use std::slice;

use windows::core::PCSTR;
use windows::Win32::Foundation::{CloseHandle, HANDLE};
use windows::Win32::System::Memory::{
  CreateFileMappingA, MapViewOfFile, UnmapViewOfFile, FILE_MAP_ALL_ACCESS, MEMORYMAPPEDVIEW_HANDLE,
};
use windows::Win32::{
  Foundation::INVALID_HANDLE_VALUE,
  Graphics::{
    Direct3D11::ID3D11Texture2D,
    Dxgi::{DXGI_OUTDUPL_FRAME_INFO, DXGI_OUTPUT_DESC},
  },
  System::Memory::PAGE_READWRITE,
};

use crate::duplicate_context::DuplicateContext;
use crate::utils::{OutputDescExt, Result};

use super::model::Capturer;

/// Capture screen to a chunk of shared memory.
pub struct SharedCapturer<'a> {
  buffer: *mut u8,
  buffer_size: usize,
  file: HANDLE,
  ctx: &'a DuplicateContext,
  texture: ID3D11Texture2D,
}

impl<'a> SharedCapturer<'a> {
  pub fn new(ctx: &'a DuplicateContext, name: &str) -> Result<Self> {
    let (buffer, buffer_size, file, texture) = Self::allocate(ctx, name)?;
    Ok(Self {
      buffer,
      buffer_size,
      file,
      texture,
      ctx,
    })
  }

  fn allocate(
    ctx: &'a DuplicateContext,
    name: &str,
  ) -> Result<(*mut u8, usize, HANDLE, ID3D11Texture2D)> {
    let (texture, desc) = ctx.create_readable_texture()?;
    let buffer_size = desc.calc_buffer_size();

    unsafe {
      let file = CreateFileMappingA(
        INVALID_HANDLE_VALUE,
        None,
        PAGE_READWRITE,
        0,
        buffer_size as u32,
        PCSTR(name.as_ptr()),
      )
      .map_err(|_| "CreateFileMappingA failed")?;

      let buffer = MapViewOfFile(
        file,                // handle to map object
        FILE_MAP_ALL_ACCESS, // read/write permission
        0,
        0,
        buffer_size,
      )
      .map_err(|_| "MapViewOfFile failed")?
      .0 as *mut u8;
      Ok((buffer, buffer_size, file, texture))
    }
  }

  fn free(&self) {
    unsafe {
      UnmapViewOfFile(MEMORYMAPPEDVIEW_HANDLE(self.buffer as isize));
      CloseHandle(self.file);
    }
  }
}

impl<'a> Capturer for SharedCapturer<'a> {
  fn buffer(&self) -> &[u8] {
    unsafe { slice::from_raw_parts(self.buffer, self.buffer_size) }
  }

  fn buffer_mut(&mut self) -> &mut [u8] {
    unsafe { slice::from_raw_parts_mut(self.buffer, self.buffer_size) }
  }

  fn desc(&self) -> Result<DXGI_OUTPUT_DESC> {
    self.ctx.desc()
  }

  fn check_buffer(&self) -> Result<()> {
    if self.buffer_size < self.desc()?.calc_buffer_size() {
      return Err("Invalid buffer length");
    } else {
      Ok(())
    }
  }

  fn capture(&mut self) -> Result<DXGI_OUTDUPL_FRAME_INFO> {
    self
      .ctx
      .capture_frame(self.buffer, self.buffer_size, &self.texture)
  }

  fn safe_capture(&mut self) -> Result<DXGI_OUTDUPL_FRAME_INFO> {
    self.check_buffer()?;
    self.capture()
  }
}

impl DuplicateContext {
  pub fn shared_capturer(&self, name: &str) -> Result<SharedCapturer> {
    SharedCapturer::new(self, name)
  }
}

impl<'a> Drop for SharedCapturer<'a> {
  fn drop(&mut self) {
    self.free()
  }
}

#[cfg(test)]
mod tests {
  use std::{thread, time::Duration};

  use crate::{capturer::model::Capturer, manager::Manager, utils::FrameInfoExt};

  #[test]
  fn shared_capturer() {
    let manager = Manager::default().unwrap();
    assert_ne!(manager.contexts.len(), 0);

    let mut capturer = manager.contexts[0]
      .shared_capturer("RustyDuplicationTest")
      .unwrap();

    // sleep for a while before capture to wait system to update the screen
    thread::sleep(Duration::from_millis(100));

    let info = capturer.safe_capture().unwrap();
    assert!(info.is_new_frame());

    let buffer = capturer.buffer();
    // ensure buffer not all zero
    let mut all_zero = true;
    for i in 0..buffer.len() {
      if buffer[i] != 0 {
        all_zero = false;
        break;
      }
    }
    assert!(!all_zero);
  }
}