xsv 0.10.2

A high performance CSV command line toolkit.
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use CliResult;
use config::{Config, Delimiter};
use select::SelectColumns;
use util;

static USAGE: &'static str = "
Select columns from CSV data efficiently.

This command lets you manipulate the columns in CSV data. You can re-order
them, duplicate them or drop them. Columns can be referenced by index or by
name if there is a header row (duplicate column names can be disambiguated with
more indexing). Finally, column ranges can be specified.

  Select the first and fourth columns:
  $ xsv select 1,4

  Select the first 4 columns (by index and by name):
  $ xsv select 1-4
  $ xsv select Header1-Header4

  Ignore the first 2 columns (by range and by omission):
  $ xsv select 3-
  $ xsv select '!1-2'

  Select the third column named 'Foo':
  $ xsv select 'Foo[2]'

  Re-order and duplicate columns arbitrarily:
  $ xsv select 3-1,Header3-Header1,Header1,Foo[2],Header1

Usage:
    xsv select [options] [--] <selection> [<input>]
    xsv select --help

Common options:
    -h, --help             Display this message
    -o, --output <file>    Write output to <file> instead of stdout.
    -n, --no-headers       When set, the first row will not be interpreted
                           as headers. (i.e., They are not searched, analyzed,
                           sliced, etc.)
    -d, --delimiter <arg>  The field delimiter for reading CSV data.
                           Must be a single character. (default: ,)
";

#[derive(RustcDecodable)]
struct Args {
    arg_input: Option<String>,
    arg_selection: SelectColumns,
    flag_output: Option<String>,
    flag_no_headers: bool,
    flag_delimiter: Option<Delimiter>,
}

pub fn run(argv: &[&str]) -> CliResult<()> {
    let args: Args = try!(util::get_args(USAGE, argv));

    let rconfig = Config::new(&args.arg_input)
                         .delimiter(args.flag_delimiter)
                         .no_headers(args.flag_no_headers)
                         .select(args.arg_selection);

    let mut rdr = try!(rconfig.reader());
    let mut wtr = try!(Config::new(&args.flag_output).writer());

    let headers = try!(rdr.byte_headers());
    let sel = try!(rconfig.selection(&*headers));

    if !rconfig.no_headers {
        try!(wtr.write(sel.iter().map(|&i| &*headers[i])));
    }
    for r in rdr.byte_records() {
        // TODO: I don't think we can do any better here. Since selection
        // operates on indices, some kind of allocation is probably required.
        // try!(wtr.write(sel.select(try!(r)[])))
        let r = try!(r);
        try!(wtr.write(sel.iter().map(|&i| &*r[i])));
    }
    try!(wtr.flush());
    Ok(())
}