"""
Generate build dependencies for Cargo.

The `build.py` script is invoked by cargo when building libcretonne to
generate Rust code from the instruction descriptions. Cargo needs to know when
it is necessary to rerun the build script.

If the build script outputs lines of the form:

    cargo:rerun-if-changed=/path/to/file

cargo will rerun the build script when those files have changed since the last
build.
"""
from __future__ import absolute_import, print_function
import os
from os.path import dirname, abspath, join


def source_files(top):
    """
    Recursively find all interesting source files and directories in the
    directory tree starting at top. Yield a path to each file.
    """
    for (dirpath, dirnames, filenames) in os.walk(top):
        yield dirpath
        for f in filenames:
            if f.endswith('.py'):
                yield join(dirpath, f)


def generate():
    print("Dependencies from meta language directory:")
    meta = dirname(abspath(__file__))
    for path in source_files(meta):
        print("cargo:rerun-if-changed=" + path)