tablestg 0.4.9

use crate::*;
use std::hash::Hash;
use std::hash::Hasher;

pub trait DKey: Hash {
    fn ok(&self, bytes: &[u8], ps: &mut PageSet) -> bool;
    fn xhash<H: Hasher>(&self, bytes: &[u8], h: &mut H);
}

/// VBuckMap root and buckets, returned by [BuckMap::save].
#[derive(
    Copy,
    Clone,
    Debug,
    Default,
    Hash,
    PartialEq,
    Eq,
    PartialOrd,
    Ord,
    serde::Serialize,
    serde::Deserialize,
)]
pub struct VBuckMapInfo {
    pub root: u64,
    pub buckets: u64,
}

/// Hash Map implemented as list of buckets, stores variable size rows.
pub struct VBuckMap<'a> {
    /// Number of buckets.
    buckets: u64,
    /// Root page.
    root: u64,
    /// Pageset.
    ps: &'a mut PageSet,
    /// Has root changed?
    new_root: bool,
}

impl<'a> VBuckMap<'a> {
    /// Start a new map with specified number of buckets.
    pub fn new(buckets: u64, ps: &'a mut PageSet) -> Self {
        let mut pt = PageTree::new(ps.new_page(), 1, ps);
        pt.resize(buckets);
        Self {
            buckets,
            root: pt.root,
            ps,
            new_root: true,
        }
    }

    /// Insert user data, must not be a duplicate key ( but this is not checked )
    pub fn insert<K: DKey>(&mut self, key: &K, user_data: &[u8]) {
        let hash = Self::hash(key);

        // println!("BuckMap insert self.root={} hash={}", self.root, hash);

        self.do_insert(user_data, hash, key)
    }

    /// Get data for specified key, returns PData, offset and length, or None if key not found.
    /// PData must be noted after processing data.
    pub fn get<K: DKey>(&mut self, key: &K) -> Option<(PData, usize, usize)> {
        let hash = Self::hash(key);

        // println!("BuckMap get self.root={} hash={}", self.root, hash);

        let pnum = self.get_page_num(hash, false);
        if pnum == 0 {
            return None;
        }
        let pdata = self.ps.load(pnum);
        if let Some((off, len)) = vbucket::Reader::new(&pdata.data).get(key, hash, self.ps) {
            Some((pdata, off, len))
        } else {
            None
        }
    }

    /// Remove a key
    pub fn remove<K: DKey>(&mut self, key: &K) -> bool {
        let hash = Self::hash(key);
        let pnum = self.get_page_num(hash, false);
        if pnum != 0 {
            let mut pdata = self.ps.load(pnum);
            let md = pdata.make_mut();
            if md.is_empty() {
                let size = self.ps.compute_size(1000); // Start page size
                md.resize(size, 0);
            }

            let mut w = vbucket::Writer::new(md);
            let result = w.remove(key, hash, self.ps);
            if result {
                pdata.changed = true;
            }
            self.ps.note(pdata);
            return result;
        }
        false
    }

    /// Iterator - returns all records (rows). Note that Iter::drop must be called before Iter drops.
    pub fn iter(self) -> Iter {
        let pnum = PageTree::new(self.root, self.buckets, self.ps).get(0, false);
        let pdata = self.ps.load(pnum);
        Iter {
            pix: 0,
            pdata,
            map: self.save(),
            pos: vbucket::Pos::start(),
        }
    }

    /// Has root and buckets changed ( so needs to be saved )?
    pub fn root_changed(&self) -> bool {
        self.new_root
    }

    /// Get the root and number of buckets. These can change on any insert.
    pub fn save(&self) -> VBuckMapInfo {
        VBuckMapInfo {
            root: self.root,
            buckets: self.buckets,
        }
    }

    /// Restore from saved root and buckets.
    pub fn restore(info: VBuckMapInfo, ps: &'a mut PageSet) -> Self {
        Self {
            root: info.root,
            buckets: info.buckets,
            ps,
            new_root: false,
        }
    }

    /// Delete everything. Map is no longer usable.
    pub fn delete(&mut self) {
        let mut pt = PageTree::new(self.root, self.buckets, self.ps);
        pt.drop_pages();
        self.root = 0;
    }

    /// Calculate hash
    fn xhash<K: DKey>(key: &K, user_data: &[u8]) -> u64 {
        let mut h = fxhash::FxHasher::default();
        key.xhash(user_data, &mut h);
        h.finish()
    }

    /// Calculate hash
    fn hash<K: DKey>(key: &K) -> u64 {
        let mut h = fxhash::FxHasher::default();
        key.hash(&mut h);
        h.finish()
    }

    fn get_page_num(&mut self, hash: u64, create: bool) -> u64 {
        let pix = hash % self.buckets;
        PageTree::new(self.root, self.buckets, self.ps).get(pix, create)
    }

    fn do_insert<K: DKey>(&mut self, user_data: &[u8], hash: u64, key: &K) {
        while self.try_insert(user_data, hash) {
            self.expand(key);
        }
    }

    fn try_insert(&mut self, user_data: &[u8], hash: u64) -> bool {
        let pnum = self.get_page_num(hash, true);
        let mut pdata = self.ps.load(pnum);

        pdata.changed = true;

        let mut md = pdata.make_mut();
        if md.is_empty() {
            let size = self.ps.compute_size(1000); // Start page size
            md.resize(size, 0);
        }

        let mut w = vbucket::Writer::new(md);

        let rsize = user_data.len();
        let space = w.space(rsize); // Extra space needed.

        if space > 0 {
            let old = vbucket::Reader::new(md);
            pdata.data = Arc::new(old.compact(md.len()));
            md = pdata.make_mut();
            w = vbucket::Writer::new(md);
            let space = w.space(rsize);

            if space > 0
            // Simple compact didn't work, need a bigger page size.
            {
                let old = vbucket::Reader::new(md);
                let new_size = self.ps.compute_size(md.len() + space);
                if new_size == 0 {
                    self.ps.note(pdata);
                    return true;
                }
                pdata.data = Arc::new(old.compact(new_size));
                md = pdata.make_mut();
                w = vbucket::Writer::new(md);
            }
        }
        w.insert(user_data, hash); // ToDo: check for full page.

        self.ps.note(pdata);
        false
    }

    fn expand<K: DKey>(&mut self, key: &K) {
        let buckets = 1 + self.buckets * 9 / 8;

        println!("expand buckets={} new buckets={}", self.buckets, buckets);

        let mut save = VBuckMap::new(buckets, self.ps).save();

        let mut iter = VBuckMap::restore(self.save(), self.ps).iter();
        while let Some(r) = iter.next(self.ps) {
            let h = Self::xhash(key, r);
            let mut m = VBuckMap::restore(save, self.ps);
            m.do_insert(r, h, key);
            save = m.save();
        }
        iter.drop(self.ps);

        self.delete();
        self.root = save.root;
        self.buckets = save.buckets;
        self.new_root = true;
    }
}

/// Iterator - returns all records (rows). Note that drop must be called before Iter drops.
pub struct Iter {
    pub pix: u64,
    pub pdata: PData,
    pub map: VBuckMapInfo,
    pub pos: vbucket::Pos,
}

impl Iter {
    pub fn next(&mut self, ps: &mut PageSet) -> Option<&[u8]> {
        if let Some((off, len)) = self.off_and_len(ps) {
            Some(&self.pdata.data[off..off + len])
        } else {
            None
        }
    }

    pub fn drop(&mut self, ps: &mut PageSet) {
        let pdata = std::mem::take(&mut self.pdata);
        ps.note(pdata);
    }

    fn off_and_len(&mut self, ps: &mut PageSet) -> Option<(usize, usize)> {
        loop {
            if let Some(x) = self.look() {
                return Some(x);
            } else if self.pix + 1 == self.map.buckets {
                return None;
            } else {
                self.pix += 1;
                let pdata = std::mem::take(&mut self.pdata);
                ps.note(pdata);
                let pnum = PageTree::new(self.map.root, self.map.buckets, ps).get(self.pix, false);
                self.pdata = ps.load(pnum);
                self.pos = vbucket::Pos::start();
            }
        }
    }

    fn look(&mut self) -> Option<(usize, usize)> {
        vbucket::Reader::new(&self.pdata.data).iter_next(&mut self.pos)
    }
}

#[cfg(test)]
#[derive(Hash)]
pub struct TestKey<'a> {
    s: &'a [u8],
}

#[cfg(test)]
impl<'a> DKey for TestKey<'a> {
    fn ok(&self, bytes: &[u8], _ps: &mut PageSet) -> bool {
        self.s == bytes
    }
    fn xhash<H: Hasher>(&self, bytes: &[u8], h: &mut H) {
        h.write(bytes);
    }
}

#[cfg(test)]
fn test(m: &mut VBuckMap, td: &[u8], i: usize) {
    let x = format!("td={} i={}", tos(td), i);

    // println!("adding {}", &x );

    let td = x.as_bytes();

    let key = TestKey { s: td };
    m.insert(&key, td);
    let (d, off, len) = m.get(&key).unwrap();
    assert_eq!(&d.data[off..off + len], td);
    m.ps.note(d);
}

#[cfg(test)]
pub fn test_vbuckmap(ps: &mut PageSet) {
    println!("testing vbuckmap");

    let mut m = VBuckMap::new(30, ps);

    test(&mut m, b"hello there", 0);
    test(&mut m, b"george", 0);

    let n = 10000;
    for i in 0..n {
        test(&mut m, b"mazzer", i);
    }

    let mut iter = m.iter();
    let mut count = 0;
    while let Some(_r) = iter.next(ps) {
        // println!( "iterating... r = {}", tos(r) );
        count += 1;
    }

    assert_eq!(count, n + 2);

    println!("iter map={:?}", &iter.map);

    iter.drop(ps);

    println!("testing vbuckmap - everything is ok");
}