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extern crate caseless;
extern crate slog;

use std::collections::HashSet;
use std::ops::Deref;

pub use config::ConfigBuilder;
pub use provider::{ConfigurationProviderBuilder, DefaultConfigurationProvider};
pub use strings::ConfigKey;
pub use values::Settings;

/// Common trait used by several objects throughout preftool that owns a slog::Logger instance.
pub trait LogOwner {
  fn logger(&self) -> &slog::Logger;
}

/// Configuration trait. Configuration is thread safe, and cloneable.
/// Clones *should* be cheap (default config object consits of cloning an
/// Arc and 3 String instances).
pub trait Configuration: Sized + Send + Sync + Clone {
  /// Type used for configuration sections.
  type Section: ConfigurationSection;

  /// Iterator type used to get child sections.
  type Sections: Iterator<Item = Self::Section>;

  /// Get a value from the configuration, if it exists.
  fn get<K: Into<ConfigKey>>(&self, key: K) -> Option<&str>;

  /// Get a sub-section from the configuration. This always returns a section,
  /// even if it is empty.
  fn get_section<K: Into<ConfigKey>>(&self, key: K) -> Self::Section;

  /// Get all child sections of this configuration, as an iterator.
  fn sections(&self) -> Self::Sections;
}

/// A (sub-)section of configuration. Can be used as normal configuration.
pub trait ConfigurationSection: Configuration {
  /// Get the current section key.
  fn key(&self) -> &ConfigKey;

  /// Get the current section path.
  fn path(&self) -> &ConfigKey;

  /// Get the current section value (if any).
  fn value(&self) -> Option<&str>;
}

/// A configuration provider.
pub trait ConfigurationProvider: Send + Sync {
  /// Try to get a value for a given key.
  fn try_get(&self, key: &ConfigKey) -> Option<&str>;

  /// Get all child keys of a given key.
  fn get_child_keys(&self, key: &ConfigKey, keys: &mut HashSet<ConfigKey>);
}

impl<P: ConfigurationProvider> ConfigurationProvider for Box<P> {
  fn try_get(&self, key: &ConfigKey) -> Option<&str> {
    self.deref().try_get(key)
  }

  fn get_child_keys(&self, key: &ConfigKey, keys: &mut HashSet<ConfigKey>) {
    self.deref().get_child_keys(key, keys)
  }
}

impl ConfigurationProvider for Box<dyn ConfigurationProvider> {
  fn try_get(&self, key: &ConfigKey) -> Option<&str> {
    self.deref().try_get(key)
  }

  fn get_child_keys(&self, key: &ConfigKey, keys: &mut HashSet<ConfigKey>) {
    self.deref().get_child_keys(key, keys)
  }
}

/// A configuration source. Produces one or more configuration providers.
pub trait ConfigurationSource {
  fn build<B: ConfigurationBuilder>(self, builder: B) -> std::io::Result<B>;
}

/// A configuration builder.
pub trait ConfigurationBuilder: Sized {
  /// Resulting configuration type.
  type Config: Configuration;

  // TODO: IntoConfigurationProvider trait?
  /// Add a configuration provider to the builder.
  fn push_provider<P: ConfigurationProvider + 'static>(self, source: P) -> Self;

  /// Add a configuration source to the builder.
  fn add<S: ConfigurationSource>(self, source: S) -> std::io::Result<Self> {
    source.build(self)
  }

  /// Build the configuration.
  fn build(self) -> std::io::Result<Self::Config>;
}

mod config;
mod provider;
mod strings;
mod values;