use std::collections::BTreeMap;
use std::fs::File;
use std::path::{Path, PathBuf};

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

use object::{Object, SymbolKind};

struct ArchiveConfig<'a> {
    sess: &'a Session,
    dst: PathBuf,
    lib_search_paths: Vec<PathBuf>,
    use_gnu_style_archive: bool,
    no_builtin_ranlib: bool,
}

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

pub(crate) struct ArArchiveBuilder<'a> {
    config: ArchiveConfig<'a>,
    src_archives: Vec<(PathBuf, ar::Archive<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<(String, ArchiveEntry)>,
    update_symbols: bool,
}

impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
    fn new(sess: &'a Session, output: &Path, input: Option<&Path>) -> Self {
        use rustc_codegen_ssa::back::link::archive_search_paths;
        let config = ArchiveConfig {
            sess,
            dst: output.to_path_buf(),
            lib_search_paths: archive_search_paths(sess),
            use_gnu_style_archive: sess.target.target.options.archive_format == "gnu",
            // FIXME fix builtin ranlib on macOS
            no_builtin_ranlib: sess.target.target.options.is_like_osx,
        };

        let (src_archives, entries) = if let Some(input) = input {
            let mut archive = ar::Archive::new(File::open(input).unwrap());
            let mut entries = Vec::new();

            let mut i = 0;
            while let Some(entry) = archive.next_entry() {
                let entry = entry.unwrap();
                entries.push((
                    String::from_utf8(entry.header().identifier().to_vec()).unwrap(),
                    ArchiveEntry::FromArchive {
                        archive_index: 0,
                        entry_index: i,
                    },
                ));
                i += 1;
            }

            (vec![(input.to_owned(), archive)], entries)
        } else {
            (vec![], Vec::new())
        };

        ArArchiveBuilder {
            config,
            src_archives,
            entries,
            update_symbols: false,
        }
    }

    fn src_files(&mut self) -> Vec<String> {
        self.entries.iter().map(|(name, _)| name.clone()).collect()
    }

    fn remove_file(&mut self, name: &str) {
        let index = self
            .entries
            .iter()
            .position(|(entry_name, _)| entry_name == name)
            .expect("Tried to remove file not existing in src archive");
        self.entries.remove(index);
    }

    fn add_file(&mut self, file: &Path) {
        self.entries.push((
            file.file_name().unwrap().to_str().unwrap().to_string(),
            ArchiveEntry::File(file.to_owned()),
        ));
    }

    fn add_native_library(&mut self, name: rustc_span::symbol::Symbol) {
        let location = find_library(name, &self.config.lib_search_paths, self.config.sess);
        self.add_archive(location.clone(), |_| false)
            .unwrap_or_else(|e| {
                panic!(
                    "failed to add native library {}: {}",
                    location.to_string_lossy(),
                    e
                );
            });
    }

    fn add_rlib(
        &mut self,
        rlib: &Path,
        name: &str,
        lto: bool,
        skip_objects: bool,
    ) -> std::io::Result<()> {
        let obj_start = name.to_owned();

        self.add_archive(rlib.to_owned(), move |fname: &str| {
            // Ignore metadata files, no matter the name.
            if fname == METADATA_FILENAME {
                return true;
            }

            // Don't include Rust objects if LTO is enabled
            if lto && fname.starts_with(&obj_start) && fname.ends_with(".o") {
                return true;
            }

            // Otherwise if this is *not* a rust object and we're skipping
            // objects then skip this file
            if skip_objects && (!fname.starts_with(&obj_start) || !fname.ends_with(".o")) {
                return true;
            }

            // ok, don't skip this
            return false;
        })
    }

    fn update_symbols(&mut self) {
        self.update_symbols = true;
    }

    fn build(mut self) {
        enum BuilderKind {
            Bsd(ar::Builder<File>),
            Gnu(ar::GnuBuilder<File>),
        }

        let sess = self.config.sess;

        let mut symbol_table = BTreeMap::new();

        let mut entries = Vec::new();

        for (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,
                    entry_index,
                } => {
                    // FIXME read symbols from symtab
                    use std::io::Read;
                    let (ref _src_archive_path, ref mut src_archive) =
                        self.src_archives[archive_index];
                    let mut entry = src_archive.jump_to_entry(entry_index).unwrap();
                    let mut data = Vec::new();
                    entry.read_to_end(&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.config.no_builtin_ranlib {
                match object::File::parse(&data) {
                    Ok(object) => {
                        symbol_table.insert(entry_name.as_bytes().to_vec(), object.symbols().filter_map(|(_index, symbol)| {
                            if symbol.is_undefined() || symbol.is_local() || symbol.kind() != SymbolKind::Data && symbol.kind() != SymbolKind::Text && symbol.kind() != SymbolKind::Tls {
                                None
                            } else {
                                symbol.name().map(|name| name.as_bytes().to_vec())
                            }
                        }).collect::<Vec<_>>());
                    }
                    Err(err) => {
                        let err = err.to_string();
                        if err == "Unknown file magic" {
                            // Not an object file; skip it.
                        } else {
                            sess.fatal(&format!("error parsing `{}` during archive creation: {}", entry_name, err));
                        }
                    }
                }
            }

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

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

        // Add all files
        for (entry_name, data) in entries.into_iter() {
            let header = ar::Header::new(entry_name.into_bytes(), 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.config.no_builtin_ranlib {
            let ranlib = crate::toolchain::get_toolchain_binary(self.config.sess, "ranlib");

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

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

impl<'a> ArArchiveBuilder<'a> {
    fn add_archive<F>(&mut self, archive_path: PathBuf, mut skip: F) -> std::io::Result<()>
    where
        F: FnMut(&str) -> bool + 'static,
    {
        let mut archive = ar::Archive::new(std::fs::File::open(&archive_path)?);
        let archive_index = self.src_archives.len();

        let mut i = 0;
        while let Some(entry) = archive.next_entry() {
            let entry = entry?;
            let file_name = String::from_utf8(entry.header().identifier().to_vec()).map_err(|err| {
                std::io::Error::new(std::io::ErrorKind::InvalidData, err)
            })?;
            if !skip(&file_name) {
                self.entries.push((
                    file_name,
                    ArchiveEntry::FromArchive {
                        archive_index,
                        entry_index: i,
                    },
                ));
            }
            i += 1;
        }

        self.src_archives.push((archive_path, archive));
        Ok(())
    }
}