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    mod format;
    pub mod source;

    use std::fmt::Debug;
    use std::path::{Path, PathBuf};

    use crate::error::{ConfigError, Result};
    use crate::map::Map;
    use crate::source::Source;
    use crate::value::Value;
    use crate::Format;

    pub use self::format::FileFormat;
    use self::source::FileSource;

    pub use self::source::file::FileSourceFile;
    pub use self::source::string::FileSourceString;

    /// A configuration source backed up by a file.
    ///
    /// It supports optional automatic file format discovery.
    #[derive(Clone, Debug)]
    pub struct File<T, F> {
        source: T,

        /// Format of file (which dictates what driver to use).
        format: Option<F>,

        /// A required File will error if it cannot be found
        required: bool,
    }

    /// An extension of [`Format`](crate::Format) trait.
    ///
    /// Associates format with file extensions, therefore linking storage-agnostic notion of format to a file system.
    pub trait FileStoredFormat: Format {
        /// Returns a vector of file extensions, for instance `[yml, yaml]`.
        fn file_extensions(&self) -> &'static [&'static str];
    }

    impl<F> File<source::string::FileSourceString, F>
    where
        F: FileStoredFormat + 'static,
    {
        pub fn from_str(s: &str, format: F) -> Self {
            Self {
                format: Some(format),
                required: true,
                source: s.into(),
            }
        }
    }

    impl<F> File<source::file::FileSourceFile, F>
    where
        F: FileStoredFormat + 'static,
    {
        pub fn new(name: &str, format: F) -> Self {
            Self {
                format: Some(format),
                required: true,
                source: source::file::FileSourceFile::new(name.into()),
            }
        }
    }

    impl File<source::file::FileSourceFile, FileFormat> {
        /// Given the basename of a file, will attempt to locate a file by setting its
        /// extension to a registered format.
        pub fn with_name(name: &str) -> Self {
            Self {
                format: None,
                required: true,
                source: source::file::FileSourceFile::new(name.into()),
            }
        }
    }

    impl<'a> From<&'a Path> for File<source::file::FileSourceFile, FileFormat> {
        fn from(path: &'a Path) -> Self {
            Self {
                format: None,
                required: true,
                source: source::file::FileSourceFile::new(path.to_path_buf()),
            }
        }
    }

    impl From<PathBuf> for File<source::file::FileSourceFile, FileFormat> {
        fn from(path: PathBuf) -> Self {
            Self {
                format: None,
                required: true,
                source: source::file::FileSourceFile::new(path),
            }
        }
    }

    impl<T, F> File<T, F>
    where
        F: FileStoredFormat + 'static,
        T: FileSource<F>,
    {
        #[must_use]
        pub fn format(mut self, format: F) -> Self {
            self.format = Some(format);
            self
        }

        #[must_use]
        pub fn required(mut self, required: bool) -> Self {
            self.required = required;
            self
        }
    }

    impl<T, F> Source for File<T, F>
    where
        F: FileStoredFormat + Debug + Clone + Send + Sync + 'static,
        T: Sync + Send + FileSource<F> + 'static,
    {
        fn clone_into_box(&self) -> Box<dyn Source + Send + Sync> {
            Box::new((*self).clone())
        }

        fn collect(&self) -> Result<Map<String, Value>> {
            // Coerce the file contents to a string
            let (uri, contents, format) = match self
                .source
                .resolve(self.format.clone())
                .map_err(|err| ConfigError::Foreign(err))
            {
                Ok(result) => (result.uri, result.content, result.format),

                Err(error) => {
                    if !self.required {
                        return Ok(Map::new());
                    }

                    return Err(error);
                }
            };

            // Parse the string using the given format
            format
                .parse(uri.as_ref(), &contents)
                .map_err(|cause| ConfigError::FileParse { uri, cause })
        }
    }