timezone
 
+from .managers import LogManager
+
 
 class SluggedModel(models.Model):
 
@@ -214,6 +216,8 @@ class Log(models.Model):
     created = models.DateTimeField(auto_now_add=True)
     modified = models.DateTimeField(auto_now=True)
 
+    objects = LogManager()
+
     class Meta(object):
         ordering = ("-modified",)