#![cfg(target_os = "macos")]

use bitflags::bitflags;
use fsevent_sys::{self as fs, core_foundation as cf};
use std::{
    convert::AsRef,
    ffi::{c_void, CStr, OsStr},
    os::unix::ffi::OsStrExt,
    path::{Path, PathBuf},
    slice,
    time::Duration,
};

#[derive(Clone, Debug)]
pub struct Event {
    pub event_id: u64,
    pub flags: StreamFlags,
    pub path: PathBuf,
}

pub struct EventStream<F> {
    stream: fs::FSEventStreamRef,
    _callback: Box<F>,
}

unsafe impl<F> Send for EventStream<F> {}

impl<F> EventStream<F>
where
    F: FnMut(&[Event]) -> bool,
{
    pub fn new(paths: &[&Path], latency: Duration, callback: F) -> Self {
        unsafe {
            let callback = Box::new(callback);
            let stream_context = fs::FSEventStreamContext {
                version: 0,
                info: callback.as_ref() as *const _ as *mut c_void,
                retain: None,
                release: None,
                copy_description: None,
            };

            let cf_paths =
                cf::CFArrayCreateMutable(cf::kCFAllocatorDefault, 0, &cf::kCFTypeArrayCallBacks);
            assert!(!cf_paths.is_null());

            for path in paths {
                let path_bytes = path.as_os_str().as_bytes();
                let cf_url = cf::CFURLCreateFromFileSystemRepresentation(
                    cf::kCFAllocatorDefault,
                    path_bytes.as_ptr() as *const i8,
                    path_bytes.len() as cf::CFIndex,
                    false,
                );
                let cf_path = cf::CFURLCopyFileSystemPath(cf_url, cf::kCFURLPOSIXPathStyle);
                cf::CFArrayAppendValue(cf_paths, cf_path);
                cf::CFRelease(cf_path);
                cf::CFRelease(cf_url);
            }

            let stream = fs::FSEventStreamCreate(
                cf::kCFAllocatorDefault,
                Self::trampoline,
                &stream_context,
                cf_paths,
                fs::kFSEventStreamEventIdSinceNow,
                latency.as_secs_f64(),
                fs::kFSEventStreamCreateFlagFileEvents
                    | fs::kFSEventStreamCreateFlagNoDefer
                    | fs::kFSEventStreamCreateFlagWatchRoot,
            );
            cf::CFRelease(cf_paths);

            EventStream {
                stream,
                _callback: callback,
            }
        }
    }

    pub fn run(self) {
        unsafe {
            fs::FSEventStreamScheduleWithRunLoop(
                self.stream,
                cf::CFRunLoopGetCurrent(),
                cf::kCFRunLoopDefaultMode,
            );

            fs::FSEventStreamStart(self.stream);
            cf::CFRunLoopRun();

            fs::FSEventStreamFlushSync(self.stream);
            fs::FSEventStreamStop(self.stream);
            fs::FSEventStreamRelease(self.stream);
        }
    }

    extern "C" fn trampoline(
        stream_ref: fs::FSEventStreamRef,
        info: *mut ::std::os::raw::c_void,
        num: usize,                                 // size_t numEvents
        event_paths: *mut ::std::os::raw::c_void,   // void *eventPaths
        event_flags: *const ::std::os::raw::c_void, // const FSEventStreamEventFlags eventFlags[]
        event_ids: *const ::std::os::raw::c_void,   // const FSEventStreamEventId eventIds[]
    ) {
        unsafe {
            let event_paths = event_paths as *const *const ::std::os::raw::c_char;
            let e_ptr = event_flags as *mut u32;
            let i_ptr = event_ids as *mut u64;
            let callback = (info as *mut F).as_mut().unwrap();

            let paths = slice::from_raw_parts(event_paths, num);
            let flags = slice::from_raw_parts_mut(e_ptr, num);
            let ids = slice::from_raw_parts_mut(i_ptr, num);

            let mut events = Vec::with_capacity(num);
            for p in 0..num {
                let path_c_str = CStr::from_ptr(paths[p]);
                let path = PathBuf::from(OsStr::from_bytes(path_c_str.to_bytes()));
                if let Some(flag) = StreamFlags::from_bits(flags[p]) {
                    events.push(Event {
                        event_id: ids[p],
                        flags: flag,
                        path,
                    });
                } else {
                    debug_assert!(false, "unknown flag set for fs event: {}", flags[p]);
                }
            }

            if !callback(&events) {
                fs::FSEventStreamStop(stream_ref);
                cf::CFRunLoopStop(cf::CFRunLoopGetCurrent());
            }
        }
    }
}

// Synchronize with
// /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/FSEvents.framework/Versions/A/Headers/FSEvents.h
bitflags! {
  #[repr(C)]
  pub struct StreamFlags: u32 {
    const NONE = 0x00000000;
    const MUST_SCAN_SUBDIRS = 0x00000001;
    const USER_DROPPED = 0x00000002;
    const KERNEL_DROPPED = 0x00000004;
    const IDS_WRAPPED = 0x00000008;
    const HISTORY_DONE = 0x00000010;
    const ROOT_CHANGED = 0x00000020;
    const MOUNT = 0x00000040;
    const UNMOUNT = 0x00000080;
    const ITEM_CREATED = 0x00000100;
    const ITEM_REMOVED = 0x00000200;
    const INODE_META_MOD = 0x00000400;
    const ITEM_RENAMED = 0x00000800;
    const ITEM_MODIFIED = 0x00001000;
    const FINDER_INFO_MOD = 0x00002000;
    const ITEM_CHANGE_OWNER = 0x00004000;
    const ITEM_XATTR_MOD = 0x00008000;
    const IS_FILE = 0x00010000;
    const IS_DIR = 0x00020000;
    const IS_SYMLINK = 0x00040000;
    const OWN_EVENT = 0x00080000;
    const IS_HARDLINK = 0x00100000;
    const IS_LAST_HARDLINK = 0x00200000;
    const ITEM_CLONED = 0x400000;
  }
}

impl std::fmt::Display for StreamFlags {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        if self.contains(StreamFlags::MUST_SCAN_SUBDIRS) {
            let _d = write!(f, "MUST_SCAN_SUBDIRS ");
        }
        if self.contains(StreamFlags::USER_DROPPED) {
            let _d = write!(f, "USER_DROPPED ");
        }
        if self.contains(StreamFlags::KERNEL_DROPPED) {
            let _d = write!(f, "KERNEL_DROPPED ");
        }
        if self.contains(StreamFlags::IDS_WRAPPED) {
            let _d = write!(f, "IDS_WRAPPED ");
        }
        if self.contains(StreamFlags::HISTORY_DONE) {
            let _d = write!(f, "HISTORY_DONE ");
        }
        if self.contains(StreamFlags::ROOT_CHANGED) {
            let _d = write!(f, "ROOT_CHANGED ");
        }
        if self.contains(StreamFlags::MOUNT) {
            let _d = write!(f, "MOUNT ");
        }
        if self.contains(StreamFlags::UNMOUNT) {
            let _d = write!(f, "UNMOUNT ");
        }
        if self.contains(StreamFlags::ITEM_CREATED) {
            let _d = write!(f, "ITEM_CREATED ");
        }
        if self.contains(StreamFlags::ITEM_REMOVED) {
            let _d = write!(f, "ITEM_REMOVED ");
        }
        if self.contains(StreamFlags::INODE_META_MOD) {
            let _d = write!(f, "INODE_META_MOD ");
        }
        if self.contains(StreamFlags::ITEM_RENAMED) {
            let _d = write!(f, "ITEM_RENAMED ");
        }
        if self.contains(StreamFlags::ITEM_MODIFIED) {
            let _d = write!(f, "ITEM_MODIFIED ");
        }
        if self.contains(StreamFlags::FINDER_INFO_MOD) {
            let _d = write!(f, "FINDER_INFO_MOD ");
        }
        if self.contains(StreamFlags::ITEM_CHANGE_OWNER) {
            let _d = write!(f, "ITEM_CHANGE_OWNER ");
        }
        if self.contains(StreamFlags::ITEM_XATTR_MOD) {
            let _d = write!(f, "ITEM_XATTR_MOD ");
        }
        if self.contains(StreamFlags::IS_FILE) {
            let _d = write!(f, "IS_FILE ");
        }
        if self.contains(StreamFlags::IS_DIR) {
            let _d = write!(f, "IS_DIR ");
        }
        if self.contains(StreamFlags::IS_SYMLINK) {
            let _d = write!(f, "IS_SYMLINK ");
        }
        if self.contains(StreamFlags::OWN_EVENT) {
            let _d = write!(f, "OWN_EVENT ");
        }
        if self.contains(StreamFlags::IS_LAST_HARDLINK) {
            let _d = write!(f, "IS_LAST_HARDLINK ");
        }
        if self.contains(StreamFlags::IS_HARDLINK) {
            let _d = write!(f, "IS_HARDLINK ");
        }
        if self.contains(StreamFlags::ITEM_CLONED) {
            let _d = write!(f, "ITEM_CLONED ");
        }
        write!(f, "")
    }
}

#[test]
fn test_event_stream() {
    use std::{fs, sync::mpsc, time::Duration};
    use tempdir::TempDir;

    let dir = TempDir::new("test_observe").unwrap();
    let path = dir.path().canonicalize().unwrap();
    fs::write(path.join("a"), "a contents").unwrap();

    let (tx, rx) = mpsc::channel();
    let stream = EventStream::new(&[&path], Duration::from_millis(50), move |events| {
        tx.send(events.to_vec()).is_ok()
    });
    std::thread::spawn(move || stream.run());

    fs::write(path.join("b"), "b contents").unwrap();
    let events = rx.recv_timeout(Duration::from_millis(500)).unwrap();
    let event = events.last().unwrap();
    assert_eq!(event.path, path.join("b"));
    assert!(event.flags.contains(StreamFlags::ITEM_CREATED));

    fs::remove_file(path.join("a")).unwrap();
    let events = rx.recv_timeout(Duration::from_millis(500)).unwrap();
    let event = events.last().unwrap();
    assert_eq!(event.path, path.join("a"));
    assert!(event.flags.contains(StreamFlags::ITEM_REMOVED));
}