use std::{collections::HashSet, fs, path::PathBuf, str::FromStr};

use image::{GenericImageView, Rgba};
use kd_tree::{KdMap, KdPoint};
use num::Integer;

use crate::{
	chart::{Difficulty, SongCache},
	context::Error,
	score::guess_chart_name,
};

/// How many sub-segments to split each side into
pub const SPLIT_FACTOR: u32 = 8;
pub const IMAGE_VEC_DIM: usize = (SPLIT_FACTOR * SPLIT_FACTOR * 3) as usize;

#[derive(Debug, Clone)]
pub struct ImageVec {
	pub colors: [f32; IMAGE_VEC_DIM],
}

impl ImageVec {
	// {{{ (Image => vector) encoding
	fn from_image(image: &impl GenericImageView<Pixel = Rgba<u8>>) -> ImageVec {
		let mut colors = [0.0; IMAGE_VEC_DIM];
		let chunk_width = image.width() / SPLIT_FACTOR;
		let chunk_height = image.height() / SPLIT_FACTOR;
		for i in 0..(SPLIT_FACTOR * SPLIT_FACTOR) {
			let (iy, ix) = i.div_rem(&SPLIT_FACTOR);
			let cropped = image.view(
				chunk_width * ix,
				chunk_height * iy,
				chunk_width,
				chunk_height,
			);

			let mut r = 0;
			let mut g = 0;
			let mut b = 0;
			let mut count = 0;

			for (_, _, pixel) in cropped.pixels() {
				r += pixel.0[0] as u64;
				g += pixel.0[1] as u64;
				b += pixel.0[2] as u64;
				count += 1;
			}

			let count = count as f64;
			let r = r as f64 / count;
			let g = g as f64 / count;
			let b = b as f64 / count;
			colors[i as usize * 3 + 0] = r as f32;
			colors[i as usize * 3 + 1] = g as f32;
			colors[i as usize * 3 + 2] = b as f32;
		}

		Self { colors }
	}
	// }}}
}

impl KdPoint for ImageVec {
	type Dim = typenum::U75;
	type Scalar = f32;

	fn dim() -> usize {
		IMAGE_VEC_DIM
	}

	fn at(&self, i: usize) -> Self::Scalar {
		self.colors[i]
	}
}

pub struct JacketCache {
	// TODO: make this private
	pub tree: KdMap<ImageVec, u32>,
}

impl JacketCache {
	// {{{ Generate tree
	// This is a bit inefficient (using a hash set), but only runs once
	pub fn new(data_dir: &PathBuf, song_cache: &mut SongCache) -> Result<Self, Error> {
		let jacket_dir = data_dir.join("jackets");

		if jacket_dir.exists() {
			fs::remove_dir_all(&jacket_dir).expect("Could not delete jacket dir");
		}

		fs::create_dir_all(&jacket_dir).expect("Could not create jacket dir");

		let mut jackets: HashSet<(PathBuf, u32)> = HashSet::new();
		let entries = fs::read_dir(data_dir.join("songs")).expect("Couldn't read songs directory");
		for entry in entries {
			let dir = entry?;
			let raw_dir_name = dir.file_name();
			let dir_name = raw_dir_name.to_str().unwrap();
			for entry in fs::read_dir(dir.path()).expect("Couldn't read song directory") {
				let file = entry?;
				let raw_name = file.file_name();
				let name = raw_name.to_str().unwrap().strip_suffix(".jpg").unwrap();

				if !name.ends_with("_256") {
					continue;
				}
				let name = name.strip_suffix("_256").unwrap();

				let difficulty = match name {
					"0" => Some(Difficulty::PST),
					"1" => Some(Difficulty::PRS),
					"2" => Some(Difficulty::FTR),
					"3" => Some(Difficulty::BYD),
					"4" => Some(Difficulty::ETR),
					"base" => None,
					"base_night" => None,
					"base_ja" => None,
					_ => Err(format!("Unknown jacket suffix {}", name))?,
				};

				let (song, chart) = guess_chart_name(dir_name, &song_cache, difficulty, true)?;

				jackets.insert((file.path(), song.id));

				let contents = fs::read(file.path())?.leak();

				if name == "base" {
					let item = song_cache.lookup_mut(song.id).unwrap();

					for chart in item.charts_mut() {
						let difficulty_num = match chart.difficulty {
							Difficulty::PST => "0",
							Difficulty::PRS => "1",
							Difficulty::FTR => "2",
							Difficulty::BYD => "3",
							Difficulty::ETR => "4",
						};

						// We only want to create this path if there's no overwrite for this
						// jacket.
						let specialized_path = PathBuf::from_str(
							&file
								.path()
								.to_str()
								.unwrap()
								.replace("base_night", difficulty_num)
								.replace("base", difficulty_num),
						)
						.unwrap();

						let dest = chart.jacket_path(data_dir);
						if !specialized_path.exists() && !dest.exists() {
							std::os::unix::fs::symlink(file.path(), dest)
								.expect("Could not symlink jacket");
							chart.cached_jacket = Some(contents);
						}
					}
				} else if difficulty.is_some() {
					std::os::unix::fs::symlink(file.path(), chart.jacket_path(data_dir))
						.expect("Could not symlink jacket");
					let chart = song_cache.lookup_chart_mut(chart.id).unwrap();
					chart.cached_jacket = Some(contents);
				}
			}
		}

		let mut entries = vec![];

		for (path, song_id) in jackets {
			match image::io::Reader::open(path) {
				Ok(reader) => {
					let image = reader.decode()?;
					entries.push((ImageVec::from_image(&image), song_id))
				}
				_ => continue,
			}
		}

		let result = Self {
			tree: KdMap::build_by_ordered_float(entries),
		};

		Ok(result)
	}
	// }}}
	// {{{ Recognise
	#[inline]
	pub fn recognise(
		&self,
		image: &impl GenericImageView<Pixel = Rgba<u8>>,
	) -> Option<(f32, &u32)> {
		self.tree
			.nearest(&ImageVec::from_image(image))
			.map(|p| (p.squared_distance.sqrt(), &p.item.1))
	}
	// }}}
}