//! Structures that show where code or semantic elements came from

use std::fmt;
use std::hash::Hash;
use std::ops::{Add, AddAssign, Range};

use futures::future::join_all;
use trait_set::trait_set;

use crate::error::ErrPos;
use crate::interner::{Interner, Tok};
use crate::name::Sym;
use crate::{api, match_mapping, sym};

trait_set! {
	pub trait GetSrc = FnMut(&Sym) -> Tok<String>;
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Pos {
	None,
	SlotTarget,
	/// Used in functions to denote the generated code that carries on the
	/// location of the call. Not allowed in the const tree.
	Inherit,
	Gen(CodeGenInfo),
	/// Range and file
	SrcRange(SrcRange),
	Multi(Vec<Pos>),
}
impl Pos {
	pub fn pretty_print(&self, get_src: &mut impl GetSrc) -> String {
		match self {
			Self::Gen(g) => g.to_string(),
			Self::SrcRange(sr) => sr.pretty_print(&get_src(&sr.path)),
			// Can't pretty print partial and meta-location
			other => format!("{other:?}"),
		}
	}
	pub async fn from_api(api: &api::Location, i: &Interner) -> Self {
		match_mapping!(api, api::Location => Pos {
			None, Inherit, SlotTarget,
			Gen(cgi => CodeGenInfo::from_api(cgi, i).await),
			Multi(v => join_all(v.iter().map(|l| Pos::from_api(l, i))).await)
		} {
			api::Location::SourceRange(sr) => Self::SrcRange(SrcRange::from_api(sr, i).await)
		})
	}
	pub fn to_api(&self) -> api::Location {
		match_mapping!(self, Pos => api::Location {
			None, Inherit, SlotTarget,
			Gen(cgi.to_api()),
			Multi(v => v.iter().map(|pos| pos.to_api()).collect()),
		} {
			Self::SrcRange(sr) => api::Location::SourceRange(sr.to_api()),
		})
	}
}
impl fmt::Display for Pos {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Pos::Inherit => f.write_str("Unresolved inherited position"),
			Pos::SlotTarget => f.write_str("Unresolved slot target position"),
			Pos::None => f.write_str("N/A"),
			Pos::Gen(g) => write!(f, "{g}"),
			Pos::SrcRange(sr) => write!(f, "{sr}"),
			Pos::Multi(posv) => {
				write!(f, "{}", posv[0])?;
				for pos in posv {
					write!(f, "+{}", pos)?;
				}
				Ok(())
			},
		}
	}
}
impl Add for Pos {
	type Output = Pos;
	fn add(self, rhs: Self) -> Self::Output {
		match (self, rhs) {
			(Pos::Multi(l), Pos::Multi(r)) => Pos::Multi(l.into_iter().chain(r).collect()),
			(Pos::None, any) => any,
			(any, Pos::None) => any,
			(Pos::Multi(v), single) => Pos::Multi(v.into_iter().chain([single]).collect()),
			(single, Pos::Multi(v)) => Pos::Multi([single].into_iter().chain(v).collect()),
			(l, r) => Pos::Multi(vec![l, r]),
		}
	}
}
impl AddAssign for Pos {
	fn add_assign(&mut self, rhs: Self) {
		let mut tmp = Pos::None;
		std::mem::swap(&mut tmp, self);
		*self = tmp + rhs;
	}
}

/// Exact source code location. Includes where the code was loaded from, what
/// the original source code was, and a byte range.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct SrcRange {
	pub(crate) path: Sym,
	pub(crate) range: Range<u32>,
}
impl SrcRange {
	pub fn new(range: Range<u32>, path: &Sym) -> Self {
		Self { range: range.clone(), path: path.clone() }
	}
	/// Create a dud [SourceRange] for testing. Its value is unspecified and
	/// volatile.
	pub async fn mock(i: &Interner) -> Self { Self { range: 0..1, path: sym!(test; i) } }
	/// Path the source text was loaded from
	pub fn path(&self) -> Sym { self.path.clone() }
	/// Byte range
	pub fn range(&self) -> Range<u32> { self.range.clone() }
	/// 0-based index of first byte
	pub fn start(&self) -> u32 { self.range.start }
	/// 0-based index of last byte + 1
	pub fn end(&self) -> u32 { self.range.end }
	/// Syntactic location
	pub fn pos(&self) -> Pos { Pos::SrcRange(self.clone()) }
	/// Transform the numeric byte range
	pub fn map_range(&self, map: impl FnOnce(Range<u32>) -> Range<u32>) -> Self {
		Self { range: map(self.range()), path: self.path() }
	}
	pub fn pretty_print(&self, src: &str) -> String {
		let (sl, sc) = pos2lc(src, self.range.start);
		let (el, ec) = pos2lc(src, self.range.end);
		match (el == sl, ec <= sc + 1) {
			(true, true) => format!("{sl}:{sc}"),
			(true, false) => format!("{sl}:{sc}..{ec}"),
			(false, _) => format!("{sl}:{sc}..{el}:{ec}"),
		}
	}
	pub fn zw(path: Sym, pos: u32) -> Self { Self { path, range: pos..pos } }
	pub async fn from_api(api: &api::SourceRange, i: &Interner) -> Self {
		Self { path: Sym::from_api(api.path, i).await, range: api.range.clone() }
	}
	pub fn to_api(&self) -> api::SourceRange {
		api::SourceRange { path: self.path.to_api(), range: self.range.clone() }
	}
	pub fn to(&self, rhs: &Self) -> Self {
		assert_eq!(self.path, rhs.path, "Range continues across files");
		Self { path: self.path(), range: self.start().min(rhs.start())..self.end().max(rhs.end()) }
	}
}
impl From<SrcRange> for ErrPos {
	fn from(val: SrcRange) -> Self { val.pos().into() }
}
impl fmt::Display for SrcRange {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self.range.len() {
			0 => write!(f, "{}:{}", self.path(), self.range.start),
			n => write!(f, "{}:{}+{}", self.path(), self.range.start, n),
		}
	}
}

/// Information about a code generator attached to the generated code
#[derive(Clone, PartialEq, Eq, Hash)]
pub struct CodeGenInfo {
	/// formatted like a Rust namespace
	pub generator: Sym,
	/// Unformatted user message with relevant circumstances and parameters
	pub details: Tok<String>,
}
impl CodeGenInfo {
	/// A codegen marker with no user message and parameters
	pub async fn new_short(generator: Sym, i: &Interner) -> Self {
		Self { generator, details: i.i("").await }
	}
	/// A codegen marker with a user message or parameters
	pub async fn new_details(generator: Sym, details: impl AsRef<str>, i: &Interner) -> Self {
		Self { generator, details: i.i(details.as_ref()).await }
	}
	/// Syntactic location
	pub fn pos(&self) -> Pos { Pos::Gen(self.clone()) }
	pub async fn from_api(api: &api::CodeGenInfo, i: &Interner) -> Self {
		Self {
			generator: Sym::from_api(api.generator, i).await,
			details: Tok::from_api(api.details, i).await,
		}
	}
	pub fn to_api(&self) -> api::CodeGenInfo {
		api::CodeGenInfo { generator: self.generator.to_api(), details: self.details.to_api() }
	}
}
impl fmt::Debug for CodeGenInfo {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "CodeGenInfo({self})") }
}
impl fmt::Display for CodeGenInfo {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		write!(f, "generated by {}", self.generator)?;
		if !self.details.is_empty() { write!(f, ", details: {}", self.details) } else { write!(f, ".") }
	}
}

#[must_use]
fn pos2lc(s: &str, i: u32) -> (u32, u32) {
	s.chars()
		.take(i.try_into().unwrap())
		.fold((1, 1), |(line, col), char| if char == '\n' { (line + 1, 1) } else { (line, col + 1) })
}