use crate::{
    config::Config,
    error::{PRes, PersyError},
    id::{index_id_to_segment_id_meta, IndexId, PersyId, RecRef},
    index::{
        keeper::{Extractor, IndexSegmentKeeper, IndexSegmentKeeperTx},
        serialization::IndexSerialization,
    },
    locks::RwLockManager,
    persy::PersyImpl,
    snapshot::SnapshotId,
    transaction::Transaction,
};
use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use std::{
    fmt::Display,
    io::{Cursor, Read, Write},
    str,
    sync::Arc,
};

use data_encoding::BASE64URL_NOPAD;

/// Enum of all the possible Key or Value types for indexes
#[derive(Clone)]
pub enum IndexTypeId {
    U8,
    U16,
    U32,
    U64,
    U128,
    I8,
    I16,
    I32,
    I64,
    I128,
    F32W,
    F64W,
    STRING,
    PERSYID,
    BYTEVEC,
}

impl From<u8> for IndexTypeId {
    fn from(val: u8) -> IndexTypeId {
        match val {
            1 => IndexTypeId::U8,
            2 => IndexTypeId::U16,
            3 => IndexTypeId::U32,
            4 => IndexTypeId::U64,
            14 => IndexTypeId::U128,
            5 => IndexTypeId::I8,
            6 => IndexTypeId::I16,
            7 => IndexTypeId::I32,
            8 => IndexTypeId::I64,
            15 => IndexTypeId::I128,
            9 => IndexTypeId::F32W,
            10 => IndexTypeId::F64W,
            12 => IndexTypeId::STRING,
            13 => IndexTypeId::PERSYID,
            16 => IndexTypeId::BYTEVEC,
            _ => panic!("type node defined for {}", val),
        }
    }
}

pub trait WrapperType<T>: Clone + From<T> + Extractor + Ord {
    fn value(self) -> T;
}
/// Trait implemented by all supported types in the index
pub trait IndexType: Display + IndexOrd + Clone + IndexSerialization {
    type Wrapper: WrapperType<Self>;
    fn get_id() -> u8;
    fn get_type_id() -> IndexTypeId;
}

pub trait IndexOrd {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering;
}

macro_rules! impl_index_ord {
    ($($t:ty),+) => {
        $(
        impl IndexOrd for $t {
            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
                std::cmp::Ord::cmp(self, other)
            }
        }
        )+
    };
}

impl_index_ord!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, String, PersyId, ByteVec);

impl IndexOrd for f32 {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        if self.is_nan() {
            if other.is_nan() {
                std::cmp::Ordering::Equal
            } else {
                std::cmp::Ordering::Less
            }
        } else if other.is_nan() {
            std::cmp::Ordering::Greater
        } else {
            std::cmp::PartialOrd::partial_cmp(self, other).unwrap()
        }
    }
}

impl IndexOrd for f64 {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        if self.is_nan() {
            if other.is_nan() {
                std::cmp::Ordering::Equal
            } else {
                std::cmp::Ordering::Less
            }
        } else if other.is_nan() {
            std::cmp::Ordering::Greater
        } else {
            std::cmp::PartialOrd::partial_cmp(self, other).unwrap()
        }
    }
}

/// Wrapper for `Vec<u8>` for use it in index keys or values
#[derive(Debug, PartialOrd, PartialEq, Clone, Ord, Eq)]
pub struct ByteVec(pub Vec<u8>);

impl From<Vec<u8>> for ByteVec {
    fn from(f: Vec<u8>) -> ByteVec {
        ByteVec(f)
    }
}
impl From<ByteVec> for Vec<u8> {
    fn from(f: ByteVec) -> Vec<u8> {
        f.0
    }
}

impl Display for ByteVec {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", BASE64URL_NOPAD.encode(&self.0))
    }
}

impl std::str::FromStr for ByteVec {
    type Err = PersyError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(ByteVec(BASE64URL_NOPAD.decode(s.as_bytes())?))
    }
}

pub const INDEX_META_PREFIX: &str = "+_M";
pub const INDEX_DATA_PREFIX: &str = "+_D";

pub fn index_name_from_meta_segment(segment_name: &str) -> String {
    let mut name = segment_name.to_string();
    name.drain(..INDEX_META_PREFIX.len());
    name
}
pub fn format_segment_name_meta(index_name: &str) -> String {
    format!("{}{}", INDEX_META_PREFIX, index_name)
}

pub fn format_segment_name_data(index_name: &str) -> String {
    format!("{}{}", INDEX_DATA_PREFIX, index_name)
}

/// Define the behavior of the index in case a key value pair already exists
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum ValueMode {
    /// An error will return if a key value pair already exists
    EXCLUSIVE,
    /// The value will be add to a list of values for the key, duplicate value will be collapsed to
    /// only one entry
    CLUSTER,
    /// The existing value will be replaced with the new value if a key value pair already exists
    REPLACE,
}

impl From<u8> for ValueMode {
    fn from(value: u8) -> Self {
        match value {
            1 => ValueMode::EXCLUSIVE,
            2 => ValueMode::CLUSTER,
            3 => ValueMode::REPLACE,
            _ => unreachable!("is impossible to get a value mode from values not 1,2,3"),
        }
    }
}

impl ValueMode {
    fn to_u8(&self) -> u8 {
        match self {
            ValueMode::EXCLUSIVE => 1,
            ValueMode::CLUSTER => 2,
            ValueMode::REPLACE => 3,
        }
    }
}

pub struct Indexes {
    index_locks: RwLockManager<IndexId>,
    config: Arc<Config>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct IndexConfig {
    name: String,
    root: Option<RecRef>,
    pub key_type: u8,
    pub value_type: u8,
    page_min: usize,
    page_max: usize,
    pub value_mode: ValueMode,
}

impl IndexConfig {
    fn serialize(&self, w: &mut dyn Write) -> PRes<()> {
        if let Some(ref root) = self.root {
            w.write_u64::<BigEndian>(root.page)?;
            w.write_u32::<BigEndian>(root.pos)?;
        } else {
            w.write_u64::<BigEndian>(0)?;
            w.write_u32::<BigEndian>(0)?;
        }
        w.write_u8(self.key_type)?;
        w.write_u8(self.value_type)?;
        w.write_u32::<BigEndian>(self.page_min as u32)?;
        w.write_u32::<BigEndian>(self.page_max as u32)?;
        w.write_u8(self.value_mode.to_u8())?;
        w.write_u16::<BigEndian>(self.name.len() as u16)?;
        w.write_all(self.name.as_bytes())?;
        Ok(())
    }
    fn deserialize(r: &mut dyn Read) -> PRes<IndexConfig> {
        let index_root_page = r.read_u64::<BigEndian>()?;
        let index_root_pos = r.read_u32::<BigEndian>()?;
        let key_type = r.read_u8()?;
        let value_type = r.read_u8()?;
        let page_min = r.read_u32::<BigEndian>()? as usize;
        let page_max = r.read_u32::<BigEndian>()? as usize;
        let value_mode = ValueMode::from(r.read_u8()?);

        let name_size = r.read_u16::<BigEndian>()? as usize;
        let mut slice: Vec<u8> = vec![0; name_size];
        r.read_exact(&mut slice)?;
        let name: String = str::from_utf8(&slice[0..name_size])?.into();
        let root = if index_root_page != 0 && index_root_pos != 0 {
            Some(RecRef::new(index_root_page, index_root_pos))
        } else {
            None
        };
        Ok(IndexConfig {
            name,
            root,
            key_type,
            value_type,
            page_min,
            page_max,
            value_mode,
        })
    }

    pub fn check<K: IndexType, V: IndexType>(&self) -> PRes<()> {
        if self.key_type != K::get_id() {
            Err(PersyError::IndexTypeMismatch("key type".into()))
        } else if self.value_type != V::get_id() {
            Err(PersyError::IndexTypeMismatch("value type".into()))
        } else {
            Ok(())
        }
    }
    pub fn get_root(&self) -> Option<RecRef> {
        self.root.clone()
    }
}

fn error_map(err: PersyError) -> PersyError {
    if let PersyError::SegmentNotFound = err {
        PersyError::IndexNotFound
    } else {
        err
    }
}

impl Indexes {
    pub fn new(config: &Arc<Config>) -> Indexes {
        Indexes {
            index_locks: Default::default(),
            config: config.clone(),
        }
    }

    pub fn create_index<K, V>(
        p: &PersyImpl,
        tx: &mut Transaction,
        name: &str,
        min: usize,
        max: usize,
        value_mode: ValueMode,
    ) -> PRes<()>
    where
        K: IndexType,
        V: IndexType,
    {
        if min > max / 2 {
            return Err(PersyError::IndexMinElementsShouldBeAtLeastDoubleOfMax);
        }
        let segment_name_meta = format_segment_name_meta(name);
        p.create_segment(tx, &segment_name_meta)?;
        let segment_name_data = format_segment_name_data(name);
        p.create_segment(tx, &segment_name_data)?;
        let cfg = IndexConfig {
            name: name.to_string(),
            root: None,
            key_type: K::get_id(),
            value_type: V::get_id(),
            page_min: min,
            page_max: max,
            value_mode,
        };
        let mut scfg = Vec::new();
        cfg.serialize(&mut scfg)?;
        p.insert_record(tx, &segment_name_meta, &scfg)?;
        Ok(())
    }

    pub fn drop_index(p: &PersyImpl, tx: &mut Transaction, name: &str) -> PRes<()> {
        let segment_name_meta = format_segment_name_meta(name);
        p.drop_segment(tx, &segment_name_meta)?;
        let segment_name_data = format_segment_name_data(name);
        p.drop_segment(tx, &segment_name_data)?;
        Ok(())
    }

    pub fn update_index_root(
        p: &PersyImpl,
        tx: &mut Transaction,
        index_id: &IndexId,
        root: Option<RecRef>,
    ) -> PRes<()> {
        let segment_meta = index_id_to_segment_id_meta(index_id);
        let (id, mut config) =
            if let Some((rid, content, _)) = p.scan_tx(tx, segment_meta.clone()).map_err(error_map)?.next(p, tx) {
                (rid, IndexConfig::deserialize(&mut Cursor::new(content))?)
            } else {
                return Err(PersyError::IndexNotFound);
            };

        if config.root != root {
            config.root = root;
            let mut scfg = Vec::new();
            config.serialize(&mut scfg)?;
            p.update(tx, segment_meta, &id.0, &scfg)?;
        }
        Ok(())
    }

    pub fn get_index_tx(p: &PersyImpl, tx: &Transaction, index_id: &IndexId) -> PRes<(IndexConfig, u16)> {
        let segment_meta = index_id_to_segment_id_meta(index_id);
        if let Some((_, content, version)) = p.scan_tx(tx, segment_meta).map_err(error_map)?.next(p, tx) {
            Ok((IndexConfig::deserialize(&mut Cursor::new(content))?, version))
        } else {
            Err(PersyError::IndexNotFound)
        }
    }

    pub fn get_config_id(p: &PersyImpl, tx: &mut Transaction, index_id: &IndexId) -> PRes<PersyId> {
        let segment_meta = index_id_to_segment_id_meta(index_id);
        if let Some((id, _, _)) = p.scan_tx(tx, segment_meta).map_err(error_map)?.next(p, tx) {
            Ok(id)
        } else {
            Err(PersyError::IndexNotFound)
        }
    }

    pub fn get_index(p: &PersyImpl, snapshot_id: SnapshotId, index_id: &IndexId) -> PRes<IndexConfig> {
        let segment_meta = index_id_to_segment_id_meta(index_id);
        p.scan_snapshot(segment_meta, snapshot_id)
            .map_err(error_map)?
            .next(p)
            .map(|(_, content)| IndexConfig::deserialize(&mut Cursor::new(content)))
            .unwrap_or(Err(PersyError::IndexNotFound))
    }

    pub fn get_index_keeper<'a, K: IndexType, V: IndexType>(
        p: &'a PersyImpl,
        snapshot: SnapshotId,
        index_id: &IndexId,
    ) -> PRes<IndexSegmentKeeper<'a>> {
        let config = Indexes::get_index(p, snapshot, index_id)?;
        config.check::<K, V>()?;
        Ok(IndexSegmentKeeper::new(
            &config.name,
            index_id,
            config.root,
            p,
            snapshot,
            config.value_mode,
        ))
    }

    pub fn get_index_keeper_tx<'a, K: IndexType, V: IndexType>(
        p: &'a PersyImpl,
        tx: &'a mut Transaction,
        index_id: &IndexId,
    ) -> PRes<IndexSegmentKeeperTx<'a, K, V>> {
        let (config, version) = Indexes::get_index_tx(p, tx, index_id)?;
        config.check::<K, V>()?;
        Ok(IndexSegmentKeeperTx::new(
            &config.name,
            index_id,
            config.root,
            version,
            p,
            tx,
            config.value_mode,
            config.page_min,
            config.page_max,
        ))
    }

    pub fn check_index<K: IndexType, V: IndexType>(
        p: &PersyImpl,
        tx: &mut Transaction,
        index_id: &IndexId,
    ) -> PRes<()> {
        let (config, _version) = Indexes::get_index_tx(p, tx, index_id)?;
        config.check::<K, V>()
    }

    #[allow(dead_code)]
    pub fn write_lock(&self, indexes: &[IndexId]) -> PRes<()> {
        self.index_locks
            .lock_all_write(indexes, self.config.transaction_lock_timeout().clone())
    }

    pub fn read_lock(&self, index: IndexId) -> PRes<()> {
        self.index_locks
            .lock_all_read(&[index], self.config.transaction_lock_timeout().clone())
    }

    pub fn read_lock_all(&self, indexes: &[IndexId]) -> PRes<()> {
        self.index_locks
            .lock_all_read(indexes, self.config.transaction_lock_timeout().clone())
    }

    pub fn read_unlock(&self, index: IndexId) -> PRes<()> {
        self.index_locks.unlock_all_read(&[index])
    }
    pub fn read_unlock_all(&self, indexes: &[IndexId]) -> PRes<()> {
        self.index_locks.unlock_all_read(indexes)
    }

    #[allow(dead_code)]
    pub fn write_unlock(&self, indexes: &[IndexId]) -> PRes<()> {
        self.index_locks.unlock_all_write(indexes)
    }
}

#[cfg(test)]
mod tests {
    use super::{ByteVec, IndexConfig, ValueMode};
    use std::io::Cursor;

    #[test]
    fn test_config_ser_des() {
        let cfg = IndexConfig {
            name: "abc".to_string(),
            root: None,
            key_type: 1,
            value_type: 1,
            page_min: 10,
            page_max: 30,
            value_mode: ValueMode::REPLACE,
        };

        let mut buff = Vec::new();
        cfg.serialize(&mut Cursor::new(&mut buff)).expect("serialization works");
        let read = IndexConfig::deserialize(&mut Cursor::new(&mut buff)).expect("deserialization works");
        assert_eq!(cfg, read);
    }

    #[test]
    fn test_bytevec_to_from_string() {
        let bv = ByteVec(vec![10, 20]);
        let nbv = bv.to_string().parse().unwrap();
        assert_eq!(bv, nbv);
    }
}