use crate::vm::obj::error::ParseError;
use std::{
    convert::TryFrom,
    fmt::Debug,
};

pub const MAGIC: u64 = 0xDEAD_BEA7_BA5E_BA11;

#[derive(Debug)]
pub struct Object {
    pub header: Header,
    pub sections: Vec<Box<dyn Section>>,
}

#[derive(Debug, Clone, Copy)]
pub struct Header {
    pub version: u16,
    pub sections: u16,
}

macro_rules! section_kind {
    (
        pub enum $enum_name:ident {
            $($name:ident = $value:expr),* $(,)?
        }
    ) => {

        #[derive(Debug, Clone, Copy)]
        #[repr(u8)]
        pub enum $enum_name {
            $($name = $value),*
        }

        impl TryFrom<u8> for SectionKind {
            type Error = ParseError;

            fn try_from(other: u8) -> std::result::Result<Self, Self::Error> {
                match other {
                    $(
                        $value => Ok($enum_name::$name),
                    )*
                    _ => Err(ParseError::UnknownSectionKind { kind: other }),
                }
            }
        }
    };
}

section_kind! {
    pub enum SectionKind {
        Data = 0x00,
        Code = 0x10,
        Meta = 0xFF,
    }
}

pub trait Section: Debug {
    fn header(&self) -> SectionHeader;
}

#[derive(Debug, Clone, Copy)]
pub struct SectionHeader {
    pub kind: SectionKind,
    pub checksum: u32,
    pub len: u64,
}

#[derive(Debug, Clone)]
pub struct DataSection {
    pub header: SectionHeader,
    pub load_location: u64,
    pub contents: Vec<u8>,
}

impl Section for DataSection {
    fn header(&self) -> SectionHeader {
        self.header
    }
}

#[derive(Debug, Clone)]
pub struct CodeSection {
    pub header: SectionHeader,
    pub load_location: u64,
    pub contents: Vec<u8>,
}

impl Section for CodeSection {
    fn header(&self) -> SectionHeader {
        self.header
    }
}

#[derive(Debug, Clone)]
pub struct MetaSection {
    pub header: SectionHeader,
    pub entry_count: u64,
    pub entries: Vec<(String, Vec<u8>)>,
}

impl Section for MetaSection {
    fn header(&self) -> SectionHeader {
        self.header
    }
}