use std::cell::RefCell;
use std::sync::Arc;

use sexp::SourcePosition;

use crate::asm::instr::flatten::labels_to_skips;
use crate::asm::parse::{ParserContext, ParserState};
use crate::module::{CrsnExtension, CrsnUniq};
use crate::runtime::program::Program;
use crate::builtin::BuiltinOps;
use crate::runtime::run_thread::{RunState, ThreadInfo, ThreadToken};
use crate::runtime::frame::REG_COUNT;

pub mod data;
pub mod error;
pub mod instr;
pub mod parse;
pub mod patches;

/// Parse a program from string and assemble a low level instruction sequence from it.
pub fn assemble(source: &str, uniq : &CrsnUniq, mut parsers: Vec<Box<dyn CrsnExtension>>) -> Result<Arc<Program>, error::CrsnError> {
    parsers.insert(0, BuiltinOps::new());
    for p in &mut parsers {
        p.init(uniq);
    }

    let parsers_arc = Arc::new(parsers);

    // remove first line if it looks like a shebang
    let source = if source.starts_with("#!") {
        if let Some(nl) = source.find('\n') {
            &source[nl + 1..]
        } else {
            source
        }
    } else {
        source
    };

    let ti = Arc::new(ThreadInfo {
        id: ThreadToken(0),
        uniq: Default::default(),
        program: Program::new(vec![], parsers_arc.clone()).unwrap(),
        cycle_time: Default::default(),
        extensions: parsers_arc.clone(),
    });

    let pcx = ParserContext {
        parsers: &parsers_arc,
        state: RefCell::new(ParserState {
            reg_aliases: Default::default(),
            reg_alias_stack: vec![],
            global_reg_aliases: Default::default(),
            constants: Default::default(),

            // This is a fake thread to pass to constant expressions when evaluating them.
            // This allows to evaluate nearly all instructions at compile time.
            const_eval: RunState {
                thread_info: ti.clone(),
                frame: Default::default(),
                call_stack: vec![],
                global_regs: [0; REG_COUNT],
                ext_data: Default::default()
            },
            const_eval_ti: ti,
            parsing_expr: false
        }),
    };

    let ops = parse::parse(source, &SourcePosition::default(), &pcx)?;
    let ops = labels_to_skips(ops)?;

    Ok(Program::new(ops, parsers_arc)?)
}