factor out os-specific battery detection code

stub out osx for now, will come back with a real implementation later

4 files changed, 158 insertions, 0 deletions

diff --git a/src/power/mod.rs b/src/power/mod.rs
new file mode 100644
index 0000000..afe5194
--- /dev/null
+++ b/src/power/mod.rs
@@ -0,0 +1,86 @@
+use std;
+
+use std::io::Read;
+
+mod sys;
+
+// XXX maybe extract this out into a separate crate?
+
+#[derive(Debug)]
+pub struct PowerInfo {
+    power_supplies: Vec<sys::PowerSupplyInfo>,
+}
+
+impl PowerInfo {
+    pub fn new() -> PowerInfo {
+        let power_supplies = sys::power_supplies();
+
+        PowerInfo {
+            power_supplies,
+        }
+    }
+
+    pub fn battery_usage(&self) -> Option<f64> {
+        let mut total_now = 0;
+        let mut total_full = 0;
+        for battery in self.batteries() {
+            if let Some(now) = battery.energy_now {
+                total_now += now;
+            }
+            else {
+                return None;
+            }
+            if let Some(full) = battery.energy_full {
+                total_full += full;
+            }
+            else {
+                return None;
+            }
+        }
+
+        if total_full > 0 {
+            Some((total_now as f64) / (total_full as f64))
+        }
+        else {
+            None
+        }
+    }
+
+    pub fn charging(&self) -> bool {
+        for mains in self.mains() {
+            if mains.online == Some(true) {
+                return true;
+            }
+        }
+        false
+    }
+
+    pub fn has_batteries(&self) -> bool {
+        self.batteries().count() > 0
+    }
+
+    fn batteries(&self) -> impl Iterator<Item=&sys::PowerSupplyInfo> {
+        self.power_supplies
+            .iter()
+            .filter(|p| p.ty == sys::PowerSupplyType::Battery)
+    }
+
+    fn mains(&self) -> impl Iterator<Item=&sys::PowerSupplyInfo> {
+        self.power_supplies
+            .iter()
+            .filter(|p| p.ty == sys::PowerSupplyType::AC)
+    }
+}
+
+fn slurp<T, U>(path: U) -> Option<T>
+where
+    T: std::str::FromStr,
+    U: AsRef<std::path::Path>,
+{
+    let mut contents = String::new();
+    std::fs::File::open(path).ok().and_then(|mut fh| {
+        fh.read_to_string(&mut contents)
+            .ok()
+            .and_then(|_| contents.trim().parse().ok())
+    })
+}
diff --git a/src/power/sys/linux.rs b/src/power/sys/linux.rs
new file mode 100644
index 0000000..670498a
--- /dev/null
+++ b/src/power/sys/linux.rs
@@ -0,0 +1,45 @@
+use walkdir;
+
+pub fn power_supplies() -> Vec<super::PowerSupplyInfo> {
+    let mut power_supplies = vec![];
+    for entry in walkdir::WalkDir::new("/sys/class/power_supply/")
+        .min_depth(1)
+        .max_depth(1)
+        .follow_links(true)
+    {
+        let entry = entry.unwrap();
+
+        let name = entry
+            .path()
+            .file_name()
+            .unwrap()
+            .to_string_lossy()
+            .into_owned();
+        let ty = super::super::slurp(entry.path().join("type"))
+            .map(|t: String| super::PowerSupplyType::from_str(&t))
+            .expect("couldn't find power supply type");
+        let energy_full = super::super::slurp(entry.path().join("energy_full"));
+        let energy_now = super::super::slurp(entry.path().join("energy_now"));
+        let online =
+            super::super::slurp(entry.path().join("online")).map(|n: u8| n != 0);
+
+        power_supplies.push(super::PowerSupplyInfo {
+            name,
+            ty,
+            energy_now,
+            energy_full,
+            online,
+        })
+    }
+    power_supplies
+}
+
+impl super::PowerSupplyType {
+    fn from_str(ty: &str) -> Self {
+        match ty {
+            "Mains" => super::PowerSupplyType::AC,
+            "Battery" => super::PowerSupplyType::Battery,
+            _ => panic!("unknown power supply type {}", ty),
+        }
+    }
+}
diff --git a/src/power/sys/macos.rs b/src/power/sys/macos.rs
new file mode 100644
index 0000000..a0455ac
--- /dev/null
+++ b/src/power/sys/macos.rs
@@ -0,0 +1,3 @@
+pub fn power_supplies() -> Vec<super::PowerSupplyInfo> {
+    vec![]
+}
diff --git a/src/power/sys/mod.rs b/src/power/sys/mod.rs
new file mode 100644
index 0000000..b6bb469
--- /dev/null
+++ b/src/power/sys/mod.rs
@@ -0,0 +1,24 @@
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(target_os = "linux")]
+pub use self::linux::*;
+
+#[cfg(target_os = "macos")]
+mod macos;
+#[cfg(target_os = "macos")]
+pub use self::macos::*;
+
+#[derive(PartialEq, Eq, Debug, Clone)]
+pub enum PowerSupplyType {
+    AC,
+    Battery,
+}
+
+#[derive(Debug, Clone)]
+pub struct PowerSupplyInfo {
+    pub name: String,
+    pub ty: PowerSupplyType,
+    pub energy_now: Option<u64>,
+    pub energy_full: Option<u64>,
+    pub online: Option<bool>,
+}