feature: add some doc to README.md

README.md

@@ -1,3 +1,157 @@
 # django-ntfy
 
-Django's email backend which is used to send messages to ntfy.sh (or self hostated instace) instead of actually sending an email.
+Django's email backend which is used to send messages to ntfy.sh (or self-hosted instace) instead of actually sending an email.
+
+
+# Installation
+
+First you need to install the package:
+```bash
+pip install django-ntfy
+```
+
+You need to configure the NTFY url and topic `settings.py`:
+```python
+NTFY_BASE_URL = "https://ntfy.sh/"
+NTFY_DEFAULT_TOPIC = "my-original-topic-name"
+```
+
+Now if you want use NTFY backend to propagate errors instead of ordinary EMAIL_BACKEND, you can set:
+```python
+LOGGING = {
+    ...
+    "handlers": {
+        ...
+        "mail_admins": {
+            "level": "ERROR",
+            "class": "django.utils.log.AdminEmailHandler",
+            "email_backend": "django_ntfy.NtfyBackend",
+        }
+        ...
+    }
+    ...
+}
+```
+
+Note the you may also want to set `EMAIL_BACKEND="django_ntfy.NtfyBackend"` directly, but be aware that once you do it, you won't be able to send any emails, because everything will published only to NTFY topic. (This still might be useful for some debugging purposes or staging servers).
+
+# Backends
+
+## NtfyBackend
+
+Replacement of django's default EmailBackend. It is used to publish a topic to ntfy.sh instead of sending and email. Note the some fields may not be useful here such as recievers address.
+
+Note ntfy message options options see [NFTY publish docs](https://docs.ntfy.sh/publish/).
+
+### Variables
+* `NTFY_BASE_URL` - type str, required, basic url on ntfy server
+* `NTFY_DEFAULT_TOPIC` - type str, required, default topic when publishing a message
+* `NTFY_MESSAGE_SIZE_LIMIT` - type int, default 1000, limits the body/message size (note that ntfy.sh discards long messages)
+* `NTFY_SEND_ATTACHMENTS` - type bool, default False, sends attachments as extra messages into ntfy.sh (experimental)
+
+* `NTFY_DEFAULT_ICON_URL` - type :str, default None, Url of custom icon used in the message
+* `NTFY_DEFAULT_TAGS` - type list of str, default [], Tags of the message
+* `NTFY_DEFAULT_PRIORITY` - 1 to 5, default None , Priority of the message
+
+### Signals
+Content of the message sent to NTFY server can be also altered using signals.
+
+## topic_signal
+Alters the topic of output messages.
+
+```python
+from django.core.mail import EmailMessage
+from django_ntfy import topic_signal
+
+def topic_handler(sender, message: EmailMessage) -> str:
+    ...
+    return "topic"
+
+topic_signal.connect(topic_handler, dispatch_uid="ntfy_topic")
+```
+
+## icon_signal
+Alters the icon of output messages.
+
+```python
+from django.core.mail import EmailMessage
+from django_ntfy import icon_signal
+
+def icon_handler(sender, message: EmailMessage) -> str:
+    ...
+    return "https://ntfy.sh/_site/images/favicon.ico"
+
+icon_signal.connect(icon_handler, dispatch_uid="ntfy_icon")
+```
+
+## tags_signal
+Alters the tags of output messages.
+
+```python
+from django.core.mail import EmailMessage
+from django_ntfy import tags_signal
+
+def tags_handler(sender, message: EmailMessage) -> list[str]:
+    ...
+    return ["warning", "skull"]
+
+tags_signal.connect(tags_handler, dispatch_uid="ntfy_tags")
+```
+
+## actions_signal
+Alters the actions of output messages.
+
+```python
+from django.core.mail import EmailMessage
+from django_ntfy import actions_signal
+
+def actions_handler(sender, message: EmailMessage) -> list[dict]:
+    ...
+    return [
+        {
+            "action": "view",
+            "label": "Ok",
+            "url": "https://example.com/ok",
+        },
+        {
+            "action": "http",
+            "label": "Cancel",
+            "url": "https://example.com/cancel",
+            "body": json.dumps({"a": "b"}),
+            "clear": True,
+        },
+    ]
+
+actions_signal.connect(actions_handler, dispatch_uid="ntfy_actions")
+```
+
+## priority_signal
+Alters the priority of output messages.
+
+```python
+from django.core.mail import EmailMessage
+from django_ntfy import priority_signal
+
+def priority_handler(sender, message: EmailMessage) -> int:
+    ...
+    return 5
+
+priority_signal.connect(tags_handler, dispatch_uid="ntfy_priority")
+```
+
+
+## ExponentialRateLimitBackends
+This backend can be used to group multiple email backends together (e.g. `NtfyBackend` and `EmailBackend`). It also provides some bacis Rate limit support so that your emailbox / topic is not flooded with same messages.
+
+To set it you can simply do it like this:
+```python
+EMAIL_EXPONENTIAL_RATE_LIMIT_BACKENDS = [
+    "django.core.mail.backends.smtp.EmailBackend",
+    "django_ntfy.NtfyBackend",
+]
+```
+
+If you want to disable RateLimit functionality you configure it via
+```python
+EMAIL_EXPONENTIAL_RATE_LIMIT_TIMEOUT = 0
+```