use std::fs;
use std::path::{Path, PathBuf};
use std::process::{self, Command};

use super::path::{Dirs, RelPath};
use super::rustc_info::{get_file_name, get_rustc_version, get_toolchain_name};
use super::utils::{remove_dir_if_exists, spawn_and_wait, try_hard_link, CargoProject, Compiler};
use super::SysrootKind;

static DIST_DIR: RelPath = RelPath::DIST;
static BIN_DIR: RelPath = RelPath::DIST.join("bin");
static LIB_DIR: RelPath = RelPath::DIST.join("lib");

pub(crate) fn build_sysroot(
    dirs: &Dirs,
    channel: &str,
    sysroot_kind: SysrootKind,
    cg_clif_dylib_src: &Path,
    bootstrap_host_compiler: &Compiler,
    target_triple: String,
) -> Compiler {
    eprintln!("[BUILD] sysroot {:?}", sysroot_kind);

    DIST_DIR.ensure_fresh(dirs);
    BIN_DIR.ensure_exists(dirs);
    LIB_DIR.ensure_exists(dirs);

    let is_native = bootstrap_host_compiler.triple == target_triple;

    // Copy the backend
    let cg_clif_dylib_path = if cfg!(windows) {
        // Windows doesn't have rpath support, so the cg_clif dylib needs to be next to the
        // binaries.
        BIN_DIR
    } else {
        LIB_DIR
    }
    .to_path(dirs)
    .join(cg_clif_dylib_src.file_name().unwrap());
    try_hard_link(cg_clif_dylib_src, &cg_clif_dylib_path);

    // Build and copy rustc and cargo wrappers
    let wrapper_base_name = get_file_name("____", "bin");
    let toolchain_name = get_toolchain_name();
    for wrapper in ["rustc-clif", "rustdoc-clif", "cargo-clif"] {
        let wrapper_name = wrapper_base_name.replace("____", wrapper);

        let mut build_cargo_wrapper_cmd = Command::new(&bootstrap_host_compiler.rustc);
        build_cargo_wrapper_cmd
            .env("TOOLCHAIN_NAME", toolchain_name.clone())
            .arg(RelPath::SCRIPTS.to_path(dirs).join(&format!("{wrapper}.rs")))
            .arg("-o")
            .arg(DIST_DIR.to_path(dirs).join(wrapper_name))
            .arg("-Cstrip=debuginfo");
        spawn_and_wait(build_cargo_wrapper_cmd);
    }

    let host = build_sysroot_for_triple(
        dirs,
        channel,
        bootstrap_host_compiler.clone(),
        &cg_clif_dylib_path,
        sysroot_kind,
    );
    host.install_into_sysroot(&DIST_DIR.to_path(dirs));

    if !is_native {
        build_sysroot_for_triple(
            dirs,
            channel,
            {
                let mut bootstrap_target_compiler = bootstrap_host_compiler.clone();
                bootstrap_target_compiler.triple = target_triple.clone();
                bootstrap_target_compiler.set_cross_linker_and_runner();
                bootstrap_target_compiler
            },
            &cg_clif_dylib_path,
            sysroot_kind,
        )
        .install_into_sysroot(&DIST_DIR.to_path(dirs));
    }

    // Copy std for the host to the lib dir. This is necessary for the jit mode to find
    // libstd.
    for lib in host.libs {
        let filename = lib.file_name().unwrap().to_str().unwrap();
        if filename.contains("std-") && !filename.contains(".rlib") {
            try_hard_link(&lib, LIB_DIR.to_path(dirs).join(lib.file_name().unwrap()));
        }
    }

    let mut target_compiler = {
        let dirs: &Dirs = &dirs;
        let rustc_clif =
            RelPath::DIST.to_path(&dirs).join(wrapper_base_name.replace("____", "rustc-clif"));
        let rustdoc_clif =
            RelPath::DIST.to_path(&dirs).join(wrapper_base_name.replace("____", "rustdoc-clif"));

        Compiler {
            cargo: bootstrap_host_compiler.cargo.clone(),
            rustc: rustc_clif.clone(),
            rustdoc: rustdoc_clif.clone(),
            rustflags: String::new(),
            rustdocflags: String::new(),
            triple: target_triple,
            runner: vec![],
        }
    };
    if !is_native {
        target_compiler.set_cross_linker_and_runner();
    }
    target_compiler
}

struct SysrootTarget {
    triple: String,
    libs: Vec<PathBuf>,
}

impl SysrootTarget {
    fn install_into_sysroot(&self, sysroot: &Path) {
        if self.libs.is_empty() {
            return;
        }

        let target_rustlib_lib = sysroot.join("lib").join("rustlib").join(&self.triple).join("lib");
        fs::create_dir_all(&target_rustlib_lib).unwrap();

        for lib in &self.libs {
            try_hard_link(lib, target_rustlib_lib.join(lib.file_name().unwrap()));
        }
    }
}

pub(crate) static ORIG_BUILD_SYSROOT: RelPath = RelPath::SOURCE.join("build_sysroot");
pub(crate) static BUILD_SYSROOT: RelPath = RelPath::DOWNLOAD.join("sysroot");
pub(crate) static SYSROOT_RUSTC_VERSION: RelPath = BUILD_SYSROOT.join("rustc_version");
pub(crate) static SYSROOT_SRC: RelPath = BUILD_SYSROOT.join("sysroot_src");
pub(crate) static STANDARD_LIBRARY: CargoProject =
    CargoProject::new(&BUILD_SYSROOT, "build_sysroot");
pub(crate) static RTSTARTUP_SYSROOT: RelPath = RelPath::BUILD.join("rtstartup");

#[must_use]
fn build_sysroot_for_triple(
    dirs: &Dirs,
    channel: &str,
    compiler: Compiler,
    cg_clif_dylib_path: &Path,
    sysroot_kind: SysrootKind,
) -> SysrootTarget {
    match sysroot_kind {
        SysrootKind::None => build_rtstartup(dirs, &compiler)
            .unwrap_or(SysrootTarget { triple: compiler.triple, libs: vec![] }),
        SysrootKind::Llvm => build_llvm_sysroot_for_triple(compiler),
        SysrootKind::Clif => {
            build_clif_sysroot_for_triple(dirs, channel, compiler, &cg_clif_dylib_path)
        }
    }
}

#[must_use]
fn build_llvm_sysroot_for_triple(compiler: Compiler) -> SysrootTarget {
    let default_sysroot = super::rustc_info::get_default_sysroot(&compiler.rustc);

    let mut target_libs = SysrootTarget { triple: compiler.triple, libs: vec![] };

    for entry in fs::read_dir(
        default_sysroot.join("lib").join("rustlib").join(&target_libs.triple).join("lib"),
    )
    .unwrap()
    {
        let entry = entry.unwrap();
        if entry.file_type().unwrap().is_dir() {
            continue;
        }
        let file = entry.path();
        let file_name_str = file.file_name().unwrap().to_str().unwrap();
        if (file_name_str.contains("rustc_")
            && !file_name_str.contains("rustc_std_workspace_")
            && !file_name_str.contains("rustc_demangle"))
            || file_name_str.contains("chalk")
            || file_name_str.contains("tracing")
            || file_name_str.contains("regex")
        {
            // These are large crates that are part of the rustc-dev component and are not
            // necessary to run regular programs.
            continue;
        }
        target_libs.libs.push(file);
    }

    target_libs
}

#[must_use]
fn build_clif_sysroot_for_triple(
    dirs: &Dirs,
    channel: &str,
    mut compiler: Compiler,
    cg_clif_dylib_path: &Path,
) -> SysrootTarget {
    match fs::read_to_string(SYSROOT_RUSTC_VERSION.to_path(dirs)) {
        Err(e) => {
            eprintln!("Failed to get rustc version for patched sysroot source: {}", e);
            eprintln!("Hint: Try `./y.rs prepare` to patch the sysroot source");
            process::exit(1);
        }
        Ok(source_version) => {
            let rustc_version = get_rustc_version(&compiler.rustc);
            if source_version != rustc_version {
                eprintln!("The patched sysroot source is outdated");
                eprintln!("Source version: {}", source_version.trim());
                eprintln!("Rustc version:  {}", rustc_version.trim());
                eprintln!("Hint: Try `./y.rs prepare` to update the patched sysroot source");
                process::exit(1);
            }
        }
    }

    let mut target_libs = SysrootTarget { triple: compiler.triple.clone(), libs: vec![] };

    if let Some(rtstartup_target_libs) = build_rtstartup(dirs, &compiler) {
        rtstartup_target_libs.install_into_sysroot(&RTSTARTUP_SYSROOT.to_path(dirs));

        target_libs.libs.extend(rtstartup_target_libs.libs);
    }

    let build_dir = STANDARD_LIBRARY.target_dir(dirs).join(&compiler.triple).join(channel);

    if !super::config::get_bool("keep_sysroot") {
        // Cleanup the deps dir, but keep build scripts and the incremental cache for faster
        // recompilation as they are not affected by changes in cg_clif.
        remove_dir_if_exists(&build_dir.join("deps"));
    }

    // Build sysroot
    let mut rustflags = " -Zforce-unstable-if-unmarked -Cpanic=abort".to_string();
    rustflags.push_str(&format!(" -Zcodegen-backend={}", cg_clif_dylib_path.to_str().unwrap()));
    // Necessary for MinGW to find rsbegin.o and rsend.o
    rustflags
        .push_str(&format!(" --sysroot={}", RTSTARTUP_SYSROOT.to_path(dirs).to_str().unwrap()));
    if channel == "release" {
        rustflags.push_str(" -Zmir-opt-level=3");
    }
    compiler.rustflags += &rustflags;
    let mut build_cmd = STANDARD_LIBRARY.build(&compiler, dirs);
    if channel == "release" {
        build_cmd.arg("--release");
    }
    build_cmd.env("__CARGO_DEFAULT_LIB_METADATA", "cg_clif");
    if compiler.triple.contains("apple") {
        build_cmd.env("CARGO_PROFILE_RELEASE_SPLIT_DEBUGINFO", "packed");
    }
    spawn_and_wait(build_cmd);

    for entry in fs::read_dir(build_dir.join("deps")).unwrap() {
        let entry = entry.unwrap();
        if let Some(ext) = entry.path().extension() {
            if ext == "rmeta" || ext == "d" || ext == "dSYM" || ext == "clif" {
                continue;
            }
        } else {
            continue;
        };
        target_libs.libs.push(entry.path());
    }

    target_libs
}

fn build_rtstartup(dirs: &Dirs, compiler: &Compiler) -> Option<SysrootTarget> {
    if !compiler.triple.ends_with("windows-gnu") {
        return None;
    }

    RTSTARTUP_SYSROOT.ensure_fresh(dirs);

    let rtstartup_src = SYSROOT_SRC.to_path(dirs).join("library").join("rtstartup");
    let mut target_libs = SysrootTarget { triple: compiler.triple.clone(), libs: vec![] };

    for file in ["rsbegin", "rsend"] {
        let obj = RTSTARTUP_SYSROOT.to_path(dirs).join(format!("{file}.o"));
        let mut build_rtstartup_cmd = Command::new(&compiler.rustc);
        build_rtstartup_cmd
            .arg("--target")
            .arg(&compiler.triple)
            .arg("--emit=obj")
            .arg("-o")
            .arg(&obj)
            .arg(rtstartup_src.join(format!("{file}.rs")));
        spawn_and_wait(build_rtstartup_cmd);
        target_libs.libs.push(obj.clone());
    }

    Some(target_libs)
}