diff.rs

static USAGE: &str = r#"
Find the difference between two CSVs with ludicrous speed.

Note that diff does not support stdin. A file path is required for both arguments.

Examples:

Find the difference between two CSVs:
    qsv diff left.csv right.csv

Find the difference between two CSVs. The right CSV has no headers:
    qsv diff left.csv --no-headers-right right-noheaders.csv

Find the difference between two CSVs. The left CSV uses a tab as the delimiter:
    qsv diff --delimiter-left '\t' left.csv right-tab.tsv
    # or ';' as the delimiter
    qsv diff --delimiter-left ';' left.csv right-semicolon.csv

Find the difference between two CSVs. The output CSV uses a tab as the delimiter
and is written to a file:
    qsv diff -o diff-tab.tsv --delimiter-output '\t' left.csv right.csv
    # or ';' as the delimiter
    qsv diff -o diff-semicolon.csv --delimiter-output ';' left.csv right.csv

Find the difference between two CSVs, but only for the first two columns:
    qsv diff --key 0,1 left.csv right.csv

Find the difference between two CSVs, but only for the first two columns and
sort the result by the first and second column:
    qsv diff -k 0,1 --sort-columns 0,1 left.csv right.csv

Find the difference between two CSVs, but do not output headers in the result:
    qsv diff --no-headers-output left.csv right.csv

Find the difference between two CSVs. Both CSVs have no headers, but the result should have
headers, so generic headers will be used in the form of: _col_1, _col_2, etc.:
    qsv diff --no-headers-left --no-headers-right left.csv right.csv

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

Usage:
    qsv diff [options] [<input-left>] [<input-right>]
    qsv diff --help

diff options:
    --no-headers-left           When set, the first row will be considered as part of
                                the left CSV to diff. (When not set, the
                                first row is the header row and will be skipped during
                                the diff. It will always appear in the output.)
    --no-headers-right          When set, the first row will be considered as part of
                                the right CSV to diff. (When not set, the
                                first row is the header row and will be skipped during
                                the diff. It will always appear in the output.)
    --no-headers-output         When set, the diff result won't have a header row in
                                it's output. If not set and both CSVs have no headers,
                                headers in the result will be: _col_1,_col_2, etc.
    --delimiter-left <arg>      The field delimiter for reading CSV data on the left.
                                Must be a single character. (default: ,)
    --delimiter-right <arg>     The field delimiter for reading CSV data on the right.
                                Must be a single character. (default: ,)
    --delimiter-output <arg>    The field delimiter for writing the CSV diff result.
                                Must be a single character. (default: ,)
    -k, --key <arg...>          The column indices that uniquely identify a record
                                as a comma separated list of indices, e.g. 0,1,2.
                                (default: 0)
    --sort-columns <arg...>     The column indices by which the diff result should be
                                sorted as a comma separated list of indices, e.g. 0,1,2.
                                Records in the diff result that are marked as "modified"
                                ("delete" and "add" records that have the same key,
                                but have different content) will always be kept together
                                in the sorted diff result and so won't be sorted
                                independently from each other.
    -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.
"#;

use std::io::{self, Write};

use csv_diff::{
    csv_diff::CsvByteDiffBuilder, csv_headers::Headers, diff_result::DiffByteRecords,
    diff_row::DiffByteRecord,
};
use serde::Deserialize;

use super::rename::rename_headers_all_generic;
use crate::{
    clitypes::CliError,
    config::{Config, Delimiter},
    util, CliResult,
};

#[derive(Deserialize)]
struct Args {
    arg_input_left:         Option<String>,
    arg_input_right:        Option<String>,
    flag_output:            Option<String>,
    flag_jobs:              Option<usize>,
    flag_no_headers_left:   bool,
    flag_no_headers_right:  bool,
    flag_no_headers_output: bool,
    flag_delimiter_left:    Option<Delimiter>,
    flag_delimiter_right:   Option<Delimiter>,
    flag_delimiter_output:  Option<Delimiter>,
    flag_key:               Option<String>,
    flag_sort_columns:      Option<String>,
}

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

    let rconfig_left = Config::new(&args.arg_input_left)
        .delimiter(args.flag_delimiter_left)
        .no_headers(args.flag_no_headers_left);

    let rconfig_right = Config::new(&args.arg_input_right)
        .delimiter(args.flag_delimiter_right)
        .no_headers(args.flag_no_headers_right);

    if rconfig_left.is_stdin() || rconfig_right.is_stdin() {
        return fail_incorrectusage_clierror!(
            "diff does not support stdin. A file path is required for both arguments."
        );
    }

    let primary_key_cols = match args.flag_key {
        None => vec![0],
        Some(s) => s
            .split(',')
            .map(str::parse::<usize>)
            .collect::<Result<Vec<_>, _>>()
            .map_err(|err| CliError::Other(err.to_string()))?,
    };

    let sort_cols = args
        .flag_sort_columns
        .map(|s| {
            s.split(',')
                .map(str::parse::<usize>)
                .collect::<Result<Vec<_>, _>>()
                .map_err(|err| CliError::Other(err.to_string()))
        })
        .transpose()?;

    let wtr = Config::new(&args.flag_output)
        .delimiter(args.flag_delimiter_output)
        .writer()?;
    let csv_rdr_left = rconfig_left.reader()?;
    let csv_rdr_right = rconfig_right.reader()?;

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

    let Ok(csv_diff) = CsvByteDiffBuilder::new()
        .primary_key_columns(primary_key_cols)
        .build()
    else {
        return fail_clierror!("Cannot instantiate diff");
    };

    let mut diff_byte_records = csv_diff
        .diff(csv_rdr_left.into(), csv_rdr_right.into())
        .try_to_diff_byte_records()?;

    match sort_cols {
        Some(sort_cols) => {
            diff_byte_records
                .sort_by_columns(sort_cols)
                .map_err(|e| CliError::Other(e.to_string()))?;
        },
        None => {
            diff_byte_records.sort_by_line();
        },
    }

    let mut csv_diff_writer = CsvDiffWriter::new(wtr, args.flag_no_headers_output);
    Ok(csv_diff_writer.write_diff_byte_records(diff_byte_records)?)
}

struct CsvDiffWriter<W: Write> {
    csv_writer: csv::Writer<W>,
    no_headers: bool,
}

impl<W: Write> CsvDiffWriter<W> {
    const fn new(csv_writer: csv::Writer<W>, no_headers: bool) -> Self {
        Self {
            csv_writer,
            no_headers,
        }
    }

    fn write_headers(&mut self, headers: &Headers, num_columns: Option<usize>) -> csv::Result<()> {
        match (headers.headers_left(), headers.headers_right()) {
            (Some(lbh), Some(_rbh)) => {
                // currently, `diff` can only handle two CSVs that have the same
                // headers ordering, so in this case we can either choose the left
                // or right headers, because both are the same
                if !self.no_headers {
                    lbh.write_diffresult_header(&mut self.csv_writer)?;
                }
            },
            (Some(bh), None) | (None, Some(bh)) => {
                if !self.no_headers {
                    bh.write_diffresult_header(&mut self.csv_writer)?;
                }
            },
            (None, None) => {
                if let (Some(num_cols), false) = (num_columns.filter(|&c| c > 0), self.no_headers) {
                    let headers_generic = rename_headers_all_generic(num_cols);
                    let mut new_rdr = csv::Reader::from_reader(headers_generic.as_bytes());
                    let new_headers = new_rdr.byte_headers()?;
                    new_headers.write_diffresult_header(&mut self.csv_writer)?;
                }
            },
        }

        Ok(())
    }

    fn write_diff_byte_records(&mut self, diff_byte_records: DiffByteRecords) -> io::Result<()> {
        self.write_headers(diff_byte_records.headers(), diff_byte_records.num_columns())?;
        for dbr in diff_byte_records {
            self.write_diff_byte_record(&dbr)?;
        }
        self.csv_writer.flush()?;
        Ok(())
    }

    fn write_diff_byte_record(&mut self, diff_byte_record: &DiffByteRecord) -> csv::Result<()> {
        let add_sign: &[u8] = &b"+"[..];
        let remove_sign: &[u8] = &b"-"[..];

        match diff_byte_record {
            DiffByteRecord::Add(add) => {
                let mut vec = vec![add_sign];
                vec.extend(add.byte_record());
                self.csv_writer.write_record(vec)
            },
            DiffByteRecord::Modify {
                delete,
                add,
                // TODO: this should be used in the future to highlight the column where differences
                // occur
                field_indices: _field_indices,
            } => {
                let mut vec_del = vec![remove_sign];
                vec_del.extend(delete.byte_record());
                self.csv_writer.write_record(vec_del)?;

                let mut vec_add = vec![add_sign];
                vec_add.extend(add.byte_record());
                self.csv_writer.write_record(vec_add)
            },
            DiffByteRecord::Delete(del) => {
                let mut vec = vec![remove_sign];
                vec.extend(del.byte_record());
                self.csv_writer.write_record(vec)
            },
        }
    }
}

trait WriteDiffResultHeader {
    fn write_diffresult_header<W: Write>(&self, csv_writer: &mut csv::Writer<W>)
        -> csv::Result<()>;
}

impl WriteDiffResultHeader for csv::ByteRecord {
    fn write_diffresult_header<W: Write>(
        &self,
        csv_writer: &mut csv::Writer<W>,
    ) -> csv::Result<()> {
        if !self.is_empty() {
            let mut new_header = vec![&b"diffresult"[..]];
            new_header.extend(self);
            csv_writer.write_record(new_header)?;
        }
        Ok(())
    }
}