pub mod ffmpeg;
mod filter;

use self::{
	ffmpeg::{FfmpegOutput, FfmpegOutputFormat},
	filter::Filter
};
use crate::{
	iotro::{intro, outro},
	project::{Project, ProjectLecture, ProjectSourceMetadata, Resolution},
	question::Question,
	render::ffmpeg::{Ffmpeg, FfmpegInput},
	time::{format_date, format_time, Time}
};
use anyhow::{bail, Context};
use camino::{Utf8Path as Path, Utf8PathBuf as PathBuf};
use console::style;
use std::{
	borrow::Cow,
	collections::VecDeque,
	fs::{self, File},
	io::Write as _,
	process::{Command, Stdio}
};

const INTRO_LEN: Time = Time {
	seconds: 3,
	micros: 0
};
const OUTRO_LEN: Time = Time {
	seconds: 5,
	micros: 0
};
const TRANSITION_LEN: Time = Time {
	seconds: 0,
	micros: 200_000
};
const QUESTION_FADE_LEN: Time = Time {
	seconds: 0,
	micros: 400_000
};
const FF_MULTIPLIER: usize = 8;
// logo sizes at full hd, will be scaled to source resolution
const FF_LOGO_SIZE: usize = 128;
const LOGO_SIZE: usize = 96;

fn cmd() -> Command {
	#[cfg(feature = "mem_limit")]
	let mut cmd = {
		// we use systemd-run to limit the process memory
		// I tried others like ulimit, chpst or isolate, but none worked
		let mut cmd = Command::new("systemd-run");
		cmd.arg("--scope")
			.arg("-q")
			.arg("--expand-environment=no")
			.arg("-p")
			.arg(format!("MemoryMax={}", crate::MEM_LIMIT.read().unwrap()))
			.arg("--user");
		// we use busybox ash for having a shell that outputs commands with -x
		cmd.arg("busybox");
		cmd
	};
	#[cfg(not(feature = "mem_limit"))]
	let mut cmd = Command::new("busybox");
	cmd.arg("ash")
		.arg("-exuo")
		.arg("pipefail")
		.arg("-c")
		.arg("exec \"$0\" \"${@}\"");
	cmd
}

fn ffprobe() -> Command {
	let mut cmd = cmd();
	cmd.arg("ffprobe")
		.arg("-v")
		.arg("error")
		.arg("-of")
		.arg("default=noprint_wrappers=1:nokey=1");
	cmd
}

fn read_output(cmd: &mut Command) -> anyhow::Result<String> {
	let out = cmd.stderr(Stdio::inherit()).output()?;
	if !out.status.success() {
		bail!(
			"Executed command failed with exit status {:?}",
			out.status.code()
		);
	}
	String::from_utf8(out.stdout)
		.context("Command returned non-utf8 output")
		.map(|str| str.trim().into())
}

fn ffprobe_video(query: &str, input: &Path) -> anyhow::Result<String> {
	read_output(
		ffprobe()
			.arg("-select_streams")
			.arg("v:0")
			.arg("-show_entries")
			.arg(query)
			.arg(input)
	)
}

fn ffprobe_audio(query: &str, concat_input: &Path) -> anyhow::Result<String> {
	read_output(
		ffprobe()
			.arg("-select_streams")
			.arg("a:0")
			.arg("-show_entries")
			.arg(query)
			.arg("-safe")
			.arg("0")
			.arg("-f")
			.arg("concat")
			.arg(concat_input)
	)
}

pub(crate) struct Renderer<'a> {
	/// The directory with all the sources.
	directory: &'a Path,

	/// The slug (i.e. 23ws-malo2-231016).
	slug: String,
	/// The target directory.
	target: PathBuf,
	/// The format to use for intermediate products
	format: FfmpegOutputFormat
}

fn svg2mkv(
	meta: &ProjectSourceMetadata,
	svg: PathBuf,
	mkv: PathBuf,
	format: FfmpegOutputFormat,
	duration: Time
) -> anyhow::Result<()> {
	let mut ffmpeg = Ffmpeg::new(FfmpegOutput {
		duration: Some(duration),
		time_base: Some(meta.source_tbn),
		fps_mode_vfr: true,
		..FfmpegOutput::new(format, mkv)
	});
	ffmpeg.add_input(FfmpegInput {
		loop_input: true,
		fps: Some(meta.source_fps),
		..FfmpegInput::new(svg)
	});
	ffmpeg.add_filter(Filter::GenerateSilence {
		video: "0".into(),
		output: "out".into()
	});
	ffmpeg.set_filter_output("out");
	ffmpeg.run()
}

fn svg2png(svg: &Path, png: &Path, width: usize, height: usize) -> anyhow::Result<()> {
	let mut cmd = cmd();
	cmd.arg("inkscape")
		.arg("-w")
		.arg(width.to_string())
		.arg("-h")
		.arg(height.to_string());
	cmd.arg(svg).arg("-o").arg(png);

	let status = cmd.status()?;
	if status.success() {
		Ok(())
	} else {
		bail!("inkscape failed with exit code {:?}", status.code())
	}
}

impl<'a> Renderer<'a> {
	pub(crate) fn new(directory: &'a Path, project: &Project) -> anyhow::Result<Self> {
		let slug = format!(
			"{}-{}",
			project.lecture.course,
			format_date(project.lecture.date)
		);
		let target = directory.join(&slug);
		fs::create_dir_all(&target)?;

		let first: PathBuf = directory.join(
			project
				.source
				.files
				.first()
				.context("No source files present")?
		);
		let height: u32 = ffprobe_video("stream=height", &first)?
			.split('\n')
			.next()
			.unwrap()
			.parse()?;
		let format = if height < 1080 {
			FfmpegOutputFormat::AvcAac
		} else {
			FfmpegOutputFormat::Av1Flac
		};

		Ok(Self {
			directory,
			slug,
			target,
			format
		})
	}

	pub(crate) fn recording_mkv(&self) -> PathBuf {
		self.target.join("recording.mkv")
	}

	fn intro_mkv(&self) -> PathBuf {
		self.target.join("intro.mkv")
	}

	fn outro_mkv(&self) -> PathBuf {
		self.target.join("outro.mkv")
	}

	fn question_svg(&self, q_idx: usize) -> PathBuf {
		self.target.join(format!("question{q_idx}.svg"))
	}

	fn question_png(&self, q_idx: usize) -> PathBuf {
		self.target.join(format!("question{q_idx}.png"))
	}

	pub(crate) fn preprocess(&self, project: &mut Project) -> anyhow::Result<()> {
		assert!(!project.progress.preprocessed);

		let recording_txt = self.target.join("recording.txt");
		let mut file = File::create(&recording_txt)?;
		for filename in &project.source.files {
			writeln!(file, "file '{}'", self.directory.join(filename))?;
		}
		drop(file);

		println!();
		println!(
			" {} {}",
			style("==>").bold().cyan(),
			style("Concatenating Video and Normalising Audio ...").bold()
		);

		let source_sample_rate =
			ffprobe_audio("stream=sample_rate", &recording_txt)?.parse()?;
		let recording_mkv = self.recording_mkv();
		let mut ffmpeg = Ffmpeg::new(FfmpegOutput::new(
			FfmpegOutputFormat::Av1Flac,
			recording_mkv.clone()
		));
		ffmpeg.add_input(FfmpegInput {
			concat: true,
			..FfmpegInput::new(recording_txt)
		});
		ffmpeg.enable_loudnorm(project.source.stereo);
		ffmpeg.run()?;

		let width = ffprobe_video("stream=width", &recording_mkv)?.parse()?;
		let height = ffprobe_video("stream=height", &recording_mkv)?.parse()?;
		let source_res = match (width, height) {
			(3840, 2160) => Resolution::UHD,
			(2560, 1440) => Resolution::WQHD,
			(1920, 1080) => Resolution::FullHD,
			(1280, 720) => Resolution::HD,
			(640, 360) => Resolution::nHD,
			(width, height) => bail!("Unknown resolution: {width}x{height}")
		};
		project.source.metadata = Some(ProjectSourceMetadata {
			source_duration: ffprobe_video("format=duration", &recording_mkv)?.parse()?,
			source_fps: ffprobe_video("stream=r_frame_rate", &recording_mkv)?.parse()?,
			source_tbn: ffprobe_video("stream=time_base", &recording_mkv)?.parse()?,
			source_res,
			source_sample_rate
		});

		Ok(())
	}

	/// Prepare assets like intro, outro and questions.
	pub(crate) fn render_assets(&self, project: &Project) -> anyhow::Result<()> {
		let metadata = project.source.metadata.as_ref().unwrap();

		println!();
		println!(
			" {} {}",
			style("==>").bold().cyan(),
			style("Preparing assets ...").bold()
		);

		// render intro to svg then mp4
		let intro_svg = self.target.join("intro.svg");
		fs::write(
			&intro_svg,
			intro(metadata.source_res, &project.lecture)
				.to_string_pretty()
				.into_bytes()
		)?;
		let intro_mkv = self.intro_mkv();
		svg2mkv(metadata, intro_svg, intro_mkv, self.format, INTRO_LEN)?;

		// render outro to svg then mp4
		let outro_svg = self.target.join("outro.svg");
		fs::write(
			&outro_svg,
			outro(&project.lecture.lang, metadata.source_res)
				.to_string_pretty()
				.into_bytes()
		)?;
		let outro_mkv = self.outro_mkv();
		svg2mkv(metadata, outro_svg, outro_mkv, self.format, OUTRO_LEN)?;

		// copy logo then render to png
		let logo_svg = self.target.join("logo.svg");
		fs::write(
			&logo_svg,
			include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/logo.svg"))
		)?;
		let logo_png = self.target.join("logo.png");
		let logo_size = LOGO_SIZE * metadata.source_res.width() / 1920;
		svg2png(&logo_svg, &logo_png, logo_size, logo_size)?;

		// copy fastforward then render to png
		let fastforward_svg = self.target.join("fastforward.svg");
		fs::write(
			&fastforward_svg,
			include_bytes!(concat!(
				env!("CARGO_MANIFEST_DIR"),
				"/assets/fastforward.svg"
			))
		)?;
		let fastforward_png = self.target.join("fastforward.png");
		let ff_logo_size = FF_LOGO_SIZE * metadata.source_res.width() / 1920;
		svg2png(
			&fastforward_svg,
			&fastforward_png,
			ff_logo_size,
			ff_logo_size
		)?;

		// write questions then render to png
		for (q_idx, (_, _, q_text)) in project.source.questions.iter().enumerate() {
			let q = Question::new(metadata.source_res, &project.lecture.lang, q_text)
				.finish()
				.to_string_pretty()
				.into_bytes();
			let q_svg = self.question_svg(q_idx);
			let q_png = self.question_png(q_idx);
			fs::write(&q_svg, q)?;
			svg2png(
				&q_svg,
				&q_png,
				metadata.source_res.width(),
				metadata.source_res.height()
			)?;
		}

		Ok(())
	}

	/// Get the video file for a specific resolution, completely finished.
	fn video_file_res(&self, res: Resolution) -> PathBuf {
		let extension = match res.format() {
			FfmpegOutputFormat::Av1Flac => "mkv",
			FfmpegOutputFormat::Av1Opus => "webm",
			FfmpegOutputFormat::AvcAac => "mp4"
		};
		self.target
			.join(format!("{}-{}p.{extension}", self.slug, res.height()))
	}

	/// Get the video file directly outputed to further transcode.
	pub(crate) fn video_file_output(&self) -> PathBuf {
		self.target.join(format!("{}.mkv", self.slug))
	}

	pub(crate) fn render(&self, project: &mut Project) -> anyhow::Result<PathBuf> {
		let source_res = project.source.metadata.as_ref().unwrap().source_res;

		let output = self.video_file_output();
		let mut ffmpeg = Ffmpeg::new(FfmpegOutput {
			video_bitrate: Some(source_res.bitrate() * 3),
			..FfmpegOutput::new(self.format, output.clone())
		});

		// add all of our inputs
		let intro = ffmpeg.add_input(FfmpegInput::new(self.intro_mkv()));
		let rec_file = self.recording_mkv();
		let outro = ffmpeg.add_input(FfmpegInput::new(self.outro_mkv()));
		let logo = ffmpeg.add_input(FfmpegInput::new(self.target.join("logo.png")));
		let ff = ffmpeg.add_input(FfmpegInput::new(self.target.join("fastforward.png")));

		let mut part1: Cow<'static, str> = intro.into();
		let mut part3: Cow<'static, str> = outro.into();

		// the recording is fun because of all the fast forwarding
		let mut part2 = VecDeque::<Cow<'static, str>>::new();
		let mut part2_ts = VecDeque::new();
		let mut part2_start_of_the_end = None;
		let mut part2_end_of_the_start = None;

		// ok so ff is fun. we will add the ff'ed section as well as the part between
		// the previous ff'ed section and our new section, unless we are the first.
		project.source.fast.sort();
		for (i, (ff_st, ff_end)) in project.source.fast.iter().rev().enumerate() {
			if let Some(prev_end) = part2_end_of_the_start {
				let duration = prev_end - *ff_end;
				let recffbetween = ffmpeg.add_input(FfmpegInput {
					start: Some(*ff_end),
					duration: Some(duration),
					..FfmpegInput::new(rec_file.clone())
				});
				part2.push_front(recffbetween.into());
				part2_ts.push_front(Some((*ff_end, duration)));
			} else {
				part2_start_of_the_end = Some(*ff_end);
			}
			part2_end_of_the_start = Some(*ff_st);

			let recffpart = ffmpeg.add_input(FfmpegInput {
				start: Some(*ff_st),
				duration: Some(*ff_end - *ff_st),
				..FfmpegInput::new(rec_file.clone())
			});

			let recff = format!("recff{i}");
			ffmpeg.add_filter(Filter::FastForward {
				input: recffpart.into(),
				ffinput: ff.clone().into(),
				multiplier: FF_MULTIPLIER,
				output: recff.clone().into()
			});
			part2.push_front(recff.into());
			part2_ts.push_front(None);
		}

		// if the recording was not ff'ed, perform a normal trim
		let start = project.source.start.unwrap();
		let end = project.source.end.unwrap();
		let part2_last_part_duration;
		if part2.is_empty() {
			part2_last_part_duration = end - start;
			let rectrim = ffmpeg.add_input(FfmpegInput {
				start: Some(start),
				duration: Some(part2_last_part_duration),
				..FfmpegInput::new(rec_file.clone())
			});
			part2.push_back(rectrim.into());
			part2_ts.push_back(Some((start, part2_last_part_duration)));
		}
		// otherwise add the first and last parts separately
		else {
			let duration = part2_end_of_the_start.unwrap() - start;
			let rectrimst = ffmpeg.add_input(FfmpegInput {
				start: Some(start),
				duration: Some(duration),
				..FfmpegInput::new(rec_file.clone())
			});
			part2.push_front(rectrimst.into());
			part2_ts.push_front(Some((start, duration)));

			let part2_start_of_the_end = part2_start_of_the_end.unwrap();
			part2_last_part_duration = end - part2_start_of_the_end;
			let rectrimend = ffmpeg.add_input(FfmpegInput {
				start: Some(part2_start_of_the_end),
				duration: Some(part2_last_part_duration),
				..FfmpegInput::new(rec_file.clone())
			});
			part2.push_back(rectrimend.into());
			part2_ts.push_back(Some((part2_start_of_the_end, part2_last_part_duration)));
		}

		// ok now we have a bunch of parts and a bunch of questions that want to get
		// overlayed over those parts.
		project.source.questions.sort();
		let mut q_idx = 0;
		for (i, ts) in part2_ts.iter().enumerate() {
			let Some((start, duration)) = ts else {
				continue;
			};
			loop {
				if q_idx >= project.source.questions.len() {
					break;
				}
				let (q_start, q_end, _) = &project.source.questions[q_idx];
				if q_start < start {
					bail!(
						"Question starting at {} did not fit into the video",
						format_time(*q_start)
					);
				}
				if q_start >= start && *q_end <= *start + *duration {
					// add the question as input to ffmpeg
					let q_inp = ffmpeg.add_input(FfmpegInput {
						loop_input: true,
						fps: Some(project.source.metadata.as_ref().unwrap().source_fps),
						duration: Some(*q_end - *q_start),
						..FfmpegInput::new(self.question_png(q_idx))
					});

					// fade in the question
					let q_fadein = format!("q{q_idx}fin");
					ffmpeg.add_filter(Filter::FadeAlpha {
						input: q_inp.into(),
						direction: "in",
						start: Time {
							seconds: 0,
							micros: 0
						},
						duration: QUESTION_FADE_LEN,
						output: q_fadein.clone().into()
					});

					// fade out the question
					let q_fadeout = format!("q{q_idx}fout");
					ffmpeg.add_filter(Filter::FadeAlpha {
						input: q_fadein.into(),
						direction: "out",
						start: *q_end - *q_start - QUESTION_FADE_LEN,
						duration: QUESTION_FADE_LEN,
						output: q_fadeout.clone().into()
					});

					// move the question to the correct timestamp
					let q_pts = format!("q{q_idx}pts");
					ffmpeg.add_filter(Filter::VideoOffset {
						input: q_fadeout.into(),
						seconds: *q_start - *start,
						output: q_pts.clone().into()
					});

					// overlay the part in question
					let q_overlay = format!("q{q_idx}o");
					ffmpeg.add_filter(Filter::Overlay {
						video_input: part2[i].clone(),
						overlay_input: q_pts.into(),
						x: "0".into(),
						y: "0".into(),
						repeatlast: false,
						output: q_overlay.clone().into()
					});
					part2[i] = q_overlay.into();

					q_idx += 1;
					continue;
				}
				break;
			}
		}
		if q_idx < project.source.questions.len() {
			bail!(
				"Question starting at {} did not fit into the video before it was over",
				format_time(project.source.questions[q_idx].0)
			);
		}

		// fade out the intro
		let introfade = "introfade";
		ffmpeg.add_filter(Filter::Fade {
			input: part1,
			direction: "out",
			start: INTRO_LEN - TRANSITION_LEN,
			duration: TRANSITION_LEN,
			output: introfade.into()
		});
		part1 = introfade.into();

		// fade in the recording
		let recfadein = "recfadein";
		ffmpeg.add_filter(Filter::Fade {
			input: part2.pop_front().unwrap(),
			direction: "in",
			start: Time {
				seconds: 0,
				micros: 0
			},
			duration: TRANSITION_LEN,
			output: recfadein.into()
		});
		part2.push_front(recfadein.into());

		// fade out the recording
		let recfadeout = "recfadeout";
		ffmpeg.add_filter(Filter::Fade {
			input: part2.pop_back().unwrap(),
			direction: "out",
			start: part2_last_part_duration - TRANSITION_LEN,
			duration: TRANSITION_LEN,
			output: recfadeout.into()
		});
		part2.push_back(recfadeout.into());

		// fade in the outro
		let outrofade = "outrofade";
		ffmpeg.add_filter(Filter::Fade {
			input: part3,
			direction: "in",
			start: Time {
				seconds: 0,
				micros: 0
			},
			duration: TRANSITION_LEN,
			output: outrofade.into()
		});
		part3 = outrofade.into();

		// concatenate everything
		let mut parts = part2;
		parts.push_front(part1);
		parts.push_back(part3);
		let concat = "concat";
		ffmpeg.add_filter(Filter::Concat {
			inputs: parts,
			output: concat.into()
		});

		// overlay the logo
		let logoalpha = "logoalpha";
		ffmpeg.add_filter(Filter::Alpha {
			input: logo.into(),
			alpha: 0.5,
			output: logoalpha.into()
		});
		let overlay = "overlay";
		let overlay_off_x = 130 * source_res.width() / 3840;
		let overlay_off_y = 65 * source_res.height() / 2160;
		ffmpeg.add_filter(Filter::Overlay {
			video_input: concat.into(),
			overlay_input: logoalpha.into(),
			x: format!("main_w-overlay_w-{overlay_off_x}").into(),
			y: format!("main_h-overlay_h-{overlay_off_y}").into(),
			repeatlast: true,
			output: overlay.into()
		});

		// we're done :)
		ffmpeg.set_filter_output(overlay);
		ffmpeg.run()?;

		Ok(output)
	}

	pub fn rescale(
		&self,
		lecture: &ProjectLecture,
		res: Resolution
	) -> anyhow::Result<PathBuf> {
		let input = self.video_file_output();
		let output = self.video_file_res(res);

		println!();
		println!(
			" {} {}",
			style("==>").bold().cyan(),
			style(format!("Rescaling to {}p", res.height())).bold()
		);

		let mut ffmpeg = Ffmpeg::new(FfmpegOutput {
			video_bitrate: Some(res.bitrate()),

			title: Some(format!(
				"{} {} {}",
				lecture.label,
				lecture.lang.from,
				(lecture.lang.format_date_long)(lecture.date)
			)),
			author: Some(lecture.docent.clone()),
			album: Some(lecture.course.clone()),
			year: Some(lecture.date.year.to_string()),
			comment: Some(lecture.lang.video_created_by_us.into()),
			language: Some(lecture.lang.lang.into()),

			..FfmpegOutput::new(res.format(), output.clone()).enable_faststart()
		});
		ffmpeg.add_input(FfmpegInput::new(input));
		ffmpeg.rescale_video(res);
		ffmpeg.run()?;
		Ok(output)
	}
}