// Copyright 2017 TiKV Project Authors. Licensed under Apache-2.0.

use engine_traits::{DecodeProperties, IndexHandles};
use std::collections::HashMap;
use std::io::Read;
use std::ops::{Deref, DerefMut};
use std::u64;

use rocksdb::{
    DBEntryType, TablePropertiesCollector, TablePropertiesCollectorFactory, TitanBlobIndex,
    UserCollectedProperties,
};
use tikv_util::codec::number::{self, NumberEncoder};
use tikv_util::codec::{Error, Result};

const PROP_TOTAL_SIZE: &str = "tikv.total_size";
const PROP_SIZE_INDEX: &str = "tikv.size_index";
const PROP_RANGE_INDEX: &str = "tikv.range_index";
pub const DEFAULT_PROP_SIZE_INDEX_DISTANCE: u64 = 4 * 1024 * 1024;
pub const DEFAULT_PROP_KEYS_INDEX_DISTANCE: u64 = 40 * 1024;

fn get_entry_size(value: &[u8], entry_type: DBEntryType) -> std::result::Result<u64, ()> {
    match entry_type {
        DBEntryType::Put => Ok(value.len() as u64),
        DBEntryType::BlobIndex => match TitanBlobIndex::decode(value) {
            Ok(index) => Ok(index.blob_size + value.len() as u64),
            Err(_) => Err(()),
        },
        _ => Err(()),
    }
}

// Deprecated. Only for compatible issue from v2.0 or older version.
#[derive(Debug, Default)]
pub struct SizeProperties {
    pub total_size: u64,
    pub index_handles: IndexHandles,
}

impl SizeProperties {
    pub fn encode(&self) -> UserProperties {
        let mut props = UserProperties::new();
        props.encode_u64(PROP_TOTAL_SIZE, self.total_size);
        props.encode_handles(PROP_SIZE_INDEX, &self.index_handles);
        props
    }

    pub fn decode<T: DecodeProperties>(props: &T) -> Result<SizeProperties> {
        let mut res = SizeProperties::default();
        res.total_size = props.decode_u64(PROP_TOTAL_SIZE)?;
        res.index_handles = props.decode_handles(PROP_SIZE_INDEX)?;
        Ok(res)
    }
}

pub struct UserProperties(pub HashMap<Vec<u8>, Vec<u8>>);

impl Deref for UserProperties {
    type Target = HashMap<Vec<u8>, Vec<u8>>;
    fn deref(&self) -> &HashMap<Vec<u8>, Vec<u8>> {
        &self.0
    }
}

impl DerefMut for UserProperties {
    fn deref_mut(&mut self) -> &mut HashMap<Vec<u8>, Vec<u8>> {
        &mut self.0
    }
}

impl UserProperties {
    pub fn new() -> UserProperties {
        UserProperties(HashMap::new())
    }

    fn encode(&mut self, name: &str, value: Vec<u8>) {
        self.insert(name.as_bytes().to_owned(), value);
    }

    pub fn encode_u64(&mut self, name: &str, value: u64) {
        let mut buf = Vec::with_capacity(8);
        buf.encode_u64(value).unwrap();
        self.encode(name, buf);
    }

    pub fn encode_handles(&mut self, name: &str, handles: &IndexHandles) {
        self.encode(name, handles.encode())
    }
}

impl DecodeProperties for UserProperties {
    fn decode(&self, k: &str) -> Result<&[u8]> {
        match self.0.get(k.as_bytes()) {
            Some(v) => Ok(v.as_slice()),
            None => Err(Error::KeyNotFound),
        }
    }
}

// FIXME: This is a temporary hack to implement a foreign trait on a foreign
// type until the engine abstraction situation is straightened out.
pub struct UserCollectedPropertiesDecoder<'a>(pub &'a UserCollectedProperties);

impl<'a> DecodeProperties for UserCollectedPropertiesDecoder<'a> {
    fn decode(&self, k: &str) -> Result<&[u8]> {
        match self.0.get(k.as_bytes()) {
            Some(v) => Ok(v),
            None => Err(Error::KeyNotFound),
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Copy)]
pub enum RangeOffsetKind {
    Size,
    Keys,
}

#[derive(Debug, Default, Clone)]
pub struct RangeOffsets {
    pub size: u64,
    pub keys: u64,
}

impl RangeOffsets {
    fn get(&self, kind: RangeOffsetKind) -> u64 {
        match kind {
            RangeOffsetKind::Keys => self.keys,
            RangeOffsetKind::Size => self.size,
        }
    }
}

#[derive(Debug, Default)]
pub struct RangeProperties {
    pub offsets: Vec<(Vec<u8>, RangeOffsets)>,
}

impl RangeProperties {
    pub fn get(&self, key: &[u8]) -> &RangeOffsets {
        let idx = self
            .offsets
            .binary_search_by_key(&key, |&(ref k, _)| k)
            .unwrap();
        &self.offsets[idx].1
    }

    pub fn encode(&self) -> UserProperties {
        let mut buf = Vec::with_capacity(1024);
        for (k, offsets) in &self.offsets {
            buf.encode_u64(k.len() as u64).unwrap();
            buf.extend(k);
            buf.encode_u64(offsets.size).unwrap();
            buf.encode_u64(offsets.keys).unwrap();
        }
        let mut props = UserProperties::new();
        props.encode(PROP_RANGE_INDEX, buf);
        props
    }

    pub fn decode<T: DecodeProperties>(props: &T) -> Result<RangeProperties> {
        match RangeProperties::decode_from_range_properties(props) {
            Ok(res) => return Ok(res),
            Err(e) => info!("decode to RangeProperties failed with err: {:?}, try to decode to SizeProperties, maybe upgrade from v2.0 or older version?", e),
        }
        SizeProperties::decode(props).map(|res| res.into())
    }

    fn decode_from_range_properties<T: DecodeProperties>(props: &T) -> Result<RangeProperties> {
        let mut res = RangeProperties::default();
        let mut buf = props.decode(PROP_RANGE_INDEX)?;
        while !buf.is_empty() {
            let klen = number::decode_u64(&mut buf)?;
            let mut k = vec![0; klen as usize];
            buf.read_exact(&mut k)?;
            let mut offsets = RangeOffsets::default();
            offsets.size = number::decode_u64(&mut buf)?;
            offsets.keys = number::decode_u64(&mut buf)?;
            res.offsets.push((k, offsets));
        }
        Ok(res)
    }

    pub fn get_approximate_size_in_range(&self, start: &[u8], end: &[u8]) -> u64 {
        self.get_approximate_distance_in_range(RangeOffsetKind::Size, start, end)
    }

    pub fn get_approximate_keys_in_range(&self, start: &[u8], end: &[u8]) -> u64 {
        self.get_approximate_distance_in_range(RangeOffsetKind::Keys, start, end)
    }

    fn get_approximate_distance_in_range(
        &self,
        kind: RangeOffsetKind,
        start: &[u8],
        end: &[u8],
    ) -> u64 {
        assert!(start <= end);
        if start == end {
            return 0;
        }
        let start_offset = match self.offsets.binary_search_by_key(&start, |&(ref k, _)| k) {
            Ok(idx) => self.offsets[idx].1.get(kind),
            Err(next_idx) => {
                if next_idx == 0 {
                    0
                } else {
                    self.offsets[next_idx - 1].1.get(kind)
                }
            }
        };

        let end_offset = match self.offsets.binary_search_by_key(&end, |&(ref k, _)| k) {
            Ok(idx) => self.offsets[idx].1.get(kind),
            Err(next_idx) => {
                if next_idx == 0 {
                    0
                } else {
                    self.offsets[next_idx - 1].1.get(kind)
                }
            }
        };

        if end_offset < start_offset {
            panic!(
                "start {:?} end {:?} start_offset {} end_offset {}",
                start, end, start_offset, end_offset
            );
        }
        end_offset - start_offset
    }

    // equivalent to range(Excluded(start_key), Excluded(end_key))
    pub fn take_excluded_range(
        mut self,
        start_key: &[u8],
        end_key: &[u8],
    ) -> Vec<(Vec<u8>, RangeOffsets)> {
        let start_offset = match self
            .offsets
            .binary_search_by_key(&start_key, |&(ref k, _)| k)
        {
            Ok(idx) => {
                if idx == self.offsets.len() - 1 {
                    return vec![];
                } else {
                    idx + 1
                }
            }
            Err(next_idx) => next_idx,
        };

        let end_offset = match self.offsets.binary_search_by_key(&end_key, |&(ref k, _)| k) {
            Ok(idx) => {
                if idx == 0 {
                    return vec![];
                } else {
                    idx - 1
                }
            }
            Err(next_idx) => {
                if next_idx == 0 {
                    return vec![];
                } else {
                    next_idx - 1
                }
            }
        };

        if start_offset > end_offset {
            return vec![];
        }

        self.offsets.drain(start_offset..=end_offset).collect()
    }

    pub fn smallest_key(&self) -> Option<Vec<u8>> {
        self.offsets.first().map(|(k, _)| k.to_owned())
    }

    pub fn largest_key(&self) -> Option<Vec<u8>> {
        self.offsets.last().map(|(k, _)| k.to_owned())
    }
}

impl From<SizeProperties> for RangeProperties {
    fn from(p: SizeProperties) -> RangeProperties {
        let mut res = RangeProperties::default();
        for (key, size_handle) in p.index_handles.into_map() {
            let mut range = RangeOffsets::default();
            range.size = size_handle.offset;
            res.offsets.push((key, range));
        }
        res
    }
}

pub struct RangePropertiesCollector {
    props: RangeProperties,
    last_offsets: RangeOffsets,
    last_key: Vec<u8>,
    cur_offsets: RangeOffsets,
    prop_size_index_distance: u64,
    prop_keys_index_distance: u64,
}

impl Default for RangePropertiesCollector {
    fn default() -> Self {
        RangePropertiesCollector {
            props: RangeProperties::default(),
            last_offsets: RangeOffsets::default(),
            last_key: vec![],
            cur_offsets: RangeOffsets::default(),
            prop_size_index_distance: DEFAULT_PROP_SIZE_INDEX_DISTANCE,
            prop_keys_index_distance: DEFAULT_PROP_KEYS_INDEX_DISTANCE,
        }
    }
}

impl RangePropertiesCollector {
    pub fn new(prop_size_index_distance: u64, prop_keys_index_distance: u64) -> Self {
        RangePropertiesCollector {
            prop_size_index_distance,
            prop_keys_index_distance,
            ..Default::default()
        }
    }

    fn size_in_last_range(&self) -> u64 {
        self.cur_offsets.size - self.last_offsets.size
    }

    fn keys_in_last_range(&self) -> u64 {
        self.cur_offsets.keys - self.last_offsets.keys
    }

    fn insert_new_point(&mut self, key: Vec<u8>) {
        self.last_offsets = self.cur_offsets.clone();
        self.props.offsets.push((key, self.cur_offsets.clone()));
    }
}

impl TablePropertiesCollector for RangePropertiesCollector {
    fn add(&mut self, key: &[u8], value: &[u8], entry_type: DBEntryType, _: u64, _: u64) {
        // size
        let size = match get_entry_size(value, entry_type) {
            Ok(entry_size) => key.len() as u64 + entry_size,
            Err(_) => return,
        };
        self.cur_offsets.size += size;
        // keys
        self.cur_offsets.keys += 1;
        // Add the start key for convenience.
        if self.last_key.is_empty()
            || self.size_in_last_range() >= self.prop_size_index_distance
            || self.keys_in_last_range() >= self.prop_keys_index_distance
        {
            self.insert_new_point(key.to_owned());
        }
        self.last_key.clear();
        self.last_key.extend_from_slice(key);
    }

    fn finish(&mut self) -> HashMap<Vec<u8>, Vec<u8>> {
        if self.size_in_last_range() > 0 || self.keys_in_last_range() > 0 {
            let key = self.last_key.clone();
            self.insert_new_point(key);
        }
        self.props.encode().0
    }
}

pub struct RangePropertiesCollectorFactory {
    pub prop_size_index_distance: u64,
    pub prop_keys_index_distance: u64,
}

impl Default for RangePropertiesCollectorFactory {
    fn default() -> Self {
        RangePropertiesCollectorFactory {
            prop_size_index_distance: DEFAULT_PROP_SIZE_INDEX_DISTANCE,
            prop_keys_index_distance: DEFAULT_PROP_KEYS_INDEX_DISTANCE,
        }
    }
}

impl TablePropertiesCollectorFactory for RangePropertiesCollectorFactory {
    fn create_table_properties_collector(&mut self, _: u32) -> Box<dyn TablePropertiesCollector> {
        Box::new(RangePropertiesCollector::new(
            self.prop_size_index_distance,
            self.prop_keys_index_distance,
        ))
    }
}

#[cfg(test)]
mod tests {
    use engine::rocks::{DBEntryType, TablePropertiesCollector};
    use rand::Rng;

    use super::*;

    #[test]
    fn test_range_properties() {
        let cases = [
            ("a", 0, 1),
            // handle "a": size(size = 1, offset = 1),keys(1,1)
            ("b", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8, 1),
            ("c", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4, 1),
            ("d", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2, 1),
            ("e", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8, 1),
            // handle "e": size(size = DISTANCE + 4, offset = DISTANCE + 5),keys(4,5)
            ("f", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4, 1),
            ("g", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2, 1),
            ("h", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8, 1),
            ("i", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4, 1),
            // handle "i": size(size = DISTANCE / 8 * 9 + 4, offset = DISTANCE / 8 * 17 + 9),keys(4,5)
            ("j", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2, 1),
            ("k", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2, 1),
            // handle "k": size(size = DISTANCE + 2, offset = DISTANCE / 8 * 25 + 11),keys(2,11)
            ("l", 0, DEFAULT_PROP_KEYS_INDEX_DISTANCE / 2),
            ("m", 0, DEFAULT_PROP_KEYS_INDEX_DISTANCE / 2),
            //handle "m": keys = DEFAULT_PROP_KEYS_INDEX_DISTANCE,offset = 11+DEFAULT_PROP_KEYS_INDEX_DISTANCE
            ("n", 1, DEFAULT_PROP_KEYS_INDEX_DISTANCE),
            //handle "n": keys = DEFAULT_PROP_KEYS_INDEX_DISTANCE, offset = 11+2*DEFAULT_PROP_KEYS_INDEX_DISTANCE
            ("o", 1, 1),
            // handle　"o": keys = 1, offset = 12 + 2*DEFAULT_PROP_KEYS_INDEX_DISTANCE
        ];

        let mut collector = RangePropertiesCollector::default();
        for &(k, vlen, count) in &cases {
            let v = vec![0; vlen as usize];
            for _ in 0..count {
                collector.add(k.as_bytes(), &v, DBEntryType::Put, 0, 0);
            }
        }
        for &(k, vlen, _) in &cases {
            let v = vec![0; vlen as usize];
            collector.add(k.as_bytes(), &v, DBEntryType::Other, 0, 0);
        }
        let result = UserProperties(collector.finish());

        let props = RangeProperties::decode(&result).unwrap();
        assert_eq!(props.smallest_key().unwrap(), cases[0].0.as_bytes());
        assert_eq!(
            props.largest_key().unwrap(),
            cases[cases.len() - 1].0.as_bytes()
        );
        assert_eq!(
            props.get_approximate_size_in_range(b"", b"k"),
            DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8 * 25 + 11
        );
        assert_eq!(props.get_approximate_keys_in_range(b"", b"k"), 11 as u64);

        assert_eq!(props.offsets.len(), 7);
        let a = props.get(b"a".as_ref());
        assert_eq!(a.size, 1);
        let e = props.get(b"e".as_ref());
        assert_eq!(e.size, DEFAULT_PROP_SIZE_INDEX_DISTANCE + 5);
        let i = props.get(b"i".as_ref());
        assert_eq!(i.size, DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8 * 17 + 9);
        let k = props.get(b"k".as_ref());
        assert_eq!(k.size, DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8 * 25 + 11);
        let m = props.get(b"m".as_ref());
        assert_eq!(m.keys, 11 + DEFAULT_PROP_KEYS_INDEX_DISTANCE);
        let n = props.get(b"n".as_ref());
        assert_eq!(n.keys, 11 + 2 * DEFAULT_PROP_KEYS_INDEX_DISTANCE);
        let o = props.get(b"o".as_ref());
        assert_eq!(o.keys, 12 + 2 * DEFAULT_PROP_KEYS_INDEX_DISTANCE);
        let empty = RangeOffsets::default();
        let cases = [
            (" ", "k", k, &empty, 3),
            (" ", " ", &empty, &empty, 0),
            ("k", "k", k, k, 0),
            ("a", "k", k, a, 2),
            ("a", "i", i, a, 1),
            ("e", "h", e, e, 0),
            ("b", "h", e, a, 1),
            ("g", "g", i, i, 0),
        ];
        for &(start, end, end_idx, start_idx, count) in &cases {
            let props = RangeProperties::decode(&result).unwrap();
            let size = end_idx.size - start_idx.size;
            assert_eq!(
                props.get_approximate_size_in_range(start.as_bytes(), end.as_bytes()),
                size
            );
            let keys = end_idx.keys - start_idx.keys;
            assert_eq!(
                props.get_approximate_keys_in_range(start.as_bytes(), end.as_bytes()),
                keys
            );
            assert_eq!(
                props
                    .take_excluded_range(start.as_bytes(), end.as_bytes())
                    .len(),
                count
            );
        }
    }

    #[test]
    fn test_range_properties_with_blob_index() {
        let cases = [
            ("a", 0),
            // handle "a": size(size = 1, offset = 1),keys(1,1)
            ("b", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8),
            ("c", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4),
            ("d", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2),
            ("e", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8),
            // handle "e": size(size = DISTANCE + 4, offset = DISTANCE + 5),keys(4,5)
            ("f", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4),
            ("g", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2),
            ("h", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8),
            ("i", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 4),
            // handle "i": size(size = DISTANCE / 8 * 9 + 4, offset = DISTANCE / 8 * 17 + 9),keys(4,5)
            ("j", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2),
            ("k", DEFAULT_PROP_SIZE_INDEX_DISTANCE / 2),
            // handle "k": size(size = DISTANCE + 2, offset = DISTANCE / 8 * 25 + 11),keys(2,11)
        ];

        let handles = ["a", "e", "i", "k"];

        let mut rng = rand::thread_rng();
        let mut collector = RangePropertiesCollector::default();
        let mut extra_value_size: u64 = 0;
        for &(k, vlen) in &cases {
            if handles.contains(&k) || rng.gen_range(0, 2) == 0 {
                let v = vec![0; vlen as usize - extra_value_size as usize];
                extra_value_size = 0;
                collector.add(k.as_bytes(), &v, DBEntryType::Put, 0, 0);
            } else {
                let mut blob_index = TitanBlobIndex::default();
                blob_index.blob_size = vlen - extra_value_size;
                let v = blob_index.encode();
                extra_value_size = v.len() as u64;
                collector.add(k.as_bytes(), &v, DBEntryType::BlobIndex, 0, 0);
            }
        }
        let result = UserProperties(collector.finish());

        let props = RangeProperties::decode(&result).unwrap();
        assert_eq!(props.smallest_key().unwrap(), cases[0].0.as_bytes());
        assert_eq!(
            props.largest_key().unwrap(),
            cases[cases.len() - 1].0.as_bytes()
        );
        assert_eq!(
            props.get_approximate_size_in_range(b"e", b"i"),
            DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8 * 9 + 4
        );
        assert_eq!(
            props.get_approximate_size_in_range(b"", b"k"),
            DEFAULT_PROP_SIZE_INDEX_DISTANCE / 8 * 25 + 11
        );
    }
}