#!/usr/bin/env fuchsia-vendored-python
# Copyright 2021 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""
Updates the Fuchsia platform version.
"""

import argparse
import fileinput
import json
import os
import secrets
import sys


def _generate_random_abi_revision(already_used: set[int]) -> int:
    """Generates a random 64-bit ABI revision, avoiding values in
    `already_used` and other reserved ranges."""
    while True:
        # Reserve values in the top 1/256th of the space.
        candidate = secrets.randbelow(0xF000_0000_0000_0000)

        # If the ABI revision has already been used, discard it and go buy a
        # lottery ticket.
        if candidate not in already_used:
            return candidate


def update_version_history(
    new_api_level: int, version_history_path: str
) -> bool:
    """Updates version_history.json to include the given Fuchsia API level.

    The ABI revision for this API level is set to a new random value that has not
    been used before.
    """
    try:
        with open(version_history_path, "r+") as f:
            version_history = json.load(f)
            versions = version_history["data"]["api_levels"]
            if str(new_api_level) in versions:
                print(
                    f"error: Fuchsia API level {new_api_level} is already defined.",
                    file=sys.stderr,
                )
                return False

            abi_revision = _generate_random_abi_revision(
                set(int(v["abi_revision"], 16) for v in versions.values())
            )
            versions[str(new_api_level)] = dict(
                # Print `abi_revision` in hex, with a leading 0x, with capital
                # letters, padded to 16 chars.
                abi_revision=f"0x{abi_revision:016X}",
                phase="supported",
            )
            f.seek(0)
            json.dump(version_history, f, indent=4)
            # JSON dump does not include a new line at the end.
            f.write("\n")
            f.truncate()
            return True
    except FileNotFoundError:
        print(
            f"""error: Unable to open '{version_history_path}'.
Did you run this script from the root of the source tree?""",
            file=sys.stderr,
        )
        return False


def _create_owners_file(level_dir_path: str) -> None:
    """Creates an OWNERS file in `level_dir_path` with limited approvers."""
    owners_path = os.path.join(level_dir_path, "OWNERS")

    print(f"Creating {owners_path}")
    with open(owners_path, "w") as f:
        f.write("include /sdk/history/FROZEN_API_LEVEL_OWNERS\n")


def _update_availability_levels(
    new_api_level: int, availability_levels_file: str
) -> bool:
    """Adds the given Fuchsia API level to the C preprocessor defines file.

    Assumes lines are sorted in decreasing order of API level.
    """
    # Look for the most recent line and replace it with the line for the new
    # level and itself.
    last_api_level = new_api_level - 1
    line_format = "#define FUCHSIA_INTERNAL_LEVEL_{level}_() {level}"
    most_recent_api_level_line = line_format.format(level=last_api_level)
    new_line = line_format.format(level=new_api_level)

    try:
        with fileinput.FileInput(availability_levels_file, inplace=True) as f:
            for line in f:
                print(
                    line.replace(
                        most_recent_api_level_line,
                        f"{new_line}\n{most_recent_api_level_line}",
                    ),
                    end="",
                )
        return True
    except FileNotFoundError:
        print(
            f"""error: Unable to open '{availability_levels_file}'.
Did you run this script from the root of the source tree?""",
            file=sys.stderr,
        )
        return False


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--new-api-level", type=int, required=True)
    parser.add_argument("--sdk-version-history-path", required=True)
    parser.add_argument("--availability-levels-file-path", required=True)
    parser.add_argument("--root-source-dir", required=True)

    args = parser.parse_args()

    new_level = args.new_api_level

    if not update_version_history(new_level, args.sdk_version_history_path):
        return 1

    level_dir_path = os.path.join(
        args.root_source_dir, "sdk", "history", str(new_level)
    )

    try:
        os.makedirs(level_dir_path, exist_ok=True)
    except Exception as e:
        print(f"Failed to create directory for new level: {e}")
        return 1

    _create_owners_file(level_dir_path)

    # TODO(https://fxbug.dev/349622444): Enable building with
    # `FUCHSIA_INTERNAL_LEVEL_NEXT_()` undefined to ensure there are no stray
    # instances of `NEXT` that have not been converted to the new level.
    # Otherwise, perhaps use a preprocessor condition. This would avoid the need
    # to regenerate `availability_levels_file_path` twice but would include a
    # preprocessor condition in the production code. Do the same for the Rust
    # macros.
    sysroot_api_file = "zircon/public/sysroot/sdk/sysroot.api"
    if not _update_availability_levels(
        new_level, args.availability_levels_file_path
    ):
        return 1

    # Before printing, rebase the paths to what a developer would use from `//`.
    history = os.path.relpath(
        args.sdk_version_history_path, args.root_source_dir
    )
    level_dir = os.path.relpath(level_dir_path, args.root_source_dir)
    availability_levels_file = os.path.relpath(
        args.availability_levels_file_path, args.root_source_dir
    )
    print(
        f"""
API level {new_level} has been added.
Now run `fx build //zircon/public/sysroot/sdk:sysroot_sdk_verify_api`, and follow the instructions to update `//{sysroot_api_file}` (unless `update_goldens=true`).
Then run `git add -u {history} {availability_levels_file} {sysroot_api_file} && git add {level_dir}`."""
    )
    return 0


if __name__ == "__main__":
    sys.exit(main())