//! Creation of ar archives like for the lib and staticlib crate type

use std::collections::BTreeMap;
use std::fs::File;
use std::io::{self, Read, Seek};
use std::path::{Path, PathBuf};

use rustc_codegen_ssa::back::archive::{ArchiveBuilder, ArchiveBuilderBuilder};
use rustc_session::Session;

use object::read::archive::ArchiveFile;
use object::{Object, ObjectSymbol, ReadCache};

#[derive(Debug)]
enum ArchiveEntry {
    FromArchive { archive_index: usize, file_range: (u64, u64) },
    File(PathBuf),
}

pub(crate) struct ArArchiveBuilderBuilder;

impl ArchiveBuilderBuilder for ArArchiveBuilderBuilder {
    fn new_archive_builder<'a>(&self, sess: &'a Session) -> Box<dyn ArchiveBuilder<'a> + 'a> {
        Box::new(ArArchiveBuilder {
            sess,
            use_gnu_style_archive: sess.target.archive_format == "gnu",
            // FIXME fix builtin ranlib on macOS
            no_builtin_ranlib: sess.target.is_like_osx,

            src_archives: vec![],
            entries: vec![],
        })
    }

    fn create_dll_import_lib(
        &self,
        _sess: &Session,
        _lib_name: &str,
        _dll_imports: &[rustc_session::cstore::DllImport],
        _tmpdir: &Path,
        _is_direct_dependency: bool,
    ) -> PathBuf {
        bug!("creating dll imports is not supported");
    }
}

pub(crate) struct ArArchiveBuilder<'a> {
    sess: &'a Session,
    use_gnu_style_archive: bool,
    no_builtin_ranlib: bool,

    src_archives: Vec<File>,
    // Don't use `HashMap` here, as the order is important. `rust.metadata.bin` must always be at
    // the end of an archive for linkers to not get confused.
    entries: Vec<(Vec<u8>, ArchiveEntry)>,
}

impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
    fn add_file(&mut self, file: &Path) {
        self.entries.push((
            file.file_name().unwrap().to_str().unwrap().to_string().into_bytes(),
            ArchiveEntry::File(file.to_owned()),
        ));
    }

    fn add_archive(
        &mut self,
        archive_path: &Path,
        mut skip: Box<dyn FnMut(&str) -> bool + 'static>,
    ) -> std::io::Result<()> {
        let read_cache = ReadCache::new(std::fs::File::open(&archive_path)?);
        let archive = ArchiveFile::parse(&read_cache).unwrap();
        let archive_index = self.src_archives.len();

        for entry in archive.members() {
            let entry = entry.map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))?;
            let file_name = String::from_utf8(entry.name().to_vec())
                .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))?;
            if !skip(&file_name) {
                self.entries.push((
                    file_name.into_bytes(),
                    ArchiveEntry::FromArchive { archive_index, file_range: entry.file_range() },
                ));
            }
        }

        self.src_archives.push(read_cache.into_inner());
        Ok(())
    }

    fn build(mut self: Box<Self>, output: &Path) -> bool {
        enum BuilderKind {
            Bsd(ar::Builder<File>),
            Gnu(ar::GnuBuilder<File>),
        }

        let sess = self.sess;

        let mut symbol_table = BTreeMap::new();

        let mut entries = Vec::new();

        for (mut entry_name, entry) in self.entries {
            // FIXME only read the symbol table of the object files to avoid having to keep all
            // object files in memory at once, or read them twice.
            let data = match entry {
                ArchiveEntry::FromArchive { archive_index, file_range } => {
                    // FIXME read symbols from symtab
                    let src_read_cache = &mut self.src_archives[archive_index];

                    src_read_cache.seek(io::SeekFrom::Start(file_range.0)).unwrap();
                    let mut data = std::vec::from_elem(0, usize::try_from(file_range.1).unwrap());
                    src_read_cache.read_exact(&mut data).unwrap();

                    data
                }
                ArchiveEntry::File(file) => std::fs::read(file).unwrap_or_else(|err| {
                    sess.fatal(&format!(
                        "error while reading object file during archive building: {}",
                        err
                    ));
                }),
            };

            if !self.no_builtin_ranlib {
                if symbol_table.contains_key(&entry_name) {
                    // The ar crate can't handle creating a symbol table in case of multiple archive
                    // members with the same name. Work around this by prepending a number until we
                    // get a unique name.
                    for i in 1.. {
                        let new_name = format!("{}_", i)
                            .into_bytes()
                            .into_iter()
                            .chain(entry_name.iter().copied())
                            .collect::<Vec<_>>();
                        if !symbol_table.contains_key(&new_name) {
                            entry_name = new_name;
                            break;
                        }
                    }
                }

                match object::File::parse(&*data) {
                    Ok(object) => {
                        symbol_table.insert(
                            entry_name.to_vec(),
                            object
                                .symbols()
                                .filter_map(|symbol| {
                                    if symbol.is_undefined() || symbol.is_local() {
                                        None
                                    } else {
                                        symbol.name().map(|name| name.as_bytes().to_vec()).ok()
                                    }
                                })
                                .collect::<Vec<_>>(),
                        );
                    }
                    Err(err) => {
                        let err = err.to_string();
                        if err == "Unknown file magic" {
                            // Not an object file; skip it.
                        } else if object::read::archive::ArchiveFile::parse(&*data).is_ok() {
                            // Nested archive file; skip it.
                        } else {
                            sess.fatal(&format!(
                                "error parsing `{}` during archive creation: {}",
                                String::from_utf8_lossy(&entry_name),
                                err
                            ));
                        }
                    }
                }
            }

            entries.push((entry_name, data));
        }

        let mut builder = if self.use_gnu_style_archive {
            BuilderKind::Gnu(
                ar::GnuBuilder::new(
                    File::create(output).unwrap_or_else(|err| {
                        sess.fatal(&format!(
                            "error opening destination during archive building: {}",
                            err
                        ));
                    }),
                    entries.iter().map(|(name, _)| name.clone()).collect(),
                    ar::GnuSymbolTableFormat::Size32,
                    symbol_table,
                )
                .unwrap(),
            )
        } else {
            BuilderKind::Bsd(
                ar::Builder::new(
                    File::create(output).unwrap_or_else(|err| {
                        sess.fatal(&format!(
                            "error opening destination during archive building: {}",
                            err
                        ));
                    }),
                    symbol_table,
                )
                .unwrap(),
            )
        };

        let any_members = !entries.is_empty();

        // Add all files
        for (entry_name, data) in entries.into_iter() {
            let header = ar::Header::new(entry_name, data.len() as u64);
            match builder {
                BuilderKind::Bsd(ref mut builder) => builder.append(&header, &mut &*data).unwrap(),
                BuilderKind::Gnu(ref mut builder) => builder.append(&header, &mut &*data).unwrap(),
            }
        }

        // Finalize archive
        std::mem::drop(builder);

        if self.no_builtin_ranlib {
            let ranlib = crate::toolchain::get_toolchain_binary(self.sess, "ranlib");

            // Run ranlib to be able to link the archive
            let status = std::process::Command::new(ranlib)
                .arg(output)
                .status()
                .expect("Couldn't run ranlib");

            if !status.success() {
                self.sess.fatal(&format!("Ranlib exited with code {:?}", status.code()));
            }
        }

        any_members
    }
}