use std::mem;

use ansi_to_tui::IntoText;
use mlua::{AnyUserData, ExternalError, ExternalResult, FromLua, IntoLua, Lua, Table, UserData, UserDataMethods, Value};

use super::{Span, Style};

const LEFT: u8 = 0;
const CENTER: u8 = 1;
const RIGHT: u8 = 2;

#[derive(Clone, FromLua)]
pub struct Line(pub(super) ratatui::text::Line<'static>);

impl TryFrom<Table<'_>> for Line {
	type Error = mlua::Error;

	fn try_from(tb: Table) -> Result<Self, Self::Error> {
		let seq: Vec<_> = tb.sequence_values().filter_map(|v| v.ok()).collect();
		let mut spans = Vec::with_capacity(seq.len());
		for value in seq {
			if let Value::UserData(ud) = value {
				if let Ok(span) = ud.take::<Span>() {
					spans.push(span.0);
				} else if let Ok(line) = ud.take::<Line>() {
					let style = line.0.style;
					spans.extend(line.0.spans.into_iter().map(|mut span| {
						span.style = style.patch(span.style);
						span
					}));
				} else {
					return Err("expected a table of Spans or Lines".into_lua_err());
				}
			}
		}
		Ok(Self(ratatui::text::Line::from(spans)))
	}
}

impl TryFrom<mlua::String<'_>> for Line {
	type Error = mlua::Error;

	fn try_from(s: mlua::String) -> Result<Self, Self::Error> {
		Ok(Self(ratatui::text::Line::from(s.to_string_lossy().into_owned())))
	}
}

impl Line {
	pub fn install(lua: &Lua, ui: &Table) -> mlua::Result<()> {
		let new = lua.create_function(|_, (_, value): (Table, Value)| match value {
			Value::Table(tb) => Line::try_from(tb),
			Value::String(s) => Line::try_from(s),
			_ => Err("expected a String, or a table of Spans and Lines".into_lua_err()),
		})?;

		let parse = lua.create_function(|_, code: mlua::String| {
			let Some(line) = code.as_bytes().split_inclusive(|&b| b == b'\n').next() else {
				return Ok(Line(Default::default()));
			};

			let mut lines = line.into_text().into_lua_err()?.lines;
			if lines.is_empty() {
				return Ok(Line(Default::default()));
			}

			Ok(Line(mem::take(&mut lines[0])))
		})?;

		let line = lua.create_table_from([
			("parse", parse.into_lua(lua)?),
			// Alignment
			("LEFT", LEFT.into_lua(lua)?),
			("CENTER", CENTER.into_lua(lua)?),
			("RIGHT", RIGHT.into_lua(lua)?),
		])?;

		line.set_metatable(Some(lua.create_table_from([("__call", new)])?));

		ui.raw_set("Line", line)
	}
}

impl UserData for Line {
	fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
		crate::impl_style_shorthands!(methods, 0.style);

		methods.add_function("width", |_, ud: AnyUserData| Ok(ud.borrow_mut::<Self>()?.0.width()));
		methods.add_function("style", |_, (ud, value): (AnyUserData, Value)| {
			{
				let mut me = ud.borrow_mut::<Self>()?;
				me.0.style = match value {
					Value::Nil => ratatui::style::Style::default(),
					Value::Table(tb) => Style::try_from(tb)?.0,
					Value::UserData(ud) => ud.borrow::<Style>()?.0,
					_ => return Err("expected a Style or Table or nil".into_lua_err()),
				};
			}
			Ok(ud)
		});
		methods.add_function("align", |_, (ud, align): (AnyUserData, u8)| {
			ud.borrow_mut::<Self>()?.0.alignment = Some(match align {
				CENTER => ratatui::layout::Alignment::Center,
				RIGHT => ratatui::layout::Alignment::Right,
				_ => ratatui::layout::Alignment::Left,
			});
			Ok(ud)
		});
	}
}