use std::collections::HashMap;
use std::sync::Arc;

use crate::asm::data::literal::{Addr, Label, RoutineName};
use crate::asm::instr::Op;
use crate::asm::instr::op::OpKind;
use crate::builtin::defs::{Barrier, BuiltinOp};
use crate::module::CrsnExtension;
use crate::runtime::fault::Fault;

#[derive(Debug)]
pub struct Program {
    pub ops: Vec<Op>,
    pub extensions: Arc<Vec<Box<dyn CrsnExtension>>>,
    routines: HashMap<RoutineName, Addr>,
    far_labels: HashMap<Label, Addr>,
    /// Barriers from-to (inclusive).
    /// Standalone barriers have both addresses the same.
    barriers: Vec<(Addr, Addr)>,
}

impl Program {
    pub fn new(ops: Vec<Op>, extensions: Arc<Vec<Box<dyn CrsnExtension>>>) -> anyhow::Result<Arc<Self>> {
        let mut p = Self {
            ops,
            extensions,
            routines: Default::default(),
            far_labels: Default::default(),
            barriers: Default::default(),
        };
        p.scan()?;
        Ok(Arc::new(p))
    }

    /// Find all the named things
    fn scan(&mut self) -> anyhow::Result<()> {
        let mut barrier_starts: HashMap<&Label, Addr> = HashMap::new();
        for (pos, op) in self.ops.iter().enumerate() {
            match &op.kind {
                OpKind::BuiltIn(BuiltinOp::FarLabel(name)) => {
                    self.far_labels.insert(name.clone(), pos.into());
                }
                OpKind::BuiltIn(BuiltinOp::Routine(name)) => {
                    self.routines.insert(name.clone(), pos.into());
                }
                OpKind::BuiltIn(
                    BuiltinOp::Barrier {
                        kind: Barrier::Open(lbl), ..
                    }
                ) => {
                    barrier_starts.insert(lbl, pos.into());
                }
                OpKind::BuiltIn(
                    BuiltinOp::Barrier {
                        kind: Barrier::Close(lbl),
                        msg,
                    }
                ) => {
                    if let Some(start_pos) = barrier_starts.remove(lbl) {
                        self.barriers.push((start_pos, pos.into()));
                        self.far_labels.insert(lbl.clone(), pos.into());
                    } else {
                        anyhow::bail!("Block barrier \"{:?}\" closed without being open!", msg);
                    }
                }
                OpKind::BuiltIn(
                    BuiltinOp::Barrier {
                        kind: Barrier::Standalone,
                        ..
                    }
                ) => {
                    self.barriers.push((pos.into(), pos.into()));
                }
                _ => {}
            }
        }

        if !barrier_starts.is_empty() {
            anyhow::bail!("Some block barriers open without being closed!");
        }

        trace!("Program scanned: {:?}", self);

        Ok(())
    }

    /// Read a program instruction at address
    pub fn read(&self, addr: Addr) -> &Op {
        if addr.0 >= self.ops.len() as u64 {
            &Op { kind: OpKind::BuiltIn(BuiltinOp::Halt), cond: None }
        } else {
            &self.ops[addr.0 as usize]
        }
    }

    /// Return error if any barrier is crossed during a jump / skip
    pub fn validate_jump(&self, mut from: Addr, mut to: Addr) -> Result<(), Fault> {
        if from > to {
            std::mem::swap(&mut from, &mut to);
        }

        for (b0, b1) in &self.barriers {
            if b0 != b1 {
                // block barrier that only partially intersects the jump
                if (*b0 >= from && *b0 <= to) != (*b1 >= from && *b1 <= to) {
                    if let OpKind::BuiltIn(BuiltinOp::Barrier { msg, .. }) = &self.read(*b0).kind {
                        return Err(Fault::JumpThroughBarrier {
                            msg: msg.clone().unwrap_or("BLOCK BARRIER".into())
                        });
                    } else {
                        unreachable!();
                    }
                }
            } else {
                // point barrier
                if *b0 >= from && *b0 <= to {
                    if let OpKind::BuiltIn(BuiltinOp::Barrier { msg, .. }) = &self.read(*b0).kind {
                        return Err(Fault::JumpThroughBarrier {
                            msg: msg.clone().unwrap_or("POINT BARRIER".into())
                        });
                    } else {
                        unreachable!();
                    }
                }
            }
        }
        Ok(())
    }

    /// Find routine by name
    pub fn find_routine(&self, name: &RoutineName) -> Result<Addr, Fault> {
        self.routines.get(name).copied()
            .ok_or_else(|| Fault::NoSuchRoutine { routine: name.clone() })
    }

    /// Find far label by name
    pub fn find_far_label(&self, name: &Label) -> Result<Addr, Fault> {
        self.far_labels.get(name).copied()
            .ok_or_else(|| Fault::NoSuchLabel { label: name.clone() })
    }
}