use std::fmt::Display;
use std::io::{stdin, stdout, Read, Write};

use rustc_hash::FxHashMap;

use crate::error::RuntimeError;

use super::lox_std::init_std;
use super::Value;

pub struct Runtime {
    globals: FxHashMap<String, Value>,

    in_stream: Box<dyn std::io::BufRead>,
    out_stream: Box<dyn std::io::Write>,
}

impl Runtime {
    pub fn new(in_stream: Box<dyn std::io::Read>, out_stream: Box<dyn std::io::Write>) -> Self {
        let in_stream = Box::new(std::io::BufReader::new(in_stream));
        let mut runtime = Runtime {
            globals: FxHashMap::default(),
            in_stream,
            out_stream,
        };

        init_std(&mut runtime);

        runtime
    }

    pub fn globals(&self) -> &FxHashMap<String, Value> {
        &self.globals
    }

    pub fn get_global(&self, name: &str) -> Result<Value, RuntimeError> {
        self.globals
            .get(name)
            .cloned()
            .ok_or_else(|| RuntimeError::GlobalNotDefined { name: name.to_owned() })
    }

    pub fn define_global(&mut self, name: impl Into<String>, value: Value) {
        let name = name.into();
        self.globals.insert(name, value);
    }

    pub fn assign_global(&mut self, name: &str, value: Value) -> Result<(), RuntimeError> {
        if let Some(old_value) = self.globals.get_mut(name) {
            *old_value = value;
            Ok(())
        } else {
            Err(RuntimeError::GlobalNotDefined { name: name.to_owned() })
        }
    }
}

impl Default for Runtime {
    fn default() -> Self {
        Runtime::new(Box::new(std::io::BufReader::new(stdin())), Box::new(stdout()))
    }
}

impl std::fmt::Debug for Runtime {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Runtime").field("globals", &self.globals).finish()
    }
}

impl Display for Runtime {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Globals:")?;

        for (name, value) in self.globals.iter() {
            write!(f, "\n\t{name} = {value}")?;
        }

        Ok(())
    }
}

impl Drop for Runtime {
    fn drop(&mut self) {
        self.out_stream.flush().unwrap();
    }
}

impl Read for Runtime {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        self.in_stream.read(buf)
    }
}

impl Write for Runtime {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        self.out_stream.write(buf)
    }

    fn flush(&mut self) -> std::io::Result<()> {
        self.out_stream.flush()
    }
}