# Copyright 2018 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

import hashlib

from pants.base.fingerprint_strategy import FingerprintStrategy

from pants.contrib.go.targets.go_binary import GoBinary


class GoBinaryFingerprintStrategy(FingerprintStrategy):
    """Build flags aware fingerprint strategy.

    This enables support for runtime merging of build flags (e.g.: config file, per-target, CLI),
    which impact the output binary.
    """

    def __init__(self, get_build_flags_func):
        """
        :param func get_build_flags_func: Partial function that merges build_flags
        """
        self._get_build_flags_func = get_build_flags_func

    def compute_fingerprint(self, target):
        fp = target.payload.fingerprint()
        if not isinstance(target, GoBinary):
            return fp

        hasher = hashlib.sha1()
        hasher.update(fp.encode())
        hasher.update(str(self._get_build_flags_func(target)).encode())
        return hasher.hexdigest()

    def __hash__(self):
        return hash((type(self), self._get_build_flags_func))

    def __eq__(self, other):
        return (
            type(self) == type(other)
            and self._get_build_flags_func.args == other._get_build_flags_func.args
        )