// This file is part of the uutils coreutils package.
//
// For the full copyright and license information, please view the LICENSE
// file that was distributed with this source code.

// spell-checker:ignore datastructures rstat rposition cflags ctable

use crate::conversion_tables::ConversionTable;
use crate::datastructures::ConversionMode;
use crate::progress::ReadStat;

const NEWLINE: u8 = b'\n';
const SPACE: u8 = b' ';

/// Split a slice into chunks, padding or truncating as necessary.
///
/// The slice `buf` is split on newlines, then each block is resized
/// to `cbs` bytes, padding with spaces if necessary. This function
/// expects the input bytes to be ASCII-encoded.
///
/// If `sync` is true and there has been at least one partial record
/// read from the input (as indicated in `rstat`), then leave an
/// all-spaces block at the end. Otherwise, remove the last block if
/// it is all spaces.
fn block(buf: &[u8], cbs: usize, sync: bool, rstat: &mut ReadStat) -> Vec<Vec<u8>> {
    let mut blocks = buf
        .split(|&e| e == NEWLINE)
        .map(|split| split.to_vec())
        .fold(Vec::new(), |mut blocks, mut split| {
            if split.len() > cbs {
                rstat.records_truncated += 1;
            }
            split.resize(cbs, SPACE);
            blocks.push(split);

            blocks
        });

    // If `sync` is true and there has been at least one partial
    // record read from the input, then leave the all-spaces block at
    // the end. Otherwise, remove it.
    if let Some(last) = blocks.last() {
        if (!sync || rstat.reads_partial == 0) && last.iter().all(|&e| e == SPACE) {
            blocks.pop();
        }
    }

    blocks
}

/// Trims padding from each cbs-length partition of buf
/// as specified by conv=unblock and cbs=N
/// Expects ascii encoded data
fn unblock(buf: &[u8], cbs: usize) -> Vec<u8> {
    buf.chunks(cbs).fold(Vec::new(), |mut acc, block| {
        if let Some(last_char_idx) = block.iter().rposition(|&e| e != SPACE) {
            // Include text up to last space.
            acc.extend(&block[..=last_char_idx]);
        }

        acc.push(NEWLINE);
        acc
    })
}

/// Apply the specified conversion, blocking, and/or unblocking in the right order.
///
/// The `mode` specifies the combination of conversion, blocking, and
/// unblocking to apply and the order in which to apply it. This
/// function is responsible only for applying the operations.
///
/// `buf` is the buffer of input bytes to transform. This function
/// mutates this input and also returns a new buffer of bytes
/// representing the result of the transformation.
///
/// `rstat` maintains a running total of the number of partial and
/// complete blocks read before calling this function. In certain
/// settings of `mode`, this function will update the number of
/// records truncated; that's why `rstat` is borrowed mutably.
pub(crate) fn conv_block_unblock_helper(
    buf: Vec<u8>,
    mode: &ConversionMode,
    rstat: &mut ReadStat,
) -> Vec<u8> {
    fn apply_conversion(buf: Vec<u8>, ct: &ConversionTable) -> impl Iterator<Item = u8> + '_ {
        buf.into_iter().map(|b| ct[b as usize])
    }

    match mode {
        ConversionMode::ConvertOnly(ct) => apply_conversion(buf, ct).collect(),
        ConversionMode::BlockThenConvert(ct, cbs, sync) => {
            let blocks = block(&buf, *cbs, *sync, rstat);
            blocks
                .into_iter()
                .flat_map(|block| apply_conversion(block, ct))
                .collect()
        }
        ConversionMode::ConvertThenBlock(ct, cbs, sync) => {
            let buf: Vec<_> = apply_conversion(buf, ct).collect();
            block(&buf, *cbs, *sync, rstat)
                .into_iter()
                .flatten()
                .collect()
        }
        ConversionMode::BlockOnly(cbs, sync) => block(&buf, *cbs, *sync, rstat)
            .into_iter()
            .flatten()
            .collect(),
        ConversionMode::UnblockThenConvert(ct, cbs) => {
            let buf = unblock(&buf, *cbs);
            apply_conversion(buf, ct).collect()
        }
        ConversionMode::ConvertThenUnblock(ct, cbs) => {
            let buf: Vec<_> = apply_conversion(buf, ct).collect();
            unblock(&buf, *cbs)
        }
        ConversionMode::UnblockOnly(cbs) => unblock(&buf, *cbs),
    }
}

#[cfg(test)]
mod tests {

    use crate::blocks::{block, unblock};
    use crate::progress::ReadStat;

    const NEWLINE: u8 = b'\n';
    const SPACE: u8 = b' ';

    #[test]
    fn block_test_no_nl() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(res, vec![vec![0u8, 1u8, 2u8, 3u8]]);
    }

    #[test]
    fn block_test_no_nl_short_record() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8];
        let res = block(&buf, 8, false, &mut rs);

        assert_eq!(
            res,
            vec![vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE]]
        );
    }

    #[test]
    fn block_test_no_nl_trunc() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8, 4u8];
        let res = block(&buf, 4, false, &mut rs);

        // Commented section(s) should be truncated and appear for reference only.
        assert_eq!(res, vec![vec![0u8, 1u8, 2u8, 3u8 /*, 4u8*/]]);
        assert_eq!(rs.records_truncated, 1);
    }

    #[test]
    fn block_test_nl_gt_cbs_trunc() {
        let mut rs = ReadStat::default();
        let buf = [
            0u8, 1u8, 2u8, 3u8, 4u8, NEWLINE, 0u8, 1u8, 2u8, 3u8, 4u8, NEWLINE, 5u8, 6u8, 7u8, 8u8,
        ];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(
            res,
            vec![
                // Commented section(s) should be truncated and appear for reference only.
                vec![0u8, 1u8, 2u8, 3u8],
                // vec![4u8, SPACE, SPACE, SPACE],
                vec![0u8, 1u8, 2u8, 3u8],
                // vec![4u8, SPACE, SPACE, SPACE],
                vec![5u8, 6u8, 7u8, 8u8],
            ]
        );
        assert_eq!(rs.records_truncated, 2);
    }

    #[test]
    fn block_test_surrounded_nl() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8, NEWLINE, 4u8, 5u8, 6u8, 7u8, 8u8];
        let res = block(&buf, 8, false, &mut rs);

        assert_eq!(
            res,
            vec![
                vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE],
                vec![4u8, 5u8, 6u8, 7u8, 8u8, SPACE, SPACE, SPACE],
            ]
        );
    }

    #[test]
    fn block_test_multiple_nl_same_cbs_block() {
        let mut rs = ReadStat::default();
        let buf = [
            0u8, 1u8, 2u8, 3u8, NEWLINE, 4u8, NEWLINE, 5u8, 6u8, 7u8, 8u8, 9u8,
        ];
        let res = block(&buf, 8, false, &mut rs);

        assert_eq!(
            res,
            vec![
                vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE],
                vec![4u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE],
                vec![5u8, 6u8, 7u8, 8u8, 9u8, SPACE, SPACE, SPACE],
            ]
        );
    }

    #[test]
    fn block_test_multiple_nl_diff_cbs_block() {
        let mut rs = ReadStat::default();
        let buf = [
            0u8, 1u8, 2u8, 3u8, NEWLINE, 4u8, 5u8, 6u8, 7u8, NEWLINE, 8u8, 9u8,
        ];
        let res = block(&buf, 8, false, &mut rs);

        assert_eq!(
            res,
            vec![
                vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE],
                vec![4u8, 5u8, 6u8, 7u8, SPACE, SPACE, SPACE, SPACE],
                vec![8u8, 9u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE],
            ]
        );
    }

    #[test]
    fn block_test_end_nl_diff_cbs_block() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8, NEWLINE];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(res, vec![vec![0u8, 1u8, 2u8, 3u8]]);
    }

    #[test]
    fn block_test_end_nl_same_cbs_block() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, NEWLINE];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(res, vec![vec![0u8, 1u8, 2u8, SPACE]]);
    }

    #[test]
    fn block_test_double_end_nl() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, NEWLINE, NEWLINE];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(
            res,
            vec![vec![0u8, 1u8, 2u8, SPACE], vec![SPACE, SPACE, SPACE, SPACE]]
        );
    }

    #[test]
    fn block_test_start_nl() {
        let mut rs = ReadStat::default();
        let buf = [NEWLINE, 0u8, 1u8, 2u8, 3u8];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(
            res,
            vec![vec![SPACE, SPACE, SPACE, SPACE], vec![0u8, 1u8, 2u8, 3u8]]
        );
    }

    #[test]
    fn block_test_double_surrounded_nl_no_trunc() {
        let mut rs = ReadStat::default();
        let buf = [0u8, 1u8, 2u8, 3u8, NEWLINE, NEWLINE, 4u8, 5u8, 6u8, 7u8];
        let res = block(&buf, 8, false, &mut rs);

        assert_eq!(
            res,
            vec![
                vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE],
                vec![SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE],
                vec![4u8, 5u8, 6u8, 7u8, SPACE, SPACE, SPACE, SPACE],
            ]
        );
    }

    #[test]
    fn block_test_double_surrounded_nl_double_trunc() {
        let mut rs = ReadStat::default();
        let buf = [
            0u8, 1u8, 2u8, 3u8, NEWLINE, NEWLINE, 4u8, 5u8, 6u8, 7u8, 8u8,
        ];
        let res = block(&buf, 4, false, &mut rs);

        assert_eq!(
            res,
            vec![
                // Commented section(s) should be truncated and appear for reference only.
                vec![0u8, 1u8, 2u8, 3u8],
                vec![SPACE, SPACE, SPACE, SPACE],
                vec![4u8, 5u8, 6u8, 7u8 /*, 8u8*/],
            ]
        );
        assert_eq!(rs.records_truncated, 1);
    }

    #[test]
    fn unblock_test_full_cbs() {
        let buf = [0u8, 1u8, 2u8, 3u8, 4u8, 5u8, 6u8, 7u8];
        let res = unblock(&buf, 8);

        assert_eq!(res, vec![0u8, 1u8, 2u8, 3u8, 4u8, 5u8, 6u8, 7u8, NEWLINE]);
    }

    #[test]
    fn unblock_test_all_space() {
        let buf = [SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE];
        let res = unblock(&buf, 8);

        assert_eq!(res, vec![NEWLINE]);
    }

    #[test]
    fn unblock_test_decoy_spaces() {
        let buf = [0u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, 7u8];
        let res = unblock(&buf, 8);

        assert_eq!(
            res,
            vec![0u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, 7u8, NEWLINE],
        );
    }

    #[test]
    fn unblock_test_strip_single_cbs() {
        let buf = [0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE];
        let res = unblock(&buf, 8);

        assert_eq!(res, vec![0u8, 1u8, 2u8, 3u8, NEWLINE]);
    }

    #[test]
    fn unblock_test_strip_multi_cbs() {
        let buf = vec![
            vec![0u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE],
            vec![0u8, 1u8, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE],
            vec![0u8, 1u8, 2u8, SPACE, SPACE, SPACE, SPACE, SPACE],
            vec![0u8, 1u8, 2u8, 3u8, SPACE, SPACE, SPACE, SPACE],
        ]
        .into_iter()
        .flatten()
        .collect::<Vec<_>>();

        let res = unblock(&buf, 8);

        let exp = vec![
            vec![0u8, NEWLINE],
            vec![0u8, 1u8, NEWLINE],
            vec![0u8, 1u8, 2u8, NEWLINE],
            vec![0u8, 1u8, 2u8, 3u8, NEWLINE],
        ]
        .into_iter()
        .flatten()
        .collect::<Vec<_>>();

        assert_eq!(res, exp);
    }
}
