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+# sentrum
+
+Daemon that monitors the Bitcoin blockchain for transactions involving your
+wallets and sends you notifications in many different channels (ntfy push
+notifications, email, telegram, nostr, arbitrary command, etc).
+
+## Installation
+
+Either:
+
+* Compile from source using `cargo install sentrum`
+* Download the binary from the [releases page](releases)
+* If using archlinux, install it from the [AUR](https://aur.archlinux.org/packages/sentrum)
+
+## Configuration
+
+### Config file path
+
+It will look for a `sentrum.toml` configuration file located in any of these
+directories (with this priority):
+
+1. Current working directory
+2. `$XDG_CONFIG_HOME/sentrum`
+3. `~/.config/sentrum`
+4. `/etc/sentrum` (more appropriate if running as a systemd service)
+
+Alternatively, you can pass the configuration file path as an argument in the
+invocation and that will override any of the above.
+
+**Start by copying the sample configuration to where you want it.** E.g.
+
+```bash
+cp sentrum.sample.toml sentrum.toml
+sudo cp sentrum.sample.toml /etc/sentrum/sentrum.toml
+```
+
+or
+
+```bash
+sudo cp sentrum.sample.toml /etc/sentrum/sentrum.toml
+```
+
+### What to configure
+
+You can use the [sentrum.sample.toml](sentrum.sample.toml) file as an
+example.
+Most options have very good defaults so you don't need to change them unless you
+want to. **In the examples below, commented options showcase their defaults,
+unless explicitly said otherwise.**
+
+#### Required
+
+* `wallets`: what wallets you want to monitor
+* `actions`: what actions you want to take once a relevant transaction is found
+
+#### Optional
+
+* `electrum`: by default, public electrum servers are used. You can configure it
+  to connect to your own
+* `message`: this allows you to configure the subject and body templates of the
+  notification message and choose the relevant data from the transaction that
+you want to include
+
+## Wallets
+
+For each wallet you want to track, add the following configuration:
+
+```toml
+[[wallets]]
+# Identifier for naming purposes (required)
+name = "alice"
+# Wallet xpub (required)
+xpub = "xpub6CkXHzuU1NyHUFNiQZLq2bgt6QPqjZbwpJ1MDgDeo4bWZ8ZP7HZr7v9WTLCQFhxVhqiJNcw5wSKE77rkAK1SzcuHjt36ZUibBHezGzGL9h9"
+# Script kind ("legacy","nested_segwit","segwit","taproot") (optional)
+#kind = "segwit"
+```
+
+It assumes a BIP84 (native segwit, `bc1` style addresses) wallet. If your wallet
+has a different script kind add the field `kind = "legacy"` (or `nested_segwit`,
+or `taproot`).
+
+More complex wallet types are supported by providing `primary = "<desc>"` and
+`change = "<desc>"` wallet descriptors instead of `xpub =` and `kind = `.
+
+## Actions
+
+For each new relevant transaction, you can take multiple actions. For each
+action you desire to take, you need to add the configuration:
+
+```toml
+[[actions]]
+# Action type (required)
+type =  "<INSERT ACTION KIND>"
+<.... INSERT ACTION SPECIFIC CONFIGURATION HERE...>
+```
+
+Below we explain the configuration for each action kind. You can have multiple
+actions of the same kind (e.g. you want to send multiple emails from different
+accounts for some reason).
+
+### ntfy
+
+This is the best straightforward way to get push notifications on a smartphone.
+
+1. Install the android/iOS app following the relevant links in https://ntfy.sh
+2. If you don't run your own ntfy self-hosted server, create an account at
+   ntfy.sh
+3. Open the app, give it the needed permissions and configure your account
+   credentials
+4. Click on the `+` button and create a "topic", preferably named `sentrum`
+   since that's what will be used by default.
+
+Then you just need to add the relevant configuration:
+
+```toml
+[[actions]]
+type =  "ntfy"
+# Credentials (required if you use a public server like the default one)
+credentials.username = "<YOUR USERNAME HERE>"
+credentials.password = "<YOUR PASSWORD HERE>"
+# ntfy server (optional)
+#url = "https://ntfy.sh"
+# notification channel name (optional)
+#topic = "sentrum"
+# Proxy used to connect (optional, defaults to None)
+#proxy = "socks5://127.0.0.1:9050"
+# Priority ("max", "high", "default", "low", "min") (optional)
+#priority = "default"
+```
+
+### nostr
+
+Get notified by a nostr [NIP04 encrypted
+DM](https://github.com/nostr-protocol/nips/blob/master/04.md) (leaks metadata
+but widely supported) or a
+[NIP59 GiftWrap sealed sender DM](https://github.com/nostr-protocol/nips/blob/master/59.md)
+(more private but not supported by many clients). Add:
+
+```toml
+[[actions]]
+type = "nostr"
+# Which npub to send the DM (required)
+recipient = "<YOUR npub, hex pubkey, nprofile or nip05>"
+# If NIP59 giftwrap DMs should be used instead of NIP04 (optional)
+#sealed_dm = false
+# Which relays to use to send DMs
+#relays = ["wss://nostr.bitcoiner.social", "wss://nostr.oxtr.dev", "wss://nostr.orangepill.dev", "wss://relay.damus.io"]
+```
+
+### email
+
+You need to add the configuration below and essentially configure an
+authenticated connection to your email provider's SMTP server. I cannot help you
+out with every provider's weird rules (maybe you need to allow 3rd party apps
+for gmail, who knows).
+
+```toml
+[[actions]]
+type =  "email"
+# SMTP server (required)
+server = "<insert smtp server url (e.g. smtp.gmail.com)"
+# SMTP connection type ("tls", "starttls" or "plain") (optional)
+#connection = "tls"
+# SMTP port (optional, defaults to 587 for TLS, 465 for STARTTLS and 25 for plain connections
+#port = 1025
+# SMTP credentials (required in most cases)
+credentials.authentication_identity = "<insert login email>"
+credentials.secret = "<insert password>"
+# Accept self signed certificates (needed if you are using protonmail-bridge) (optional)
+#self_signed_cert = false
+# Configure sender (required)
+from = "sentrum <youremailhere@host.tld>"
+# Configure recipient (optional, defaults to the same as the "from" sender)
+#to = "sentrum <youremailhere@host.tld>"
+```
+
+### telegram
+
+1. Create a new bot using [@Botfather](https://t.me/botfather) to get a token in the format `123456789:blablabla`.
+2. Optionally configure the bot (name, profile pic, etc) with @Botfather
+3. Open a chat with your bot
+4. Add the relevant config:
+
+```toml
+[[actions]]
+type =  "telegram"
+# Auth token of the bot created with @Botfather (required)
+bot_token = "<insert bot token>"
+# 10-digit user id of the DM recipient, go to your profile to get it (required)
+user_id = 1234567890
+```
+
+### command
+
+Runs an external command where you can use transaction details as arguments.
+You can check what parameters (such as `{wallet}` or `{tx_net}` you can use in
+the [message](#message) configuration, since they are the same.
+
+```toml
+[[actions]]
+type = "command"
+cmd = "notify-send"
+args = ["[{wallet}] new tx: {tx_net} sats"]
+```
+
+
+### terminal_print
+
+Justs prints the notification text in the terminal. You can potentially pipe it
+to something else.
+
+```toml
+[[actions]]
+type =  "terminal_print"
+```
+
+### desktop_notification
+
+Displays the transaction message as a native desktop notification on the same
+computer sentrum is running.
+
+```toml
+[[actions]]
+type =  "desktop_notification"
+```
+
+## Message
+
+You can configure the message template and it applies to almost every action
+type. This configuration is entirely optional since the default templates will
+be used if omitted.
+
+Here is the default template:
+
+```toml
+[message]
+subject = "[{wallet}] new transaction"
+body = "net: {tx_net} sats, balance: {total_balance} sats, txid: {txid_short}"
+# Can be "plain", "markdown" or "html"
+format = "plain"
+# Configure blockexplorer urls. This is used to create the {tx_url} parameter
+block_explorers.mainnet = "https://mempool.space/tx/{txid}"
+block_explorers.testnet = "https://mempool.space/testnet/tx/{txid}"
+block_explorers.signet = "https://mempool.space/signet/tx/{txid}"
+```
+
+In the subject and body templates, you can use the following parameters:
+
+* `{tx_net}`: difference between the owned outputs and owned inputs
+* `{wallet}`: name of the configured wallet
+* `{total_balance}`: total balance of the wallet
+* `{txid}`: txid of the transaction
+* `{txid_short}`: truncated txid, easier on the eyes
+* `{received}`: sum of owned outputs
+* `{sent}`: sum of owned inputs
+* `{fee}`: transaction fee
+* `{current_height}`: current blockheight
+* `{tx_height}`: blockheight transaction confirmation
+* `{confs}`: number of transaction confirmations (0 for unconfirmed)
+* `{conf_timestamp}`: timestamp of the first confirmation in the `%Y-%m-%d %H:%M:%S` format
+* `{tx_url}`: a block explorer URL to the transaction
+
+## Electrum server
+
+By default, public electrum servers will be used. I **strongly suggest
+configuring your own electrum server if you want privacy (as you should)**.
+
+The defaults are:
+
+```toml
+[electrum]
+# Defaults:
+# - mainnet: ssl://fulcrum.sethforprivacy.com:50002
+# - testnet: ssl://electrum.blockstream.info:60002
+# - signet: ssl://mempool.space:60602
+# Use "tcp://" if you are connecting without SSL (e.g. "tcp://localhost:50001"
+# or "tcp://fwafiuesngirdghrdhgiurdhgirdgirdhgrd.onion:50001"
+url = "ssl://fulcrum.sethforprivacy.com:50002"
+# blockchain network ("bitcoin", "testnet", "signet", "regtest")
+network = "bitcoin"
+# Optional socks5 proxy (defaults to None)
+#socks5 = 127.0.0.1:9050
+# If using ssl with a trusted certificate, set this to true
+certificate_validation = false
+```
+
+# Usage
+
+Just run `sentrum` without arguments (uses default config search paths) or
+`sentrum <path/to/config/file>`.
+
+You can pass the `--test` flag to send a single test notification to all
+configured actions.
+
+By default, only new transactions can trigger actions. If you pass
+`--notify-past-txs`, it will send notifications of past transactions
+in the initial wallet sync. If you have a long transaction history, this will
+spam your notification channels for every transaction.
+
+## systemd service
+
+The ideal use-case is as a long running daemon, so it makes sense to configure
+it as a systemd service.
+
+If you are installing `sentrum` manually (e.g. from the releases page), you
+should:
+
+1. Create a new `sentrum` user:
+
+```bash
+sudo useradd -d /var/lib/sentrum -m sentrum
+```
+
+2. Place the `sentrum.toml` configuration file in `/etc/sentrum`:
+
+```bash
+sudo mkdir -p /etc/sentrum
+sudo cp sentrum.toml /etc/sentrum
+sudo chown -R sentrum:sentrum /etc/sentrum
+```
+
+3. Copy the [contrib/sentrum.service](contrib/sentrum.service) into the
+   `/etc/systemd/system`
+
+3. Reload systemd so that the service file can be found:
+
+```bash
+sudo systemclt daemon-reload
+```
+
+4. Enable and start the service:
+
+```bash
+sudo systemclt enable --now sentrum.service
+```
+
+5. Check if everything is fine with `systemctl status sentrum`
+
+6. Check the logs with `journalctl -fu sentrum`
+
+# Future Work
+
+* More action types:
+    - Matrix DM
+    - SimpleX chat DM
+    - IRC
+    - XMPP
+    - Whatsapp/Signal using linked devices (harder)
+    - HTTP request
+* More wallet types:
+    - Single Address (blocked by
+    https://github.com/bitcoindevkit/bdk/issues/759)
+    - Collections of wallets as a single entity
+* Notifications for the first tx confirmation and after N confirmations
+* Filtering notifications by the transaction amounts (e.g. no action for
+transactions smaller than 1M sats)
+* Debian package (using `cargo-deb`)
+* Allow per wallet actions
+* Support other blockchain backends (bitcoind-rpc, explora, block filters, dojo)
+* Maybe create a little web UI that helps with writing the configuration
+* Incentivize node distributions to package sentrum