pub mod error;
pub mod index_store;
pub mod meta_store;

use std::convert::TryFrom;
use std::path::Path;
use std::sync::Arc;

use error::{IndexResolverError, Result};
use index_store::{IndexStore, MapIndexStore};
use meilisearch_types::error::ResponseError;
use meilisearch_types::index_uid::IndexUid;
use meta_store::{HeedMetaStore, IndexMetaStore};
use milli::heed::Env;
use milli::update::{DocumentDeletionResult, IndexerConfig};
use time::OffsetDateTime;
use tokio::task::spawn_blocking;
use uuid::Uuid;

use crate::index::{error::Result as IndexResult, Index};
use crate::options::IndexerOpts;
use crate::tasks::task::{DocumentDeletion, Task, TaskContent, TaskEvent, TaskId, TaskResult};
use crate::update_file_store::UpdateFileStore;

use self::meta_store::IndexMeta;

pub type HardStateIndexResolver = IndexResolver<HeedMetaStore, MapIndexStore>;

#[cfg(not(test))]
pub use real::IndexResolver;

#[cfg(test)]
pub use test::MockIndexResolver as IndexResolver;

pub fn create_index_resolver(
    path: impl AsRef<Path>,
    index_size: usize,
    indexer_opts: &IndexerOpts,
    meta_env: Arc<milli::heed::Env>,
    file_store: UpdateFileStore,
) -> anyhow::Result<HardStateIndexResolver> {
    let uuid_store = HeedMetaStore::new(meta_env)?;
    let index_store = MapIndexStore::new(&path, index_size, indexer_opts)?;
    Ok(IndexResolver::new(uuid_store, index_store, file_store))
}

mod real {
    use super::*;

    pub struct IndexResolver<U, I> {
        pub(super) index_uuid_store: U,
        pub(super) index_store: I,
        pub(super) file_store: UpdateFileStore,
    }

    impl IndexResolver<HeedMetaStore, MapIndexStore> {
        pub fn load_dump(
            src: impl AsRef<Path>,
            dst: impl AsRef<Path>,
            index_db_size: usize,
            env: Arc<Env>,
            indexer_opts: &IndexerOpts,
        ) -> anyhow::Result<()> {
            HeedMetaStore::load_dump(&src, env)?;
            let indexes_path = src.as_ref().join("indexes");
            let indexes = indexes_path.read_dir()?;
            let indexer_config = IndexerConfig::try_from(indexer_opts)?;
            for index in indexes {
                Index::load_dump(&index?.path(), &dst, index_db_size, &indexer_config)?;
            }

            Ok(())
        }
    }

    impl<U, I> IndexResolver<U, I>
    where
        U: IndexMetaStore,
        I: IndexStore,
    {
        pub fn new(index_uuid_store: U, index_store: I, file_store: UpdateFileStore) -> Self {
            Self {
                index_uuid_store,
                index_store,
                file_store,
            }
        }

        pub async fn process_document_addition_batch(&self, mut tasks: Vec<Task>) -> Vec<Task> {
            fn get_content_uuid(task: &Task) -> Uuid {
                match task {
                    Task {
                        content: TaskContent::DocumentAddition { content_uuid, .. },
                        ..
                    } => *content_uuid,
                    _ => panic!("unexpected task in the document addition batch"),
                }
            }

            let content_uuids = tasks.iter().map(get_content_uuid).collect::<Vec<_>>();

            match tasks.first() {
                Some(Task {
                    id,
                    content:
                        TaskContent::DocumentAddition {
                            merge_strategy,
                            primary_key,
                            allow_index_creation,
                            index_uid,
                            ..
                        },
                    ..
                }) => {
                    let primary_key = primary_key.clone();
                    let method = *merge_strategy;

                    let index = if *allow_index_creation {
                        self.get_or_create_index(index_uid.clone(), *id).await
                    } else {
                        self.get_index(index_uid.as_str().to_string()).await
                    };

                    // If the index doesn't exist and we are not allowed to create it with the first
                    // task, we must fails the whole batch.
                    let now = OffsetDateTime::now_utc();
                    let index = match index {
                        Ok(index) => index,
                        Err(e) => {
                            let error = ResponseError::from(e);
                            for task in tasks.iter_mut() {
                                task.events.push(TaskEvent::Failed {
                                    error: error.clone(),
                                    timestamp: now,
                                });
                            }
                            return tasks;
                        }
                    };

                    let file_store = self.file_store.clone();
                    let result = spawn_blocking(move || {
                        index.update_documents(
                            method,
                            primary_key,
                            file_store,
                            content_uuids.into_iter(),
                        )
                    })
                    .await;

                    let event = match result {
                        Ok(Ok(result)) => TaskEvent::Succeeded {
                            timestamp: OffsetDateTime::now_utc(),
                            result: TaskResult::DocumentAddition {
                                indexed_documents: result.indexed_documents,
                            },
                        },
                        Ok(Err(e)) => TaskEvent::Failed {
                            timestamp: OffsetDateTime::now_utc(),
                            error: e.into(),
                        },
                        Err(e) => TaskEvent::Failed {
                            timestamp: OffsetDateTime::now_utc(),
                            error: IndexResolverError::from(e).into(),
                        },
                    };

                    for task in tasks.iter_mut() {
                        task.events.push(event.clone());
                    }

                    tasks
                }
                _ => panic!("invalid batch!"),
            }
        }

        pub async fn delete_content_file(&self, content_uuid: Uuid) -> Result<()> {
            self.file_store.delete(content_uuid).await?;
            Ok(())
        }

        pub async fn process_task(&self, task: &Task) -> Result<TaskResult> {
            match &task.content {
                TaskContent::DocumentAddition { .. } => {
                    panic!("updates should be handled by batch")
                }
                TaskContent::DocumentDeletion {
                    deletion: DocumentDeletion::Ids(ids),
                    index_uid,
                } => {
                    let ids = ids.clone();
                    let index = self.get_index(index_uid.clone().into_inner()).await?;

                    let DocumentDeletionResult {
                        deleted_documents, ..
                    } = spawn_blocking(move || index.delete_documents(&ids)).await??;

                    Ok(TaskResult::DocumentDeletion { deleted_documents })
                }
                TaskContent::DocumentDeletion {
                    deletion: DocumentDeletion::Clear,
                    index_uid,
                } => {
                    let index = self.get_index(index_uid.clone().into_inner()).await?;
                    let deleted_documents = spawn_blocking(move || -> IndexResult<u64> {
                        let number_documents = index.stats()?.number_of_documents;
                        index.clear_documents()?;
                        Ok(number_documents)
                    })
                    .await??;

                    Ok(TaskResult::ClearAll { deleted_documents })
                }
                TaskContent::SettingsUpdate {
                    settings,
                    is_deletion,
                    allow_index_creation,
                    index_uid,
                } => {
                    let index = if *is_deletion || !*allow_index_creation {
                        self.get_index(index_uid.clone().into_inner()).await?
                    } else {
                        self.get_or_create_index(index_uid.clone(), task.id).await?
                    };

                    let settings = settings.clone();
                    spawn_blocking(move || index.update_settings(&settings.check())).await??;

                    Ok(TaskResult::Other)
                }
                TaskContent::IndexDeletion { index_uid } => {
                    let index = self.delete_index(index_uid.clone().into_inner()).await?;

                    let deleted_documents = spawn_blocking(move || -> IndexResult<u64> {
                        Ok(index.stats()?.number_of_documents)
                    })
                    .await??;

                    Ok(TaskResult::ClearAll { deleted_documents })
                }
                TaskContent::IndexCreation {
                    primary_key,
                    index_uid,
                } => {
                    let index = self.create_index(index_uid.clone(), task.id).await?;

                    if let Some(primary_key) = primary_key {
                        let primary_key = primary_key.clone();
                        spawn_blocking(move || index.update_primary_key(primary_key)).await??;
                    }

                    Ok(TaskResult::Other)
                }
                TaskContent::IndexUpdate {
                    primary_key,
                    index_uid,
                } => {
                    let index = self.get_index(index_uid.clone().into_inner()).await?;

                    if let Some(primary_key) = primary_key {
                        let primary_key = primary_key.clone();
                        spawn_blocking(move || index.update_primary_key(primary_key)).await??;
                    }

                    Ok(TaskResult::Other)
                }
                _ => unreachable!("Invalid task for index resolver"),
            }
        }

        pub async fn dump(&self, path: impl AsRef<Path>) -> Result<()> {
            for (_, index) in self.list().await? {
                index.dump(&path)?;
            }
            self.index_uuid_store.dump(path.as_ref().to_owned()).await?;
            Ok(())
        }

        async fn create_index(&self, uid: IndexUid, creation_task_id: TaskId) -> Result<Index> {
            match self.index_uuid_store.get(uid.into_inner()).await? {
                (uid, Some(_)) => Err(IndexResolverError::IndexAlreadyExists(uid)),
                (uid, None) => {
                    let uuid = Uuid::new_v4();
                    let index = self.index_store.create(uuid).await?;
                    match self
                        .index_uuid_store
                        .insert(
                            uid,
                            IndexMeta {
                                uuid,
                                creation_task_id,
                            },
                        )
                        .await
                    {
                        Err(e) => {
                            match self.index_store.delete(uuid).await {
                                Ok(Some(index)) => {
                                    index.close();
                                }
                                Ok(None) => (),
                                Err(e) => log::error!("Error while deleting index: {:?}", e),
                            }
                            Err(e)
                        }
                        Ok(()) => Ok(index),
                    }
                }
            }
        }

        /// Get or create an index with name `uid`.
        pub async fn get_or_create_index(&self, uid: IndexUid, task_id: TaskId) -> Result<Index> {
            match self.create_index(uid, task_id).await {
                Ok(index) => Ok(index),
                Err(IndexResolverError::IndexAlreadyExists(uid)) => self.get_index(uid).await,
                Err(e) => Err(e),
            }
        }

        pub async fn list(&self) -> Result<Vec<(String, Index)>> {
            let uuids = self.index_uuid_store.list().await?;
            let mut indexes = Vec::new();
            for (name, IndexMeta { uuid, .. }) in uuids {
                match self.index_store.get(uuid).await? {
                    Some(index) => indexes.push((name, index)),
                    None => {
                        // we found an unexisting index, we remove it from the uuid store
                        let _ = self.index_uuid_store.delete(name).await;
                    }
                }
            }

            Ok(indexes)
        }

        pub async fn delete_index(&self, uid: String) -> Result<Index> {
            match self.index_uuid_store.delete(uid.clone()).await? {
                Some(IndexMeta { uuid, .. }) => match self.index_store.delete(uuid).await? {
                    Some(index) => {
                        index.clone().close();
                        Ok(index)
                    }
                    None => Err(IndexResolverError::UnexistingIndex(uid)),
                },
                None => Err(IndexResolverError::UnexistingIndex(uid)),
            }
        }

        pub async fn get_index(&self, uid: String) -> Result<Index> {
            match self.index_uuid_store.get(uid).await? {
                (name, Some(IndexMeta { uuid, .. })) => {
                    match self.index_store.get(uuid).await? {
                        Some(index) => Ok(index),
                        None => {
                            // For some reason we got a uuid to an unexisting index, we return an error,
                            // and remove the uuid from the uuid store.
                            let _ = self.index_uuid_store.delete(name.clone()).await;
                            Err(IndexResolverError::UnexistingIndex(name))
                        }
                    }
                }
                (name, _) => Err(IndexResolverError::UnexistingIndex(name)),
            }
        }

        pub async fn get_index_creation_task_id(&self, index_uid: String) -> Result<TaskId> {
            let (uid, meta) = self.index_uuid_store.get(index_uid).await?;
            meta.map(
                |IndexMeta {
                     creation_task_id, ..
                 }| creation_task_id,
            )
            .ok_or(IndexResolverError::UnexistingIndex(uid))
        }
    }
}

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

    use nelson::Mocker;

    pub enum MockIndexResolver<U, I> {
        Real(super::real::IndexResolver<U, I>),
        Mock(Mocker),
    }

    impl MockIndexResolver<HeedMetaStore, MapIndexStore> {
        pub fn load_dump(
            src: impl AsRef<Path>,
            dst: impl AsRef<Path>,
            index_db_size: usize,
            env: Arc<Env>,
            indexer_opts: &IndexerOpts,
        ) -> anyhow::Result<()> {
            super::real::IndexResolver::load_dump(src, dst, index_db_size, env, indexer_opts)
        }
    }

    impl<U, I> MockIndexResolver<U, I>
    where
        U: IndexMetaStore,
        I: IndexStore,
    {
        pub fn new(index_uuid_store: U, index_store: I, file_store: UpdateFileStore) -> Self {
            Self::Real(super::real::IndexResolver {
                index_uuid_store,
                index_store,
                file_store,
            })
        }

        pub fn mock(mocker: Mocker) -> Self {
            Self::Mock(mocker)
        }

        pub async fn process_document_addition_batch(&self, tasks: Vec<Task>) -> Vec<Task> {
            match self {
                IndexResolver::Real(r) => r.process_document_addition_batch(tasks).await,
                IndexResolver::Mock(m) => unsafe {
                    m.get("process_document_addition_batch").call(tasks)
                },
            }
        }

        pub async fn process_task(&self, task: &Task) -> Result<TaskResult> {
            match self {
                IndexResolver::Real(r) => r.process_task(task).await,
                IndexResolver::Mock(m) => unsafe { m.get("process_task").call(task) },
            }
        }

        pub async fn dump(&self, path: impl AsRef<Path>) -> Result<()> {
            match self {
                IndexResolver::Real(r) => r.dump(path).await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        /// Get or create an index with name `uid`.
        pub async fn get_or_create_index(&self, uid: IndexUid, task_id: TaskId) -> Result<Index> {
            match self {
                IndexResolver::Real(r) => r.get_or_create_index(uid, task_id).await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        pub async fn list(&self) -> Result<Vec<(String, Index)>> {
            match self {
                IndexResolver::Real(r) => r.list().await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        pub async fn delete_index(&self, uid: String) -> Result<Index> {
            match self {
                IndexResolver::Real(r) => r.delete_index(uid).await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        pub async fn get_index(&self, uid: String) -> Result<Index> {
            match self {
                IndexResolver::Real(r) => r.get_index(uid).await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        pub async fn get_index_creation_task_id(&self, index_uid: String) -> Result<TaskId> {
            match self {
                IndexResolver::Real(r) => r.get_index_creation_task_id(index_uid).await,
                IndexResolver::Mock(_) => todo!(),
            }
        }

        pub async fn delete_content_file(&self, content_uuid: Uuid) -> Result<()> {
            match self {
                IndexResolver::Real(r) => r.delete_content_file(content_uuid).await,
                IndexResolver::Mock(m) => unsafe {
                    m.get("delete_content_file").call(content_uuid)
                },
            }
        }
    }

    // TODO: ignoring this test, it has become too complex to maintain, and rather implement
    // handler logic test.
    // proptest! {
    //     #[test]
    //     #[ignore]
    //     fn test_process_task(
    //         task in any::<Task>().prop_filter("IndexUid should be Some", |s| s.index_uid.is_some()),
    //         index_exists in any::<bool>(),
    //         index_op_fails in any::<bool>(),
    //         any_int in any::<u64>(),
    //         ) {
    //         actix_rt::System::new().block_on(async move {
    //             let uuid = Uuid::new_v4();
    //             let mut index_store = MockIndexStore::new();
    //
    //             let mocker = Mocker::default();
    //
    //             // Return arbitrary data from index call.
    //             match &task.content {
    //                 TaskContent::DocumentAddition{primary_key, ..} => {
    //                     let result = move || if !index_op_fails {
    //                         Ok(DocumentAdditionResult { indexed_documents: any_int, number_of_documents: any_int })
    //                     } else {
    //                         // return this error because it's easy to generate...
    //                         Err(IndexError::DocumentNotFound("a doc".into()))
    //                     };
    //                     if primary_key.is_some() {
    //                         mocker.when::<String, IndexResult<IndexMeta>>("update_primary_key")
    //                             .then(move |_| Ok(IndexMeta{ created_at: OffsetDateTime::now_utc(), updated_at: OffsetDateTime::now_utc(), primary_key: None }));
    //                     }
    //                     mocker.when::<(IndexDocumentsMethod, Option<String>, UpdateFileStore, IntoIter<Uuid>), IndexResult<DocumentAdditionResult>>("update_documents")
    //                             .then(move |(_, _, _, _)| result());
    //                 }
    //                 TaskContent::SettingsUpdate{..} => {
    //                     let result = move || if !index_op_fails {
    //                         Ok(())
    //                     } else {
    //                         // return this error because it's easy to generate...
    //                         Err(IndexError::DocumentNotFound("a doc".into()))
    //                     };
    //                     mocker.when::<&Settings<Checked>, IndexResult<()>>("update_settings")
    //                             .then(move |_| result());
    //                 }
    //                 TaskContent::DocumentDeletion(DocumentDeletion::Ids(_ids)) => {
    //                     let result = move || if !index_op_fails {
    //                         Ok(DocumentDeletionResult { deleted_documents: any_int as u64, remaining_documents: any_int as u64 })
    //                     } else {
    //                         // return this error because it's easy to generate...
    //                         Err(IndexError::DocumentNotFound("a doc".into()))
    //                     };
    //
    //                     mocker.when::<&[String], IndexResult<DocumentDeletionResult>>("delete_documents")
    //                             .then(move |_| result());
    //                 },
    //                 TaskContent::DocumentDeletion(DocumentDeletion::Clear) => {
    //                     let result = move || if !index_op_fails {
    //                         Ok(())
    //                     } else {
    //                         // return this error because it's easy to generate...
    //                         Err(IndexError::DocumentNotFound("a doc".into()))
    //                     };
    //                     mocker.when::<(), IndexResult<()>>("clear_documents")
    //                         .then(move |_| result());
    //                 },
    //                 TaskContent::IndexDeletion => {
    //                     mocker.when::<(), ()>("close")
    //                         .times(index_exists as usize)
    //                         .then(move |_| ());
    //                 }
    //                 TaskContent::IndexUpdate { primary_key }
    //                 | TaskContent::IndexCreation { primary_key } => {
    //                     if primary_key.is_some() {
    //                         let result = move || if !index_op_fails {
    //                             Ok(IndexMeta{ created_at: OffsetDateTime::now_utc(), updated_at: OffsetDateTime::now_utc(), primary_key: None })
    //                         } else {
    //                             // return this error because it's easy to generate...
    //                             Err(IndexError::DocumentNotFound("a doc".into()))
    //                         };
    //                         mocker.when::<String, IndexResult<IndexMeta>>("update_primary_key")
    //                             .then(move |_| result());
    //                         }
    //                 }
    //                 TaskContent::Dump { .. } => { }
    //             }
    //
    //             mocker.when::<(), IndexResult<IndexStats>>("stats")
    //         .then(|()| Ok(IndexStats { size: 0, number_of_documents: 0, is_indexing: Some(false), field_distribution: BTreeMap::new() }));
    //
    //             let index = Index::mock(mocker);
    //
    //             match &task.content {
    //                 // an unexisting index should trigger an index creation in the folllowing cases:
    //                 TaskContent::DocumentAddition { allow_index_creation: true, .. }
    //                 | TaskContent::SettingsUpdate { allow_index_creation: true, is_deletion: false, .. }
    //                 | TaskContent::IndexCreation { .. } if !index_exists => {
    //                     index_store
    //                         .expect_create()
    //                         .once()
    //                         .withf(move |&found| !index_exists || found == uuid)
    //                         .returning(move |_| Box::pin(ok(index.clone())));
    //                 },
    //                 TaskContent::IndexDeletion => {
    //                     index_store
    //                         .expect_delete()
    //                         // this is called only if the index.exists
    //                         .times(index_exists as usize)
    //                         .withf(move |&found| !index_exists || found == uuid)
    //                         .returning(move |_| Box::pin(ok(Some(index.clone()))));
    //                 }
    //                 // if index already exists, create index will return an error
    //                 TaskContent::IndexCreation { .. } if index_exists => (),
    //                 TaskContent::Dump { .. } => (),
    //                 // The index exists and get should be called
    //                 _ if index_exists => {
    //                     index_store
    //                         .expect_get()
    //                         .once()
    //                         .withf(move |&found| found == uuid)
    //                         .returning(move |_| Box::pin(ok(Some(index.clone()))));
    //                 },
    //                 // the index doesn't exist and shouldn't be created, the uuidstore will return an error, and get_index will never be called.
    //                 _ => (),
    //             }
    //
    //             let mut uuid_store = MockIndexMetaStore::new();
    //             uuid_store
    //                 .expect_get()
    //                 .returning(move |uid| {
    //                     Box::pin(ok((uid, index_exists.then(|| crate::index_resolver::meta_store::IndexMeta {uuid, creation_task_id: 0 }))))
    //                 });
    //
    //             // we sould only be creating an index if the index doesn't alredy exist
    //             uuid_store
    //                 .expect_insert()
    //                 .withf(move |_, _| !index_exists)
    //                 .returning(|_, _| Box::pin(ok(())));
    //
    //             uuid_store
    //                 .expect_delete()
    //                 .times(matches!(task.content, TaskContent::IndexDeletion) as usize)
    //                 .returning(move |_| Box::pin(ok(index_exists.then(|| crate::index_resolver::meta_store::IndexMeta { uuid, creation_task_id: 0}))));
    //
    //             let mocker = Mocker::default();
    //             let update_file_store = UpdateFileStore::mock(mocker);
    //             let index_resolver = IndexResolver::new(uuid_store, index_store, update_file_store);
    //
    //             let batch = Batch { id: Some(1), created_at: OffsetDateTime::now_utc(), content: crate::tasks::batch::BatchContent::IndexUpdate(task.clone()) };
    //             if index_resolver.accept(&batch) {
    //                 let result = index_resolver.process_batch(batch).await;
    //
    //                 // Test for some expected output scenarios:
    //                 // Index creation and deletion cannot fail because of a failed index op, since they
    //                 // don't perform index ops.
    //                 if index_op_fails && !matches!(task.content, TaskContent::IndexDeletion | TaskContent::IndexCreation { primary_key: None } | TaskContent::IndexUpdate { primary_key: None } | TaskContent::Dump { .. })
    //                     || (index_exists && matches!(task.content, TaskContent::IndexCreation { .. }))
    //                     || (!index_exists && matches!(task.content, TaskContent::IndexDeletion
    //                                                                 | TaskContent::DocumentDeletion(_)
    //                                                                 | TaskContent::SettingsUpdate { is_deletion: true, ..}
    //                                                                 | TaskContent::SettingsUpdate { allow_index_creation: false, ..}
    //                                                                 | TaskContent::DocumentAddition { allow_index_creation: false, ..}
    //                                                                 | TaskContent::IndexUpdate { .. } ))
    //                 {
    //                     assert!(matches!(result.content.first().unwrap().events.last().unwrap(), TaskEvent::Failed { .. }), "{:?}", result);
    //                 } else {
    //                     assert!(matches!(result.content.first().unwrap().events.last().unwrap(), TaskEvent::Succeeded { .. }), "{:?}", result);
    //                 }
    //             }
    //         });
    //     }
    // }
}