from __future__ import annotations

import contextlib
import functools
import os.path
import shutil
import sys
import tempfile
import urllib.request
from collections.abc import Generator
from collections.abc import Sequence

import pre_commit.constants as C
from pre_commit import lang_base
from pre_commit import parse_shebang
from pre_commit.envcontext import envcontext
from pre_commit.envcontext import PatchesT
from pre_commit.envcontext import Var
from pre_commit.prefix import Prefix
from pre_commit.util import cmd_output_b
from pre_commit.util import make_executable
from pre_commit.util import win_exe

ENVIRONMENT_DIR = 'rustenv'
health_check = lang_base.basic_health_check
run_hook = lang_base.basic_run_hook


@functools.lru_cache(maxsize=1)
def get_default_version() -> str:
    # If rust is already installed, we can save a bunch of setup time by
    # using the installed version.
    #
    # Just detecting the executable does not suffice, because if rustup is
    # installed but no toolchain is available, then `cargo` exists but
    # cannot be used without installing a toolchain first.
    if cmd_output_b('cargo', '--version', check=False, cwd='/')[0] == 0:
        return 'system'
    else:
        return C.DEFAULT


def _rust_toolchain(language_version: str) -> str:
    """Transform the language version into a rust toolchain version."""
    if language_version == C.DEFAULT:
        return 'stable'
    else:
        return language_version


def get_env_patch(target_dir: str, version: str) -> PatchesT:
    return (
        ('PATH', (os.path.join(target_dir, 'bin'), os.pathsep, Var('PATH'))),
        # Only set RUSTUP_TOOLCHAIN if we don't want use the system's default
        # toolchain
        *(
            (('RUSTUP_TOOLCHAIN', _rust_toolchain(version)),)
            if version != 'system' else ()
        ),
    )


@contextlib.contextmanager
def in_env(prefix: Prefix, version: str) -> Generator[None, None, None]:
    envdir = lang_base.environment_dir(prefix, ENVIRONMENT_DIR, version)
    with envcontext(get_env_patch(envdir, version)):
        yield


def _add_dependencies(
        prefix: Prefix,
        additional_dependencies: set[str],
) -> None:
    crates = []
    for dep in additional_dependencies:
        name, _, spec = dep.partition(':')
        crate = f'{name}@{spec or "*"}'
        crates.append(crate)

    lang_base.setup_cmd(prefix, ('cargo', 'add', *crates))


def install_rust_with_toolchain(toolchain: str, envdir: str) -> None:
    with tempfile.TemporaryDirectory() as rustup_dir:
        with envcontext((('CARGO_HOME', envdir), ('RUSTUP_HOME', rustup_dir))):
            # acquire `rustup` if not present
            if parse_shebang.find_executable('rustup') is None:
                # We did not detect rustup and need to download it first.
                if sys.platform == 'win32':  # pragma: win32 cover
                    url = 'https://win.rustup.rs/x86_64'
                else:  # pragma: win32 no cover
                    url = 'https://sh.rustup.rs'

                resp = urllib.request.urlopen(url)

                rustup_init = os.path.join(rustup_dir, win_exe('rustup-init'))
                with open(rustup_init, 'wb') as f:
                    shutil.copyfileobj(resp, f)
                make_executable(rustup_init)

                # install rustup into `$CARGO_HOME/bin`
                cmd_output_b(
                    rustup_init, '-y', '--quiet', '--no-modify-path',
                    '--default-toolchain', 'none',
                )

            cmd_output_b(
                'rustup', 'toolchain', 'install', '--no-self-update',
                toolchain,
            )


def install_environment(
        prefix: Prefix,
        version: str,
        additional_dependencies: Sequence[str],
) -> None:
    envdir = lang_base.environment_dir(prefix, ENVIRONMENT_DIR, version)

    # There are two cases where we might want to specify more dependencies:
    # as dependencies for the library being built, and as binary packages
    # to be `cargo install`'d.
    #
    # Unlike e.g. Python, if we just `cargo install` a library, it won't be
    # used for compilation. And if we add a crate providing a binary to the
    # `Cargo.toml`, the binary won't be built.
    #
    # Because of this, we allow specifying "cli" dependencies by prefixing
    # with 'cli:'.
    cli_deps = {
        dep for dep in additional_dependencies if dep.startswith('cli:')
    }
    lib_deps = set(additional_dependencies) - cli_deps

    packages_to_install: set[tuple[str, ...]] = {('--path', '.')}
    for cli_dep in cli_deps:
        cli_dep = cli_dep.removeprefix('cli:')
        package, _, crate_version = cli_dep.partition(':')
        if crate_version != '':
            packages_to_install.add((package, '--version', crate_version))
        else:
            packages_to_install.add((package,))

    with contextlib.ExitStack() as ctx:
        ctx.enter_context(in_env(prefix, version))

        if version != 'system':
            install_rust_with_toolchain(_rust_toolchain(version), envdir)

            tmpdir = ctx.enter_context(tempfile.TemporaryDirectory())
            ctx.enter_context(envcontext((('RUSTUP_HOME', tmpdir),)))

        if len(lib_deps) > 0:
            _add_dependencies(prefix, lib_deps)

        for args in packages_to_install:
            cmd_output_b(
                'cargo', 'install', '--bins', '--root', envdir, *args,
                cwd=prefix.prefix_dir,
            )