use std::cell::Cell;
use std::collections::BTreeMap;

use super::parser;
use crate::rtlil;
pub use callable::Callable;
pub use types::{Type, TypeStruct, TypingContext};

mod callable;
#[cfg(never)]
pub mod lowering;
pub mod typed_ir;
pub mod types;

#[cfg(never)]
use crate::builtin_cells::get_builtins;

// pub use lowering::lower_module;

/// lots of code is still not width-aware, this constant keeps track of that
const TODO_WIDTH: u32 = 1;

fn make_pubid(id: &str) -> String {
    "\\".to_owned() + id
}

#[derive(Debug)]
pub enum CompileErrorKind {
    UndefinedReference(String),
    BadArgCount { received: usize, expected: usize },
    TodoError(String),
    TypeError { expected: Type, found: Type },
}

#[derive(Debug)]
pub struct CompileError {
    kind: CompileErrorKind,
}

impl CompileError {
    fn new(kind: CompileErrorKind) -> Self {
        Self { kind }
    }
}

/// A user-defined signal
pub struct Signal {
    /// the user-visible name of the signal
    pub name: String,
    /// the id of the signal in RTLIL
    pub il_id: String,
    /// the type of the signal
    pub typ: Type,
    // unique ID of the signal
    // pub uid: u64,
}

impl Signal {
    fn sigspec(&self) -> rtlil::SigSpec {
        rtlil::SigSpec::Wire(self.il_id.to_owned())
    }
}

pub struct Context {
    /// map callable name to callable
    callables: BTreeMap<String, Callable>,
    /// type names
    typenames: BTreeMap<String, Type>,
    types: TypingContext,
    /// map signal name to Signal
    signals: BTreeMap<String, typed_ir::Signal>,
    /// incrementing counter for unique IDs
    ids: Counter,
}

struct Counter(Cell<usize>);

impl Counter {
    fn new() -> Counter {
        Counter(Cell::new(0))
    }
    fn next(&self) -> usize {
        let next = self.0.get() + 1;
        self.0.set(next);
        next
    }
}

impl Context {
    pub fn new() -> Self {
        let tcx = TypingContext::new();
        Context {
            callables: BTreeMap::new(),
            signals: BTreeMap::new(),
            types: TypingContext::new(),
            typenames: [("Logic".to_string(), tcx.primitives.logic)].into(),
            ids: Counter::new(),
        }
    }

    fn try_get_signal(&self, signame: &str) -> Result<&typed_ir::Signal, CompileError> {
        self.signals.get(signame).ok_or_else(|| {
            CompileError::new(CompileErrorKind::UndefinedReference(signame.to_owned()))
        })
    }

    fn try_get_type(&self, typename: &str) -> Result<Type, CompileError> {
        self.typenames.get(typename).copied().ok_or_else(|| {
            CompileError::new(CompileErrorKind::UndefinedReference(typename.to_owned()))
        })
    }

    fn try_get_callable(&self, callname: &str) -> Result<&Callable, CompileError> {
        self.callables.get(callname).ok_or_else(|| {
            CompileError::new(CompileErrorKind::UndefinedReference(callname.to_owned()))
        })
    }

    fn type_expression(
        &self,
        expr: &parser::expression::Expression,
    ) -> Result<typed_ir::Expr, CompileError> {
        use parser::expression::Expression;
        let id = typed_ir::ExprId(self.ids.next() as u32);
        let t_expr = match expr {
            Expression::Path(name) => {
                let signal = self.try_get_signal(name)?;
                typed_ir::Expr {
                    id,
                    kind: typed_ir::ExprKind::Path(signal.id),
                    typ: signal.typ,
                }
            }
            Expression::Literal(_) => todo!(),
            Expression::UnOp(op) => self.type_expression(&op.a)?,
            Expression::BinOp(op) => {
                let (a, b) = (self.type_expression(&op.a)?, self.type_expression(&op.b)?);
                typed_ir::Expr {
                    id,
                    kind: typed_ir::ExprKind::Call {
                        called: typed_ir::DefId(99),
                        args: vec![a, b],
                    },
                    typ: self.types.primitives.elabnum,
                }
            }
            Expression::Call(call) => {
                let args_resolved = call
                    .args
                    .iter()
                    .map(|expr| self.type_expression(expr))
                    .collect::<Result<Vec<_>, _>>()?;
                typed_ir::Expr {
                    id,
                    kind: typed_ir::ExprKind::Call {
                        called: typed_ir::DefId(99),
                        args: args_resolved,
                    },
                    typ: self.types.primitives.elabnum,
                }
            }
        };
        Ok(t_expr)
    }

    fn type_comb(
        &mut self,
        comb: &parser::comb::CombBlock,
    ) -> Result<typed_ir::Block, CompileError> {
        let mut signals = Vec::new();

        for port in comb.ports.iter() {
            let sig_id = self.ids.next();
            let sig_typename = &port.net.typ;
            let sig_type = self.try_get_type(sig_typename.name.fragment())?;
            let sig = typed_ir::Signal {
                id: typed_ir::DefId(sig_id as u32),
                typ: sig_type,
            };
            signals.push(sig.clone());
            self.signals.insert(port.net.name.to_string(), sig);
        }

        let ret_typename = &comb.ret.name;
        let ret_type = self.try_get_type(ret_typename.fragment())?;

        let root_expr = self.type_expression(&comb.expr)?;

        // TODO: more sophisticated type compat check
        if root_expr.typ != ret_type {
            let expected = ret_type;
            let found = root_expr.typ;
            return Err(CompileError::new(CompileErrorKind::TypeError {
                expected,
                found,
            }));
        }

        Ok(typed_ir::Block {
            signals,
            expr: root_expr,
        })
    }

    pub fn type_module(&mut self, module: parser::Module) -> Result<typed_ir::Block, CompileError> {
        for item in module.items {
            let block = match &item {
                parser::ModuleItem::Comb(comb) => self.type_comb(comb)?,
                parser::ModuleItem::Proc(_) => todo!(),
                parser::ModuleItem::State(_) => todo!(),
            };
            return Ok(block);
        }
        Err(CompileError::new(CompileErrorKind::TodoError(
            "no blocks in module".to_string(),
        )))
    }
}