xan 0.52.0

The CSV magician
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use crate::config::Config;
use crate::util;
use crate::CliResult;

static USAGE: &str = "
Create a CSV file with one column representing a numerical range. This is mostly
useful when piping to the `map`, `transform` or `select -e` command to easily
generate CSV files from scratch.

By default, the output column will be named \"n\" but can be renamed using
the -c, --column-name flag.

Note that like in most programming language, the end of the range is exclusive,
but can be included with -i, --inclusive.

Example:

    Creating a range of urls files by piping `range` into `transform`:
        $ xan range 100 | xan select -e '\"somewebsite.com?id=\" ++ n as url'

Usage:
    xan range [options] <end> [<input>]
    xan range --help

range options:
    -s, --start <n>           Start of the range. [default: 0]
    --step <n>                Step of the range. [default: 1]
    -c, --column-name <name>  Name of the column containing the range.
                              [default: n]
    -i, --inclusive           Include the end bound.

Common options:
    -h, --help             Display this message
    -o, --output <file>    Write output to <file> instead of stdout.
";

#[derive(Deserialize)]
struct Args {
    arg_end: usize,
    flag_output: Option<String>,
    flag_start: usize,
    flag_step: usize,
    flag_column_name: String,
    flag_inclusive: bool,
}

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

    let mut wtr = Config::new(&args.flag_output).writer()?;

    let mut record = csv::ByteRecord::new();
    record.push_field(args.flag_column_name.as_bytes());

    wtr.write_byte_record(&record)?;

    let mut i = args.flag_start;

    while if args.flag_inclusive {
        i <= args.arg_end
    } else {
        i < args.arg_end
    } {
        record.clear();
        record.push_field((i).to_string().as_bytes());
        wtr.write_byte_record(&record)?;
        wtr.flush()?;

        i += args.flag_step;
    }

    Ok(wtr.flush()?)
}