use std::collections::HashMap;
use std::sync::atomic::AtomicU32;

use crate::asm::data::{Rd, SrcDisp};
use crate::asm::data::literal::{Label, Value};
use crate::asm::error::{AsmError, Error};
use crate::asm::instr::{Cond, Instr, Op, Routine};

/// A trait for something that can turn into multiple instructions
pub trait Flatten {
    fn flatten(self, label_num: &AtomicU32) -> Result<Vec<Op>, Error>;
}

impl Flatten for Instr {
    fn flatten(self, label_num: &AtomicU32) -> Result<Vec<Op>, Error> {
        let mut ops = vec![self.op];

        if let Some(branches) = self.branches {
            let labels = HashMap::<Cond, u32>::new();
            let branch_count = branches.len();
            let end_lbl = Label::unique(label_num);
            for (cnt, (cond, branch)) in branches.into_iter().enumerate() {
                if labels.contains_key(&cond) {
                    return Err(Error::Asm(AsmError::ConditionalAlreadyUsed(cond)));
                }

                let next_lbl = if cnt == branch_count - 1 {
                    end_lbl.clone()
                } else {
                    Label::unique(label_num)
                };
                ops.push(Op::JumpIf(!cond, next_lbl.clone()));

                for branch_instr in branch {
                    ops.extend(branch_instr.flatten(label_num)?);
                }

                if cnt != branch_count - 1 {
                    ops.push(Op::Jump(end_lbl.clone()));
                    ops.push(Op::Label(next_lbl));
                }
            }
            ops.push(Op::Label(end_lbl));
        }

        Ok(ops)
    }
}

impl Flatten for Routine {
    fn flatten(self, label_num: &AtomicU32) -> Result<Vec<Op>, Error> {
        let mut ops = vec![
            Op::Routine(self.name.clone()).into(),
        ];

        for instr in self.body {
            ops.extend(instr.flatten(label_num)?);
        }

        ops.push(Op::Barrier(Some(format!("Routine \"{}\" overrun", self.name).into())).into());
        Ok(ops)
    }
}