// Copyright 2016 Mozilla
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
// this file except in compliance with the License. You may obtain a copy of the
// License at http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.

#![allow(dead_code)]

use std::collections::{
    BTreeMap,
    BTreeSet,
    HashMap,
};
use std::iter::{
    FromIterator,
};
use std::ops::{
    Deref,
    DerefMut,
    Range,
};

extern crate mentat_core;

pub use self::mentat_core::{
    Attribute,
    AttributeBitFlags,
    DateTime,
    Entid,
    Schema,
    TypedValue,
    Utc,
    ValueType,
};

use edn::entities::{
    EntityPlace,
    TempId,
};

use errors;

/// Represents one partition of the entid space.
#[derive(Clone, Debug, Eq, Hash, Ord, PartialOrd, PartialEq)]
#[cfg_attr(feature = "syncable", derive(Serialize,Deserialize))]
pub struct Partition {
    /// The first entid in the partition.
    pub start: Entid,
    /// Maximum allowed entid in the partition.
    pub end: Entid,
    /// `true` if entids in the partition can be excised with `:db/excise`.
    pub allow_excision: bool,
    /// The next entid to be allocated in the partition.
    /// Unless you must use this directly, prefer using provided setter and getter helpers.
    pub(crate) next_entid_to_allocate: Entid,
}

impl Partition {
    pub fn new(start: Entid, end: Entid, next_entid_to_allocate: Entid, allow_excision: bool) -> Partition {
        assert!(
            start <= next_entid_to_allocate && next_entid_to_allocate <= end,
            "A partition represents a monotonic increasing sequence of entids."
        );
        Partition { start, end, next_entid_to_allocate, allow_excision }
    }

    pub fn contains_entid(&self, e: Entid) -> bool {
        (e >= self.start) && (e < self.next_entid_to_allocate)
    }

    pub fn allows_entid(&self, e: Entid) -> bool {
        (e >= self.start) && (e <= self.end)
    }

    pub fn next_entid(&self) -> Entid {
        self.next_entid_to_allocate
    }

    pub fn set_next_entid(&mut self, e: Entid) {
        assert!(self.allows_entid(e), "Partition index must be within its allocated space.");
        self.next_entid_to_allocate = e;
    }

    pub fn allocate_entids(&mut self, n: usize) -> Range<i64> {
        let idx = self.next_entid();
        self.set_next_entid(idx + n as i64);
        idx..self.next_entid()
    }
}

/// Map partition names to `Partition` instances.
#[derive(Clone, Debug, Default, Eq, Hash, Ord, PartialOrd, PartialEq)]
pub struct PartitionMap(BTreeMap<String, Partition>);

impl Deref for PartitionMap {
    type Target = BTreeMap<String, Partition>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for PartitionMap {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl FromIterator<(String, Partition)> for PartitionMap {
    fn from_iter<T: IntoIterator<Item=(String, Partition)>>(iter: T) -> Self {
        PartitionMap(iter.into_iter().collect())
    }
}

/// Represents the metadata required to query from, or apply transactions to, a Mentat store.
///
/// See https://github.com/mozilla/mentat/wiki/Thoughts:-modeling-db-conn-in-Rust.
#[derive(Clone,Debug,Default,Eq,Hash,Ord,PartialOrd,PartialEq)]
pub struct DB {
    /// Map partition name->`Partition`.
    ///
    /// TODO: represent partitions as entids.
    pub partition_map: PartitionMap,

    /// The schema of the store.
    pub schema: Schema,
}

impl DB {
    pub fn new(partition_map: PartitionMap, schema: Schema) -> DB {
        DB {
            partition_map: partition_map,
            schema: schema
        }
    }
}

/// A pair [a v] in the store.
///
/// Used to represent lookup-refs and [TEMPID a v] upserts as they are resolved.
pub type AVPair = (Entid, TypedValue);

/// Map [a v] pairs to existing entids.
///
/// Used to resolve lookup-refs and upserts.
pub type AVMap<'a> = HashMap<&'a AVPair, Entid>;

// represents a set of entids that are correspond to attributes
pub type AttributeSet = BTreeSet<Entid>;

/// The transactor is tied to `edn::ValueAndSpan` right now, but in the future we'd like to support
/// `TypedValue` directly for programmatic use.  `TransactableValue` encapsulates the interface
/// value types (i.e., values in the value place) need to support to be transacted.
pub trait TransactableValue: Clone {
    /// Coerce this value place into the given type.  This is where we perform schema-aware
    /// coercion, for example coercing an integral value into a ref where appropriate.
    fn into_typed_value(self, schema: &Schema, value_type: ValueType) -> errors::Result<TypedValue>;

    /// Make an entity place out of this value place.  This is where we limit values in nested maps
    /// to valid entity places.
    fn into_entity_place(self) -> errors::Result<EntityPlace<Self>>;

    fn as_tempid(&self) -> Option<TempId>;
}

#[cfg(test)]
mod tests {
    use super::Partition;

    #[test]
    #[should_panic(expected = "A partition represents a monotonic increasing sequence of entids.")]
    fn test_partition_limits_sanity1() {
        Partition::new(100, 1000, 1001, true);
    }

    #[test]
    #[should_panic(expected = "A partition represents a monotonic increasing sequence of entids.")]
    fn test_partition_limits_sanity2() {
        Partition::new(100, 1000, 99, true);
    }

    #[test]
    #[should_panic(expected = "Partition index must be within its allocated space.")]
    fn test_partition_limits_boundary1() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.set_next_entid(2000);
    }

    #[test]
    #[should_panic(expected = "Partition index must be within its allocated space.")]
    fn test_partition_limits_boundary2() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.set_next_entid(1001);
    }

    #[test]
    #[should_panic(expected = "Partition index must be within its allocated space.")]
    fn test_partition_limits_boundary3() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.set_next_entid(99);
    }

    #[test]
    #[should_panic(expected = "Partition index must be within its allocated space.")]
    fn test_partition_limits_boundary4() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.set_next_entid(-100);
    }

    #[test]
    #[should_panic(expected = "Partition index must be within its allocated space.")]
    fn test_partition_limits_boundary5() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.allocate_entids(901); // One more than allowed.
    }

    #[test]
    fn test_partition_limits_boundary6() {
        let mut part = Partition::new(100, 1000, 100, true);
        part.set_next_entid(100); // First entid that's allowed.
        part.set_next_entid(101); // Just after first.

        assert_eq!(101..111, part.allocate_entids(10));

        part.set_next_entid(1000); // Last entid that's allowed.
        part.set_next_entid(999); // Just before last.
    }
}