use sexp::{Sexp, SourcePosition};

use crate::asm::error::CrsnError;
use crate::asm::instr::{Flatten, InstrWithBranches};
use crate::asm::parse::arg_parser::TokenParser;
use crate::asm::parse::parse_cond::parse_cond_branch;
use crate::asm::parse::parse_routine::parse_routine;
use crate::asm::parse::ParserContext;
use crate::asm::parse::sexp_expect::{expect_list, expect_string_atom};
use crate::module::ParseRes;

use super::parse_op::parse_op;
use crate::asm::patches::NextOrErr;

pub fn parse_instructions(items: impl Iterator<Item=Sexp>, pos: SourcePosition, pcx: &ParserContext) -> Result<Box<dyn Flatten>, CrsnError> {
    let mut parsed = vec![];
    for expr in items {
        let (tokens, listpos) = expect_list(expr, false)?;

        let mut toki = tokens.into_iter();
        let (name, namepos) = expect_string_atom(toki.next_or_err(listpos.clone(), "Expected instruction name token")?)?;

        if name == "proc" {
            parsed.push(parse_routine(toki, pos.clone(), pcx)?);
            continue;
        }

        let mut token_parser = TokenParser::new(toki.collect(), listpos.clone(), pcx);
        for p in pcx.parsers {
            token_parser = match p.parse_syntax(pos.clone(), &name, token_parser) {
                Ok(ParseRes::Parsed(op)) => return Ok(op),
                Ok(ParseRes::ParsedNone) => return Ok(Box::new(())),
                Ok(ParseRes::Unknown(to_reuse)) => {
                    if to_reuse.parsing_started() {
                        panic!("Module \"{}\" started parsing syntax, but returned Unknown!", p.name());
                    }
                    to_reuse
                }
                Err(err) => {
                    return Err(err);
                }
            }
        }

        // Get back the original iterator
        let toki = token_parser.into_iter();

        let arg_tokens = TokenParser::new(toki.clone().take_while(|e| e.is_atom()).collect(), listpos.clone(), pcx);
        let branch_tokens = toki
            .skip_while(|e| e.is_atom())
            .take_while(|e| e.is_list());

        let branches = {
            let mut branches = vec![];
            for t in branch_tokens {
                branches.push(parse_cond_branch(t, pcx)?);
            }
            if branches.is_empty() {
                None
            } else {
                Some(branches)
            }
        };

        if let Some(op) = parse_op(name.as_str(), arg_tokens, namepos.clone())? {
            parsed.push(Box::new(InstrWithBranches {
                op,
                pos: namepos,
                branches,
            }));
        }
    }
    Ok(Box::new(parsed))
}