use std::borrow::Cow;

use crate::spec::{
    BinaryFormat, Cc, DebuginfoKind, Env, LinkSelfContainedDefault, LinkerFlavor, Lld, Os,
    SplitDebuginfo, TargetOptions, add_link_args, crt_objects, cvs,
};

pub(crate) fn opts() -> TargetOptions {
    let mut pre_link_args = TargetOptions::link_args(
        LinkerFlavor::Gnu(Cc::No, Lld::No),
        &[
            // Enable ASLR
            "--dynamicbase",
            // ASLR will rebase it anyway so leaving that option enabled only leads to confusion
            "--disable-auto-image-base",
        ],
    );
    add_link_args(
        &mut pre_link_args,
        LinkerFlavor::Gnu(Cc::Yes, Lld::No),
        &[
            // Tell GCC to avoid linker plugins, because we are not bundling
            // them with Windows installer, and Rust does its own LTO anyways.
            "-fno-use-linker-plugin",
            "-Wl,--dynamicbase",
            "-Wl,--disable-auto-image-base",
        ],
    );

    // Order of `late_link_args*` was found through trial and error to work with various
    // mingw-w64 versions (not tested on the CI). It's expected to change from time to time.
    let mingw_libs = &[
        "-lmsvcrt",
        "-lmingwex",
        "-lmingw32",
        "-lgcc", // alas, mingw* libraries above depend on libgcc
        // mingw's msvcrt is a weird hybrid import library and static library.
        // And it seems that the linker fails to use import symbols from msvcrt
        // that are required from functions in msvcrt in certain cases. For example
        // `_fmode` that is used by an implementation of `__p__fmode` in x86_64.
        // The library is purposely listed twice to fix that.
        //
        // See https://github.com/rust-lang/rust/pull/47483 for some more details.
        "-lmsvcrt",
        // Math functions missing in MSVCRT (they are present in UCRT) require
        // this dependency cycle: `libmingwex.a` -> `libmsvcrt.a` -> `libmingwex.a`.
        "-lmingwex",
        "-luser32",
        "-lkernel32",
    ];
    let mut late_link_args =
        TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), mingw_libs);
    add_link_args(&mut late_link_args, LinkerFlavor::Gnu(Cc::Yes, Lld::No), mingw_libs);
    // If any of our crates are dynamically linked then we need to use
    // the shared libgcc_s-dw2-1.dll. This is required to support
    // unwinding across DLL boundaries.
    let dynamic_unwind_libs = &["-lgcc_s"];
    let mut late_link_args_dynamic =
        TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), dynamic_unwind_libs);
    add_link_args(
        &mut late_link_args_dynamic,
        LinkerFlavor::Gnu(Cc::Yes, Lld::No),
        dynamic_unwind_libs,
    );
    // If all of our crates are statically linked then we can get away
    // with statically linking the libgcc unwinding code. This allows
    // binaries to be redistributed without the libgcc_s-dw2-1.dll
    // dependency, but unfortunately break unwinding across DLL
    // boundaries when unwinding across FFI boundaries.
    let static_unwind_libs = &["-lgcc_eh", "-l:libpthread.a"];
    let mut late_link_args_static =
        TargetOptions::link_args(LinkerFlavor::Gnu(Cc::No, Lld::No), static_unwind_libs);
    add_link_args(
        &mut late_link_args_static,
        LinkerFlavor::Gnu(Cc::Yes, Lld::No),
        static_unwind_libs,
    );

    TargetOptions {
        os: Os::Windows,
        env: Env::Gnu,
        vendor: "pc".into(),
        // FIXME(#13846) this should be enabled for windows
        function_sections: false,
        linker: Some("gcc".into()),
        dynamic_linking: true,
        dll_tls_export: false,
        dll_prefix: "".into(),
        dll_suffix: ".dll".into(),
        exe_suffix: ".exe".into(),
        families: cvs!["windows"],
        is_like_windows: true,
        binary_format: BinaryFormat::Coff,
        allows_weak_linkage: false,
        pre_link_args,
        pre_link_objects_self_contained: crt_objects::pre_mingw_self_contained(),
        link_self_contained: LinkSelfContainedDefault::InferredForMingw,
        late_link_args,
        late_link_args_dynamic,
        late_link_args_static,
        abi_return_struct_as_int: true,
        emit_debug_gdb_scripts: false,
        requires_uwtable: true,
        eh_frame_header: false,
        debuginfo_kind: DebuginfoKind::Dwarf,
        // FIXME(davidtwco): Support Split DWARF on Windows GNU - may require LLVM changes to
        // output DWO, despite using DWARF, doesn't use ELF..
        supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),
        mcount: "_mcount".into(),
        ..Default::default()
    }
}
