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/*******************************************************************************
*
* Copyright (c) 2026 Haixing Hu.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0.
*
******************************************************************************/
//! Provider contract for pluggable MIME detector implementations.
//!
//! A provider gives the registry a stable name, optional aliases, availability
//! checks, and a factory method for creating one detector instance. This keeps
//! detector selection independent from the concrete detector type, so
//! applications can register their own backend without changing
//! [`BoxMimeDetector`](crate::BoxMimeDetector) or
//! [`ArcMimeDetector`](crate::ArcMimeDetector).
use Debug;
use crate::;
use MimeDetectorAvailability;
/// Factory contract for MIME detector implementations.
///
/// Provider ids and aliases are matched case-insensitively by
/// [`MimeDetectorRegistry`](crate::MimeDetectorRegistry). Returning
/// [`MimeDetectorAvailability::Unavailable`] lets a provider participate in
/// fallback selection without failing the whole registry when an optional
/// backend, such as an external command, is not installed.
///
/// # Examples
///
/// Register a custom provider and create it by alias:
///
/// ```rust
/// use std::path::Path;
///
/// use qubit_io::ReadSeek;
/// use qubit_mime::{
/// MimeConfig,
/// MimeDetectionPolicy,
/// MimeDetector,
/// MimeDetectorProvider,
/// MimeDetectorRegistry,
/// MimeResult,
/// };
///
/// #[derive(Debug)]
/// struct StaticDetector;
///
/// impl MimeDetector for StaticDetector {
/// fn detect_by_filename(&self, filename: &str) -> Option<String> {
/// filename
/// .ends_with(".static")
/// .then(|| "application/x-static".to_owned())
/// }
///
/// fn detect_by_content(&self, _content: &[u8]) -> Option<String> {
/// None
/// }
///
/// fn detect(
/// &self,
/// _content: &[u8],
/// filename: Option<&str>,
/// _policy: MimeDetectionPolicy,
/// ) -> Option<String> {
/// filename.and_then(|name| self.detect_by_filename(name))
/// }
///
/// fn detect_reader(
/// &self,
/// _reader: &mut dyn ReadSeek,
/// filename: Option<&str>,
/// policy: MimeDetectionPolicy,
/// ) -> MimeResult<Option<String>> {
/// Ok(self.detect(&[], filename, policy))
/// }
///
/// fn detect_file(
/// &self,
/// file: &Path,
/// policy: MimeDetectionPolicy,
/// ) -> MimeResult<Option<String>> {
/// Ok(self.detect(
/// &[],
/// file.file_name().and_then(|name| name.to_str()),
/// policy,
/// ))
/// }
/// }
///
/// #[derive(Debug)]
/// struct StaticProvider;
///
/// impl MimeDetectorProvider for StaticProvider {
/// fn id(&self) -> &'static str {
/// "static"
/// }
///
/// fn aliases(&self) -> &'static [&'static str] {
/// &["static-detector"]
/// }
///
/// fn create(&self, _config: &MimeConfig) -> MimeResult<Box<dyn MimeDetector>> {
/// Ok(Box::new(StaticDetector))
/// }
/// }
///
/// # fn main() -> MimeResult<()> {
/// let mut registry = MimeDetectorRegistry::new();
/// registry.register(StaticProvider)?;
///
/// let detector = registry.create("static-detector", &MimeConfig::default())?;
/// assert_eq!(
/// Some("application/x-static".to_owned()),
/// detector.detect_by_filename("sample.static"),
/// );
/// # Ok(())
/// # }
/// ```