use std::{
    fs::File,
    io::{BufRead, BufReader, BufWriter, Write},
    path::{Path, PathBuf},
    process::{Command, Stdio},
};

#[cfg(feature = "rabbit")]
const NAMESPACE: &str = "🐇";
#[cfg(not(feature = "rabbit"))]
const NAMESPACE: &str = "__libafl";
const NAMESPACE_LEN: usize = NAMESPACE.as_bytes().len();

#[allow(clippy::too_many_lines)]
fn main() {
    if cfg!(any(clippy, docsrs)) {
        return; // skip when clippy or docs is running
    }

    if cfg!(not(any(target_os = "linux", target_os = "macos"))) {
        println!(
            "cargo:warning=The libafl_libfuzzer runtime may only be built for linux or macos; failing fast."
        );
        return;
    }

    println!("cargo:rerun-if-changed=libafl_libfuzzer_runtime/src");
    println!("cargo:rerun-if-changed=libafl_libfuzzer_runtime/Cargo.toml");
    println!("cargo:rerun-if-changed=libafl_libfuzzer_runtime/build.rs");

    let custom_lib_dir =
        AsRef::<Path>::as_ref(&std::env::var_os("OUT_DIR").unwrap()).join("libafl_libfuzzer");
    std::fs::create_dir_all(&custom_lib_dir)
        .expect("Couldn't create the output directory for the fuzzer runtime build");

    let lib_src: PathBuf = AsRef::<Path>::as_ref(&std::env::var_os("CARGO_MANIFEST_DIR").unwrap())
        .join("libafl_libfuzzer_runtime");

    let mut command = Command::new(std::env::var_os("CARGO").unwrap());
    command
        .env_remove("RUSTFLAGS")
        .env_remove("CARGO_ENCODED_RUSTFLAGS");

    for (var, _) in std::env::vars() {
        if var.starts_with("CARGO_PKG_") || var.starts_with("CARGO_FEATURE_") {
            command.env_remove(var);
        }
    }

    command
        .env("PATH", std::env::var_os("PATH").unwrap())
        .current_dir(&lib_src);

    let _ = std::fs::rename(lib_src.join("Cargo.toml.orig"), lib_src.join("Cargo.toml"));

    command.arg("build");

    let mut features = vec![];

    if cfg!(any(feature = "fork")) {
        features.push("fork");
    }
    if cfg!(any(feature = "introspection")) {
        features.push("libafl/introspection");
    }

    if !features.is_empty() {
        command.arg("--features").arg(features.join(","));
    }

    command
        .arg("--release")
        .arg("--no-default-features")
        .arg("--target-dir")
        .arg(&custom_lib_dir)
        .arg("--target")
        .arg(std::env::var_os("TARGET").unwrap());

    assert!(
        command.status().map_or(false, |s| s.success()),
        "Couldn't build runtime crate! Did you remember to use nightly? (`rustup default nightly` to install)"
    );

    let mut archive_path = custom_lib_dir.join(std::env::var_os("TARGET").unwrap());
    archive_path.push("release");

    if cfg!(unix) {
        archive_path.push("libafl_libfuzzer_runtime.a");
        let target_libdir = Command::new("rustc")
            .args(["--print", "target-libdir"])
            .output()
            .expect("Couldn't find rustc's target-libdir");
        let target_libdir = String::from_utf8(target_libdir.stdout).unwrap();
        let target_libdir = Path::new(target_libdir.trim());

        // NOTE: depends on llvm-tools
        let rust_objcopy = target_libdir.join("../bin/llvm-objcopy");
        let nm = target_libdir.join("../bin/llvm-nm");

        let redefined_archive_path = custom_lib_dir.join("libFuzzer.a");
        let redefined_symbols = custom_lib_dir.join("redefs.txt");

        let mut nm_child = Command::new(nm)
            .arg(&archive_path)
            .stdout(Stdio::piped())
            .spawn()
            .expect("llvm-nm works (are you using nightly?)");

        let mut redefinitions_file = BufWriter::new(File::create(&redefined_symbols).unwrap());

        let zn_prefix = if cfg!(target_os = "macos") {
            // macOS symbols have an extra `_`
            "__ZN"
        } else {
            "_ZN"
        };

        let replacement = format!("{zn_prefix}{NAMESPACE_LEN}{NAMESPACE}");

        // redefine all the rust-mangled symbols we can
        // TODO this will break when v0 mangling is stabilised
        for line in BufReader::new(nm_child.stdout.take().unwrap()).lines() {
            let line = line.unwrap();

            // Skip headers
            if line.ends_with(':') || line.is_empty() {
                continue;
            }
            let (_, symbol) = line.rsplit_once(' ').unwrap();

            if symbol.starts_with(zn_prefix) {
                writeln!(
                    redefinitions_file,
                    "{} {}",
                    symbol,
                    symbol.replacen(zn_prefix, &replacement, 1)
                )
                .unwrap();
            }
        }
        redefinitions_file.flush().unwrap();
        drop(redefinitions_file);

        assert!(
            nm_child.wait().map_or(false, |s| s.success()),
            "Couldn't link runtime crate! Do you have the llvm-tools component installed? (`rustup component add llvm-tools-preview` to install)"
        );

        let mut objcopy_command = Command::new(rust_objcopy);

        for symbol in [
            "__rust_drop_panic",
            "__rust_foreign_exception",
            "rust_begin_unwind",
            "rust_panic",
            "rust_eh_personality",
            "__rg_oom",
            "__rdl_oom",
            "__rdl_alloc",
            "__rust_alloc",
            "__rdl_dealloc",
            "__rust_dealloc",
            "__rdl_realloc",
            "__rust_realloc",
            "__rdl_alloc_zeroed",
            "__rust_alloc_zeroed",
            "__rust_alloc_error_handler",
            "__rust_no_alloc_shim_is_unstable",
            "__rust_alloc_error_handler_should_panic",
        ] {
            let mut symbol = symbol.to_string();
            // macOS symbols have an extra `_`
            if cfg!(target_os = "macos") {
                symbol.insert(0, '_');
            }

            objcopy_command
                .arg("--redefine-sym")
                .arg(format!("{symbol}={symbol}_libafl_libfuzzer_runtime"));
        }

        objcopy_command
            .arg("--redefine-syms")
            .arg(redefined_symbols)
            .args([&archive_path, &redefined_archive_path]);

        assert!(
            objcopy_command.status().map_or(false, |s| s.success()),
            "Couldn't rename allocators in the runtime crate! Do you have the llvm-tools component installed? (`rustup component add llvm-tools-preview` to install)"
        );

        #[cfg(feature = "embed-runtime")]
        {
            // NOTE: lib, .a are added always on unix-like systems as described in:
            // https://gist.github.com/novafacing/1389cbb2f0a362d7eb103e67b4468e2b
            println!(
                "cargo:rustc-env=LIBAFL_LIBFUZZER_RUNTIME_PATH={}",
                redefined_archive_path.display()
            );
        }

        println!(
            "cargo:rustc-link-search=native={}",
            custom_lib_dir.to_str().unwrap()
        );
        println!("cargo:rustc-link-lib=static=Fuzzer");

        if cfg!(target_os = "macos") {
            println!("cargo:rustc-link-lib=c++");
        } else {
            println!("cargo:rustc-link-lib=stdc++");
        }
    }
}