apps: handle err's

+ ord fn's

app_async/src/main.rs

@@ -19,6 +19,7 @@ use chgk_ledb_lib::async_db;
 use chgk_ledb_lib::questions::Question;
 use chgk_ledb_lib::questions::QuestionsConverterAsyncForStream;
 use chgk_ledb_lib::source::ReadSourceQuestionsBatchesAsync;
+use chgk_ledb_lib::util::ErrorToString;
 
 const ZIP_FILENAME: &str = "json.zip";
 const NEW_DB_FILENAME: &str = "db.dat";
@@ -48,6 +49,113 @@ struct Cli {
     measure: bool,
 }
 
+#[tokio::main]
+async fn main() {
+    let args = Cli::parse();
+
+    let mut action: Box<dyn Future<Output = _>> = match &args.command {
+        Command::Write => Box::new(write_db()),
+        Command::Print { id } => {
+            let get_question = read_from_db(*id);
+            Box::new(print_question_from(get_question))
+        }
+        Command::ZipPrint { file_num, num } => {
+            let get_question = read_from_zip(*file_num, *num);
+            Box::new(print_question_from(get_question))
+        }
+    };
+
+    if args.measure {
+        action = Box::new(measure_and_print(Box::into_pin(action)));
+    }
+
+    Box::into_pin(action).await;
+}
+
+// measure and return time elapsed in `fut` in seconds
+pub async fn measure<F: Future>(fut: F) -> f64 {
+    let start = Instant::now();
+    fut.await;
+    let elapsed = start.elapsed();
+    (elapsed.as_secs() as f64) + (elapsed.subsec_nanos() as f64 / 1_000_000_000.0)
+}
+
+pub async fn measure_and_print<F: Future>(fut: F) {
+    let m = measure(fut).await;
+    eprintln!("{}", m);
+}
+
+async fn print_question_from<F>(get_q: F)
+where
+    F: Future<Output = Result<Question, String>>,
+{
+    let q = get_q.await.expect("question not found");
+    println!("{:#?}", q)
+}
+
+async fn read_from_zip(file_num: usize, mut num: usize) -> Result<Question, String> {
+    let mut rng = thread_rng();
+    let zip_file = fs::File::open(ZIP_FILENAME).await.str_err()?;
+    let mut zip_reader = io::BufReader::new(zip_file);
+    let archive = ZipFileReader::with_tokio(&mut zip_reader).await.str_err()?;
+
+    let mut source = archive.source_questions();
+    let files_count = source.len();
+    let file_index = if file_num == 0 {
+        let files = Uniform::new(0, files_count);
+        rng.sample(files)
+    } else {
+        file_num - 1
+    };
+
+    let src = source
+        .get(file_index)
+        .await
+        .map_err(|e| format!("get file {file_num} => {e}"))?;
+    let src = stream::once(async { src });
+    pin_mut!(src);
+    let converter = src.converter();
+    let questions: Vec<_> = converter.convert().collect().await;
+    if num == 0 {
+        num = (1..=questions.len()).choose(&mut rng).unwrap();
+    }
+    let mut question = questions
+        .get(num - 1)
+        .ok_or(format!("get question #{num} => None"))?
+        .clone();
+    question.num = num as u32;
+    Ok(question)
+}
+
+async fn read_from_db(id: u32) -> Result<Question, String> {
+    let reader: async_db::Reader<Question> = async_db::Reader::new(NEW_DB_FILENAME).await?;
+
+    let len = reader.len();
+
+    let index = if id == 0 {
+        let mut rng = thread_rng();
+        let questions = Uniform::new(0, len);
+        rng.sample(questions)
+    } else {
+        id as usize - 1
+    };
+
+    reader
+        .get(index)
+        .await
+        .map_err(|e| format!("get #{index} => {e}"))
+}
+
+async fn write_db() {
+    let (tx, rx) = mpsc::unbounded_channel::<Question>();
+    tokio::try_join!(
+        tokio::spawn(zip_reader_task(tx)),
+        tokio::spawn(db_writer_task(rx))
+    )
+    .expect("tokio join");
+    println!("all done");
+}
+
 async fn zip_reader_task(tx: UnboundedSender<Question>) {
     let mut file = fs::File::open(ZIP_FILENAME).await.expect("open zip");
     let archive = ZipFileReader::with_tokio(&mut file)
@@ -73,109 +181,6 @@ async fn zip_reader_task(tx: UnboundedSender<Question>) {
     println!("read done");
 }
 
-async fn print_question_from<F>(get_q: F)
-where
-    F: Future<Output = Option<Question>>,
-{
-    let q = get_q.await.expect("question not found");
-    println!("{:#?}", q)
-}
-
-async fn read_from_zip(file_num: usize, mut num: usize) -> Option<Question> {
-    let mut rng = thread_rng();
-    let zip_file = fs::File::open(ZIP_FILENAME).await.expect("open zip file");
-    let mut zip_reader = io::BufReader::new(zip_file);
-    let archive = ZipFileReader::with_tokio(&mut zip_reader)
-        .await
-        .expect("open zip file reader");
-
-    let mut source = archive.source_questions();
-    let files_count = source.len();
-    let file_index = if file_num == 0 {
-        let files = Uniform::new(0, files_count);
-        rng.sample(files)
-    } else {
-        file_num - 1
-    };
-
-    let src = source.get(file_index).await;
-    let src = stream::once(async { src.expect("get source file") });
-    pin_mut!(src);
-    let converter = src.converter();
-    let questions: Vec<_> = converter.convert().collect().await;
-    if num == 0 {
-        num = (1..=questions.len()).choose(&mut rng).unwrap();
-    }
-    let mut question = questions.get(num - 1).expect("get question").clone();
-    question.num = num as u32;
-    Some(question)
-}
-
-// measure and return time elapsed in `fut` in seconds
-pub async fn measure<F: Future>(fut: F) -> f64 {
-    let start = Instant::now();
-    fut.await;
-    let elapsed = start.elapsed();
-    (elapsed.as_secs() as f64) + (elapsed.subsec_nanos() as f64 / 1_000_000_000.0)
-}
-
-pub async fn measure_and_print<F: Future>(fut: F) {
-    let m = measure(fut).await;
-    eprintln!("{}", m);
-}
-
-#[tokio::main]
-async fn main() {
-    let args = Cli::parse();
-
-    let mut action: Box<dyn Future<Output = _>> = match &args.command {
-        Command::Write => Box::new(write_db()),
-        Command::Print { id } => {
-            let get_question = read_from_db(*id);
-            Box::new(print_question_from(get_question))
-        }
-        Command::ZipPrint { file_num, num } => {
-            let get_question = read_from_zip(*file_num, *num);
-            Box::new(print_question_from(get_question))
-        }
-    };
-
-    if args.measure {
-        action = Box::new(measure_and_print(Box::into_pin(action)));
-    }
-
-    Box::into_pin(action).await;
-}
-
-async fn read_from_db(id: u32) -> Option<Question> {
-    let reader: async_db::Reader<Question> = async_db::Reader::new(NEW_DB_FILENAME)
-        .await
-        .expect("new db reader");
-
-    let len = reader.len();
-
-    let index = if id == 0 {
-        let mut rng = thread_rng();
-        let questions = Uniform::new(0, len);
-        rng.sample(questions)
-    } else {
-        id as usize - 1
-    };
-
-    match reader.get(index).await {
-        Ok(question) => Some(question),
-        Err(_) => None,
-    }
-}
-async fn write_db() {
-    let (tx, rx) = mpsc::unbounded_channel::<Question>();
-    tokio::try_join!(
-        tokio::spawn(zip_reader_task(tx)),
-        tokio::spawn(db_writer_task(rx))
-    )
-    .expect("tokio join");
-    println!("all done");
-}
 async fn db_writer_task(rx: UnboundedReceiver<Question>) {
     let writer_opts = WriterOpts::default();
     let mut writer: async_db::Writer<Question> =