/*
 * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
 *
 * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
 */

use super::{BlobOp, Operation, ValueClass, ValueOp, key::DeserializeBigEndian, now};
use crate::{
    BlobStore, Deserialize, IterateParams, SerializeInfallible, Store, U16_LEN, U32_LEN, U64_LEN,
    ValueKey,
    write::{BatchBuilder, BlobLink, RegistryClass},
};
use registry::{
    schema::prelude::Property,
    types::{EnumImpl, id::ObjectId},
};
use std::time::Instant;
use trc::{AddContext, StoreEvent};
use types::{
    blob::BlobClass,
    blob_hash::{BLOB_HASH_LEN, BlobHash},
};

#[derive(Debug, PartialEq, Eq)]
pub struct BlobQuota {
    pub bytes: usize,
    pub count: usize,
}

impl Store {
    pub async fn blob_exists(&self, hash: impl AsRef<BlobHash> + Sync + Send) -> trc::Result<bool> {
        self.key_exists(ValueKey {
            account_id: 0,
            collection: 0,
            document_id: 0,
            class: ValueClass::Blob(BlobOp::Commit {
                hash: hash.as_ref().clone(),
            }),
        })
        .await
        .caused_by(trc::location!())
    }

    pub async fn blob_has_access(
        &self,
        hash: impl AsRef<BlobHash> + Sync + Send,
        class: impl AsRef<BlobClass> + Sync + Send,
    ) -> trc::Result<bool> {
        let key = match class.as_ref() {
            BlobClass::Reserved {
                account_id,
                expires,
            } if *expires > now() => ValueKey {
                account_id: *account_id,
                collection: 0,
                document_id: 0,
                class: ValueClass::Blob(BlobOp::Link {
                    hash: hash.as_ref().clone(),
                    to: BlobLink::Temporary { until: *expires },
                }),
            },
            BlobClass::Linked {
                account_id,
                collection,
                document_id,
            } => ValueKey {
                account_id: *account_id,
                collection: *collection,
                document_id: *document_id,
                class: ValueClass::Blob(BlobOp::Link {
                    hash: hash.as_ref().clone(),
                    to: BlobLink::Document,
                }),
            },
            _ => return Ok(false),
        };

        self.key_exists(key).await
    }

    pub async fn purge_blobs_all_shards(&self, blob_store: BlobStore) -> trc::Result<()> {
        for shard_index in 0u8..=255 {
            self.purge_blobs(blob_store.clone(), shard_index).await?;
        }
        Ok(())
    }

    pub async fn purge_blobs(&self, blob_store: BlobStore, shard_index: u8) -> trc::Result<()> {
        let mut total_active = 0;
        let mut total_deleted = 0;
        let started = Instant::now();

        // Validate linked blobs
        let mut from_hash = BlobHash::default();
        let mut to_hash = BlobHash::new_max();
        from_hash.0[0] = shard_index;
        to_hash.0[0] = shard_index;
        let from_key = ValueKey {
            account_id: 0,
            collection: 0,
            document_id: 0,
            class: ValueClass::Blob(BlobOp::Commit { hash: from_hash }),
        };
        let to_key = ValueKey {
            account_id: u32::MAX,
            collection: u8::MAX,
            document_id: u32::MAX,
            class: ValueClass::Blob(BlobOp::Link {
                hash: to_hash,
                to: BlobLink::Document,
            }),
        };

        let mut state = BlobPurgeState::new();
        self.iterate(
            IterateParams::new(from_key, to_key).ascending(),
            |key, value| {
                let hash =
                    BlobHash::try_from_hash_slice(key.get(0..BLOB_HASH_LEN).ok_or_else(|| {
                        trc::Error::corrupted_key(key, value.into(), trc::location!())
                    })?)
                    .unwrap();

                state.update_hash(hash);
                state.process_key(key, value)?;

                Ok(true)
            },
        )
        .await
        .caused_by(trc::location!())?;

        state.finalize(BlobHash::default());

        // Delete expired or unlinked blobs
        for (_, op) in &state.delete_keys {
            if let BlobOp::Commit { hash } = op {
                blob_store
                    .delete_blob(hash.as_ref())
                    .await
                    .caused_by(trc::location!())?;
            }
        }

        // Delete hashes
        let mut batch = BatchBuilder::new();
        for (account_id, op) in state.delete_keys {
            if batch.is_large_batch() {
                self.write(batch.build_all())
                    .await
                    .caused_by(trc::location!())?;
                batch = BatchBuilder::new();
            }

            if let Some(account_id) = account_id {
                batch.with_account_id(account_id);
            }

            batch.any_op(Operation::Value {
                class: ValueClass::Blob(op),
                op: ValueOp::Clear,
            });
        }
        for (account_id, object_id) in state.delete_registry {
            if batch.is_large_batch() {
                self.write(batch.build_all())
                    .await
                    .caused_by(trc::location!())?;
                batch = BatchBuilder::new();
            }

            let item_id = object_id.id().id();
            let object_id = object_id.object().to_id();

            batch
                .clear(ValueClass::Registry(RegistryClass::Index {
                    index_id: Property::AccountId.to_id(),
                    object_id,
                    item_id,
                    key: (account_id as u64).serialize(),
                }))
                .clear(ValueClass::Registry(RegistryClass::Item {
                    object_id,
                    item_id,
                }));
        }
        if !batch.is_empty() {
            self.write(batch.build_all())
                .await
                .caused_by(trc::location!())?;
        }

        total_active += state.total_active - 1; // Exclude default hash
        total_deleted += state.total_deleted;

        trc::event!(
            Store(StoreEvent::BlobStorePurged),
            Id = shard_index as u16,
            Expires = total_deleted,
            Total = total_active,
            Elapsed = started.elapsed()
        );

        Ok(())
    }
}

struct BlobPurgeState {
    last_hash: BlobHash,
    last_hash_is_linked: bool,
    delete_keys: Vec<(Option<u32>, BlobOp)>,
    delete_registry: Vec<(u32, ObjectId)>,
    now: u64,
    total_deleted: u64,
    total_active: u64,
}

impl BlobPurgeState {
    fn new() -> Self {
        Self {
            last_hash: BlobHash::default(),
            last_hash_is_linked: true, // Avoid deleting non-existing last_hash on first iteration
            delete_keys: Vec::new(),
            delete_registry: Vec::new(),
            now: now(),
            total_deleted: 0,
            total_active: 0,
        }
    }

    pub fn update_hash(&mut self, hash: BlobHash) {
        if self.last_hash != hash {
            self.finalize(hash);
            self.last_hash_is_linked = false;
        }
    }

    pub fn finalize(&mut self, new_hash: BlobHash) {
        if !self.last_hash_is_linked {
            self.total_deleted += 1;
            self.delete_keys.push((
                None,
                BlobOp::Commit {
                    hash: std::mem::replace(&mut self.last_hash, new_hash),
                },
            ));
        } else {
            self.total_active += 1;
            self.last_hash = new_hash;
        }
    }

    pub fn process_key(&mut self, key: &[u8], value: &[u8]) -> trc::Result<()> {
        const TEMP_LINK: usize = BLOB_HASH_LEN + U32_LEN + U64_LEN;
        const DOC_LINK: usize = BLOB_HASH_LEN + U64_LEN + 1;
        const ID_LINK: usize = BLOB_HASH_LEN + U64_LEN;

        match key.len() {
            BLOB_HASH_LEN => {
                // Main blob entry
                Ok(())
            }
            TEMP_LINK => {
                // Temporary link
                let until = key.deserialize_be_u64(BLOB_HASH_LEN + U32_LEN)?;
                if until <= self.now {
                    let account_id = key.deserialize_be_u32(BLOB_HASH_LEN)?;
                    self.delete_keys.push((
                        Some(account_id),
                        BlobOp::Link {
                            hash: self.last_hash.clone(),
                            to: BlobLink::Temporary { until },
                        },
                    ));
                    if value.len() == U16_LEN + U64_LEN {
                        self.delete_registry
                            .push((account_id, ObjectId::deserialize(value)?));
                    }
                } else {
                    self.last_hash_is_linked = true;
                }
                Ok(())
            }
            DOC_LINK | ID_LINK => {
                // Document/Id link
                self.last_hash_is_linked = true;
                Ok(())
            }
            _ => Err(trc::Error::corrupted_key(
                key,
                value.into(),
                trc::location!(),
            )),
        }
    }
}