//! Guessing of MIME types by file extension.
//!
//! Uses a static list of file-extension : MIME type mappings.
//!
//! #### Note: MIME Types Returned Are Not Stable/Guaranteed
//! The media types returned for a given extension are not considered to be part of the crate's
//! stable API and are often updated in patch (#.#.x) releases to be as correct as possible.
//!
//! Additionally, only the extensions of paths/filenames are inspected in order to guess the MIME
//! type. The file that may or may not reside at that path may or may not be a valid file of the
//! returned MIME type.  Be wary of unsafe or un-validated assumptions about file structure or
//! length.
#![cfg_attr(feature = "bench", feature(test))]

extern crate mime;
extern crate phf;
extern crate unicase;

pub use mime::Mime;
use unicase::UniCase;

use std::ffi::OsStr;
use std::path::Path;

include!(concat!(env!("OUT_DIR"), "/mime_types_generated.rs"));

struct TopLevelExts {
    start: usize,
    end: usize,
    subs: phf::Map<UniCase<&'static str>, (usize, usize)>,
}

macro_rules! try_opt (
    ($expr:expr) => (
        match $expr {
            Some(val) => val,
            None => return None,
        }
    )
);

#[cfg(test)]
#[path = "mime_types.rs"]
mod mime_types_src;

/// Guess the MIME type of `path` by its extension (as defined by `Path::extension()`).
///
/// If `path` has no extension, or its extension has no known MIME type mapping,
/// then the MIME type is assumed to be `application/octet-stream`.
///
/// ## Note
/// **Guess** is the operative word here, as there are no guarantees that the contents of the file
/// that `path` points to match the MIME type associated with the path's extension.
///
/// Take care when processing files with assumptions based on the return value of this function.
pub fn guess_mime_type<P: AsRef<Path>>(path: P) -> Mime {
    guess_mime_type_opt(path)
        .unwrap_or_else(octet_stream)
}

/// Guess the MIME type of `path` by its extension (as defined by `Path::extension()`).
///
/// If `path` has no extension, or its extension has no known MIME type mapping,
/// then `None` is returned.
///
/// ## Note
/// **Guess** is the operative word here, as there are no guarantees that the contents of the file
/// that `path` points to match the MIME type associated with the path's extension.
///
/// Take care when processing files with assumptions based on the return value of this function.
pub fn guess_mime_type_opt<P: AsRef<Path>>(path: P) -> Option<Mime> {
    let ext = path.as_ref().extension().and_then(OsStr::to_str).unwrap_or("");

    get_mime_type_opt(ext)
}

/// Get the MIME type associated with a file extension.
///
/// If there is no association for the extension, or `ext` is empty,
/// `application/octet-stream` is returned.
pub fn get_mime_type(search_ext: &str) -> Mime {
    get_mime_type_opt(search_ext)
        .unwrap_or_else(octet_stream)
}

/// Get the MIME type associated with a file extension.
///
/// If there is no association for the extension, or `ext` is empty,
/// `None` is returned.
pub fn get_mime_type_opt(search_ext: &str) -> Option<Mime> {
    get_mime_type_str(search_ext)
        .map(|mime| mime.parse::<Mime>().unwrap())
}

/// Get the MIME type string associated with a file extension. Case-insensitive.
///
/// If `search_ext` is not already lowercase,
/// it will be converted to lowercase to facilitate the search.
///
/// Returns `None` if `search_ext` is empty or an associated extension was not found.
pub fn get_mime_type_str(search_ext: &str) -> Option<&'static str> {
    if search_ext.is_empty() { return None; }

    map_lookup(&MIME_TYPES, search_ext).cloned()
}

/// Get a list of known extensions for a given `Mime`. 
///
/// Ignores parameters (only searches with `<main type>/<subtype>`). Case-insensitive (for extension types).
///
/// Returns `None` if the MIME type is unknown. 
///
/// ### Wildcards
/// If the top-level of the MIME type is a wildcard (`*`), returns all extensions.
///
/// If the sub-level of the MIME type is a wildcard, returns all extensions for the top-level.
pub fn get_mime_extensions(mime: &Mime) -> Option<&'static [&'static str]> {    
    get_extensions(&mime.0, &mime.1)
}

/// Get a list of known extensions for a MIME type string. 
///
/// Ignores parameters (only searches `<main type>/<subtype>`). Case-insensitive.
///
/// Returns `None` if the MIME type is unknown.
/// 
/// ### Wildcards
/// If the top-level of the MIME type is a wildcard (`*`), returns all extensions.
///
/// If the sub-level of the MIME type is a wildcard, returns all extensions for the top-level.
///
/// ### Panics
/// If `mime_str` is not a valid MIME type specifier (naive).
pub fn get_mime_extensions_str(mut mime_str: &str) -> Option<&'static [&'static str]> {
    mime_str = mime_str.trim();

    if let Some(sep_idx) = mime_str.find(';') {
        mime_str = &mime_str[..sep_idx];
    }

    let (top, sub) = {
        let split_idx = mime_str.find('/').unwrap();
        (&mime_str[..split_idx], &mime_str[split_idx + 1 ..])
    };

    get_extensions(top, sub)
}

/// Get the extensions for a given top-level and sub-level of a MIME type
/// (`{toplevel}/{sublevel}`).
///
/// Returns `None` if `toplevel` or `sublevel` are unknown.
///
/// ### Wildcards
/// If the top-level of the MIME type is a wildcard (`*`), returns all extensions.
///
/// If the sub-level of the MIME type is a wildcard, returns all extensions for the top-level.
pub fn get_extensions(toplevel: &str, sublevel: &str) -> Option<&'static [&'static str]> {
    if toplevel == "*" {
        return Some(EXTS);
    } 
    
    let top = try_opt!(map_lookup(&REV_MAPPINGS, toplevel));

    if sublevel == "*" {
        return Some(&EXTS[top.start .. top.end]);
    } 
    
    let sub = try_opt!(map_lookup(&top.subs, sublevel));
    Some(&EXTS[sub.0 .. sub.1])
}

/// Get the MIME type for `application/octet-stream` (generic binary stream)
pub fn octet_stream() -> Mime {
    "application/octet-stream".parse().unwrap()    
}

fn map_lookup<'map, V>(map: &'map phf::Map<UniCase<&'static str>, V>, key: &str) -> Option<&'map V> {
    // This transmute should be safe as `get` will not store the reference with
    // the expanded lifetime. This is due to `Borrow` being overly strict and
    // can't have an impl for `&'static str` to `Borrow<&'a str>`.
    //
    // See https://github.com/rust-lang/rust/issues/28853#issuecomment-158735548
    let key = unsafe { ::std::mem::transmute::<_, &'static str>(key) };
    map.get(&UniCase(key))
}

#[cfg(test)]
mod tests {
    use mime::Mime;
    #[allow(deprecated, unused_imports)]
    use std::ascii::AsciiExt;
    use std::path::Path;
    use super::{get_mime_type, guess_mime_type, MIME_TYPES};
    use super::{get_mime_type_opt, guess_mime_type_opt};

    #[test]
    fn test_mime_type_guessing() {
        assert_eq!(get_mime_type("gif").to_string(), "image/gif".to_string());
        assert_eq!(get_mime_type("TXT").to_string(), "text/plain".to_string());
        assert_eq!(get_mime_type("blahblah").to_string(), "application/octet-stream".to_string());

        assert_eq!(guess_mime_type(Path::new("/path/to/file.gif")).to_string(), "image/gif".to_string());
        assert_eq!(guess_mime_type("/path/to/file.gif").to_string(), "image/gif".to_string());
    }

    #[test]
    fn test_mime_type_guessing_opt() {
        assert_eq!(get_mime_type_opt("gif").unwrap().to_string(), "image/gif".to_string());
        assert_eq!(get_mime_type_opt("TXT").unwrap().to_string(), "text/plain".to_string());
        assert_eq!(get_mime_type_opt("blahblah"), None);

        assert_eq!(guess_mime_type_opt("/path/to/file.gif").unwrap().to_string(), "image/gif".to_string());
        assert_eq!(guess_mime_type_opt("/path/to/file"), None);
    }

    #[test]
    fn test_are_mime_types_parseable() {
        for (_, mime) in &MIME_TYPES {
            mime.parse::<Mime>().unwrap();
        }
    }

    // RFC: Is this test necessary anymore? --@cybergeek94, 2/1/2016
    #[test]
    fn test_are_extensions_ascii() {
        for (ext, _) in &MIME_TYPES {
            assert!(ext.is_ascii(), "Extension not ASCII: {:?}", ext);
        }
    }

    #[test]
    fn test_are_extensions_sorted() {
        use mime_types_src::MIME_TYPES;

        for (&(ext, _), &(n_ext, _)) in MIME_TYPES.iter().zip(MIME_TYPES.iter().skip(1)) {
            assert!(
                ext <= n_ext,
                "Extensions in src/mime_types should be sorted alphabetically
                in ascending order. Failed assert: {:?} <= {:?}",
                ext, n_ext
            );
        }
    }

}

#[cfg(feature = "bench")]
mod bench {
    extern crate test;

    use self::test::Bencher;

    use super::{get_mime_type_str, MIME_TYPES};

    /// WARNING: this may take a while!
    #[bench]
    fn bench_mime_str(b: &mut Bencher) {
        for (mime_ext, _) in &MIME_TYPES {
            b.iter(|| {
                get_mime_type_str(mime_ext).expect(mime_ext);
            });
        }
    }

    #[bench]
    fn bench_mime_str_uppercase(b: &mut Bencher) {
        let uppercased : Vec<_> = MIME_TYPES.into_iter().map(|(s, _)| s.to_uppercase()).collect();

        for mime_ext in &uppercased {
            b.iter(|| {
                get_mime_type_str(mime_ext).expect(mime_ext);
            });
        }
    }
}