use sexp::{Sexp, SourcePosition, Atom, atom_s};

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, expect_any_string_atom};
use crate::asm::patches::NextOrErr;
use crate::module::ParseRes;
use crate::asm::patches::ErrSetFile;

use super::parse_op::parse_op;
use std::path::{PathBuf};
use std::convert::TryFrom;
use crate::asm::read_source_file;
use crate::asm::instr::flatten::jumps_to_skips;

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

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

        let parsing_expr = pcx.state.borrow().parsing_expr;

        if parsing_expr {
            if let Some(n) = name.strip_prefix('=') {
                name = n.to_string();
            }
        }

        if name == "include" {
            // TODO move this to a separate function and get rid of err_file()

            if parsing_expr {
                return Err(CrsnError::Parse("Illegal syntax in const expression".into(), pos.clone()));
            }

            let (mut path, _namepos) = expect_any_string_atom(toki.next_or_err(listpos.clone(), "Expected file path or name to include")?)?;

            // add extension if missing
            let last_piece = path.split('/').rev().next().unwrap();
            if !last_piece.contains('.') {
                path.push_str(".csn");
            }

            trace!("*** include, raw path: {}", path);

            let state = pcx.state.borrow();
            let this_file = &state.files[state.active_file];

            let new_file = PathBuf::try_from(path).unwrap();

            let new_pb = if !new_file.is_absolute() {
                let parent = this_file.parent().expect("file has parent");

                let fixed = parent.join(&new_file);
                trace!("Try to resolve: {}", fixed.display());

                fixed.canonicalize()?
            } else {
                new_file.to_owned()
            };
            drop(state);
            drop(new_file);

            let (old_af, af) = {
                let mut state = pcx.state.borrow_mut();
                let old_af = state.active_file;
                let af = state.files.len();
                state.active_file = af;
                state.files.push(new_pb.clone());
                (old_af, af as u32)
            };

            let loaded = read_source_file(&new_pb)
                .err_file(af)?;

            let (items, _pos) =
                expect_list(
                    sexp::parse(&loaded)
                        .map_err(|mut e| {
                            e.pos.file = af;
                            e
                        })?,
                    true)
                .err_file(af)?;

            let sub_parsed = parse_instructions(items.into_iter(), pos, pcx)
                .err_file(af)?;

            let mut flat = sub_parsed.flatten(&pcx.state.borrow().label_num)
                .err_file(af)?;

            flat.iter_mut().for_each(|op| {
                op.pos.file = af as u32;
            });

            trace!("inner falt {:#?}", flat);

            parsed.push(Box::new(flat));

            {
                let mut state = pcx.state.borrow_mut();
                state.active_file = old_af;
            }
            continue;
        }

        if name == "proc" {
            if parsing_expr {
                return Err(CrsnError::Parse("Illegal syntax in const expression".into(), pos.clone()));
            }
            parsed.push(parse_routine(toki, pos, pcx)?);
            continue;
        }

        // Let extensions parse custom syntax
        let mut token_parser = TokenParser::new(toki.collect(), &listpos, pcx);
        for p in pcx.parsers {
            token_parser = match p.parse_syntax(pos, &name, token_parser) {
                Ok(ParseRes::Parsed(op)) => {
                    parsed.push(op);
                    continue 'exprs;
                },
                Ok(ParseRes::ParsedNone) => {
                    continue 'exprs;
                },
                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 token_count = token_parser.len();
        let toki : std::vec::IntoIter<Sexp> = token_parser.into_iter();

        let branch_tokens = toki.clone().rev()
            .take_while(|e| {
                if let Sexp::List(ref items, _) = e {
                    if items.len() > 1 {
                        if let Sexp::Atom(Atom::S(ref kw), _) = items[0] {
                            if kw.ends_with('?') {
                                return true;
                            }
                        }
                    }
                }
                false
            })
            .collect::<Vec<_>>();

        if parsing_expr && !branch_tokens.is_empty() {
            return Err(CrsnError::Parse(format!("Conditional branches are not allowed in const expression: {:?}", branch_tokens).into(), pos.clone()));
        }

        let mut arg_parser = TokenParser::new(toki.take(token_count - branch_tokens.len()).collect(), &listpos, pcx);

        trace!("Parse op: {}\nargs {:?}\nbranches {:?}", name, arg_parser, branch_tokens);

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

        if parsing_expr {
            // hackity hack for const expr eval
            arg_parser.prepend(atom_s("=result"));
        }

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