# Copyright 2017 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import SCons

import os
import re
import subprocess

from pkg_resources import parse_version

_icecream_version_min = parse_version("1.1rc2")
_ccache_nocpp2_version = parse_version("3.4.1")


# I'd prefer to use value here, but amazingly, its __str__ returns the
# *initial* value of the Value and not the built value, if
# available. That seems like a bug. In the meantime, make our own very
# sinmple Substition thing.
class _BoundSubstitution:
    def __init__(self, env, expression):
        self.env = env
        self.expression = expression
        self.result = None

    def __str__(self):
        if self.result is None:
            self.result = self.env.subst(self.expression)
        return self.result


def icecc_create_env(env, target, source, for_signature):
    # Safe to assume unix here because icecream only works on Unix
    mkdir = "mkdir -p ${ICECC_VERSION.Dir('').abspath}"

    # Create the env, use awk to get just the tarball name and we store it in
    # the shell variable $ICECC_VERSION_TMP so the subsequent mv command and
    # store it in a known location.
    create_env = "ICECC_VERSION_TMP=$$($ICECC_CREATE_ENV --$ICECC_COMPILER_TYPE $CC $CXX | awk '/^creating .*\\.tar\\.gz/ { print $$2 }')"

    # Simply move our tarball to the expected locale.
    mv = "mv $$ICECC_VERSION_TMP $TARGET"

    # Daisy chain the commands and then let SCons Subst in the rest.
    cmdline = f"{mkdir} && {create_env} && {mv}"
    return cmdline


def generate(env):

    if not exists(env):
        return

    env["ICECCENVCOMSTR"] = env.get("ICECCENVCOMSTR", "Generating environment: $TARGET")
    env["ICECC_COMPILTER_TYPE"] = env.get(
        "ICECC_COMPILER_TYPE", os.path.basename(env.WhereIs("${CC}"))
    )
    env.Append(
        BUILDERS={
            "IcecreamEnv": SCons.Builder.Builder(
                action=SCons.Action.CommandGeneratorAction(
                    icecc_create_env, {"comstr": "$ICECCENVCOMSTR"},
                )
            )
        }
    )

    # If we are going to load the ccache tool, but we haven't done so
    # yet, then explicitly do it now. We need the ccache tool to be in
    # place before we setup icecream because we need to do things a
    # little differently if ccache is in play. If you don't use the
    # TOOLS variable to configure your tools, you should explicitly
    # load the ccache tool before you load icecream.
    ccache_enabled = "CCACHE_VERSION" in env
    if "ccache" in env["TOOLS"] and not ccache_enabled:
        env.Tool("ccache")

    # Absoluteify, so we can derive ICERUN
    env["ICECC"] = env.WhereIs("$ICECC")

    if not "ICERUN" in env:
        env["ICERUN"] = env.File("$ICECC").File("icerun")

    # Absoluteify, for parity with ICECC
    env["ICERUN"] = env.WhereIs("$ICERUN")

    env["ICECC_CREATE_ENV"] = env.WhereIs(
        env.get("ICECC_CREATE_ENV", "icecc-create-env")
    )

    # We can't handle sanitizer blacklist files, so disable icecc then, and just flow through
    # icerun to prevent slamming the local system with a huge -j value.
    if any(
        f.startswith("-fsanitize-blacklist=")
        for fs in ["CCFLAGS", "CFLAGS", "CXXFLAGS"]
        for f in env[fs]
    ):
        env["ICECC"] = "$ICERUN"

    # Make CC and CXX absolute paths too. It is better for icecc.
    env["CC"] = env.WhereIs("$CC")
    env["CXX"] = env.WhereIs("$CXX")

    # Generate the deterministic name for our tarball
    icecc_version_target_filename = env.subst("${CC}${CXX}.tar.gz").replace("/", "_")[
        1:
    ]
    icecc_version_dir = env.Dir("$BUILD_ROOT/scons/icecc")
    icecc_known_version = icecc_version_dir.File(icecc_version_target_filename)

    if "ICECC_VERSION" not in env:
        # Make a predictable name for the toolchain
        env["ICECC_VERSION"] = icecc_known_version

    # Do this weaker validation as opposed to urllib.urlparse (or similar). We
    # really only support http URLs here and any other validation either
    # requires a third party module or accepts things we don't.
    elif env["ICECC_VERSION"].startswith("http"):
        env["ICECC_VERSION_URL"] = env["ICECC_VERSION"]
        env["ICECC_VERSION"] = icecc_known_version

    if env.get("ICECC_VERSION_URL"):

        # Use curl / wget to download the toolchain because SCons (and ninja)
        # are better at running shell commands than Python functions.
        curl = env.WhereIs("curl")
        wget = env.WhereIs("wget")
        if curl:
            cmdstr = "curl -L"
        elif wget:
            cmdstr = "wget"
        else:
            raise Exception(
                "You have specified an ICECC_VERSION that is a URL but you have neither wget nor curl installed."
            )

        env.Command(
            target="$ICECC_VERSION",
            source=["$CC", "$CXX"],
            action=[
                SCons.Defaults.Mkdir("${ICECC_VERSION.Dir('').abspath}"),
                cmdstr + " -o $TARGET $ICECC_VERSION_URL",
            ],
        )
    else:
        env["ICECC_VERSION"] = env.File("$ICECC_VERSION")
        env.IcecreamEnv(
            target="$ICECC_VERSION",
            source=["$ICECC_CREATE_ENV", "$CC", "$CXX"],
        )

    # Create an emitter that makes all of the targets depend on the
    # icecc_version_target (ensuring that we have read the link), which in turn
    # depends on the toolchain (ensuring that we have packaged it).
    def icecc_toolchain_dependency_emitter(target, source, env):
        if "conftest" not in str(target[0]):
            env.Requires(target, "$ICECC_VERSION")
        return target, source

    # Cribbed from Tool/cc.py and Tool/c++.py. It would be better if
    # we could obtain this from SCons.
    _CSuffixes = [".c"]
    if not SCons.Util.case_sensitive_suffixes(".c", ".C"):
        _CSuffixes.append(".C")

    _CXXSuffixes = [".cpp", ".cc", ".cxx", ".c++", ".C++"]
    if SCons.Util.case_sensitive_suffixes(".c", ".C"):
        _CXXSuffixes.append(".C")

    suffixes = _CSuffixes + _CXXSuffixes
    for object_builder in SCons.Tool.createObjBuilders(env):
        emitterdict = object_builder.builder.emitter
        for suffix in emitterdict.keys():
            if not suffix in suffixes:
                continue
            base = emitterdict[suffix]
            emitterdict[suffix] = SCons.Builder.ListEmitter(
                [base, icecc_toolchain_dependency_emitter]
            )

    if env.ToolchainIs("clang"):
        env["ENV"]["ICECC_CLANG_REMOTE_CPP"] = 1

        if ccache_enabled and env["CCACHE_VERSION"] >= _ccache_nocpp2_version:
            env.AppendUnique(CCFLAGS=["-frewrite-includes"])
            env["ENV"]["CCACHE_NOCPP2"] = 1
    else:
        env.AppendUnique(CCFLAGS=["-fdirectives-only"])
        if ccache_enabled:
            env["ENV"]["CCACHE_NOCPP2"] = 1

    if "ICECC_SCHEDULER" in env:
        env["ENV"]["USE_SCHEDULER"] = env["ICECC_SCHEDULER"]

    # Build up the string we will set in the environment to tell icecream
    # about the compiler package.
    icecc_version_string = "${ICECC_VERSION.abspath}"
    if "ICECC_VERSION_ARCH" in env:
        icecc_version_string = "${ICECC_VERSION_ARCH}:" + icecc_version_string

    # Use our BoundSubstitition class to put ICECC_VERSION into env['ENV'] with
    # substitution in play. This avoids an early subst which can behave
    # strangely.
    env["ENV"]["ICECC_VERSION"] = _BoundSubstitution(env, icecc_version_string)

    # If ccache is in play we actually want the icecc binary in the
    # CCACHE_PREFIX environment variable, not on the command line, per
    # the ccache documentation on compiler wrappers. Otherwise, just
    # put $ICECC on the command line. We wrap it in the magic "don't
    # consider this part of the build signature" sigils in the hope
    # that enabling and disabling icecream won't cause rebuilds. This
    # is unlikely to really work, since above we have maybe changed
    # compiler flags (things like -fdirectives-only), but we still try
    # to do the right thing.
    if ccache_enabled:
        env["ENV"]["CCACHE_PREFIX"] = _BoundSubstitution(env, "$ICECC")
    else:
        icecc_string = "$( $ICECC $)"
        env["CCCOM"] = " ".join([icecc_string, env["CCCOM"]])
        env["CXXCOM"] = " ".join([icecc_string, env["CXXCOM"]])
        env["SHCCCOM"] = " ".join([icecc_string, env["SHCCCOM"]])
        env["SHCXXCOM"] = " ".join([icecc_string, env["SHCXXCOM"]])

    # Make link like jobs flow through icerun so we don't kill the
    # local machine.
    #
    # TODO: Should we somehow flow SPAWN or other universal shell launch through
    # ICERUN to avoid saturating the local machine, and build something like
    # ninja pools?
    env["ARCOM"] = "$( $ICERUN $) " + env["ARCOM"]
    env["LINKCOM"] = "$( $ICERUN $) " + env["LINKCOM"]
    env["SHLINKCOM"] = "$( $ICERUN $) " + env["SHLINKCOM"]

    # Uncomment these to debug your icecc integration
    # env['ENV']['ICECC_DEBUG'] = 'debug'
    # env['ENV']['ICECC_LOGFILE'] = 'icecc.log'


def exists(env):

    icecc = env.get("ICECC", False)
    if not icecc:
        return False
    icecc = env.WhereIs(icecc)
    if not icecc:
        return False

    pipe = SCons.Action._subproc(
        env,
        SCons.Util.CLVar(icecc) + ["--version"],
        stdin="devnull",
        stderr="devnull",
        stdout=subprocess.PIPE,
    )

    if pipe.wait() != 0:
        return False

    validated = False
    for line in pipe.stdout:
        line = line.decode("utf-8")
        if validated:
            continue  # consume all data
        version_banner = re.search(r"^ICECC ", line)
        if not version_banner:
            continue
        icecc_version = re.split("ICECC (.+)", line)
        if len(icecc_version) < 2:
            continue
        icecc_version = parse_version(icecc_version[1])
        if icecc_version >= _icecream_version_min:
            validated = True

    return validated