// Copyright 2019 Raphaël Gomès <rgomes@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

use crate::utils::hg_path::HgPath;

use crate::{

    dirstate::{CopyMap, EntryState, StateMap},

    DirstateEntry, DirstatePackError, DirstateParents, DirstateParseError,

};

use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};

use std::convert::{TryFrom, TryInto};

use std::io::Cursor;

use std::time::Duration;

/// Parents are stored in the dirstate as byte hashes.

pub const PARENT_SIZE: usize = 20;

/// Dirstate entries have a static part of 8 + 32 + 32 + 32 + 32 bits.

const MIN_ENTRY_SIZE: usize = 17;

// TODO parse/pack: is mutate-on-loop better for performance?

pub fn parse_dirstate(

    state_map: &mut StateMap,

    copy_map: &mut CopyMap,

    contents: &[u8],

) -> Result<DirstateParents, DirstateParseError> {

    if contents.len() < PARENT_SIZE * 2 {

        return Err(DirstateParseError::TooLittleData);

    }

    let mut curr_pos = PARENT_SIZE * 2;

    let parents = DirstateParents {

        p1: contents[..PARENT_SIZE].try_into().unwrap(),

        p2: contents[PARENT_SIZE..curr_pos].try_into().unwrap(),

    };

    while curr_pos < contents.len() {

        if curr_pos + MIN_ENTRY_SIZE > contents.len() {

            return Err(DirstateParseError::Overflow);

        }

        let entry_bytes = &contents[curr_pos..];

        let mut cursor = Cursor::new(entry_bytes);

        let state = EntryState::try_from(cursor.read_u8()?)?;

        let mode = cursor.read_i32::<BigEndian>()?;

        let size = cursor.read_i32::<BigEndian>()?;

        let mtime = cursor.read_i32::<BigEndian>()?;

        let path_len = cursor.read_i32::<BigEndian>()? as usize;

        if path_len > contents.len() - curr_pos {

            return Err(DirstateParseError::Overflow);

        }

        // Slice instead of allocating a Vec needed for `read_exact`

        let path = &entry_bytes[MIN_ENTRY_SIZE..MIN_ENTRY_SIZE + (path_len)];

        let (path, copy) = match memchr::memchr(0, path) {

            None => (path, None),

            Some(i) => (&path[..i], Some(&path[(i + 1)..])),

        };

        if let Some(copy_path) = copy {

            copy_map.insert(

                HgPath::new(path).to_owned(),

                HgPath::new(copy_path).to_owned(),

            );

        };

        state_map.insert(

            HgPath::new(path).to_owned(),

            DirstateEntry {

                state,

                mode,

                size,

                mtime,

            },

        );

        curr_pos = curr_pos + MIN_ENTRY_SIZE + (path_len);

    }

    Ok(parents)

}

/// `now` is the duration in seconds since the Unix epoch

pub fn pack_dirstate(

    state_map: &mut StateMap,

    copy_map: &CopyMap,

    parents: DirstateParents,

    now: Duration,

) -> Result<Vec<u8>, DirstatePackError> {

    // TODO move away from i32 before 2038.

    let now: i32 = now.as_secs().try_into().expect("time overflow");

    let expected_size: usize = state_map

        .iter()

        .map(|(filename, _)| {

            let mut length = MIN_ENTRY_SIZE + filename.len();

            if let Some(copy) = copy_map.get(filename) {

                length += copy.len() + 1;

            }

            length

        })

        .sum();

    let expected_size = expected_size + PARENT_SIZE * 2;

    let mut packed = Vec::with_capacity(expected_size);

    let mut new_state_map = vec![];

    packed.extend(&parents.p1);

    packed.extend(&parents.p2);

    for (filename, entry) in state_map.iter() {

        let new_filename = filename.to_owned();

        let mut new_mtime: i32 = entry.mtime;

        if entry.state == EntryState::Normal && entry.mtime == now {

            // The file was last modified "simultaneously" with the current

            // write to dirstate (i.e. within the same second for file-

            // systems with a granularity of 1 sec). This commonly happens

            // for at least a couple of files on 'update'.

            // The user could change the file without changing its size

            // within the same second. Invalidate the file's mtime in

            // dirstate, forcing future 'status' calls to compare the

            // contents of the file if the size is the same. This prevents

            // mistakenly treating such files as clean.

            new_mtime = -1;

            new_state_map.push((

                filename.to_owned(),

                DirstateEntry {

                    mtime: new_mtime,

                    ..*entry

                },

            ));

        }

        let mut new_filename = new_filename.into_vec();

        if let Some(copy) = copy_map.get(filename) {

            new_filename.push('\0' as u8);

            new_filename.extend(copy.bytes());

        }

        packed.write_u8(entry.state.into())?;

        packed.write_i32::<BigEndian>(entry.mode)?;

        packed.write_i32::<BigEndian>(entry.size)?;

        packed.write_i32::<BigEndian>(new_mtime)?;

        packed.write_i32::<BigEndian>(new_filename.len() as i32)?;

        packed.extend(new_filename)

    }

    if packed.len() != expected_size {

        return Err(DirstatePackError::BadSize(expected_size, packed.len()));

    }

    state_map.extend(new_state_map);

    Ok(packed)

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test_pack_dirstate_empty() {

        let parents = DirstateParents {

            p1: *b"12345678910111213141",

            p2: *b"00000000000000000000",

        };

        let now = Duration::new(15000000, 0);

        let expected = b"1234567891011121314100000000000000000000".to_vec();

        assert_eq!(

            expected,

            pack_dirstate(&mut state_map, &copymap, parents, now).unwrap()

        );

        assert!(state_map.is_empty())

    }

    #[test]

    fn test_pack_dirstate_one_entry() {

        let expected_state_map: StateMap = [(

            HgPathBuf::from_bytes(b"f1"),

            DirstateEntry {

                state: EntryState::Normal,

                mode: 0o644,

                size: 0,

                mtime: 791231220,

            },

        )]

        .iter()

        .cloned()

        .collect();

        let mut state_map = expected_state_map.clone();

        let parents = DirstateParents {

            p1: *b"12345678910111213141",

            p2: *b"00000000000000000000",

        };

        let now = Duration::new(15000000, 0);

        let expected = [

            49, 50, 51, 52, 53, 54, 55, 56, 57, 49, 48, 49, 49, 49, 50, 49,

            51, 49, 52, 49, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,

            48, 48, 48, 48, 48, 48, 48, 48, 110, 0, 0, 1, 164, 0, 0, 0, 0, 47,

            41, 58, 244, 0, 0, 0, 2, 102, 49,

        ]

        .to_vec();

        assert_eq!(

            expected,

            pack_dirstate(&mut state_map, &copymap, parents, now).unwrap()

        );

        assert_eq!(expected_state_map, state_map);

    }

    #[test]

    fn test_pack_dirstate_one_entry_with_copy() {

        let expected_state_map: StateMap = [(

            HgPathBuf::from_bytes(b"f1"),

            DirstateEntry {

                state: EntryState::Normal,

                mode: 0o644,

                size: 0,

                mtime: 791231220,

            },

        )]

        .iter()

        .cloned()

        .collect();

        let mut state_map = expected_state_map.clone();

        copymap.insert(

            HgPathBuf::from_bytes(b"f1"),

            HgPathBuf::from_bytes(b"copyname"),

        );

        let parents = DirstateParents {

            p1: *b"12345678910111213141",

            p2: *b"00000000000000000000",

        };

        let now = Duration::new(15000000, 0);

        let expected = [

            49, 50, 51, 52, 53, 54, 55, 56, 57, 49, 48, 49, 49, 49, 50, 49,

            51, 49, 52, 49, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,

            48, 48, 48, 48, 48, 48, 48, 48, 110, 0, 0, 1, 164, 0, 0, 0, 0, 47,

            41, 58, 244, 0, 0, 0, 11, 102, 49, 0, 99, 111, 112, 121, 110, 97,

            109, 101,

        ]

        .to_vec();

        assert_eq!(

            expected,

            pack_dirstate(&mut state_map, &copymap, parents, now).unwrap()

        );

        assert_eq!(expected_state_map, state_map);

    }

    #[test]

    fn test_parse_pack_one_entry_with_copy() {

        let mut state_map: StateMap = [(

            HgPathBuf::from_bytes(b"f1"),

            DirstateEntry {

                state: EntryState::Normal,

                mode: 0o644,

                size: 0,

                mtime: 791231220,

            },

        )]

        .iter()

        .cloned()

        .collect();

        copymap.insert(

            HgPathBuf::from_bytes(b"f1"),

            HgPathBuf::from_bytes(b"copyname"),

        );

        let parents = DirstateParents {

            p1: *b"12345678910111213141",

            p2: *b"00000000000000000000",

        };

        let now = Duration::new(15000000, 0);

        let result =

            pack_dirstate(&mut state_map, &copymap, parents.clone(), now)

                .unwrap();

        let new_parents = parse_dirstate(

            &mut new_state_map,

            &mut new_copy_map,

            result.as_slice(),

        )

        .unwrap();

        assert_eq!(

            (parents, state_map, copymap),

            (new_parents, new_state_map, new_copy_map)

        )

    }

    #[test]

    fn test_parse_pack_multiple_entries_with_copy() {

        let mut state_map: StateMap = [

            (

                HgPathBuf::from_bytes(b"f1"),

                DirstateEntry {

                    state: EntryState::Normal,

                    mode: 0o644,

                    size: 0,

                    mtime: 791231220,

                },

            ),

            (

                HgPathBuf::from_bytes(b"f2"),

                DirstateEntry {

                    state: EntryState::Merged,

                    mode: 0o777,

                    size: 1000,

                    mtime: 791231220,

                },

            ),

            (

                HgPathBuf::from_bytes(b"f3"),

                DirstateEntry {

                    state: EntryState::Removed,

                    mode: 0o644,

                    size: 234553,

                    mtime: 791231220,

                },

            ),

            (

                HgPathBuf::from_bytes(b"f4\xF6"),

                DirstateEntry {

                    state: EntryState::Added,