covid19db 2.0.5

Utility for building and accessing COVID-19 datasets
Documentation 
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/* Parser

Copyright (c) 2019-2020 John Goerzen

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

use csv;
use serde::{de, Deserialize, Deserializer};
use std::error::Error;
use std::fmt::Display;
use std::fs::File;
use std::str::FromStr;

#[allow(dead_code)]
pub fn date_from_str<'de, S, D>(deserializer: D) -> Result<S, D::Error>
where
    S: FromStr,      // Required for S::from_str...
    S::Err: Display, // Required for .map_err(de::Error::custom)
    D: Deserializer<'de>,
{
    let s: String = Deserialize::deserialize(deserializer)?;
    S::from_str(&s).map_err(de::Error::custom)
}

pub fn rec_to_struct<'a, A: serde::Deserialize<'a>>(
    record: &'a csv::StringRecord,
) -> Result<A, csv::Error> {
    record.deserialize(None)
}

pub fn parse_init_file(file: File) -> Result<csv::Reader<File>, Box<dyn Error>> {
    let rdr = csv::ReaderBuilder::new()
        .delimiter(b',')
        .flexible(true)
        .from_reader(file);
    Ok(rdr)
}

/*

This type signature with hints from https://stackoverflow.com/questions/27535289/what-is-the-correct-way-to-return-an-iterator-or-any-other-trait
*/
pub fn parse_records<'a, A: std::io::Read>(
    byteiter: csv::ByteRecordsIter<'a, A>,
) -> impl Iterator<Item = csv::StringRecord> + 'a {
    byteiter.map(|x| csv::StringRecord::from_byte_record_lossy(x.expect("Error in parse_records")))
}

#[allow(dead_code)]
pub fn parse_record(rec: csv::ByteRecord) -> csv::StringRecord {
    csv::StringRecord::from_byte_record_lossy(rec)
}