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//! BookCrossing data extraction.
//!
//! The BookCrossing CSV files are corrupt, so this command extracts them and fixes
//! up the character sets to make them well-formed CSV.
use std::fs::File;
use std::io::Write;
use std::path::PathBuf;

use zip::ZipArchive;

use crate::prelude::*;

#[derive(Args, Debug)]
pub struct Extract {
    /// The zip file to read.
    #[arg(name = "ZIPFILE")]
    zipfile: PathBuf,

    /// The CSV file to write.
    #[arg(name = "OUTFILE")]
    outfile: PathBuf,
}

impl Command for Extract {
    fn exec(&self) -> Result<()> {
        info!("reading {:?}", self.zipfile);
        let file = File::open(&self.zipfile)?;
        let mut zip = ZipArchive::new(file)?;
        let mut entry = zip.by_name("BX-Book-Ratings.csv")?;
        let mut data = entry.read_all_sized()?;

        info!("cleaning up data file");

        debug!("removing non-ASCII characters and carriage returns");
        data.retain(|b| *b < 128 && *b != b'\r');

        debug!("replacing semicolons to make CSV");
        // can this be done with retain_with?
        for i in 0..data.len() {
            let c = data[i];
            if c == b';' {
                data[i] = b',';
            }
        }

        debug!("splitting CSV header");
        let data = String::from_utf8(data)?;
        let pos = if let Some(p) = data.find('\n') {
            p
        } else {
            error!("no newline found, corrupt input data?");
            return Err(anyhow!("corrupt data"));
        };
        let (hdr, rest) = data.split_at(pos + 1);
        if !hdr.starts_with("\"User-ID\",") {
            error!("unexpected file header found");
            info!("found header: “{}“", hdr);
            info!("expected cleaned header to begin with “\"User-ID\",“");
            return Err(anyhow!("corrupt data"));
        }

        info!("writing cleaned output");
        let mut out = File::create(&self.outfile)?;
        write!(out, "user,isbn,rating\n")?;
        let csvin = csv::Reader::from_reader(rest.as_bytes());
        for row in csvin.into_records() {
            let row = row?;
            let user = row.get(0).ok_or(anyhow!("invalid CSV row"))?;
            let isbn = row.get(1).ok_or(anyhow!("invalid CSV row"))?;
            let rating = row.get(2).ok_or(anyhow!("invalid CSV row"))?;

            let mut isbn = isbn.to_uppercase();
            isbn.retain(|c| (c >= '0' && c <= '9') || c == 'X');

            if isbn.len() > 0 {
                write!(out, "{},{},{}\n", user, isbn, rating)?;
            }
        }

        Ok(())
    }
}