use std::{

    collections::HashMap,

    path::{Path, PathBuf},

    time::Duration,

};

#[cfg(feature = "encryption")]

use bonsaidb_core::document::KeyId;

use bonsaidb_core::schema::{Schema, SchemaName};

use sysinfo::{RefreshKind, System, SystemExt};

#[cfg(feature = "encryption")]

use crate::vault::AnyVaultKeyStorage;

use crate::{

    storage::{DatabaseOpener, StorageSchemaOpener},

    Error,

};

#[cfg(feature = "password-hashing")]

mod argon;

#[cfg(feature = "password-hashing")]

pub use argon::*;

/// Configuration options for [`Storage`](crate::storage::Storage).

#[non_exhaustive]

pub struct StorageConfiguration {

    /// The path to the database. Defaults to `db.bonsaidb` if not specified.

    pub path: Option<PathBuf>,

    /// The unique id of the server. If not specified, the server will randomly

    /// generate a unique id on startup. If the server generated an id and this

    /// value is subsequently set, the generated id will be overridden by the

    /// one specified here.

    pub unique_id: Option<u64>,

    /// The vault key storage to use. If not specified,

    /// [`LocalVaultKeyStorage`](crate::vault::LocalVaultKeyStorage) will be

    /// used with the server's data folder as the path. This is **incredibly

    /// insecure and should not be used outside of testing**.

    ///

    /// For secure encryption, it is important to store the vault keys in a

    /// location that is separate from the database. If the keys are on the same

    /// hardware as the encrypted content, anyone with access to the disk will

    /// be able to decrypt the stored data.

    #[cfg(feature = "encryption")]

    pub vault_key_storage: Option<Box<dyn AnyVaultKeyStorage>>,

    /// The default encryption key for the database. If specified, all documents

    /// will be stored encrypted at-rest using the key specified. Having this

    /// key specified will also encrypt views. Without this, views will be

    /// stored unencrypted.

    #[cfg(feature = "encryption")]

    pub default_encryption_key: Option<KeyId>,

    /// Configuration options related to background tasks.

    pub workers: Tasks,

    /// Configuration options related to views.

    pub views: Views,

    /// Controls how the key-value store persists keys, on a per-database basis.

    pub key_value_persistence: KeyValuePersistence,

    /// Password hashing configuration.

    #[cfg(feature = "password-hashing")]

    pub argon: ArgonConfiguration,

    pub(crate) initial_schemas: HashMap<SchemaName, Box<dyn DatabaseOpener>>,

}

impl Default for StorageConfiguration {

}

impl StorageConfiguration {

    /// Registers the schema provided.

    pub fn register_schema<S: Schema>(&mut self) -> Result<(), Error> {

        self.initial_schemas

}

/// Configuration options for background tasks.

pub struct Tasks {

    /// Defines how many workers should be spawned to process tasks. This

    /// defaults to the 2x the number of cpu cores available to the system or 4, whichever is larger.

    pub worker_count: usize,

}

impl SystemDefault for Tasks {

}

/// Configuration options for views.

pub struct Views {

    /// If true, the database will scan all views during the call to

    /// `open_local`. This will cause database opening to take longer, but once

    /// the database is open, no request will need to wait for the integrity to

    /// be checked. However, for faster startup time, you may wish to delay the

    /// integrity scan. Default value is `false`.

    pub check_integrity_on_open: bool,

}

/// Rules for persisting key-value changes. Default persistence is to

/// immediately persist all changes. While this ensures data integrity, the

/// overhead of the key-value store can be significantly reduced by utilizing

/// lazy persistence strategies that delay writing changes until certain

/// thresholds have been met.

///

/// ## Immediate persistence

///

/// The default persistence mode will trigger commits always:

///

/// ```rust

/// # use bonsaidb_local::config::KeyValuePersistence;

/// # use std::time::Duration;

/// assert!(!KeyValuePersistence::default().should_commit(0, Duration::ZERO));

/// assert!(KeyValuePersistence::default().should_commit(1, Duration::ZERO));

/// ```

///

/// ## Lazy persistence

///

/// Lazy persistence allows setting multiple thresholds, allowing for customized

/// behavior that can help tune performance, especially under write-heavy loads.

///

/// It is good practice to include one [`PersistenceThreshold`] that has no

/// duration, as it will ensure that the in-memory cache cannot exceed a certain

/// size. This number is counted for each database indepenently.

///

/// ```rust

/// # use bonsaidb_local::config::{KeyValuePersistence, PersistenceThreshold};

/// # use std::time::Duration;

/// #

/// let persistence = KeyValuePersistence::lazy([

///     PersistenceThreshold::after_changes(1).and_duration(Duration::from_secs(120)),

///     PersistenceThreshold::after_changes(10).and_duration(Duration::from_secs(10)),

///     PersistenceThreshold::after_changes(100),

/// ]);

///

/// // After 1 change and 60 seconds, no changes would be committed:

/// assert!(!persistence.should_commit(1, Duration::from_secs(60)));

/// // But on or after 120 seconds, that change will be committed:

/// assert!(persistence.should_commit(1, Duration::from_secs(120)));

///

/// // After 10 changes and 10 seconds, changes will be committed:

/// assert!(persistence.should_commit(10, Duration::from_secs(10)));

///

/// // Once 100 changes have been accumulated, this ruleset will always commit

/// // regardless of duration.

/// assert!(persistence.should_commit(100, Duration::ZERO));

/// ```

#[must_use]

pub struct KeyValuePersistence(KeyValuePersistenceInner);

enum KeyValuePersistenceInner {

    Immediate,

    Lazy(Vec<PersistenceThreshold>),

}

impl Default for KeyValuePersistence {

    /// Returns [`KeyValuePersistence::immediate()`].

}

impl KeyValuePersistence {

    /// Returns a ruleset that commits all changes immediately.

    /// Returns a ruleset that lazily commits data based on a list of thresholds.

    /// Returns true if these rules determine that the outstanding changes should be persisted.

    #[must_use]

        } else {

                    {

                    }

                }

            }

        }

}

/// A threshold controlling lazy commits. For a threshold to apply, both

/// `number_of_changes` must be met or surpassed and `duration` must have

/// elpased since the last commit.

///

/// A threshold with a duration of zero will not wait any time to persist

/// changes once the specified `number_of_changes` has been met or surpassed.

#[must_use]

pub struct PersistenceThreshold {

    /// The minimum number of changes that must have occurred for this threshold to apply.

    pub number_of_changes: usize,

    /// The amount of time that must elapse since the last write for this threshold to apply.

    pub duration: Duration,

}

impl PersistenceThreshold {

    /// Returns a threshold that applies after a number of changes have elapsed.

    /// Sets the duration of this threshold to `duration` and returns self.

}

/// Storage configuration builder methods.

pub trait Builder: Default {

    /// Creates a default configuration with `path` set.

    /// Registers the schema and returns self.

    fn with_schema<S: Schema>(self) -> Result<Self, Error>;

    /// Sets [`StorageConfiguration::path`](StorageConfiguration#structfield.path) to `path` and returns self.

    fn path<P: AsRef<Path>>(self, path: P) -> Self;

    /// Sets [`StorageConfiguration::unique_id`](StorageConfiguration#structfield.unique_id) to `unique_id` and returns self.

    fn unique_id(self, unique_id: u64) -> Self;

    /// Sets [`StorageConfiguration::vault_key_storage`](StorageConfiguration#structfield.vault_key_storage) to `key_storage` and returns self.

    #[cfg(feature = "encryption")]

    fn vault_key_storage<VaultKeyStorage: AnyVaultKeyStorage>(

        self,

        key_storage: VaultKeyStorage,

    ) -> Self;

    /// Sets [`StorageConfiguration::default_encryption_key`](StorageConfiguration#structfield.default_encryption_key) to `path` and returns self.

    #[cfg(feature = "encryption")]

    fn default_encryption_key(self, key: KeyId) -> Self;

    /// Sets [`Tasks::worker_count`] to `worker_count` and returns self.

    fn tasks_worker_count(self, worker_count: usize) -> Self;

    /// Sets [`Views::check_integrity_on_open`] to `check` and returns self.

    fn check_view_integrity_on_open(self, check: bool) -> Self;

    /// Sets [`StorageConfiguration::key_value_persistence`](StorageConfiguration#structfield.key_value_persistence) to `persistence` and returns self.

    fn key_value_persistence(self, persistence: KeyValuePersistence) -> Self;

}

impl Builder for StorageConfiguration {

    fn with_schema<S: Schema>(mut self) -> Result<Self, Error> {

    #[cfg(feature = "encryption")]

    #[cfg(feature = "encryption")]

}

pub(crate) trait SystemDefault: Sized {

    fn default_for(system: &System) -> Self;

}