use std::iter::Peekable;
use source_span::Span;
use crate::Located;
use crate::syntax::{
	token,
	Token,
	Parsable,
	Error,
	Result,
	peek,
	consume,
	consume_token,
	parse_list,
	parse_numeral
};

mod ast;
pub mod display;

pub use ast::*;

fn server_error<L>(lexer: &mut Peekable<L>, mut loc: Span) -> Result<Located<Error>> where L: Iterator<Item=Result<Located<Token>>> {
	use Token::*;

	let token = consume(lexer)?;
	let id_loc = token.span();
	match token.into_inner() {
		Ident(name) => {
			match name.as_str() {
				"error" => {
					let token = consume(lexer)?;
					let message_loc = token.span();
					match token.into_inner() {
						Litteral(token::Litteral::String(message)) => {
							loc = loc.union(consume_token(lexer, End)?);
							Ok(Error::Server(message).at(loc))
						},
						unexpected => Err(Error::UnexpectedToken(Ident(unexpected.to_string()), None).at(message_loc))
					}
				},
				unexpected => Err(Error::UnexpectedToken(Ident(unexpected.to_string()), None).at(id_loc))
			}
		},
		unexpected => Err(Error::UnexpectedToken(unexpected, None).at(id_loc))
	}
}

fn peek_server_error<L>(lexer: &mut Peekable<L>, loc: &Span) -> Result<()> where L: Iterator<Item=Result<Located<Token>>> {
	use Token::*;

	let token = peek(lexer)?;
	match token.as_ref() {
		Ident(name) => {
			match name.as_str() {
				"error" => Err(server_error(lexer, loc.clone())?),
				_ => Ok(())
			}
		},
		_ => Ok(())
	}
}

impl Parsable for CheckSat {
	fn parse<L>(lexer: &mut Peekable<L>) -> Result<Located<CheckSat>> where L: Iterator<Item=Result<Located<Token>>> {
		use Token::*;

		let token = consume(lexer)?;
		let loc = token.span();
		match token.into_inner() {
			Ident(name) => {
				match name.as_str() {
					"sat" => {
						Ok(Located::new(crate::response::CheckSat::Sat, loc))
					},
					"unsat" => {
						Ok(Located::new(crate::response::CheckSat::Unsat, loc))
					},
					"unknown" => {
						Ok(Located::new(crate::response::CheckSat::Unknown, loc))
					},
					unexpected => Err(Error::UnexpectedToken(Ident(unexpected.to_string()), None).at(loc))
				}
			},
			Begin => Err(server_error(lexer, loc)?),
			unexpected => Err(Error::UnexpectedToken(unexpected, None).at(loc))
		}
	}
}

impl Parsable for Model {
	fn parse<L>(lexer: &mut Peekable<L>) -> Result<Located<Model>> where L: Iterator<Item=Result<Located<Token>>> {
		use Token::*;

		let mut loc = consume_token(lexer, Begin)?;
		peek_server_error(lexer, &loc)?;

		let mut definitions;
		let mut sorts = Vec::new();

		match peek(lexer)?.as_ref() {
			// this "model" keyword token does not appear in the SMT2-lib specification.
			// however it seems to be pretty standard... In this case we can also have sorts and
			// functions declarations in the model.
			Ident(ref name) if name.as_str() == "model" => {
				consume(lexer)?;
				definitions = Vec::new();
				loop {
					let token = consume(lexer)?;
					let item_loc = token.span();
					match token.into_inner() {
						Begin => {
							let token = peek(lexer)?;
							let id_loc = token.span();
							match token.as_ref() {
								Ident(ref name) => {
									match name.as_ref() {
										"define-fun" | "define-fun-rec" | "define-funs-rec" => {
											let def = Definition::parse_at(lexer, item_loc)?;
											definitions.push(def);
										},
										"declare-sort" => { // non standard
											consume(lexer)?;
											let id = Symbol::parse(lexer)?;
											let arity = parse_numeral(lexer)?;

											let decl_loc = item_loc.union(consume_token(lexer, End)?);

											let decl = Located::new(SortDeclaration {
												id: id,
												arity: arity
											}, decl_loc);

											sorts.push(decl);
										},
										"declare-fun" => { // non standard
											consume(lexer)?;
											let _id = Symbol::parse(lexer)?;
											consume_token(lexer, Begin)?;
											let _args: Vec<Located<Sort>> = parse_list(lexer, &mut loc)?;
											let _return_sort = Sort::parse(lexer)?;

											let _decl_loc = item_loc.union(consume_token(lexer, End)?);

											// TODO should we keep the non-standard function declaration?
										},
										unexpected => return Err(Error::UnexpectedToken(Ident(unexpected.to_string()), None).at(id_loc))
									}
								},
								unexpected => return Err(Error::UnexpectedToken(unexpected.clone(), None).at(id_loc))
							}
						},
						End => {
							break
						},
						unexpected => return Err(Error::UnexpectedToken(unexpected, None).at(item_loc))
					}
				}
			},
			_ => {
				definitions = parse_list(lexer, &mut loc)?;
			}
		}

		Ok(Located::new(Model {
			sorts: sorts,
			definitions: definitions
		}, loc))
	}
}

impl Definition {
	fn parse_at<L>(lexer: &mut Peekable<L>, mut loc: Span) -> Result<Located<Definition>> where L: Iterator<Item=Result<Located<Token>>> {
		use Token::*;

		let token = consume(lexer)?;
		let id_loc = token.span();

		let rec;
		let declarations;
		let bodies;

		match token.into_inner() {
			Ident(name) => {
				match name.as_str() {
					"define-fun" => {
						rec = true;
						let id = Symbol::parse(lexer)?;
						consume_token(lexer, Begin)?;
						let args = parse_list(lexer, &mut loc)?;
						let return_sort = Sort::parse(lexer)?;
						let body = Term::parse(lexer)?;

						let def_loc = id.span().union(body.span());

						declarations = vec![Located::new(Declaration {
							id: id,
							args: args,
							return_sort: return_sort
						}, def_loc)];

						bodies = vec![body];
					},
					"define-fun-rec" => {
						rec = true;
						let id = Symbol::parse(lexer)?;
						consume_token(lexer, Begin)?;
						let args = parse_list(lexer, &mut loc)?;
						let return_sort = Sort::parse(lexer)?;
						let body = Term::parse(lexer)?;

						let def_loc = id.span().union(body.span());

						declarations = vec![Located::new(Declaration {
							id: id,
							args: args,
							return_sort: return_sort
						}, def_loc)];

						bodies = vec![body];
					},
					"define-funs-rec" => {
						rec = true;
						consume_token(lexer, Begin)?;
						declarations = parse_list(lexer, &mut loc)?;
						consume_token(lexer, Begin)?;
						bodies = parse_list(lexer, &mut loc)?;
					},
					// "declare-sort" => {
					//	 let id = Symbol::parse(lexer)?;
					//	 let arity = parse_numeral(lexer)?;
					// },
					unexpected => return Err(Error::UnexpectedToken(Ident(unexpected.to_string()), None).at(id_loc))
				}
			},
			unexpected => return Err(Error::UnexpectedToken(unexpected, None).at(id_loc))
		}

		loc = loc.union(consume_token(lexer, End)?);

		Ok(Located::new(Definition {
			rec: rec,
			declarations: declarations,
			bodies: bodies,
			comments: String::new()
		}, loc))
	}
}

impl Parsable for Definition {
	fn parse<L>(lexer: &mut Peekable<L>) -> Result<Located<Definition>> where L: Iterator<Item=Result<Located<Token>>> {
		use Token::*;

		let loc = consume_token(lexer, Begin)?;
		Self::parse_at(lexer, loc)
	}
}

impl Parsable for Declaration {
	fn parse<L>(lexer: &mut Peekable<L>) -> Result<Located<Declaration>> where L: Iterator<Item=Result<Located<Token>>> {
		use Token::*;

		let mut loc = consume_token(lexer, Begin)?;
		let id = Symbol::parse(lexer)?;
		consume_token(lexer, Begin)?;
		let args = parse_list(lexer, &mut loc)?;
		let return_sort = Sort::parse(lexer)?;
		loc = loc.union(consume_token(lexer, End)?);

		Ok(Located::new(Declaration {
			id: id,
			args: args,
			return_sort: return_sort
		}, loc))
	}
}