use std::fs::File;
use std::io::prelude::*;
use std::io::BufReader;
use std::path::Path;

use super::errors::GenericError;
use super::vm::VariableType;
use super::vm::{Command, CompiledReid};

#[cfg(feature = "compiler")]
pub fn open_source(path: &Path) -> Result<String, GenericError> {
    let file = File::open(path)?;
    let mut reader = BufReader::new(file);
    let mut text = String::new();
    reader.read_to_string(&mut text)?;
    Ok(text)
}

#[cfg(feature = "compiler")]
pub fn into_bytecode(compiled: &CompiledReid) -> Vec<u8> {
    let mut list = Vec::new();
    let cloned = compiled.list.clone().into_iter();
    for item in cloned {
        list.append(&mut item.into_u8());
    }
    list
}

#[cfg(feature = "compiler")]
pub fn write_bytecode(bytecode: Vec<u8>, path: &Path) -> Result<(), GenericError> {
    let mut file = File::create(path)?;
    file.write_all(&bytecode)?;
    Ok(())
}

pub fn open_bytecode(path: &Path) -> Result<CompiledReid, GenericError> {
    let file = File::open(path)?;
    let mut reader = BufReader::new(file);
    let mut commands = Vec::new();
    let mut iter = reader.fill_buf()?.iter().peekable();
    while iter.peek().is_some() {
        if let Some(command) = Command::from_u8(&mut iter) {
            commands.push(command);
        } else {
            return Err(GenericError::CorruptedBytecode);
        }
    }
    Ok(CompiledReid { list: commands })
}

impl VariableType {
    #[cfg(feature = "compiler")]
    fn into_u8(self) -> u8 {
        match self {
            VariableType::TypeString => 0,
            VariableType::TypeI32 => 1,
        }
    }

    fn from_u8(num: u8) -> Option<VariableType> {
        match num {
            0 => Some(VariableType::TypeString),
            1 => Some(VariableType::TypeI32),
            _ => None,
        }
    }
}

impl Command {
    #[cfg(feature = "compiler")]
    fn id(&self) -> u8 {
        match *self {
            Command::InitializeVariable(..) => 0,
            Command::BeginScope => 1,
            Command::EndScope => 2,
            Command::Pop(..) => 3,
            Command::Push(..) => 4,
            Command::AssignVariable(..) => 5,
            Command::VarToReg(..) => 6,
            Command::StringLit(..) => 7,
            Command::I32Lit(..) => 8,
            Command::FunctionCall(..) => 9,
            Command::Add => 10,
            Command::Subtract => 11,
            Command::Mult => 12,
            Command::Pow => 13,
            Command::Div => 14,
            Command::Mod => 15,
        }
    }

    fn from_u8<'a, T: Iterator<Item = &'a u8>>(iter: &mut T) -> Option<Command> {
        let id = iter.next()?;
        match id {
            0 => {
                let heapid = u16::from_be_bytes([*iter.next()?, *iter.next()?]);
                Some(Command::InitializeVariable(
                    heapid,
                    VariableType::from_u8(*iter.next()?)?,
                ))
            }
            1 => Some(Command::BeginScope),
            2 => Some(Command::EndScope),
            3 => Some(Command::Pop(*iter.next()?)),
            4 => Some(Command::Push(*iter.next()?)),
            5 => {
                let heapid = u16::from_be_bytes([*iter.next()?, *iter.next()?]);
                Some(Command::AssignVariable(heapid, *iter.next()?))
            }
            6 => {
                let heapid = u16::from_be_bytes([*iter.next()?, *iter.next()?]);
                Some(Command::VarToReg(heapid, *iter.next()?))
            }
            7 => {
                let len = u32::from_be_bytes([
                    *iter.next()?,
                    *iter.next()?,
                    *iter.next()?,
                    *iter.next()?,
                ]);
                let string = String::from_utf8(iter.take(len as usize).cloned().collect()).ok()?;
                Some(Command::StringLit(string))
            }
            8 => {
                let num = i32::from_be_bytes([
                    *iter.next()?,
                    *iter.next()?,
                    *iter.next()?,
                    *iter.next()?,
                ]);
                Some(Command::I32Lit(num))
            }
            9 => {
                let funcid = u16::from_be_bytes([*iter.next()?, *iter.next()?]);
                Some(Command::FunctionCall(funcid))
            }
            10 => Some(Command::Add),
            11 => Some(Command::Subtract),
            12 => Some(Command::Mult),
            13 => Some(Command::Pow),
            14 => Some(Command::Div),
            15 => Some(Command::Mod),
            _ => None,
        }
    }

    #[cfg(feature = "compiler")]
    fn into_u8(self) -> Vec<u8> {
        let mut list = Vec::new();
        list.push(self.id());
        match &self {
            Command::InitializeVariable(heapid, variabletype) => {
                let heapid = heapid.to_be_bytes();
                list.append(&mut vec![heapid[0], heapid[1], variabletype.into_u8()])
            }
            Command::BeginScope => (),
            Command::EndScope => (),
            Command::Pop(regid) => list.push(*regid),
            Command::Push(regid) => list.push(*regid),
            Command::AssignVariable(heapid, regid) => {
                let heapid = heapid.to_be_bytes();
                list.append(&mut vec![heapid[0], heapid[1], *regid]);
            }
            Command::VarToReg(heapid, regid) => {
                let heapid = heapid.to_be_bytes();
                list.append(&mut vec![heapid[0], heapid[1], *regid]);
            }
            Command::StringLit(string) => {
                let string = string.as_bytes();
                let len = (string.len() as u32).to_be_bytes();
                list.append(&mut vec![len[0], len[1], len[2], len[3]]);
                list.append(&mut string.to_vec());
            }
            Command::I32Lit(num) => {
                let num = num.to_be_bytes();
                list.append(&mut vec![num[0], num[1], num[2], num[3]]);
            }
            Command::FunctionCall(funcid) => {
                let funcid = funcid.to_be_bytes();
                list.append(&mut vec![funcid[0], funcid[1]]);
            }
            Command::Add => (),
            Command::Subtract => (),
            Command::Mult => (),
            Command::Pow => (),
            Command::Div => (),
            Command::Mod => (),
        }
        list
    }
}