add EWW_BATTERY support in (free|open|net)bsd (#645)

* add `EWW_BATTERY` support in (free|open|net)bsd

* add `EWW_BATTERY` support in (free|open|net)bsd

---------

Co-authored-by: ElKowar <dev@elkowar.dev>

CHANGELOG.md

@@ -52,6 +52,7 @@ All notable changes to eww will be listed here, starting at changes since versio
 - Made `and`, `or` and `?:` lazily evaluated in simplexpr (By: ModProg)
 - Add Vanilla CSS support (By: Ezequiel Ramis)
 - Add `jq` function, offering jq-style json processing
+- Add support for the `EWW_BATTERY` magic variable in FreeBSD, OpenBSD, and NetBSD (By: dangerdyke)
 - Add `justify` property to the label widget, allowing text justification (By: n3oney)
 - Add `EWW_TIME` magic variable (By: Erenoit)
 - Add trigonometric functions (`sin`, `cos`, `tan`, `cot`) and degree/radian conversions (`degtorad`, `radtodeg`) (By: end-4)

crates/eww/src/config/system_stats.rs

@@ -1,4 +1,4 @@
-use crate::util::IterAverage;
+use crate::{regex, util::IterAverage};
 use anyhow::{Context, Result};
 use once_cell::sync::Lazy;
 use std::{fs::read_to_string, sync::Mutex};
@@ -202,8 +202,54 @@ pub fn get_battery_capacity() -> Result<String> {
     Ok(serde_json::to_string(&(Data { batteries, total_avg: (current / total) * 100_f64 })).unwrap())
 }
 
+#[cfg(any(target_os = "netbsd", target_os = "freebsd", target_os = "openbsd"))]
+pub fn get_battery_capacity() -> Result<String> {
+    let batteries = String::from_utf8(
+        // I have only tested `apm` on FreeBSD, but it *should* work on all of the listed targets,
+        // based on what I can tell from their online man pages.
+        std::process::Command::new("apm")
+            .output()
+            .context("\nError while getting the battery values on bsd, with `apm`: ")?
+            .stdout,
+    )?;
+
+    // `apm` output should look something like this:
+    // $ apm
+    // ...
+    // Remaining battery life: 87%
+    // Remaining battery time: unknown
+    // Number of batteries: 1
+    // Battery 0
+    //         Battery Status: charging
+    //         Remaining battery life: 87%
+    //         Remaining battery time: unknown
+    // ...
+    // last 4 lines are repeated for each battery.
+    // see also:
+    // https://www.freebsd.org/cgi/man.cgi?query=apm&manpath=FreeBSD+13.1-RELEASE+and+Ports
+    // https://man.openbsd.org/amd64/apm.8
+    // https://man.netbsd.org/apm.8
+    let mut json = String::from('{');
+    let re_total = regex!(r"(?m)^Remaining battery life: (\d+)%");
+    let re_single = regex!(r"(?sm)^Battery (\d+):.*?Status: (\w+).*?(\d+)%");
+    for bat in re_single.captures_iter(&batteries) {
+        json.push_str(&format!(
+            r#""BAT{}": {{ "status": "{}", "capacity": {} }}, "#,
+            bat.get(1).unwrap().as_str(),
+            bat.get(2).unwrap().as_str(),
+            bat.get(3).unwrap().as_str(),
+        ))
+    }
+
+    json.push_str(&format!(r#""total_avg": {}}}"#, re_total.captures(&batteries).unwrap().get(1).unwrap().as_str()));
+    Ok(json)
+}
+
 #[cfg(not(target_os = "macos"))]
 #[cfg(not(target_os = "linux"))]
+#[cfg(not(target_os = "netbsd"))]
+#[cfg(not(target_os = "freebsd"))]
+#[cfg(not(target_os = "openbsd"))]
 pub fn get_battery_capacity() -> Result<String> {
     Err(anyhow::anyhow!("Eww doesn't support your OS for getting the battery capacity"))
 }