use std::io::Read;
use std::io::Write;
use std::ops::Range;
use std::process::Command;
use std::process::Stdio;
use std::rc::Rc;
use std::sync::Once;

use ariadne::Fmt;
use ariadne::Label;
use ariadne::Report;
use ariadne::ReportKind;
use crypto::digest::Digest;
use crypto::sha2::Sha512;
use mlua::Function;
use mlua::Lua;
use regex::Captures;
use regex::Regex;

use crate::cache::cache::Cached;
use crate::cache::cache::CachedError;
use crate::compiler::compiler::Compiler;
use crate::compiler::compiler::Target;
use crate::document::document::Document;
use crate::document::element::ElemKind;
use crate::document::element::Element;
use crate::parser::parser::Parser;
use crate::parser::rule::RegexRule;
use crate::parser::source::Source;
use crate::parser::source::Token;
use crate::parser::util;

#[derive(Debug, PartialEq, Eq)]
enum TexKind {
	Block,
	Inline,
}

impl From<&TexKind> for ElemKind {
	fn from(value: &TexKind) -> Self {
		match value {
			TexKind::Inline => ElemKind::Inline,
			_ => ElemKind::Block,
		}
	}
}

#[derive(Debug)]
struct Tex {
	location: Token,
	block: TexKind,
	env: String,
	tex: String,
	caption: Option<String>,
}

impl Tex {
	fn new(
		location: Token,
		block: TexKind,
		env: String,
		tex: String,
		caption: Option<String>,
	) -> Self {
		Self {
			location,
			block,
			env,
			tex,
			caption,
		}
	}

	fn format_latex(fontsize: &String, preamble: &String, tex: &String) -> FormattedTex {
		FormattedTex(format!(
			r"\documentclass[{}pt,preview]{{standalone}}
{}
\begin{{document}}
\begin{{preview}}
{}
\end{{preview}}
\end{{document}}",
			fontsize, preamble, tex
		))
	}
}

struct FormattedTex(String);

impl FormattedTex {
	/// Renders latex to svg
	fn latex_to_svg(&self, exec: &String, fontsize: &String) -> Result<String, String> {
		print!("Rendering LaTex `{}`... ", self.0);
		let process = match Command::new(exec)
			.arg("--fontsize")
			.arg(fontsize)
			.stdout(Stdio::piped())
			.stdin(Stdio::piped())
			.spawn()
		{
			Err(e) => return Err(format!("Could not spawn `{exec}`: {}", e)),
			Ok(process) => process,
		};

		if let Err(e) = process.stdin.unwrap().write_all(self.0.as_bytes()) {
			panic!("Unable to write to `latex2svg`'s stdin: {}", e);
		}

		let mut result = String::new();
		match process.stdout.unwrap().read_to_string(&mut result) {
			Err(e) => panic!("Unable to read `latex2svg` stdout: {}", e),
			Ok(_) => {}
		}
		println!("Done!");

		Ok(result)
	}
}

impl Cached for FormattedTex {
	type Key = String;
	type Value = String;

	fn sql_table() -> &'static str {
		"CREATE TABLE IF NOT EXISTS cached_tex (
				digest TEXT PRIMARY KEY,
				svg    BLOB NOT NULL);"
	}

	fn sql_get_query() -> &'static str {
		"SELECT svg FROM cached_tex WHERE digest = (?1)"
	}

	fn sql_insert_query() -> &'static str {
		"INSERT INTO cached_tex (digest, svg) VALUES (?1, ?2)"
	}

	fn key(&self) -> <Self as Cached>::Key {
		let mut hasher = Sha512::new();
		hasher.input(self.0.as_bytes());

		hasher.result_str()
	}
}

impl Element for Tex {
	fn location(&self) -> &Token {
		&self.location
	}

	fn kind(&self) -> ElemKind {
		(&self.block).into()
	}

	fn element_name(&self) -> &'static str {
		"LaTeX"
	}

	fn to_string(&self) -> String {
		format!("{self:#?}")
	}

	fn compile(&self, compiler: &Compiler, document: &dyn Document) -> Result<String, String> {
		match compiler.target() {
			Target::HTML => {
				static CACHE_INIT: Once = Once::new();
				CACHE_INIT.call_once(|| {
					if let Some(mut con) = compiler.cache() {
						if let Err(e) = FormattedTex::init(&mut con) {
							eprintln!("Unable to create cache table: {e}");
						}
					}
				});

				let exec = document
					.get_variable(format!("tex.{}.exec", self.env).as_str())
					.map_or("latex2svg".to_string(), |var| var.to_string());
				// FIXME: Because fontsize is passed as an arg, verify that it cannot be used to execute python/shell code
				let fontsize = document
					.get_variable(format!("tex.{}.fontsize", self.env).as_str())
					.map_or("12".to_string(), |var| var.to_string());
				let preamble = document
					.get_variable(format!("tex.{}.preamble", self.env).as_str())
					.map_or("".to_string(), |var| var.to_string());
				let prepend = if self.block == TexKind::Inline {
					"".to_string()
				} else {
					document
						.get_variable(format!("tex.{}.block_prepend", self.env).as_str())
						.map_or("".to_string(), |var| var.to_string() + "\n")
				};

				let latex = match self.block {
					TexKind::Inline => {
						Tex::format_latex(&fontsize, &preamble, &format!("${{{}}}$", self.tex))
					}
					_ => Tex::format_latex(&fontsize, &preamble, &format!("{prepend}{}", self.tex)),
				};

				if let Some(mut con) = compiler.cache() {
					match latex.cached(&mut con, |s| s.latex_to_svg(&exec, &fontsize)) {
						Ok(s) => Ok(s),
						Err(e) => match e {
							CachedError::SqlErr(e) => {
								Err(format!("Querying the cache failed: {e}"))
							}
							CachedError::GenErr(e) => Err(e),
						},
					}
				} else {
					latex.latex_to_svg(&exec, &fontsize)
				}
			}
			_ => todo!("Unimplemented"),
		}
	}
}

pub struct TexRule {
	re: [Regex; 2],
}

impl TexRule {
	pub fn new() -> Self {
		Self {
			re: [
				Regex::new(r"\$\|(?:\[(.*)\])?(?:((?:\\.|[^\\\\])*?)\|\$)?").unwrap(),
				Regex::new(r"\$(?:\[(.*)\])?(?:((?:\\.|[^\\\\])*?)\$)?").unwrap(),
			],
		}
	}
}

impl RegexRule for TexRule {
	fn name(&self) -> &'static str {
		"Tex"
	}

	fn regexes(&self) -> &[regex::Regex] {
		&self.re
	}

	fn on_regex_match(
		&self,
		index: usize,
		parser: &dyn Parser,
		document: &dyn Document,
		token: Token,
		matches: Captures,
	) -> Vec<Report<'_, (Rc<dyn Source>, Range<usize>)>> {
		let mut reports = vec![];

		let tex_env = matches
			.get(1)
			.and_then(|env| Some(env.as_str().trim_start().trim_end()))
			.and_then(|env| (!env.is_empty()).then_some(env))
			.unwrap_or("main");

		let tex_content = match matches.get(2) {
			// Unterminated `$`
			None => {
				reports.push(
					Report::build(ReportKind::Error, token.source(), token.start())
						.with_message("Unterminated Tex Code")
						.with_label(
							Label::new((token.source().clone(), token.range.clone()))
								.with_message(format!(
									"Missing terminating `{}` after first `{}`",
									["|$", "$"][index].fg(parser.colors().info),
									["$|", "$"][index].fg(parser.colors().info)
								))
								.with_color(parser.colors().error),
						)
						.finish(),
				);
				return reports;
			}
			Some(content) => {
				let processed = util::process_escaped(
					'\\',
					["|$", "$"][index],
					content.as_str().trim_start().trim_end(),
				);

				if processed.is_empty() {
					reports.push(
						Report::build(ReportKind::Warning, token.source(), content.start())
							.with_message("Empty Tex Code")
							.with_label(
								Label::new((token.source().clone(), content.range()))
									.with_message("Tex code is empty")
									.with_color(parser.colors().warning),
							)
							.finish(),
					);
				}
				processed
			}
		};

		// TODO: Caption

		parser.push(
			document,
			Box::new(Tex::new(
				token,
				if index == 1 {
					TexKind::Inline
				} else {
					TexKind::Block
				},
				tex_env.to_string(),
				tex_content,
				None,
			)),
		);

		reports
	}

	// TODO
	fn lua_bindings<'lua>(&self, _lua: &'lua Lua) -> Vec<(String, Function<'lua>)> {
		vec![]
	}
}