# Copyright 2017 The Bazel Authors. All rights reserved.
#
# 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.
"""Tools for dealing with Docker Image layers."""

load(":list.bzl", "reverse")
load(":path.bzl", _get_runfile_path = "runfile")

def get_from_target(unused_ctx, target):
    if hasattr(target, "docker_layers"):
        return target.docker_layers
    else:
        # TODO(mattmoor): Use containerregistry.client's FromTarball
        # to create an entry from a tarball base image.
        return []

def assemble(ctx, layers, tags_to_names, output):
    """Create the full image from the list of layers."""
    layers = [l["layer"] for l in layers]
    args = [
        "--output=" + output.path,
    ] + [
        "--tags=" + tag + "=@" + tags_to_names[tag].path
        for tag in tags_to_names
    ] + ["--layer=" + l.path for l in layers]
    inputs = layers + tags_to_names.values()
    ctx.action(
        executable = ctx.executable.join_layers,
        arguments = args,
        inputs = inputs,
        outputs = [output],
        mnemonic = "JoinLayers",
    )

def incremental_load(ctx, layers, images, output):
    """Generate the incremental load statement."""
    ctx.template_action(
        template = ctx.file.incremental_load_template,
        substitutions = {
            "%{load_statements}": "\n".join([
                "incr_load '%s' '%s' '%s'" % (
                    _get_runfile_path(ctx, l["name"]),
                    _get_runfile_path(ctx, l["id"]),
                    _get_runfile_path(ctx, l["layer"]),
                )
                # The last layer is the first in the list of layers.
                # We reverse to load the layer from the parent to the child.
                for l in reverse(layers)
            ]),
            "%{tag_statements}": "\n".join([
                "tag_layer '%s' '%s' '%s'" % (
                    img,
                    _get_runfile_path(ctx, images[img]["name"]),
                    _get_runfile_path(ctx, images[img]["id"]),
                )
                for img in images
            ]),
        },
        output = output,
        executable = True,
    )

tools = {
    "incremental_load_template": attr.label(
        default = Label("//tools/build_defs/docker:incremental_load_template"),
        single_file = True,
        allow_files = True,
    ),
    "join_layers": attr.label(
        default = Label("//tools/build_defs/docker:join_layers"),
        cfg = "host",
        executable = True,
        allow_files = True,
    ),
}