import os
from cache import hash_dict


def build_ccache_env(project):
    """
    Configure compiler caching layer safely.
    """

    env = {}

    # ----------------------------
    # enable ccache
    # ----------------------------
    env["USE_CCACHE"] = "1"
    env["CCACHE_DIR"] = "/var/cache/ccache"

    # ----------------------------
    # distcc + ccache integration
    # critical ordering fix
    # ----------------------------
    env["CC"] = "ccache gcc"
    env["CXX"] = "ccache g++"

    # ensure distcc wraps AFTER ccache
    env["CCACHE_PREFIX"] = "distcc"

    # ----------------------------
    # tuning for distributed builds
    # ----------------------------
    env["CCACHE_COMPRESS"] = "1"
    env["CCACHE_COMPRESSLEVEL"] = "5"
    env["CCACHE_MAXSIZE"] = "20G"

    # ----------------------------
    # project-specific salt
    # ensures correct cache isolation
    # ----------------------------
    env["CCACHE_SLOPPINESS"] = "time_macros,locale"

    env["FESTER_CCACHE_KEY"] = hash_dict(project.get("build_env", {}))

    return env