import sys
import os

import SCons

PACKAGE_ALIAS_MAP = "AIB_PACKAGE_ALIAS_MAP"
AUTO_ARCHIVE_MAKE_ARCHIVE_CONTENT = """
import os
import sys

USAGE = '''
Usage: {} ARCHIVE_TYPE ARCHIVE_NAME ROOT_DIRECTORY FILES...

FILES should be absolute paths or relative to ROOT_DIRECTORY.

ARCHIVE_TYPE is one of zip or tar.
'''

if __name__ == "__main__":
    if len(sys.argv) < 4:
        print(sys.argv[0], "takes at minimum four arguments.")
        print(USAGE.format(sys.argv[0]))
        sys.exit(1)

    archive_type = sys.argv[1]
    archive_name = sys.argv[2]
    root_dir = sys.argv[3]
    files = sys.argv[4:]

    if archive_type not in ("zip", "tar"):
        print("unsupported archive_type", archive_type)
        print(USAGE.format(sys.argv[0]))
        sys.exit(1)

    if archive_type == "zip":
        import zipfile
        archive = zipfile.ZipFile(archive_name, mode='w', compression=zipfile.ZIP_DEFLATED)
        add_file = archive.write
    else:
        import tarfile
        archive = tarfile.open(archive_name, mode='w:gz')
        add_file = archive.add

    os.chdir(root_dir)

    for filename in files:
        add_file(filename)

    archive.close()
"""


def add_package_name_alias(env, component, role, name):
    """Add a package name mapping for the combination of component and role."""
    # Verify we didn't get a None or empty string for any argument
    if not name:
        raise Exception(
            "when setting a package name alias must provide a name parameter"
        )
    if not component:
        raise Exception("No component provided for package name alias")
    if not role:
        raise Exception("No role provided for package name alias")
    env[PACKAGE_ALIAS_MAP][(component, role)] = name


def get_package_name(env, component, role):
    """Return the package file name for the component and role combination."""
    basename = env[PACKAGE_ALIAS_MAP].get(
        (component, role), "{component}-{role}".format(component=component, role=role)
    )

    return basename


def collect_transitive_files(env, entry, cache=None):
    """
    Collect all installed and transitively installed files for entry.
    """
    if not cache:
        cache = set()

    files = set()
    stack = [entry]

    # Find all the files directly contained in the component DAG for entry and
    # it's dependencies.
    while stack:
        s = stack.pop()
        if s in cache:
            continue
        cache.add(s)

        stack.extend(s.dependencies)
        files.update(s.files)

    # Now we will call the scanner to find the transtive files of any files that
    # we found from the component DAG.
    non_transitive_files = files.copy()
    for f in non_transitive_files:
        # scan_for_transitive_install is memoized so it's safe to call it in
        # this loop. If it hasn't already run for a file we need to run it
        # anyway.
        transitive_files = set(env.GetTransitivelyInstalledFiles(f))
        files.update(transitive_files)

    return list(files)


def auto_archive_gen(first_env, make_archive_script, pkg_fmt):
    """Generate an archive task function for pkg_fmt where pkg_fmt is one of zip, tar, or auto."""

    if pkg_fmt == "auto":
        if first_env["PLATFORM"] == "win32":
            pkg_fmt = "zip"
        else:
            pkg_fmt = "tar"

    def auto_archive(env, component, role):
        pkg_name = get_package_name(env, component, role)
        install_alias = "install-{component}{role}".format(
            component=component,
            role="" if env.GetRoleDeclaration(role).silent else "-" + role,
        )

        if pkg_fmt == "zip":
            pkg_suffix = "$AUTO_ARCHIVE_ZIP_SUFFIX"
        else:
            pkg_suffix = "$AUTO_ARCHIVE_TARBALL_SUFFIX"

        archive = env.AutoArchive(
            target="#{}.{}".format(pkg_name, pkg_suffix),
            source=[make_archive_script] + env.Alias(install_alias),
            __AUTO_ARCHIVE_TYPE=pkg_fmt,
            AIB_COMPONENT=component,
            AIB_ROLE=role,
        )

        # TODO: perhaps caching of packages / tarballs should be
        # configurable? It's possible someone would want to do it.
        env.NoCache(archive)
        return archive

    return auto_archive


def archive_builder(source, target, env, for_signature):
    """Build archives of the AutoInstall'd sources."""
    if not source:
        return []

    source = env.Flatten([source])
    common_ancestor = None

    # Get the path elements that make up both DESTDIR and PREFIX. Then
    # iterate the dest_dir_elems with the prefix path elements
    # stripped off the end of the path converting them to strings for
    # joining to make the common_ancestor.
    #
    # We pass the common_ancestor to tar via -C so that $PREFIX is
    # preserved in the tarball.
    dest_dir_elems = env.Dir("$DESTDIR").get_abspath()
    prefix_elems = env.subst("$PREFIX")

    # In python slicing a string with [:-0] gives an empty string. So
    # make sure we have a prefix to slice off before trying it.
    if prefix_elems:
        common_ancestor = dest_dir_elems[: -len(prefix_elems)]
    else:
        common_ancestor = dest_dir_elems

    archive_type = env["__AUTO_ARCHIVE_TYPE"]
    make_archive_script = source[0].get_abspath()
    tar_cmd = env.WhereIs("tar")
    if archive_type == "tar" and tar_cmd:
        command_prefix = "{tar} -C {common_ancestor} -czf {archive_name}"
    else:
        command_prefix = "{python} {make_archive_script} {archive_type} {archive_name} {common_ancestor}"

    archive_name = env.File(target[0]).get_abspath()
    command_prefix = command_prefix.format(
        tar=tar_cmd,
        python=sys.executable,
        archive_type=archive_type,
        archive_name=archive_name,
        make_archive_script=make_archive_script,
        common_ancestor=common_ancestor,
    )

    # If we are just being invoked for our signature, we can omit the indirect dependencies
    # found by expanding the transitive dependencies, since we really only have a hard dependency
    # on our direct dependencies.
    if for_signature:
        return command_prefix

    component = env["AIB_COMPONENT"]
    role = env["AIB_ROLE"]
    entry = env["AIB_ALIAS_MAP"][component][role]

    # Pre-process what should be in the archive. We need to pass the
    # set of known installed files along to the transitive dependency
    # walk so we can filter out files that aren't in the install
    # directory.
    installed = set(env.FindInstalledFiles())

    # Collect all the installed files for our entry. This is doing a pure DAG
    # walk idea of what should be. So we filter out any that are not in the
    # installed set.
    transitive_files = [
        f for f in
        collect_transitive_files(env, entry)
        if f in installed
    ]
    if not transitive_files:
        return []

    # The env["ESCAPE"] function is used by scons to make arguments
    # valid for the platform that we're running on. For instance it
    # will properly quote paths that have spaces in them on Posix
    # platforms and handle \ / on Windows.
    escape_func = env.get("ESCAPE", lambda x: x)

    # TODO: relpath is costly, and we do it for every file in the archive here.
    # We should find a way to avoid the repeated relpath invocation, probably by
    # bucketing by directory.
    relative_files = [
        escape_func(os.path.relpath(file.get_abspath(), common_ancestor))
        for file in transitive_files
    ]

    return "{prefix} {files}".format(
        prefix=command_prefix,
        files=" ".join(relative_files)
    )


def exists(env):
    return True


def generate(env):
    if not env.get("AUTO_INSTALL_ENABLED"):
        env.Tool("auto_install_binaries")

    bld = SCons.Builder.Builder(
        action=SCons.Action.CommandGeneratorAction(
            archive_builder,
            {"cmdstr": "Building package ${TARGETS[0]} from ${SOURCES[1:]}"},
        )
    )
    env.Append(BUILDERS={"AutoArchive": bld})
    env["AUTO_ARCHIVE_TARBALL_SUFFIX"] = env.get(
        "AUTO_ARCHIVE_TARBALL_SUFFIX", "tar.gz"
    )
    env["AUTO_ARCHIVE_ZIP_SUFFIX"] = env.get("AUTO_ARCHIVE_ZIP_SUFFIX", "zip")
    env[PACKAGE_ALIAS_MAP] = {}

    env.AddMethod(add_package_name_alias, "AddPackageNameAlias")

    # TODO: $BUILD_ROOT should be $VARIANT_DIR after we fix our dir
    # setup later on.
    make_archive_script = env.Textfile(
        target="$BUILD_ROOT/aib_make_archive.py",
        source=[AUTO_ARCHIVE_MAKE_ARCHIVE_CONTENT],
    )

    env.AppendUnique(
        AIB_TASKS={
            "tar": (auto_archive_gen(env, make_archive_script, "tar"), False),
            "zip": (auto_archive_gen(env, make_archive_script, "zip"), False),
            "archive": (auto_archive_gen(env, make_archive_script, "auto"), False),
        }
    )