//! How to use from C
//!
//! ```c
//! gifski *g = gifski_new(&(GifskiSettings){});
//! gifski_set_file_output(g, "file.gif");
//!
//! for(int i=0; i < frames; i++) {
//!      int res = gifski_add_frame_rgba(g, i, width, height, buffer, 5);
//!      if (res != GIFSKI_OK) break;
//! }
//! int res = gifski_finish(g);
//! if (res != GIFSKI_OK) return;
//! ```
//!
//! It's safe and efficient to call `gifski_add_frame_*` in a loop as fast as you can get frames,
//! because it blocks and waits until previous frames are written.

use super::*;
use std::os::raw::{c_char, c_int, c_void};
use std::ptr;
use std::mem;
use std::slice;
use std::thread;
use std::fs;
use std::io;
use std::sync::Arc;
use std::sync::Mutex;
use std::fs::File;
use std::ffi::CStr;
use std::path::{PathBuf, Path};
mod c_api_error;
use self::c_api_error::*;

/// Settings for creating a new encoder instance. See `gifski_new`
#[repr(C)]
#[derive(Copy, Clone)]
pub struct GifskiSettings {
    /// Resize to max this width if non-0
    pub width: u32,
    /// Resize to max this height if width is non-0. Note that aspect ratio is not preserved.
    pub height: u32,
    /// 1-100, but useful range is 50-100. Recommended to set to 100.
    pub quality: u8,
    /// If true, looping is disabled. Recommended false (looping on).
    pub once: bool,
    /// Lower quality, but faster encode.
    pub fast: bool,
}

#[repr(C)]
#[derive(Copy, Clone)]
pub struct ARGB8 {
    pub a: u8,
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

/// Opaque handle used in methods. Note that the handle pointer is actually `Arc<GifskiHandleInternal>`,
/// but `Arc::into_raw` is nice enough to point past the counter.
#[repr(C)]
pub struct GifskiHandle {
    _opaque: usize,
}
pub struct GifskiHandleInternal {
    writer: Mutex<Option<Writer>>,
    collector: Mutex<Option<Collector>>,
    progress: Mutex<Option<ProgressCallback>>,
    /// Bool set to true when the thread has been set up,
    /// prevents re-setting of the thread after finish()
    write_thread: Mutex<(bool, Option<thread::JoinHandle<GifskiError>>)>,
}

/// Call to start the process
///
/// See `gifski_add_frame_png_file` and `gifski_end_adding_frames`
#[no_mangle]
pub unsafe extern "C" fn gifski_new(settings: *const GifskiSettings) -> *const GifskiHandle {
    let settings = if let Some(s) = settings.as_ref() {s} else {
        return ptr::null_mut();
    };
    let s = Settings {
        width: if settings.width > 0 { Some(settings.width) } else { None },
        height: if settings.height > 0 { Some(settings.height) } else { None },
        quality: settings.quality,
        once: settings.once,
        fast: settings.fast,
    };

    if let Ok((collector, writer)) = new(s) {
        Arc::into_raw(Arc::new(GifskiHandleInternal {
            writer: Mutex::new(Some(writer)),
            write_thread: Mutex::new((false, None)),
            collector: Mutex::new(Some(collector)),
            progress: Mutex::new(None),
        })) as *const GifskiHandle
    } else {
        ptr::null_mut()
    }
}

/// File path must be valid UTF-8. This function is asynchronous.
///
/// Delay is in 1/100ths of a second.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_add_frame_png_file(handle: *const GifskiHandle, index: u32, file_path: *const c_char, delay: u16) -> GifskiError {
    if file_path.is_null() {
        return GifskiError::NULL_ARG;
    }
    let g = match borrow(handle) {
        Some(g) => g,
        None => return GifskiError::NULL_ARG,
    };
    let path = if let Ok(s) = CStr::from_ptr(file_path).to_str() {
        PathBuf::from(s)
    } else {
        return GifskiError::INVALID_INPUT;
    };
    if let Some(ref mut c) = *g.collector.lock().unwrap() {
        c.add_frame_png_file(index as usize, path, delay).into()
    } else {
        eprintln!("frames can't be added any more, because gifski_end_adding_frames has been called already");
        GifskiError::INVALID_STATE
    }
}

/// Pixels is an array width×height×4 bytes large. The array is copied, so you can free/reuse it immediately.
///
/// Delay is in 1/100ths of a second.
///
/// While you add frames, `gifski_set_file_output()` should have been called already.
/// If `gifski_set_file_output()` hasn't been called, it may make `gifski_add_frame_*` block and wait for
/// writing to start.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_add_frame_rgba(handle: *const GifskiHandle, index: u32, width: u32, height: u32, pixels: *const RGBA8, delay: u16) -> GifskiError {
    if pixels.is_null() {
        return GifskiError::NULL_ARG;
    }
    let pixels = slice::from_raw_parts(pixels, width as usize * height as usize);
    add_frame_rgba(handle, index, ImgVec::new(pixels.to_owned(), width as usize, height as usize), delay)
}

fn add_frame_rgba(handle: *const GifskiHandle, index: u32, frame: ImgVec<RGBA8>, delay: u16) -> GifskiError {
    let g = match unsafe { borrow(handle) } {
        Some(g) => g,
        None => return GifskiError::NULL_ARG,
    };
    if let Some(ref mut c) = *g.collector.lock().unwrap() {
        c.add_frame_rgba(index as usize, frame, delay).into()
    } else {
        eprintln!("frames can't be added any more, because gifski_end_adding_frames has been called already");
        GifskiError::INVALID_STATE
    }
}

/// Same as `gifski_add_frame_rgba`, except it expects components in ARGB order.
///
/// Bytes per row must be multiple of 4 and greater or equal width×4.
#[no_mangle]
pub unsafe extern "C" fn gifski_add_frame_argb(handle: *const GifskiHandle, index: u32, width: u32, bytes_per_row: u32, height: u32, pixels: *const ARGB8, delay: u16) -> GifskiError {
    if pixels.is_null() {
        return GifskiError::NULL_ARG;
    }
    let width = width as usize;
    let stride = bytes_per_row as usize / mem::size_of_val(&*pixels);
    if stride < width {
        return GifskiError::INVALID_INPUT;
    }
    let pixels = slice::from_raw_parts(pixels, stride * height as usize);
    add_frame_rgba(handle, index, ImgVec::new(pixels.chunks(stride).flat_map(|r| r[0..width].iter().map(|p| RGBA8 {
        r: p.r,
        g: p.g,
        b: p.b,
        a: p.a,
    })).collect(), width as usize, height as usize), delay)
}

/// Same as `gifski_add_frame_rgba`, except it expects RGB components (3 bytes per pixel).
///
/// Bytes per row must be multiple of 3 and greater or equal width×3.
#[no_mangle]
pub unsafe extern "C" fn gifski_add_frame_rgb(handle: *const GifskiHandle, index: u32, width: u32, bytes_per_row: u32, height: u32, pixels: *const RGB8, delay: u16) -> GifskiError {
    if pixels.is_null() {
        return GifskiError::NULL_ARG;
    }
    let width = width as usize;
    let stride = bytes_per_row as usize / mem::size_of_val(&*pixels );
    if stride < width {
        return GifskiError::INVALID_INPUT;
    }
    let pixels = slice::from_raw_parts(pixels, stride * height as usize);
    add_frame_rgba(handle, index, ImgVec::new(pixels.chunks(stride).flat_map(|r| r[0..width].iter().map(|&p| p.into())).collect(), width as usize, height as usize), delay)
}

/// Optional. Allows deprecated `gifski_write` to finish.
#[no_mangle]
pub unsafe extern "C" fn gifski_end_adding_frames(handle: *const GifskiHandle) -> GifskiError {
    let g = match borrow(handle) {
        Some(g) => g,
        None => return GifskiError::NULL_ARG,
    };
    match g.collector.lock().unwrap().take() {
        Some(_) => GifskiError::OK,
        None => {
            eprintln!("gifski_end_adding_frames has been called already");
            GifskiError::INVALID_STATE
        },
    }
}

/// Get a callback for frame processed, and abort processing if desired.
///
/// The callback is called once per frame.
/// It gets arbitrary pointer (`user_data`) as an argument. `user_data` can be `NULL`.
/// The callback must be thread-safe (it will be called from another thread).
///
/// The callback must return `1` to continue processing, or `0` to abort.
///
/// Must be called before `gifski_set_file_output()` to take effect.
#[no_mangle]
pub unsafe extern "C" fn gifski_set_progress_callback(handle: *const GifskiHandle, cb: unsafe extern fn(*mut c_void) -> c_int, user_data: *mut c_void) {
    let g = match borrow(handle) {
        Some(g) => g,
        None => return,
    };
    *g.progress.lock().unwrap() = Some(ProgressCallback::new(cb, user_data));
}

/// Deprecated. Do not use. Use `gifski_set_file_output` instead.
///
/// Blocks the current thread. Starts writing to the `destination` and keeps waiting
/// for more frames being set by another thread, until `gifski_end_adding_frames()` is called.
///
/// This call will block until the entire file is written. You will need to add frames on another thread.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_write(handle: *const GifskiHandle, destination: *const c_char) -> GifskiError {
    let g = match borrow(handle) {
        Some(g) => g,
        None => return GifskiError::NULL_ARG,
    };
    let (file, path) = match prepare_for_file_writing(g, destination) {
        Ok(res) => res,
        Err(err) => return err,
    };
    gifski_write_sync_internal(g, file, Some(path))
}

/// Start writing to the `destination`. This has to be called before any frames are added.
///
/// This call will not block.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_set_file_output(handle: *const GifskiHandle, destination: *const c_char) -> GifskiError {
    if handle.is_null() {
        return GifskiError::NULL_ARG;
    }
    let g = retain(handle);
    let (file, path) = match prepare_for_file_writing(&g, destination) {
        Ok(res) => res,
        Err(err) => return err,
    };
    let mut t = g.write_thread.lock().unwrap();
    if t.0 {
        eprintln!("gifski_set_file_output/gifski_set_write_callback has been called already");
        return GifskiError::INVALID_STATE;
    }
    *t = (true, Some(thread::spawn({
        let g = Arc::clone(&g);
        move || {
            gifski_write_sync_internal(&g, file, Some(path))
        }
    })));
    GifskiError::OK
}


fn prepare_for_file_writing(g: &GifskiHandleInternal, destination: *const c_char) -> Result<(File, PathBuf), GifskiError> {
    if destination.is_null() {
        return Err(GifskiError::NULL_ARG);
    }
    let path = if let Ok(s) = unsafe { CStr::from_ptr(destination).to_str() } {
        Path::new(s)
    } else {
        return Err(GifskiError::INVALID_INPUT);
    };
    let t = g.write_thread.lock().unwrap();
    if t.0 {
        eprintln!("tried to start writing for the second time, after it has already started");
        return Err(GifskiError::INVALID_STATE);
    }
    match File::create(path) {
        Ok(file) => Ok((file, path.into())),
        Err(err) => Err(err.kind().into()),
    }
}

struct CallbackWriter {
    cb: unsafe extern fn(usize, *const u8, *mut c_void) -> c_int,
    user_data: *mut c_void,
}

unsafe impl Send for CallbackWriter {}

impl io::Write for CallbackWriter {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        match unsafe {(self.cb)(buf.len(), buf.as_ptr(), self.user_data)} {
            0 => Ok(buf.len()),
            x => Err(GifskiError::from(x).into()),
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        match unsafe {(self.cb)(0, ptr::null(), self.user_data)} {
            0 => Ok(()),
            x => Err(GifskiError::from(x).into()),
        }
    }
}

/// Start writing via callback (any buffer, file, whatever you want). This has to be called before any frames are added.
/// This call will not block.
///
/// The callback function receives 3 arguments:
///  - size of the buffer to write, in bytes. IT MAY BE ZERO (when it's zero, either do nothing, or flush internal buffers if necessary).
///  - pointer to the buffer.
///  - context pointer to arbitary user data, same as passed in to this function.
///
/// The callback should return 0 (`GIFSKI_OK`) on success, and non-zero on error.
///
/// The callback function must be thread-safe.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_set_write_callback(handle: *const GifskiHandle, cb: Option<unsafe extern fn(usize, *const u8, *mut c_void) -> c_int>, user_data: *mut c_void) -> GifskiError {
    if handle.is_null() {
        return GifskiError::NULL_ARG;
    }
    let cb = match cb {
        Some(cb) => cb,
        None => return GifskiError::NULL_ARG,
    };
    let g = retain(handle);
    let writer = CallbackWriter {cb, user_data};
    let mut t = g.write_thread.lock().unwrap();
    if t.0 {
        eprintln!("gifski_set_file_output/gifski_set_write_callback has been called already");
        return GifskiError::INVALID_STATE;
    }
    *t = (true, Some(thread::spawn({
        let g = Arc::clone(&g);
        move || {
            gifski_write_sync_internal(&g, writer, None)
        }
    })));
    GifskiError::OK
}


fn gifski_write_sync_internal<W: Write + Send>(g: &GifskiHandleInternal, file: W, path: Option<PathBuf>) -> GifskiError {
    if let Some(writer) = g.writer.lock().unwrap().take() {
        let mut tmp;
        let mut progress: &mut dyn ProgressReporter = &mut NoProgress {};
        if let Some(cb) = g.progress.lock().unwrap().take() {
            tmp = cb;
            progress = &mut tmp;
        }
        match writer.write(file, progress).into() {
            res @ GifskiError::OK |
            res @ GifskiError::ALREADY_EXISTS => res,
            err => {
                if let Some(path) = path {
                    let _ = fs::remove_file(path); // clean up unfinished file
                }
                err
            },
        }
    } else {
        eprintln!("gifski_set_file_output or gifski_write_* has been called once already");
        GifskiError::INVALID_STATE
    }
}

unsafe fn borrow<'a>(handle: *const GifskiHandle) -> Option<&'a GifskiHandleInternal> {
    let g = handle as *const GifskiHandleInternal;
    g.as_ref()
}

/// get refcount++ without dropping the handle
unsafe fn retain(arc_ptr: *const GifskiHandle) -> Arc<GifskiHandleInternal> {
    let arc_ptr = arc_ptr as *const GifskiHandleInternal;
    let tmp = Arc::from_raw(arc_ptr);
    let g = Arc::clone(&tmp);
    let _ = Arc::into_raw(tmp);
    g
}

/// The last step:
///  - stops accepting any more frames (gifski_add_frame_* calls are blocked)
///  - blocks and waits until all already-added frames have finished writing
///
/// Returns final status of write operations. Remember to check the return value!
///
/// After this call, the handle is freed and can't be used any more.
///
/// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
#[no_mangle]
pub unsafe extern "C" fn gifski_finish(g: *const GifskiHandle) -> GifskiError {
    if g.is_null() {
        return GifskiError::NULL_ARG;
    }
    let g = Arc::from_raw(g as *const GifskiHandleInternal);

    // dropping of the collector (if any) completes writing
    *g.collector.lock().unwrap() = None;

    let thread = g.write_thread.lock().unwrap().1.take();
    if let Some(thread) = thread {
        thread.join().expect("writer thread failed")
    } else {
        eprintln!("gifski_finish called before any output has been set");
        GifskiError::OK // this will become INVALID_STATE once sync write support is dropped
    }
}

#[test]
fn c_cb() {
    let g = unsafe {gifski_new(&GifskiSettings {
        width: 1, height: 1,
        quality: 100,
        once: true,
        fast: false,
    })};
    assert!(!g.is_null());
    let mut called = false;
    unsafe extern fn cb(_s: usize, _buf: *const u8, user_data: *mut c_void) -> c_int {
        let called = user_data as *mut bool;
        *called = true;
        0
    }
    unsafe {
        assert_eq!(GifskiError::OK, gifski_set_write_callback(g, Some(cb), (&mut called) as *mut _ as _));
        assert_eq!(GifskiError::OK, gifski_add_frame_rgb(g, 0, 1, 3, 1, &RGB::new(0,0,0), 5));
        assert_eq!(GifskiError::OK, gifski_finish(g));
    }
    assert!(called);
}

#[test]
fn cant_write_after_finish() {
    let g = unsafe { gifski_new(&GifskiSettings {
        width: 1, height: 1,
        quality: 100,
        once: true,
        fast: false,
    })};
    assert!(!g.is_null());
    let mut called = false;
    unsafe extern fn cb(_s: usize, _buf: *const u8, user_data: *mut c_void) -> c_int {
        let called = user_data as *mut bool;
        *called = true;
        0
    }
    unsafe {
        assert_eq!(GifskiError::OK, gifski_set_write_callback(g, Some(cb), (&mut called) as *mut _ as _));
        assert_eq!(GifskiError::OTHER, gifski_finish(g));
    }
}

#[test]
fn c_write_failure_propagated() {
    let g = unsafe { gifski_new(&GifskiSettings {
        width: 1, height: 1,
        quality: 100,
        once: true,
        fast: false,
    })};
    assert!(!g.is_null());
    unsafe extern fn cb(_s: usize, _buf: *const u8, _user: *mut c_void) -> c_int {
        GifskiError::WRITE_ZERO as c_int
    }
    unsafe {
        assert_eq!(GifskiError::OK, gifski_set_write_callback(g, Some(cb), ptr::null_mut()));
        assert_eq!(GifskiError::OK, gifski_add_frame_rgb(g, 0, 1, 3, 1, &RGB::new(0,0,0), 5));
        assert_eq!(GifskiError::WRITE_ZERO, gifski_finish(g));
    }
}

#[test]
fn cant_write_twice() {
    let g = unsafe { gifski_new(&GifskiSettings {
        width: 1, height: 1,
        quality: 100,
        once: true,
        fast: false,
    })};
    assert!(!g.is_null());
    unsafe extern fn cb(_s: usize, _buf: *const u8, _user: *mut c_void) -> c_int {
        GifskiError::WRITE_ZERO as c_int
    }
    unsafe {
        assert_eq!(GifskiError::OK, gifski_set_write_callback(g, Some(cb), ptr::null_mut()));
        assert_eq!(GifskiError::INVALID_STATE, gifski_set_write_callback(g, Some(cb), ptr::null_mut()));
    }
}

#[test]
fn c_incomplete() {
    let g = unsafe { gifski_new(&GifskiSettings {
        width: 0, height: 0,
        quality: 100,
        once: false,
        fast: true,
    })};

    let rgb: *const RGB8 = ptr::null();
    assert_eq!(3, mem::size_of_val(unsafe { &*rgb }));

    assert!(!g.is_null());
    unsafe {
        assert_eq!(GifskiError::NULL_ARG, gifski_add_frame_rgba(g, 0, 1, 1, ptr::null(), 5));
    }
    extern fn cb(_: *mut c_void) -> c_int {
        1
    }
    unsafe {
        gifski_set_progress_callback(g, cb, ptr::null_mut());
        assert_eq!(GifskiError::OK, gifski_add_frame_rgba(g, 0, 1, 1, &RGBA::new(0, 0, 0, 0), 5));
        assert_eq!(GifskiError::OK, gifski_add_frame_rgb(g, 1, 1, 3, 1, &RGB::new(0, 0, 0), 5));
        assert_eq!(GifskiError::OK, gifski_end_adding_frames(g));
        assert_eq!(GifskiError::INVALID_STATE, gifski_end_adding_frames(g));
        assert_eq!(GifskiError::OK, gifski_finish(g));
    }
}