use std::{cell::RefCell, fmt::Display, io::Write, rc::Rc};

use rand::Rng;

use crate::{ast::Stmt, consts};

#[derive(Debug, Clone, PartialEq)]
pub enum Abool {
    Never = -1,
    Sometimes = 0,
    Always = 1,
}

impl Display for Abool {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Abool::Never => write!(f, "never"),
            Abool::Sometimes => write!(f, "sometimes"),
            Abool::Always => write!(f, "always"),
        }
    }
}

impl From<Abool> for bool {
    fn from(val: Abool) -> Self {
        match val {
            Abool::Never => false,
            Abool::Always => true,
            Abool::Sometimes => rand::thread_rng().gen(), // NOTE(Able): This is amazing and should be applied anywhere abooleans exist
        }
    }
}

#[derive(Debug, PartialEq, Clone)]
pub enum Functio {
    BfFunctio {
        instructions: Vec<u8>,
        tape_len: usize,
    },
    AbleFunctio {
        params: Vec<String>,
        body: Vec<Stmt>,
    },
}

#[derive(Debug, PartialEq, Clone)]
pub enum Value {
    Nul,
    Str(String),
    Int(i32),
    Bool(bool),
    Abool(Abool),
    Functio(Functio),
}

impl Value {
    /// Write an AbleScript value to a Brainfuck input stream by
    /// coercing the value to an integer, then truncating that integer
    /// to a single byte, then writing that byte. This should only be
    /// called on `Write`rs that cannot fail, e.g., `Vec<u8>`, because
    /// any IO errors will cause a panic.
    pub fn bf_write(&self, stream: &mut impl Write) {
        stream
            .write_all(&[self.clone().into_i32() as u8])
            .expect("Failed to write to Brainfuck input");
    }

    /// Coerce a value to an integer.
    pub fn into_i32(self) -> i32 {
        match self {
            Value::Abool(a) => a as _,
            Value::Bool(b) => b as _,
            Value::Functio(func) => match func {
                Functio::BfFunctio {
                    instructions,
                    tape_len,
                } => (instructions.len() + tape_len) as _,
                Functio::AbleFunctio { params, body } => (params.len() + body.len()) as _,
            },
            Value::Int(i) => i,
            Value::Nul => consts::ANSWER,
            Value::Str(text) => text.parse().unwrap_or(consts::ANSWER),
        }
    }

    /// Coerce a Value to a boolean. The conversion cannot fail.
    pub fn into_bool(self) -> bool {
        match self {
            Value::Abool(b) => b.into(),
            Value::Bool(b) => b,
            Value::Functio(_) => true,
            Value::Int(x) => x != 0,
            Value::Nul => true,
            Value::Str(s) => !s.is_empty(),
        }
    }
}

impl Display for Value {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Value::Nul => write!(f, "nul"),
            Value::Str(v) => write!(f, "{}", v),
            Value::Int(v) => write!(f, "{}", v),
            Value::Bool(v) => write!(f, "{}", v),
            Value::Abool(v) => write!(f, "{}", v),
            Value::Functio(v) => match v {
                Functio::BfFunctio {
                    instructions,
                    tape_len,
                } => {
                    write!(
                        f,
                        "({}) {}",
                        tape_len,
                        String::from_utf8(instructions.to_owned())
                            .expect("Brainfuck functio source should be UTF-8")
                    )
                }
                Functio::AbleFunctio { params, body } => {
                    write!(
                        f,
                        "({}) -> {:?}",
                        params.join(", "),
                        // Maybe we should have a pretty-printer for
                        // statement blocks at some point?
                        body,
                    )
                }
            },
        }
    }
}

#[derive(Debug)]
pub struct Variable {
    pub melo: bool,

    // Multiple Variables can reference the same underlying Value when
    // pass-by-reference is used, therefore we use Rc here.
    pub value: Rc<RefCell<Value>>,
}