From b18c6b8135bfdc884b0a0cf03196d3de0a343490 Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Wed, 7 Nov 2018 19:49:21 -0500
Subject: better top level error handling

---
 src/db.rs   | 23 ++++++++++++++++++++---
 src/main.rs | 46 +++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/src/db.rs b/src/db.rs
index b291e86..0d81d7e 100644
--- a/src/db.rs
+++ b/src/db.rs
@@ -1,6 +1,8 @@
 use error::Result;
 use lastfm;
 
+use failure::Fail;
+
 const SCHEMA: &'static str = "
     CREATE TABLE `tracks` (
         artist varchar(1024) NOT NULL,
@@ -17,7 +19,14 @@ pub struct DB {
 impl DB {
     pub fn new<P: AsRef<std::path::Path>>(path: &P) -> Result<DB> {
         let conn = if path.as_ref().exists() {
-            rusqlite::Connection::open(path)?
+            rusqlite::Connection::open(path)
+                .map_err(|e| {
+                    let msg = format!(
+                        "couldn't open db at {}",
+                        path.as_ref().display()
+                    );
+                    e.context(msg)
+                })?
         }
         else {
             Self::create(path)?
@@ -36,8 +45,16 @@ impl DB {
 
         if let Some(parent) = path.as_ref().parent() {
             std::fs::create_dir_all(parent)?;
-            let conn = rusqlite::Connection::open(path)?;
-            conn.execute(SCHEMA, rusqlite::NO_PARAMS)?;
+            let conn = rusqlite::Connection::open(path)
+                .map_err(|e| {
+                    let msg = format!(
+                        "couldn't create db at {}",
+                        path.as_ref().display()
+                    );
+                    e.context(msg)
+                })?;
+            conn.execute(SCHEMA, rusqlite::NO_PARAMS)
+                .map_err(|e| e.context("failed to execute schema"))?;
             Ok(conn)
         }
         else {
diff --git a/src/main.rs b/src/main.rs
index c4c255e..4d66a92 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
 #[macro_use]
 extern crate clap;
 extern crate directories;
+#[macro_use]
 extern crate failure;
 extern crate indicatif;
 extern crate reqwest;
@@ -17,15 +18,14 @@ mod lastfm;
 mod paths;
 mod db;
 
-fn main() {
-    let opts = cli::get_options();
+use error::Result;
 
-    let db = db::DB::new(&paths::dbpath())
-        .expect("failed to create db");
+fn run(opts: cli::Options) -> Result<()> {
+    let db = db::DB::new(&paths::dbpath())?;
     let lastfm = lastfm::LastFMClient::new(&opts.api_key, &opts.username);
     let exporter = exporter::Exporter::new(&db, &lastfm);
 
-    let to_fetch = exporter.tracks_to_sync().unwrap();
+    let to_fetch = exporter.tracks_to_sync()?;
     println!("need to download {} tracks", to_fetch);
 
     let bar = indicatif::ProgressBar::new(to_fetch);
@@ -35,8 +35,40 @@ fn main() {
             .template("{percent:>3}% [{wide_bar}] {eta:5}")
     );
 
-    exporter.sync(|_| { bar.inc(1); })
-        .expect("failed to update db");
+    exporter.sync(|_| { bar.inc(1); })?;
 
     bar.finish_with_message("done");
+
+    Ok(())
+}
+
+fn program_name() -> Result<String> {
+    let program = std::env::args()
+        .next()
+        .ok_or_else(|| format_err!("no program name found"))?;
+    let path = std::path::Path::new(&program);
+    let filename = path.file_name()
+        .ok_or_else(|| format_err!("invalid filename found"))?
+        .to_string_lossy()
+        .to_string();
+    Ok(filename)
+}
+
+fn main() {
+    let opts = cli::get_options();
+    match run(opts) {
+        Ok(_) => {},
+        Err(e) => {
+            let name = program_name()
+                .unwrap_or_else(|e| {
+                    eprintln!("{}", e);
+                    "?".to_string()
+                });
+            let cause = e
+                .iter_chain()
+                .fold(String::new(), |acc, x| acc + ": " + &format!("{}", x));
+            eprintln!("{}{}", name, cause);
+            std::process::exit(1);
+        }
+    }
 }
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