Rename SettingValue to Setting. (#286)

Breaking change, but the crate is fresh and there's time to yank and
republish.

src/setting.rs

@@ -0,0 +1,141 @@
+//! Configuration setting values parsed from the environment and config file:
+//! `/etc/yubico/yubikeypiv.conf`
+
+// Adapted from yubico-piv-tool:
+// <https://github.com/Yubico/yubico-piv-tool/>
+//
+// Copyright (c) 2014-2016 Yubico AB
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//   * Redistributions of source code must retain the above copyright
+//     notice, this list of conditions and the following disclaimer.
+//
+//   * Redistributions in binary form must reproduce the above
+//     copyright notice, this list of conditions and the following
+//     disclaimer in the documentation and/or other materials provided
+//     with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/// Default location of the YubiKey PIV configuration file
+pub const DEFAULT_CONFIG_FILE: &str = "/etc/yubico/yubikeypiv.conf";
+
+use std::{
+    env,
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+/// Source of how a setting was configured.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum SettingSource {
+    /// User-specified setting: sourced via `YUBIKEY_PIV_*` environment vars.
+    User,
+
+    /// Admin-specified setting: sourced via the `/etc/yubico/yubikeypiv.conf`
+    /// configuration file.
+    Admin,
+
+    /// Default setting.
+    Default,
+}
+
+impl Default for SettingSource {
+    fn default() -> Self {
+        Self::Default
+    }
+}
+
+/// Setting booleans: configuration values sourced from a file or the environment.
+///
+/// These can be configured globally in `/etc/yubico/yubikeypiv.conf` by a
+/// system administrator, or by the local user via `YUBIKEY_PIV_*` environment
+/// variables.
+#[derive(Copy, Clone, Debug)]
+pub struct Setting {
+    /// Boolean value
+    pub value: bool,
+
+    /// Source of the configuration setting (user, admin, or default)
+    pub source: SettingSource,
+}
+
+impl Setting {
+    /// Get a [`SettingValue`] value by name.
+    pub fn get(key: &str, default: bool) -> Self {
+        Self::from_file(key)
+            .or_else(|| Self::from_env(key))
+            .unwrap_or(Self {
+                value: default,
+                source: SettingSource::Default,
+            })
+    }
+
+    /// Get a boolean config value from the provided config file
+    fn from_file(key: &str) -> Option<Self> {
+        if let Ok(file) = File::open(DEFAULT_CONFIG_FILE) {
+            for line in BufReader::new(file).lines() {
+                let line = match line {
+                    Ok(line) => line,
+                    _ => continue,
+                };
+
+                if line.starts_with('#') || line.starts_with('\r') || line.starts_with('\n') {
+                    continue;
+                }
+
+                let (name, value) = {
+                    let mut parts = line.splitn(1, '=');
+                    let name = parts.next();
+                    let value = parts.next();
+                    match (name, value, parts.next()) {
+                        (Some(name), Some(value), None) => (name.trim(), value.trim()),
+                        _ => continue,
+                    }
+                };
+
+                if name == key {
+                    return Some(Setting {
+                        source: SettingSource::Admin,
+                        value: value == "1" || value == "true",
+                    });
+                }
+            }
+        }
+
+        None
+    }
+
+    /// Get a setting boolean from an environment variable
+    fn from_env(key: &str) -> Option<Self> {
+        env::var(format!("YUBIKEY_PIV_{}", key))
+            .ok()
+            .map(|value| Setting {
+                source: SettingSource::User,
+                value: value == "1" || value == "true",
+            })
+    }
+}
+
+impl Default for Setting {
+    fn default() -> Self {
+        Self {
+            value: false,
+            source: SettingSource::default(),
+        }
+    }
+}