static USAGE: &str = r#"
Sorts CSV data in alphabetical (with case-insensitive option), numerical,
reverse, unique or random (with optional seed) order.

The sort is done in lexicographical order.
https://en.wikipedia.org/wiki/Lexicographic_order

Note that this requires reading all of the CSV data into memory. If
you need to sort a large file that may not fit into memory, use the
extsort command instead.

For examples, see https://github.com/jqnatividad/qsv/blob/master/tests/test_sort.rs.

Usage:
    qsv sort [options] [<input>]
    qsv sort --help

sort options:
    -s, --select <arg>      Select a subset of columns to sort.
                            See 'qsv select --help' for the format details.
    -N, --numeric           Compare according to string numerical value
    -R, --reverse           Reverse order
    --random                Random order
    --seed <number>         Random number generator seed to use if --random is set
    -i, --ignore-case       Compare strings disregarding case
    -u, --unique            When set, identical consecutive lines will be dropped
                            to keep only one line per sorted value.
    -j, --jobs <arg>        The number of jobs to run in parallel.
                            When not set, the number of jobs is set to the
                            number of CPUs detected.

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. Namely, it will be sorted with the rest
                            of the rows. Otherwise, the first row will always
                            appear as the header row in the output.
    -d, --delimiter <arg>   The field delimiter for reading CSV data.
                            Must be a single character. (default: ,)
    --no-memcheck           Do not check if there is enough memory to load the
                            entire CSV into memory.
"#;

use std::cmp;

use rand::{rngs::StdRng, seq::SliceRandom, SeedableRng};
use rayon::prelude::*;
use serde::Deserialize;
use simdutf8::basic::from_utf8;

use self::Number::{Float, Int};
use crate::{
    cmd::dedup::iter_cmp_ignore_case,
    config::{Config, Delimiter},
    select::SelectColumns,
    util, CliResult,
};

#[derive(Deserialize)]
struct Args {
    arg_input:        Option<String>,
    flag_select:      SelectColumns,
    flag_numeric:     bool,
    flag_reverse:     bool,
    flag_random:      bool,
    flag_seed:        Option<u64>,
    flag_ignore_case: bool,
    flag_jobs:        Option<usize>,
    flag_output:      Option<String>,
    flag_no_headers:  bool,
    flag_delimiter:   Option<Delimiter>,
    flag_unique:      bool,
    flag_no_memcheck: bool,
}

pub fn run(argv: &[&str]) -> CliResult<()> {
    let args: Args = util::get_args(USAGE, argv)?;
    let numeric = args.flag_numeric;
    let reverse = args.flag_reverse;
    let random = args.flag_random;
    let rconfig = Config::new(&args.arg_input)
        .delimiter(args.flag_delimiter)
        .no_headers(args.flag_no_headers)
        .select(args.flag_select);

    // we're loading the entire file into memory, we need to check avail mem
    if let Some(path) = rconfig.path.clone() {
        util::mem_file_check(&path, false, args.flag_no_memcheck)?;
    }

    let mut rdr = rconfig.reader()?;

    let headers = rdr.byte_headers()?.clone();
    let sel = rconfig.selection(&headers)?;

    // set RAYON_NUM_THREADS
    util::njobs(args.flag_jobs);

    // Seeding RNG
    let seed = args.flag_seed;

    let ignore_case = args.flag_ignore_case;

    let mut all = rdr.byte_records().collect::<Result<Vec<_>, _>>()?;
    match (numeric, reverse, random) {
        (_, _, true) => {
            // we don't need cryptographically strong RNGs for this
            // add DevSkim lint ignores to suppress warning
            if let Some(val) = seed {
                let mut rng = StdRng::seed_from_u64(val); //DevSkim: ignore DS148264
                SliceRandom::shuffle(&mut *all, &mut rng); //DevSkim: ignore DS148264
            } else {
                let mut rng = ::rand::thread_rng();
                SliceRandom::shuffle(&mut *all, &mut rng); //DevSkim: ignore DS148264
            }
        }
        (false, false, false) => all.par_sort_by(|r1, r2| {
            let a = sel.select(r1);
            let b = sel.select(r2);
            if ignore_case {
                iter_cmp_ignore_case(a, b)
            } else {
                iter_cmp(a, b)
            }
        }),
        (true, false, false) => all.par_sort_by(|r1, r2| {
            let a = sel.select(r1);
            let b = sel.select(r2);
            iter_cmp_num(a, b)
        }),
        (false, true, false) => all.par_sort_by(|r1, r2| {
            let a = sel.select(r1);
            let b = sel.select(r2);
            if ignore_case {
                iter_cmp_ignore_case(b, a)
            } else {
                iter_cmp(b, a)
            }
        }),
        (true, true, false) => all.par_sort_by(|r1, r2| {
            let a = sel.select(r1);
            let b = sel.select(r2);
            iter_cmp_num(b, a)
        }),
    }

    let mut wtr = Config::new(&args.flag_output).writer()?;
    let mut prev: Option<csv::ByteRecord> = None;
    rconfig.write_headers(&mut rdr, &mut wtr)?;
    for r in all {
        if args.flag_unique {
            match prev {
                Some(other_r) => match iter_cmp(sel.select(&r), sel.select(&other_r)) {
                    cmp::Ordering::Equal => (),
                    _ => {
                        wtr.write_byte_record(&r)?;
                    }
                },
                None => {
                    wtr.write_byte_record(&r)?;
                }
            }

            prev = Some(r);
        } else {
            wtr.write_byte_record(&r)?;
        }
    }
    Ok(wtr.flush()?)
}

/// Order `a` and `b` lexicographically using `Ord`
#[inline]
pub fn iter_cmp<A, L, R>(mut a: L, mut b: R) -> cmp::Ordering
where
    A: Ord,
    L: Iterator<Item = A>,
    R: Iterator<Item = A>,
{
    loop {
        match (a.next(), b.next()) {
            (None, None) => return cmp::Ordering::Equal,
            (None, _) => return cmp::Ordering::Less,
            (_, None) => return cmp::Ordering::Greater,
            (Some(x), Some(y)) => match x.cmp(&y) {
                cmp::Ordering::Equal => (),
                non_eq => return non_eq,
            },
        }
    }
}

/// Try parsing `a` and `b` as numbers when ordering
#[inline]
pub fn iter_cmp_num<'a, L, R>(mut a: L, mut b: R) -> cmp::Ordering
where
    L: Iterator<Item = &'a [u8]>,
    R: Iterator<Item = &'a [u8]>,
{
    loop {
        match (next_num(&mut a), next_num(&mut b)) {
            (None, None) => return cmp::Ordering::Equal,
            (None, _) => return cmp::Ordering::Less,
            (_, None) => return cmp::Ordering::Greater,
            (Some(x), Some(y)) => match compare_num(x, y) {
                cmp::Ordering::Equal => (),
                non_eq => return non_eq,
            },
        }
    }
}

#[derive(Clone, Copy, PartialEq)]
enum Number {
    Int(i64),
    Float(f64),
}

#[inline]
fn compare_num(n1: Number, n2: Number) -> cmp::Ordering {
    match (n1, n2) {
        (Int(i1), Int(i2)) => i1.cmp(&i2),
        #[allow(clippy::cast_precision_loss)]
        (Int(i1), Float(f2)) => compare_float(i1 as f64, f2),
        #[allow(clippy::cast_precision_loss)]
        (Float(f1), Int(i2)) => compare_float(f1, i2 as f64),
        (Float(f1), Float(f2)) => compare_float(f1, f2),
    }
}

#[inline]
fn compare_float(f1: f64, f2: f64) -> cmp::Ordering {
    f1.partial_cmp(&f2).unwrap_or(cmp::Ordering::Equal)
}

#[inline]
fn next_num<'a, X>(xs: &mut X) -> Option<Number>
where
    X: Iterator<Item = &'a [u8]>,
{
    xs.next()
        .map(|bytes| from_utf8(bytes).unwrap())
        .and_then(|s| {
            if let Ok(i) = s.parse::<i64>() {
                Some(Number::Int(i))
            } else if let Ok(f) = s.parse::<f64>() {
                Some(Number::Float(f))
            } else {
                None
            }
        })
}
