From b7b8379e10e567485177e4269dd4e249d8bef600 Mon Sep 17 00:00:00 2001
From: Paul Woolcock <paul@woolcock.us>
Date: Tue, 5 Mar 2019 15:15:17 -0500
Subject: [PATCH] Add built-in support for deserializing Data from the env

---
 Cargo.toml         |  4 ++-
 src/errors.rs      |  7 ++++
 src/helpers/env.rs | 81 ++++++++++++++++++++++++++++++++++++++++++++++
 src/helpers/mod.rs | 12 +++++++
 src/lib.rs         |  3 ++
 5 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 src/helpers/env.rs

diff --git a/Cargo.toml b/Cargo.toml
index f557438..4fb88da 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,7 @@ tap-reader = "1"
 try_from = "0.3.2"
 toml = { version = "0.4.6", optional = true }
 hyper-old-types = "0.11.0"
+envy = { version = "0.4.0", optional = true }
 
 [dependencies.chrono]
 version = "0.4"
@@ -30,7 +31,8 @@ features = ["serde"]
 [features]
 default = []
 json = []
-all = ["toml", "json"]
+env = ["envy"]
+all = ["toml", "json", "env"]
 
 [build-dependencies]
 skeptic = "0.13.3"
diff --git a/src/errors.rs b/src/errors.rs
index f9fd8e6..d33e90c 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -1,5 +1,7 @@
 use std::{error, fmt, io::Error as IoError};
 
+#[cfg(feature = "env")]
+use envy::Error as EnvyError;
 use hyper_old_types::Error as HeaderParseError;
 use reqwest::{header::ToStrError as HeaderStrError, Error as HttpError, StatusCode};
 use serde_json::Error as SerdeError;
@@ -52,6 +54,9 @@ pub enum Error {
     HeaderStrError(HeaderStrError),
     /// Error parsing the http Link header
     HeaderParseError(HeaderParseError),
+    #[cfg(feature = "env")]
+    /// Error deserializing from the environment
+    Envy(EnvyError),
     /// Other errors
     Other(String),
 }
@@ -89,6 +94,7 @@ impl error::Error for Error {
             Error::TomlDe(ref e) => e.description(),
             Error::HeaderStrError(ref e) => e.description(),
             Error::HeaderParseError(ref e) => e.description(),
+            Error::Envy(ref e) => e.description(),
             Error::Other(ref e) => e,
         }
     }
@@ -128,6 +134,7 @@ from! {
     #[cfg(feature = "toml")] TomlDeError, TomlDe,
     HeaderStrError, HeaderStrError,
     HeaderParseError, HeaderParseError,
+    EnvyError, Envy,
     String, Other,
 }
 
diff --git a/src/helpers/env.rs b/src/helpers/env.rs
new file mode 100644
index 0000000..1f13acb
--- /dev/null
+++ b/src/helpers/env.rs
@@ -0,0 +1,81 @@
+use envy;
+
+use data::Data;
+use Result;
+
+/// Attempts to deserialize a Data struct from the environment
+pub fn from_env() -> Result<Data> {
+    Ok(envy::from_env()?)
+}
+
+/// Attempts to deserialize a Data struct from the environment. All keys are
+/// prefixed with the given prefix
+pub fn from_env_prefixed(prefix: &str) -> Result<Data> {
+    Ok(envy::prefixed(prefix).from_env()?)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::{
+        env,
+        ops::FnOnce,
+        panic::{catch_unwind, UnwindSafe},
+    };
+
+    fn withenv<F: FnOnce() -> R + UnwindSafe, R>(prefix: Option<&'static str>, test: F) -> R {
+        env::set_var(makekey(prefix, "BASE"), "https://example.com");
+        env::set_var(makekey(prefix, "CLIENT_ID"), "adbc01234");
+        env::set_var(makekey(prefix, "CLIENT_SECRET"), "0987dcba");
+        env::set_var(makekey(prefix, "REDIRECT"), "urn:ietf:wg:oauth:2.0:oob");
+        env::set_var(makekey(prefix, "TOKEN"), "fedc5678");
+
+        let result = catch_unwind(test);
+
+        env::remove_var(makekey(prefix, "BASE"));
+        env::remove_var(makekey(prefix, "CLIENT_ID"));
+        env::remove_var(makekey(prefix, "CLIENT_SECRET"));
+        env::remove_var(makekey(prefix, "REDIRECT"));
+        env::remove_var(makekey(prefix, "TOKEN"));
+
+        fn makekey(prefix: Option<&'static str>, key: &str) -> String {
+            if let Some(prefix) = prefix {
+                format!("{}{}", prefix, key)
+            } else {
+                key.to_string()
+            }
+        }
+
+        result.expect("failed")
+    }
+
+    #[test]
+    fn test_from_env_no_prefix() {
+        let desered = withenv(None, || from_env()).expect("Couldn't deser");
+        assert_eq!(
+            desered,
+            Data {
+                base: "https://example.com".into(),
+                client_id: "adbc01234".into(),
+                client_secret: "0987dcba".into(),
+                redirect: "urn:ietf:wg:oauth:2.0:oob".into(),
+                token: "fedc5678".into(),
+            }
+        );
+    }
+
+    #[test]
+    fn test_from_env_prefixed() {
+        let desered = withenv(Some("APP_"), || from_env_prefixed("APP_")).expect("Couldn't deser");
+        assert_eq!(
+            desered,
+            Data {
+                base: "https://example.com".into(),
+                client_id: "adbc01234".into(),
+                client_secret: "0987dcba".into(),
+                redirect: "urn:ietf:wg:oauth:2.0:oob".into(),
+                token: "fedc5678".into(),
+            }
+        );
+    }
+}
diff --git a/src/helpers/mod.rs b/src/helpers/mod.rs
index ed2b107..d1c420e 100644
--- a/src/helpers/mod.rs
+++ b/src/helpers/mod.rs
@@ -22,5 +22,17 @@ pub mod toml;
 /// ```
 pub mod json;
 
+#[cfg(feature = "env")]
+/// Helpers for deserializing a `Data` struct from the environment
+///
+/// In order to use this module, set the "env" feature in your Cargo.toml:
+///
+/// ```toml,ignore
+/// [dependencies.elefren]
+/// version = "0.18"
+/// features = ["env"]
+/// ```
+pub mod env;
+
 /// Helpers for working with the command line
 pub mod cli;
diff --git a/src/lib.rs b/src/lib.rs
index 0489873..0b1956a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -58,6 +58,9 @@ extern crate tap_reader;
 extern crate try_from;
 extern crate url;
 
+#[cfg(feature = "env")]
+extern crate envy;
+
 #[cfg(feature = "toml")]
 extern crate toml as tomlcrate;