use crate::erasure::ErasureConfig;
use serde::{Deserialize, Serialize};
use solana_metrics::datapoint;
use solana_sdk::clock::Slot;
use std::{collections::BTreeSet, ops::RangeBounds};

#[derive(Clone, Debug, Default, Deserialize, Serialize, Eq, PartialEq)]
// The Meta column family
pub struct SlotMeta {
    // The number of slots above the root (the genesis block). The first
    // slot has slot 0.
    pub slot: Slot,
    // The total number of consecutive shreds starting from index 0
    // we have received for this slot.
    pub consumed: u64,
    // The index *plus one* of the highest shred received for this slot.  Useful
    // for checking if the slot has received any shreds yet, and to calculate the
    // range where there is one or more holes: `(consumed..received)`.
    pub received: u64,
    // The timestamp of the first time a shred was added for this slot
    pub first_shred_timestamp: u64,
    // The index of the shred that is flagged as the last shred for this slot.
    pub last_index: u64,
    // The slot height of the block this one derives from.
    pub parent_slot: Slot,
    // The list of slots, each of which contains a block that derives
    // from this one.
    pub next_slots: Vec<Slot>,
    // True if this slot is full (consumed == last_index + 1) and if every
    // slot that is a parent of this slot is also connected.
    pub is_connected: bool,
    // List of start indexes for completed data slots
    pub completed_data_indexes: Vec<u32>,
}

#[derive(Clone, Debug, Default, Deserialize, Serialize, PartialEq)]
/// Index recording presence/absence of shreds
pub struct Index {
    pub slot: Slot,
    data: DataIndex,
    coding: CodingIndex,
}

#[derive(Clone, Debug, Default, Deserialize, Serialize, PartialEq)]
pub struct DataIndex {
    /// Map representing presence/absence of data shreds
    index: BTreeSet<u64>,
}

#[derive(Clone, Debug, Default, Deserialize, Serialize, PartialEq)]
/// Erasure coding information
pub struct CodingIndex {
    /// Map from set index, to hashmap from shred index to presence bool
    index: BTreeSet<u64>,
}

#[derive(Clone, Copy, Debug, Default, Deserialize, Serialize, Eq, PartialEq)]
/// Erasure coding information
pub struct ErasureMeta {
    /// Which erasure set in the slot this is
    pub set_index: u64,
    /// First coding index in the FEC set
    pub first_coding_index: u64,
    /// Size of shards in this erasure set
    pub size: usize,
    /// Erasure configuration for this erasure set
    pub config: ErasureConfig,
}

#[derive(Debug, PartialEq)]
pub enum ErasureMetaStatus {
    CanRecover,
    DataFull,
    StillNeed(usize),
}

impl Index {
    pub(crate) fn new(slot: Slot) -> Self {
        Index {
            slot,
            data: DataIndex::default(),
            coding: CodingIndex::default(),
        }
    }

    pub fn data(&self) -> &DataIndex {
        &self.data
    }
    pub fn coding(&self) -> &CodingIndex {
        &self.coding
    }

    pub fn data_mut(&mut self) -> &mut DataIndex {
        &mut self.data
    }
    pub fn coding_mut(&mut self) -> &mut CodingIndex {
        &mut self.coding
    }
}

impl CodingIndex {
    pub fn num_coding(&self) -> usize {
        self.index.len()
    }

    pub fn present_in_bounds(&self, bounds: impl RangeBounds<u64>) -> usize {
        self.index.range(bounds).count()
    }

    pub fn is_present(&self, index: u64) -> bool {
        self.index.contains(&index)
    }

    pub fn set_present(&mut self, index: u64, presence: bool) {
        if presence {
            self.index.insert(index);
        } else {
            self.index.remove(&index);
        }
    }

    pub fn set_many_present(&mut self, presence: impl IntoIterator<Item = (u64, bool)>) {
        for (idx, present) in presence.into_iter() {
            self.set_present(idx, present);
        }
    }
}

impl DataIndex {
    pub fn num_data(&self) -> usize {
        self.index.len()
    }

    pub fn present_in_bounds(&self, bounds: impl RangeBounds<u64>) -> usize {
        self.index.range(bounds).count()
    }

    pub fn is_present(&self, index: u64) -> bool {
        self.index.contains(&index)
    }

    pub fn set_present(&mut self, index: u64, presence: bool) {
        if presence {
            self.index.insert(index);
        } else {
            self.index.remove(&index);
        }
    }

    pub fn set_many_present(&mut self, presence: impl IntoIterator<Item = (u64, bool)>) {
        for (idx, present) in presence.into_iter() {
            self.set_present(idx, present);
        }
    }
}

impl SlotMeta {
    pub fn is_full(&self) -> bool {
        // last_index is std::u64::MAX when it has no information about how
        // many shreds will fill this slot.
        // Note: A full slot with zero shreds is not possible.
        if self.last_index == std::u64::MAX {
            return false;
        }

        // Should never happen
        if self.consumed > self.last_index + 1 {
            datapoint!(
                "blockstore_error",
                (
                    "error",
                    format!(
                        "Observed a slot meta with consumed: {} > meta.last_index + 1: {}",
                        self.consumed,
                        self.last_index + 1
                    ),
                    String
                )
            );
        }

        self.consumed == self.last_index + 1
    }

    pub fn is_parent_set(&self) -> bool {
        self.parent_slot != std::u64::MAX
    }

    pub(crate) fn new(slot: Slot, parent_slot: Slot) -> Self {
        SlotMeta {
            slot,
            consumed: 0,
            received: 0,
            first_shred_timestamp: 0,
            parent_slot,
            next_slots: vec![],
            is_connected: slot == 0,
            last_index: std::u64::MAX,
            completed_data_indexes: vec![],
        }
    }
}

impl ErasureMeta {
    pub fn new(set_index: u64, first_coding_index: u64, config: &ErasureConfig) -> ErasureMeta {
        ErasureMeta {
            set_index,
            first_coding_index,
            size: 0,
            config: *config,
        }
    }

    pub fn status(&self, index: &Index) -> ErasureMetaStatus {
        use ErasureMetaStatus::*;

        let num_coding = index.coding().present_in_bounds(
            self.first_coding_index..self.first_coding_index + self.config.num_coding() as u64,
        );
        let num_data = index
            .data()
            .present_in_bounds(self.set_index..self.set_index + self.config.num_data() as u64);

        let (data_missing, num_needed) = (
            self.config.num_data().saturating_sub(num_data),
            self.config.num_data().saturating_sub(num_data + num_coding),
        );

        if data_missing == 0 {
            DataFull
        } else if num_needed == 0 {
            CanRecover
        } else {
            StillNeed(num_needed)
        }
    }

    pub fn set_size(&mut self, size: usize) {
        self.size = size;
    }

    pub fn size(&self) -> usize {
        self.size
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use rand::{seq::SliceRandom, thread_rng};
    use std::iter::repeat;

    #[test]
    fn test_erasure_meta_status() {
        use ErasureMetaStatus::*;

        let set_index = 0;
        let erasure_config = ErasureConfig::default();

        let mut e_meta = ErasureMeta::new(set_index, set_index, &erasure_config);
        let mut rng = thread_rng();
        let mut index = Index::new(0);
        e_meta.size = 1;

        let data_indexes = 0..erasure_config.num_data() as u64;
        let coding_indexes = 0..erasure_config.num_coding() as u64;

        assert_eq!(e_meta.status(&index), StillNeed(erasure_config.num_data()));

        index
            .data_mut()
            .set_many_present(data_indexes.clone().zip(repeat(true)));

        assert_eq!(e_meta.status(&index), DataFull);

        index
            .coding_mut()
            .set_many_present(coding_indexes.clone().zip(repeat(true)));

        for &idx in data_indexes
            .clone()
            .collect::<Vec<_>>()
            .choose_multiple(&mut rng, erasure_config.num_data())
        {
            index.data_mut().set_present(idx, false);

            assert_eq!(e_meta.status(&index), CanRecover);
        }

        index
            .data_mut()
            .set_many_present(data_indexes.zip(repeat(true)));

        for &idx in coding_indexes
            .collect::<Vec<_>>()
            .choose_multiple(&mut rng, erasure_config.num_coding())
        {
            index.coding_mut().set_present(idx, false);

            assert_eq!(e_meta.status(&index), DataFull);
        }
    }
}
