Extract environment setup into its own script

This simplifies environment setup for shell operations

scripts/env.py

@@ -0,0 +1,166 @@
+#!/usr/bin/env python3
+import functools
+import multiprocessing
+import os
+import platform
+import sys
+import shutil
+import subprocess
+from pathlib import Path
+from typing import NoReturn
+
+
+ondk_version = "r29.5"
+
+
+def color_print(code, str):
+    if no_color:
+        print(str)
+    else:
+        str = str.replace("\n", f"\033[0m\n{code}")
+        print(f"{code}{str}\033[0m")
+
+
+def error(str) -> NoReturn:
+    color_print("\033[41;39m", f"\n! {str}\n")
+    sys.exit(1)
+
+
+def header(str):
+    color_print("\033[44;39m", f"\n{str}\n")
+
+
+class Paths:
+    def __init__(self):
+        try:
+            self.sdk = Path(os.environ["ANDROID_HOME"])
+        except KeyError:
+            try:
+                self.sdk = Path(os.environ["ANDROID_SDK_ROOT"])
+            except KeyError:
+                error(
+                    "Please set Android SDK path to environment variable ANDROID_HOME"
+                )
+
+        self.ndk = self.sdk / "ndk" / "magisk"
+        self.ndk_build = self.ndk / "ndk-build"
+        self.rust_sysroot = self.ndk / "toolchains" / "rust"
+        self.adb = self.sdk / "platform-tools" / "adb"
+        self.gradlew = Path.cwd() / "app" / "gradlew"
+
+
+@functools.cache
+def paths() -> Paths:
+    return Paths()
+
+
+def run_once(func):
+    def wrapper(*args, **kwargs):
+        if not wrapper.has_run:
+            wrapper.has_run = True
+            return func(*args, **kwargs)
+
+    wrapper.has_run = False
+    return wrapper
+
+
+@run_once
+def ensure_toolchain():
+    # Verify NDK install
+    try:
+        with open(paths().ndk / "ONDK_VERSION", "r") as ondk_ver:
+            assert ondk_ver.read().strip(" \t\r\n") == ondk_version
+    except:
+        error('Unmatched NDK. Please install/upgrade NDK with "build.py ndk"')
+
+    if sccache := shutil.which("sccache"):
+        os.environ["RUSTC_WRAPPER"] = sccache
+        os.environ["NDK_CCACHE"] = sccache
+        os.environ["CARGO_INCREMENTAL"] = "0"
+    if ccache := shutil.which("ccache"):
+        os.environ["NDK_CCACHE"] = ccache
+
+
+@run_once
+def ensure_cargo():
+    ensure_toolchain()
+
+    os.environ["CARGO_BUILD_RUSTFLAGS"] = f"-Z threads={min(8, cpu_count)}"
+    if shutil.which("rustup"):
+        # Go through rustup proxies by default if available
+        os.environ["RUSTUP_TOOLCHAIN"] = str(paths().rust_sysroot)
+    else:
+        os.environ["PATH"] = (
+            f"{paths().rust_sysroot / "bin"}{os.pathsep}{os.environ["PATH"]}"
+        )
+        # Cargo calls executables in $RUSTROOT/lib/rustlib/$TRIPLE/bin, we need
+        # to make sure the runtime linker also search $RUSTROOT/lib for libraries.
+        # This is only required on Unix, as Windows search dlls from PATH.
+        if os_name == "darwin":
+            os.environ["DYLD_FALLBACK_LIBRARY_PATH"] = str(paths().rust_sysroot / "lib")
+        elif os_name == "linux":
+            os.environ["LD_LIBRARY_PATH"] = str(paths().rust_sysroot / "lib")
+
+
+@run_once
+def ensure_jdk():
+    if "ANDROID_STUDIO" in os.environ:
+        studio = os.environ["ANDROID_STUDIO"]
+        jbr = Path(studio, "jbr")
+        if not jbr.exists():
+            jbr = Path(studio, "Contents", "jbr", "Contents", "Home")
+        if jbr.exists():
+            os.environ["PATH"] = f'{jbr / "bin"}{os.pathsep}{os.environ["PATH"]}'
+            os.environ["JAVA_HOME"] = str(jbr)
+            os.environ["JDK_HOME"] = str(jbr)
+
+    no_jdk = False
+    try:
+        proc = subprocess.run(
+            "javac -version",
+            stdout=subprocess.PIPE,
+            stderr=subprocess.DEVNULL,
+            shell=True,
+        )
+        output = proc.stdout.strip().decode("utf-8")
+        no_jdk = proc.returncode != 0 and output.startswith("javac 21")
+    except FileNotFoundError:
+        no_jdk = True
+
+    if no_jdk:
+        error(
+            "Please set Android Studio's path to environment variable ANDROID_STUDIO,\n"
+            + "or install JDK 21 and make sure 'javac' is available in PATH"
+        )
+
+
+# OS detection
+os_name = platform.system().lower()
+is_windows = False
+if os_name != "linux" and os_name != "darwin":
+    # It's possible we're using MSYS/Cygwin/MinGW, treat them all as Windows
+    is_windows = True
+    os_name = "windows"
+EXE_EXT = ".exe" if is_windows else ""
+
+no_color = False
+if is_windows:
+    try:
+        import colorama
+
+        colorama.init()
+    except ImportError:
+        # We can't do ANSI color codes in terminal on Windows without colorama
+        no_color = True
+
+# Environment detection
+if not sys.version_info >= (3, 8):
+    error("Requires Python 3.8+")
+
+cpu_count = multiprocessing.cpu_count()
+
+# When directly invoked, make it a command wrapper
+if __name__ == "__main__":
+    ensure_cargo()
+    ensure_jdk()
+    subprocess.run(sys.argv[1:])