//! This module contains simply [`Builder`] and it's related utility Values.
//! Builder is the actual struct being modified when building the LLIR.

use std::{cell::RefCell, rc::Rc};

use crate::{
    BlockData, ConstValue, FunctionData, InstructionData, InstructionKind, ModuleData,
    TerminatorKind, Type, util::match_types,
};

#[derive(Clone, Hash, Copy, PartialEq, Eq)]
pub struct ModuleValue(pub(crate) usize);

#[derive(Clone, Hash, Copy, PartialEq, Eq)]
pub struct FunctionValue(pub(crate) ModuleValue, pub(crate) usize);

#[derive(Clone, Hash, Copy, PartialEq, Eq)]
pub struct BlockValue(pub(crate) FunctionValue, pub(crate) usize);

#[derive(Clone, Hash, Copy, PartialEq, Eq)]
pub struct InstructionValue(pub(crate) BlockValue, pub(crate) usize);

#[derive(Clone)]
pub struct ModuleHolder {
    pub(crate) value: ModuleValue,
    pub(crate) data: ModuleData,
    pub(crate) functions: Vec<FunctionHolder>,
}

#[derive(Clone)]
pub struct FunctionHolder {
    pub(crate) value: FunctionValue,
    pub(crate) data: FunctionData,
    pub(crate) blocks: Vec<BlockHolder>,
}

#[derive(Clone)]
pub struct BlockHolder {
    pub(crate) value: BlockValue,
    pub(crate) data: BlockData,
    pub(crate) instructions: Vec<InstructionHolder>,
}

#[derive(Clone)]
pub struct InstructionHolder {
    pub(crate) value: InstructionValue,
    pub(crate) data: InstructionData,
}

#[derive(Clone)]
pub(crate) struct Builder {
    modules: Rc<RefCell<Vec<ModuleHolder>>>,
}

impl Builder {
    pub fn new() -> Builder {
        Builder {
            modules: Rc::new(RefCell::new(Vec::new())),
        }
    }

    pub(crate) fn add_module(&self, data: ModuleData) -> ModuleValue {
        let value = ModuleValue(self.modules.borrow().len());
        self.modules.borrow_mut().push(ModuleHolder {
            value,
            data,
            functions: Vec::new(),
        });
        value
    }

    pub(crate) unsafe fn add_function(
        &self,
        mod_val: &ModuleValue,
        data: FunctionData,
    ) -> FunctionValue {
        unsafe {
            let mut modules = self.modules.borrow_mut();
            let module = modules.get_unchecked_mut(mod_val.0);
            let value = FunctionValue(module.value, module.functions.len());
            module.functions.push(FunctionHolder {
                value,
                data,
                blocks: Vec::new(),
            });
            value
        }
    }

    pub(crate) unsafe fn add_block(&self, fun_val: &FunctionValue, data: BlockData) -> BlockValue {
        unsafe {
            let mut modules = self.modules.borrow_mut();
            let module = modules.get_unchecked_mut(fun_val.0.0);
            let function = module.functions.get_unchecked_mut(fun_val.1);
            let value = BlockValue(function.value, function.blocks.len());
            function.blocks.push(BlockHolder {
                value,
                data,
                instructions: Vec::new(),
            });
            value
        }
    }

    pub(crate) unsafe fn add_instruction(
        &self,
        block_val: &BlockValue,
        data: InstructionData,
    ) -> Result<InstructionValue, ()> {
        unsafe {
            let mut modules = self.modules.borrow_mut();
            let module = modules.get_unchecked_mut(block_val.0.0.0);
            let function = module.functions.get_unchecked_mut(block_val.0.1);
            let block = function.blocks.get_unchecked_mut(block_val.1);
            let value = InstructionValue(block.value, block.instructions.len());
            block.instructions.push(InstructionHolder { value, data });

            // Drop modules so that it is no longer mutable borrowed
            // (check_instruction requires an immutable borrow).
            drop(modules);

            self.check_instruction(&value)?;
            Ok(value)
        }
    }

    pub(crate) unsafe fn terminate(
        &self,
        block: &BlockValue,
        value: TerminatorKind,
    ) -> Result<(), ()> {
        unsafe {
            let mut modules = self.modules.borrow_mut();
            let module = modules.get_unchecked_mut(block.0.0.0);
            let function = module.functions.get_unchecked_mut(block.0.1);
            let block = function.blocks.get_unchecked_mut(block.1);
            if let Some(_) = &block.data.terminator {
                Err(())
            } else {
                block.data.terminator = Some(value);
                Ok(())
            }
        }
    }

    #[allow(dead_code)]
    pub(crate) unsafe fn module_data(&self, value: &ModuleValue) -> ModuleData {
        unsafe { self.modules.borrow().get_unchecked(value.0).data.clone() }
    }

    pub(crate) unsafe fn function_data(&self, value: &FunctionValue) -> FunctionData {
        unsafe {
            self.modules
                .borrow()
                .get_unchecked(value.0.0)
                .functions
                .get_unchecked(value.1)
                .data
                .clone()
        }
    }

    #[allow(dead_code)]
    pub(crate) unsafe fn block_data(&self, value: &BlockValue) -> BlockData {
        unsafe {
            self.modules
                .borrow()
                .get_unchecked(value.0.0.0)
                .functions
                .get_unchecked(value.0.1)
                .blocks
                .get_unchecked(value.1)
                .data
                .clone()
        }
    }

    pub(crate) unsafe fn instr_data(&self, value: &InstructionValue) -> InstructionData {
        unsafe {
            self.modules
                .borrow()
                .get_unchecked(value.0.0.0.0)
                .functions
                .get_unchecked(value.0.0.1)
                .blocks
                .get_unchecked(value.0.1)
                .instructions
                .get_unchecked(value.1)
                .data
                .clone()
        }
    }

    pub(crate) fn get_modules(&self) -> Rc<RefCell<Vec<ModuleHolder>>> {
        self.modules.clone()
    }

    pub fn check_instruction(&self, instruction: &InstructionValue) -> Result<(), ()> {
        use super::InstructionKind::*;
        unsafe {
            match self.instr_data(&instruction).kind {
                Param(_) => Ok(()),
                Constant(_) => Ok(()),
                Add(lhs, rhs) => match_types(&lhs, &rhs, &self).map(|_| ()),
                Sub(lhs, rhs) => match_types(&lhs, &rhs, &self).map(|_| ()),
                Mult(lhs, rhs) => match_types(&lhs, &rhs, &self).map(|_| ()),
                And(lhs, rhs) => match_types(&lhs, &rhs, &self).map(|_| ()),
                ICmp(_, lhs, rhs) => {
                    let t = match_types(&lhs, &rhs, self)?;
                    if t.comparable() {
                        Ok(())
                    } else {
                        Err(()) // TODO error: Types not comparable
                    }
                }
                FunctionCall(fun, params) => {
                    let param_types = self.function_data(&fun).params;
                    if param_types.len() != params.len() {
                        return Err(()); // TODO error: invalid amount of params
                    }
                    for (a, b) in param_types.iter().zip(params) {
                        if *a != b.get_type(&self)? {
                            return Err(()); // TODO error: params do not match
                        }
                    }
                    Ok(())
                }
                Phi(vals) => {
                    let mut iter = vals.iter();
                    // TODO error: Phi must contain at least one item
                    let first = iter.next().ok_or(())?;
                    for item in iter {
                        match_types(first, item, &self)?;
                    }
                    Ok(())
                }
            }
        }
    }
}

impl InstructionValue {
    pub(crate) fn get_type(&self, builder: &Builder) -> Result<Type, ()> {
        use InstructionKind::*;
        unsafe {
            match &builder.instr_data(self).kind {
                Param(nth) => builder
                    .function_data(&self.0.0)
                    .params
                    .get(*nth)
                    .copied()
                    .ok_or(()),
                Constant(c) => Ok(c.get_type()),
                Add(lhs, rhs) => match_types(lhs, rhs, &builder),
                Sub(lhs, rhs) => match_types(lhs, rhs, &builder),
                Mult(lhs, rhs) => match_types(lhs, rhs, &builder),
                And(lhs, rhs) => match_types(lhs, rhs, &builder),
                ICmp(_, _, _) => Ok(Type::Bool),
                FunctionCall(function_value, _) => Ok(builder.function_data(function_value).ret),
                Phi(values) => values.first().ok_or(()).and_then(|v| v.get_type(&builder)),
            }
        }
    }
}

impl ConstValue {
    pub fn get_type(&self) -> Type {
        use Type::*;
        match self {
            ConstValue::I8(_) => I8,
            ConstValue::I16(_) => I16,
            ConstValue::I32(_) => I32,
            ConstValue::I64(_) => I64,
            ConstValue::I128(_) => I128,
            ConstValue::U8(_) => U8,
            ConstValue::U16(_) => U16,
            ConstValue::U32(_) => U32,
            ConstValue::U64(_) => U64,
            ConstValue::U128(_) => U128,
            ConstValue::Bool(_) => Bool,
        }
    }
}

impl Type {
    pub fn comparable(&self) -> bool {
        match self {
            Type::I8 => true,
            Type::I16 => true,
            Type::I32 => true,
            Type::I64 => true,
            Type::I128 => true,
            Type::U8 => true,
            Type::U16 => true,
            Type::U32 => true,
            Type::U64 => true,
            Type::U128 => true,
            Type::Bool => true,
            Type::Void => false,
        }
    }

    pub fn signed(&self) -> bool {
        match self {
            Type::I8 => true,
            Type::I16 => true,
            Type::I32 => true,
            Type::I64 => true,
            Type::I128 => true,
            Type::U8 => false,
            Type::U16 => false,
            Type::U32 => false,
            Type::U64 => false,
            Type::U128 => false,
            Type::Bool => false,
            Type::Void => false,
        }
    }
}

impl TerminatorKind {
    pub(crate) fn get_type(&self, builder: &Builder) -> Result<Type, ()> {
        use TerminatorKind::*;
        match self {
            Ret(instr_val) => instr_val.get_type(builder),
            Branch(_) => Ok(Type::Void),
            CondBr(_, _, _) => Ok(Type::Void),
        }
    }
}