use std::convert::TryInto;

use rustc_data_structures::fx::FxHashMap;

use gimli::write::{Address, AttributeValue, EndianVec, Result, Sections, Writer};
use gimli::{RunTimeEndian, SectionId};

use crate::backend::WriteDebugInfo;

use super::DebugContext;

impl DebugContext<'_> {
    pub(crate) fn emit<P: WriteDebugInfo>(&mut self, product: &mut P) {
        let unit_range_list_id = self.dwarf.unit.ranges.add(self.unit_range_list.clone());
        let root = self.dwarf.unit.root();
        let root = self.dwarf.unit.get_mut(root);
        root.set(
            gimli::DW_AT_ranges,
            AttributeValue::RangeListRef(unit_range_list_id),
        );

        let mut sections = Sections::new(WriterRelocate::new(self.endian));
        self.dwarf.write(&mut sections).unwrap();

        let mut section_map = FxHashMap::default();
        let _: Result<()> = sections.for_each_mut(|id, section| {
            if !section.writer.slice().is_empty() {
                let section_id = product.add_debug_section(id, section.writer.take());
                section_map.insert(id, section_id);
            }
            Ok(())
        });

        let _: Result<()> = sections.for_each(|id, section| {
            if let Some(section_id) = section_map.get(&id) {
                for reloc in &section.relocs {
                    product.add_debug_reloc(&section_map, section_id, reloc);
                }
            }
            Ok(())
        });
    }
}

#[derive(Clone)]
pub(crate) struct DebugReloc {
    pub(crate) offset: u32,
    pub(crate) size: u8,
    pub(crate) name: DebugRelocName,
    pub(crate) addend: i64,
}

#[derive(Clone)]
pub(crate) enum DebugRelocName {
    Section(SectionId),
    Symbol(usize),
}

#[derive(Clone)]
pub(super) struct WriterRelocate {
    pub(super) relocs: Vec<DebugReloc>,
    pub(super) writer: EndianVec<RunTimeEndian>,
}

impl WriterRelocate {
    pub(super) fn new(endian: RunTimeEndian) -> Self {
        WriterRelocate {
            relocs: Vec::new(),
            writer: EndianVec::new(endian),
        }
    }

    pub(super) fn relocate_for_jit(
        mut self,
        jit_module: &mut cranelift_module::Module<cranelift_simplejit::SimpleJITBackend>,
    ) -> Vec<u8> {
        for reloc in self.relocs.drain(..) {
            match reloc.name {
                super::DebugRelocName::Section(_) => unreachable!(),
                super::DebugRelocName::Symbol(sym) => {
                    let addr = jit_module.get_finalized_function(
                        cranelift_module::FuncId::from_u32(sym.try_into().unwrap()),
                    );
                    let val = (addr as u64 as i64 + reloc.addend) as u64;
                    self.writer.write_udata_at(reloc.offset as usize, val, reloc.size).unwrap();
                }
            }
        }
        self.writer.into_vec()
    }
}

impl Writer for WriterRelocate {
    type Endian = RunTimeEndian;

    fn endian(&self) -> Self::Endian {
        self.writer.endian()
    }

    fn len(&self) -> usize {
        self.writer.len()
    }

    fn write(&mut self, bytes: &[u8]) -> Result<()> {
        self.writer.write(bytes)
    }

    fn write_at(&mut self, offset: usize, bytes: &[u8]) -> Result<()> {
        self.writer.write_at(offset, bytes)
    }

    fn write_address(&mut self, address: Address, size: u8) -> Result<()> {
        match address {
            Address::Constant(val) => self.write_udata(val, size),
            Address::Symbol { symbol, addend } => {
                let offset = self.len() as u64;
                self.relocs.push(DebugReloc {
                    offset: offset as u32,
                    size,
                    name: DebugRelocName::Symbol(symbol),
                    addend: addend as i64,
                });
                self.write_udata(0, size)
            }
        }
    }

    // TODO: implement write_eh_pointer

    fn write_offset(&mut self, val: usize, section: SectionId, size: u8) -> Result<()> {
        let offset = self.len() as u32;
        self.relocs.push(DebugReloc {
            offset,
            size,
            name: DebugRelocName::Section(section),
            addend: val as i64,
        });
        self.write_udata(0, size)
    }

    fn write_offset_at(
        &mut self,
        offset: usize,
        val: usize,
        section: SectionId,
        size: u8,
    ) -> Result<()> {
        self.relocs.push(DebugReloc {
            offset: offset as u32,
            size,
            name: DebugRelocName::Section(section),
            addend: val as i64,
        });
        self.write_udata_at(offset, 0, size)
    }
}