use std::fmt::Display;

use anyhow::bail;

use crate::{common::loc::LocBox, validator::predefined::get_builtin_from_name};

use super::{expr::Expr, literal::Literal, Ident, Program};

#[derive(Debug, Clone, PartialEq, PartialOrd, Hash)]
pub enum Type {
    Ref { 
        inner: Box<Type>,
        mutable: bool,
    },
    SizedArray {
        inner: Box<Type>,
        count: LocBox<Expr>,
    },
    UnsizedArray {
        inner: Box<Type>,
    },
    Owned(Ident),
    Builtin {
        name: String,
        size: u8,
        signed: bool,
    }
}

impl Type {
    pub fn get_absolute_value(&self, program: &Program) -> anyhow::Result<Self> {
        match self {
            Self::Ref { inner, .. } => inner.get_absolute_value(program),
            Self::Owned(ident) => {
                if let Some(t) = get_builtin_from_name(ident.0.as_str()) {
                    return Ok(t)
                } 
                if let Some(t) = program.curr_fn_args.get(ident) {
                    return Ok(t.inner().clone().get_absolute_value(program)?);
                } else
                if program.types.get(ident).is_some() ||
                    program.structs.get(ident).is_some() ||
                    program.enums.get(ident).is_some()
                {
                    return Ok(self.clone());
                }
                if let Some(var) = program.get_var(ident) {
                    Ok(var.1.inner().typ.clone().expect("type should be computed if were already using it").inner().clone().get_absolute_value(program)?)
                } else {
                    bail!("owo? missing value: {ident}");
                }
            }
            Self::SizedArray { .. } |
            Self::Builtin { .. } |
            Self::UnsizedArray { .. } => Ok(self.clone()),

        }
    }

    pub fn get_variable_type(&self, program: &Program) -> anyhow::Result<Self> {
        match self {
            Self::Owned(ident) => {
                if let Some(t) = program.types.get(ident) {
                    Ok(t.inner().clone())
                } else
                if let Some(var) = program.get_var(ident) {
                    Ok(var.1.inner().typ.clone().expect("type should be computed if were already using it").inner().clone())
                } else {
                    bail!("owo? missing value: {ident}");
                }
            }
            Self::Ref { .. } |
            Self::SizedArray { .. } |
            Self::Builtin { .. } |
            Self::UnsizedArray { .. } => Ok(self.clone()),

        }
    }
    pub fn is_numeric(&self, program: &Program) -> bool {
        match self {
            Self::Ref { inner, .. } => {
                inner.is_numeric(program)
            }
            Self::Owned(name) => {
                match program.types.get(&name) {
                    Some(t) => t.inner().is_numeric(program),
                    _ => false
                }
            },
            Self::SizedArray { .. } => false,
            Self::UnsizedArray { .. } => false,
            Self::Builtin { name, .. } => {
                match name.as_str() {
                    "u8" | "i8" |
                    "u16" | "i16" |
                    "u32" | "i32" |
                    "u64" | "i64" |
                    "usize" | "isize" => true,
                    _ => false,
                }
            }
        } 
    }
    // Returns None if non numeric
    pub fn is_signed(&self, program: &Program) -> Option<bool> {
        if self.is_ptr(program) {
            return Some(false);
        }
        match self {
            Self::Ref { inner, .. } => {
                inner.is_signed(program)
            }
            Self::Owned(name) => {
                match program.types.get(&name) {
                    Some(t) => t.inner().is_signed(program),
                    _ => None
                }
            },
            Self::SizedArray { .. } => None,
            Self::UnsizedArray { .. } => None,
            Self::Builtin { name, .. } => {
                match name.as_str() {
                    "i8" |
                    "i16" |
                    "i32" |
                    "i64" |
                    "isize" => Some(true),
                    "u8" |
                    "u16" |
                    "u32" |
                    "u64" |
                    "usize" => Some(false),
                    _ => None,
                }
            }
        } 
    }

    pub fn is_ptr(&self, program: &Program) -> bool {
        match self {
            Self::Owned(name) => {
                match program.types.get(&name) {
                    Some(t) => t.inner().is_ptr(program),
                    _ => false
                }
            },
            Self::Ref { .. } => true,
            _ => false
        }
    }

    pub fn is_bool(&self, program: &Program) -> bool {
        match self {
            Self::Owned(name) => {
                match program.types.get(&name) {
                    Some(t) => t.inner().is_bool(program),
                    _ => false
                }
            },
            Self::Builtin { name, .. } if name.as_str() == "bool" => true,
            _ => false
        }
    }
    pub fn size_of(&self, program: &Program) -> anyhow::Result<usize> {
        fn f(t: &Type, program: &Program, behind_a_ptr: bool) -> anyhow::Result<usize> {
            match t {
                Type::Ref { .. } => {
                    // TODO: Use the actual ptr size
                    Ok(size_of::<*const ()>())
                }
                Type::UnsizedArray { .. } => {
                    if behind_a_ptr {
                        Ok(size_of::<*const ()>())
                    } else {
                        bail!("Unsized arrays dont have a known size and must be behind a pointer");
                    }
                }
                Type::SizedArray { inner, .. } => {
                    Ok(inner.size_of(program)? )
                }
                Type::Builtin { size, .. } => {
                    Ok(*size as usize)
                }
                Type::Owned(name) => {
                    if let Some(v) = program.structs.get(&name) {
                        return Ok(v.inner().get_size(program)?);
                    }
                    if let Some(v) = program.types.get(&name) {
                        return Ok(f(v.inner(), program, behind_a_ptr)?);
                    }
                    if let Some(_) = program.enums.get(&name) {
                        return Ok(4); // TODO: Make enum size changeable
                    }
                    bail!("Unknown type '{name}'")
                }
            }
        }

        f(self, program, false)
    }
    pub fn size_of_allow_unsized_arrays(&self, program: &Program) -> anyhow::Result<usize> {
        match self.size_of(program) {
            Ok(v) => Ok(v),
            Err(e) => {
                if e.to_string().as_str() == "Unsized arrays dont have a known size and must be behind a pointer" {
                    return Ok(0);
                }
                Err(e)
            }
        }
    }
}

impl Display for Type {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Ref { inner, mutable } => {
                if *mutable {
                    write!(f, "&mut {inner}")
                } else {
                    write!(f, "&{inner}")
                }
            }
            Self::UnsizedArray { inner } => {
                write!(f, "[{inner}]")
            }
            Self::SizedArray { inner, count } => {
                match count.inner() {
                    Expr::Path(p) => {
                        write!(f, "[{inner}; {p}]")
                    }
                    Expr::Literal(_, Literal::Number(n)) => {
                        write!(f, "[{inner}; {n}]")
                    }
                    _ => unreachable!()
                }
            }
            Self::Owned(ident) => write!(f, "{ident}"),
            Self::Builtin { name, size, signed } => {
                write!(f, "(builtin) {} {}({})", name, if *signed { "signed" } else { "unsigned" }, size)
            }
        }
    }
}