#![allow(clippy::uninlined_format_args)]

use rsconf::{LinkType, Target};
use std::env;
use std::error::Error;
use std::path::{Path, PathBuf};

fn main() {
    setup_paths();

    // Add our default to enable tools that don't go through CMake, like "cargo test" and the
    // language server.

    // FISH_BUILD_DIR is set by CMake, if we are using it.
    // OUT_DIR is set by Cargo when the build script is running (not compiling)
    let default_build_dir = env::var("OUT_DIR").unwrap();
    let build_dir = option_env!("FISH_BUILD_DIR").unwrap_or(&default_build_dir);
    let build_dir = std::fs::canonicalize(build_dir).unwrap();
    let build_dir = build_dir.to_str().unwrap();
    rsconf::set_env_value("FISH_BUILD_DIR", build_dir);
    // We need to canonicalize (i.e. realpath) the manifest dir because we want to be able to
    // compare it directly as a string at runtime.
    rsconf::set_env_value(
        "CARGO_MANIFEST_DIR",
        std::fs::canonicalize(env!("CARGO_MANIFEST_DIR"))
            .unwrap()
            .as_path()
            .to_str()
            .unwrap(),
    );

    let version = &get_version(&env::current_dir().unwrap());
    // Per https://doc.rust-lang.org/cargo/reference/build-scripts.html#inputs-to-the-build-script,
    // the source directory is the current working directory of the build script
    rsconf::set_env_value("FISH_BUILD_VERSION", version);

    std::env::set_var("FISH_BUILD_VERSION", version);

    #[cfg(feature = "installable")]
    #[cfg(not(clippy))]
    {
        let cman = std::fs::canonicalize(env!("CARGO_MANIFEST_DIR")).unwrap();
        let targetman = cman.as_path().join("target").join("man");
        build_man(&targetman);
    }
    rsconf::rebuild_if_path_changed("src/libc.c");
    cc::Build::new()
        .file("src/libc.c")
        .include(build_dir)
        .compile("flibc.a");

    let mut build = cc::Build::new();
    // Add to the default library search path
    build.flag_if_supported("-L/usr/local/lib/");
    rsconf::add_library_search_path("/usr/local/lib");
    let mut target = Target::new_from(build).unwrap();
    // Keep verbose mode on until we've ironed out rust build script stuff
    target.set_verbose(true);
    detect_cfgs(&mut target);

    #[cfg(all(target_env = "gnu", target_feature = "crt-static"))]
    compile_error!("Statically linking against glibc has unavoidable crashes and is unsupported. Use dynamic linking or link statically against musl.");
}

/// Check target system support for certain functionality dynamically when the build is invoked,
/// without their having to be explicitly enabled in the `cargo build --features xxx` invocation.
///
/// We are using [`rsconf::enable_cfg()`] instead of [`rsconf::enable_feature()`] as rust features
/// should be used for things that a user can/would reasonably enable or disable to tweak or coerce
/// behavior, but here we are testing for whether or not things are supported altogether.
///
/// This can be used to enable features that we check for and conditionally compile according to in
/// our own codebase, but [can't be used to pull in dependencies](0) even if they're gated (in
/// `Cargo.toml`) behind a feature we just enabled.
///
/// [0]: https://github.com/rust-lang/cargo/issues/5499
#[rustfmt::skip]
fn detect_cfgs(target: &mut Target) {
    for (name, handler) in [
        // Ignore the first entry, it just sets up the type inference. Model new entries after the
        // second line.
        (
            "",
            &(|_: &Target| Ok(false)) as &dyn Fn(&Target) -> Result<bool, Box<dyn Error>>,
        ),
        ("bsd", &detect_bsd),
        ("gettext", &have_gettext),
        ("small_main_stack", &has_small_stack),
        // See if libc supports the thread-safe localeconv_l(3) alternative to localeconv(3).
        ("localeconv_l", &|target| {
            Ok(target.has_symbol("localeconv_l"))
        }),
        ("FISH_USE_POSIX_SPAWN", &|target| {
            Ok(target.has_header("spawn.h"))
        }),
        ("HAVE_PIPE2", &|target| {
            Ok(target.has_symbol("pipe2"))
        }),
        ("HAVE_EVENTFD", &|target| {
            // FIXME: NetBSD 10 has eventfd, but the libc crate does not expose it.
            if cfg!(target_os = "netbsd") {
                 Ok(false)
             } else {
                 Ok(target.has_header("sys/eventfd.h"))
            }
        }),
        ("HAVE_WAITSTATUS_SIGNAL_RET", &|target| {
            Ok(target.r#if("WEXITSTATUS(0x007f) == 0x7f", &["sys/wait.h"]))
        }),
    ] {
        match handler(target) {
            Err(e) => {
                rsconf::warn!("{}: {}", name, e);
                rsconf::declare_cfg(name, false);
            },
            Ok(enabled) => rsconf::declare_cfg(name, enabled),
        }
    }
}

/// Detect if we're being compiled for a BSD-derived OS, allowing targeting code conditionally with
/// `#[cfg(bsd)]`.
///
/// Rust offers fine-grained conditional compilation per-os for the popular operating systems, but
/// doesn't necessarily include less-popular forks nor does it group them into families more
/// specific than "windows" vs "unix" so we can conditionally compile code for BSD systems.
fn detect_bsd(_: &Target) -> Result<bool, Box<dyn Error>> {
    // Instead of using `uname`, we can inspect the TARGET env variable set by Cargo. This lets us
    // support cross-compilation scenarios.
    let mut target = std::env::var("TARGET").unwrap();
    if !target.chars().all(|c| c.is_ascii_lowercase()) {
        target = target.to_ascii_lowercase();
    }
    let is_bsd = target.ends_with("bsd") || target.ends_with("dragonfly");
    #[cfg(any(
        target_os = "dragonfly",
        target_os = "freebsd",
        target_os = "netbsd",
        target_os = "openbsd",
    ))]
    assert!(is_bsd, "Target incorrectly detected as not BSD!");
    Ok(is_bsd)
}

/// Detect libintl/gettext and its needed symbols to enable internationalization/localization
/// support.
fn have_gettext(target: &Target) -> Result<bool, Box<dyn Error>> {
    // The following script correctly detects and links against gettext, but so long as we are using
    // C++ and generate a static library linked into the C++ binary via CMake, we need to account
    // for the CMake option WITH_GETTEXT being explicitly disabled.
    rsconf::rebuild_if_env_changed("CMAKE_WITH_GETTEXT");
    if let Some(with_gettext) = std::env::var_os("CMAKE_WITH_GETTEXT") {
        if with_gettext.eq_ignore_ascii_case("0") {
            return Ok(false);
        }
    }

    // In order for fish to correctly operate, we need some way of notifying libintl to invalidate
    // its localizations when the locale environment variables are modified. Without the libintl
    // symbol _nl_msg_cat_cntr, we cannot use gettext even if we find it.
    let mut libraries = Vec::new();
    let mut found = 0;
    let symbols = ["gettext", "_nl_msg_cat_cntr"];
    for symbol in &symbols {
        // Historically, libintl was required in order to use gettext() and co, but that
        // functionality was subsumed by some versions of libc.
        if target.has_symbol(symbol) {
            // No need to link anything special for this symbol
            found += 1;
            continue;
        }
        for library in ["intl", "gettextlib"] {
            if target.has_symbol_in(symbol, &[library]) {
                libraries.push(library);
                found += 1;
                continue;
            }
        }
    }
    match found {
        0 => Ok(false),
        1 => Err(format!("gettext found but cannot be used without {}", symbols[1]).into()),
        _ => {
            rsconf::link_libraries(&libraries, LinkType::Default);
            Ok(true)
        }
    }
}

/// Rust sets the stack size of newly created threads to a sane value, but is at at the mercy of the
/// OS when it comes to the size of the main stack. Some platforms we support default to a tiny
/// 0.5 MiB main stack, which is insufficient for fish's MAX_EVAL_DEPTH/MAX_STACK_DEPTH values.
///
/// 0.5 MiB is small enough that we'd have to drastically reduce MAX_STACK_DEPTH to less than 10, so
/// we instead use a workaround to increase the main thread size.
fn has_small_stack(_: &Target) -> Result<bool, Box<dyn Error>> {
    #[cfg(not(any(target_os = "macos", target_os = "netbsd")))]
    return Ok(false);

    // NetBSD 10 also needs this but can't find pthread_get_stacksize_np.
    #[cfg(target_os = "netbsd")]
    return Ok(true);

    #[cfg(target_os = "macos")]
    {
        use core::ffi;

        extern "C" {
            fn pthread_get_stacksize_np(thread: *const ffi::c_void) -> usize;
            fn pthread_self() -> *const ffi::c_void;
        }

        // build.rs is executed on the main thread, so we are getting the main thread's stack size.
        // Modern macOS versions default to an 8 MiB main stack but legacy OS X have a 0.5 MiB one.
        let stack_size = unsafe { pthread_get_stacksize_np(pthread_self()) };
        const TWO_MIB: usize = 2 * 1024 * 1024 - 1;
        match stack_size {
            0..=TWO_MIB => Ok(true),
            _ => Ok(false),
        }
    }
}

fn setup_paths() {
    fn get_path(name: &str, default: &str, onvar: PathBuf) -> PathBuf {
        let mut var = PathBuf::from(env::var(name).unwrap_or(default.to_string()));
        if var.is_relative() {
            var = onvar.join(var);
        }
        var
    }

    let (prefix_from_home, prefix) = if let Ok(pre) = env::var("PREFIX") {
        (false, PathBuf::from(pre))
    } else {
        (true, PathBuf::from(".local/"))
    };

    // If someone gives us a $PREFIX, we need it to be absolute.
    // Otherwise we would try to get it from $HOME and that won't really work.
    if !prefix_from_home && prefix.is_relative() {
        panic!("Can't have relative prefix");
    }

    rsconf::rebuild_if_env_changed("PREFIX");
    rsconf::set_env_value("PREFIX", prefix.to_str().unwrap());

    let datadir = get_path("DATADIR", "share/", prefix.clone());
    rsconf::set_env_value("DATADIR", datadir.to_str().unwrap());
    rsconf::rebuild_if_env_changed("DATADIR");

    let datadir_subdir = if prefix_from_home {
        "fish/install"
    } else {
        "fish"
    };
    rsconf::set_env_value("DATADIR_SUBDIR", datadir_subdir);

    let bindir = get_path("BINDIR", "bin/", prefix.clone());
    rsconf::set_env_value("BINDIR", bindir.to_str().unwrap());
    rsconf::rebuild_if_env_changed("BINDIR");

    let sysconfdir = get_path(
        "SYSCONFDIR",
        // If we get our prefix from $HOME, we should use the system's /etc/
        // ~/.local/share/etc/ makes no sense
        if prefix_from_home { "/etc/" } else { "etc/" },
        datadir.clone(),
    );
    rsconf::set_env_value("SYSCONFDIR", sysconfdir.to_str().unwrap());
    rsconf::rebuild_if_env_changed("SYSCONFDIR");

    let localedir = get_path("LOCALEDIR", "locale/", datadir.clone());
    rsconf::set_env_value("LOCALEDIR", localedir.to_str().unwrap());
    rsconf::rebuild_if_env_changed("LOCALEDIR");

    let docdir = get_path("DOCDIR", "doc/fish", datadir.clone());
    rsconf::set_env_value("DOCDIR", docdir.to_str().unwrap());
    rsconf::rebuild_if_env_changed("DOCDIR");
}

fn get_version(src_dir: &Path) -> String {
    use std::fs::read_to_string;
    use std::process::Command;

    if let Ok(var) = std::env::var("FISH_BUILD_VERSION") {
        return var;
    }

    let path = PathBuf::from(src_dir).join("version");
    if let Ok(strver) = read_to_string(path) {
        return strver.to_string();
    }

    let args = &["describe", "--always", "--dirty=-dirty"];
    if let Ok(output) = Command::new("git").args(args).output() {
        let rev = String::from_utf8_lossy(&output.stdout).trim().to_string();
        if !rev.is_empty() {
            // If it contains a ".", we have a proper version like "3.7",
            // or "23.2.1-1234-gfab1234"
            if rev.contains('.') {
                return rev;
            }
            // If it doesn't, we probably got *just* the commit SHA,
            // like "f1242abcdef".
            // So we prepend the crate version so it at least looks like
            // "3.8-gf1242abcdef"
            // This lacks the commit *distance*, but that can't be helped without
            // tags.
            let version = env!("CARGO_PKG_VERSION").to_owned();
            return version + "-g" + &rev;
        }
    }

    // git did not tell us a SHA either because it isn't installed,
    // or because it refused (safe.directory applies to `git describe`!)
    // So we read the SHA ourselves.
    fn get_git_hash() -> Result<String, Box<dyn std::error::Error>> {
        let gitdir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(".git");

        // .git/HEAD contains ref: refs/heads/branch
        let headpath = gitdir.join("HEAD");
        let headstr = read_to_string(headpath)?;
        let headref = headstr.split(' ').collect::<Vec<_>>()[1].trim();

        // .git/refs/heads/branch contains the SHA
        let refpath = gitdir.join(headref);
        // Shorten to 9 characters (what git describe does currently)
        let refstr = &read_to_string(refpath)?[0..9];
        let refstr = refstr.trim();

        let version = env!("CARGO_PKG_VERSION").to_owned();
        Ok(version + "-g" + refstr)
    }

    get_git_hash().expect("Could not get a version. Either set $FISH_BUILD_VERSION or install git.")
}

#[cfg(feature = "installable")]
// disable clippy because otherwise it would panic without sphinx
#[cfg(not(clippy))]
fn build_man(build_dir: &Path) {
    use std::process::Command;
    let mandir = build_dir;
    let sec1dir = mandir.join("man1");
    let docsrc_path = std::fs::canonicalize(env!("CARGO_MANIFEST_DIR"))
        .unwrap()
        .as_path()
        .join("doc_src");
    let docsrc = docsrc_path.to_str().unwrap();
    let args = &[
        "-j",
        "auto",
        "-q",
        "-b",
        "man",
        "-c",
        docsrc,
        // doctree path - put this *above* the man1 dir to exclude it.
        // this is ~6M
        "-d",
        mandir.to_str().unwrap(),
        docsrc,
        sec1dir.to_str().unwrap(),
    ];
    let _ = std::fs::create_dir_all(sec1dir.to_str().unwrap());

    rsconf::rebuild_if_env_changed("FISH_BUILD_DOCS");
    if env::var("FISH_BUILD_DOCS") == Ok("0".to_string()) {
        println!("cargo:warning=Skipping man pages because $FISH_BUILD_DOCS is set to 0");
        return;
    }

    // We run sphinx to build the man pages.
    // Every error here is fatal so cargo doesn't cache the result
    // - if we skipped the docs with sphinx not installed, installing it would not then build the docs.
    // That means you need to explicitly set $FISH_BUILD_DOCS=0 (`FISH_BUILD_DOCS=0 cargo install --path .`),
    // which is unfortunate - but the docs are pretty important because they're also used for --help.
    match Command::new("sphinx-build").args(args).spawn() {
        Err(x) if x.kind() == std::io::ErrorKind::NotFound => {
            if env::var("FISH_BUILD_DOCS") == Ok("1".to_string()) {
                panic!("Could not find sphinx-build to build man pages.\nInstall sphinx or disable building the docs by setting $FISH_BUILD_DOCS=0.");
            }
            println!("cargo:warning=Cannot find sphinx-build to build man pages.");
            println!("cargo:warning=If you install it now you need to run `cargo clean` and rebuild, or set $FISH_BUILD_DOCS=1 explicitly.");
        }
        Err(x) => {
            // Another error - permissions wrong etc
            panic!("Error starting sphinx-build to build man pages: {:?}", x);
        }
        Ok(mut x) => match x.wait() {
            Err(err) => {
                panic!(
                    "Error waiting for sphinx-build to build man pages: {:?}",
                    err
                );
            }
            Ok(out) => {
                if out.success() {
                    // Success!
                    return;
                } else {
                    panic!("sphinx-build failed to build the man pages.");
                }
            }
        },
    }
}