// 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.

package com.google.devtools.build.lib.rules.platform;

import static com.google.devtools.build.lib.packages.Attribute.attr;

import com.google.devtools.build.lib.analysis.RuleDefinition;
import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
import com.google.devtools.build.lib.analysis.platform.ConstraintValueInfo;
import com.google.devtools.build.lib.analysis.platform.PlatformInfo;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.syntax.Type;
import com.google.devtools.build.lib.util.FileTypeSet;

/** Rule definition for {@link Platform}. */
public class PlatformRule implements RuleDefinition {
  public static final String RULE_NAME = "platform";
  public static final String CONSTRAINT_VALUES_ATTR = "constraint_values";
  public static final String PARENTS_PLATFORM_ATTR = "parents";
  public static final String REMOTE_EXECUTION_PROPS_ATTR = "remote_execution_properties";
  static final String HOST_PLATFORM_ATTR = "host_platform";
  static final String TARGET_PLATFORM_ATTR = "target_platform";
  static final String CPU_CONSTRAINTS_ATTR = "cpu_constraints";
  static final String OS_CONSTRAINTS_ATTR = "os_constraints";

  @Override
  public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment env) {
    /* <!-- #BLAZE_RULE(platform).NAME -->
    <!-- #END_BLAZE_RULE.NAME --> */
    return builder
        .advertiseProvider(PlatformInfo.class)

        /* <!-- #BLAZE_RULE(platform).ATTRIBUTE(constraint_values) -->
        The combination of constraint choices that this platform comprises. In order for a platform
        to apply to a given environment, the environment must have at least the values in this list.

        <p>Each <code>constraint_value</code> in this list must be for a different
        <code>constraint_setting</code>. For example, you cannot define a platform that requires the
        cpu architecture to be both <code>@bazel_tools//platforms:x86_64</code> and
        <code>@bazel_tools//platforms:arm</code>.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(
            attr(CONSTRAINT_VALUES_ATTR, BuildType.LABEL_LIST)
                .allowedFileTypes(FileTypeSet.NO_FILE)
                .mandatoryProviders(ConstraintValueInfo.PROVIDER.id()))

        /* <!-- #BLAZE_RULE(platform).ATTRIBUTE(parents) -->
        The label of a <code>platform</code> target that this platform should inherit from. Although
        the attribute takes a list, there should be no more than one platform present. Any
        constraint_settings not set directly on this platform will be found in the parent platform.
        See the section on <a href="#platform_inheritance">Platform Inheritance</a> for details.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(
            attr(PARENTS_PLATFORM_ATTR, BuildType.LABEL_LIST)
                .allowedFileTypes(FileTypeSet.NO_FILE)
                .mandatoryProviders(PlatformInfo.PROVIDER.id()))

        /* <!-- #BLAZE_RULE(platform).ATTRIBUTE(remote_execution_properties) -->
        A string used to configure a remote execution platform. Actual builds make no attempt to
        interpret this, it is treated as opaque data that can be used by a specific SpawnRunner.
        This can include data from the parent platform's "remote_execution_properties" attribute,
        by using the macro "{PARENT_REMOTE_EXECUTION_PROPERTIES}". See the section on
        <a href="#platform_inheritance">Platform Inheritance</a> for details.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(attr(REMOTE_EXECUTION_PROPS_ATTR, Type.STRING))

        // Undocumented. Indicates that this platform should auto-configure the platform constraints
        // based on the current host OS and CPU settings.
        .add(
            attr(HOST_PLATFORM_ATTR, Type.BOOLEAN)
                .value(false)
                .undocumented("Should only be used by internal packages."))
        // Undocumented. Indicates that this platform should auto-configure the platform constraints
        // based on the current OS and CPU settings.
        .add(
            attr(TARGET_PLATFORM_ATTR, Type.BOOLEAN)
                .value(false)
                .undocumented("Should only be used by internal packages."))
        // Undocumented. Indicates to the rule which constraint_values to use for automatic CPU
        // mapping.
        .add(
            attr(CPU_CONSTRAINTS_ATTR, BuildType.LABEL_LIST)
                .allowedFileTypes(FileTypeSet.NO_FILE)
                .mandatoryProviders(ConstraintValueInfo.PROVIDER.id())
                .undocumented("Should only be used by internal packages."))
        // Undocumented. Indicates to the rule which constraint_values to use for automatic CPU
        // mapping.
        .add(
            attr(OS_CONSTRAINTS_ATTR, BuildType.LABEL_LIST)
                .allowedFileTypes(FileTypeSet.NO_FILE)
                .mandatoryProviders(ConstraintValueInfo.PROVIDER.id())
                .undocumented("Should only be used by internal packages."))
        .build();
  }

  @Override
  public Metadata getMetadata() {
    return Metadata.builder()
        .name(RULE_NAME)
        .ancestors(PlatformBaseRule.class)
        .factoryClass(Platform.class)
        .build();
  }
}
/*<!-- #BLAZE_RULE (NAME = platform, TYPE = OTHER, FAMILY = Platform)[GENERIC_RULE] -->

<p>This rule defines a new platform -- a named collection of constraint choices (such as cpu
architecture or compiler version) describing an environment in which part of the build may run.
See the <a href="https://docs.bazel.build/versions/master/platforms.html">Platforms</a> page for
more details.

<h4 id="platform_examples">Example</h4>
<p>
  This defines a platform that describes any environment running Linux on ARM.
</p>
<pre class="code">
platform(
    name = "linux_arm",
    constraint_values = [
        "@bazel_tools//platforms:linux",
        "@bazel_tools//platforms:arm",
    ],
)
</pre>

<h3 id="platform_inheritance">Platform Inheritance</h4>
<p>
  Platforms may use the "parents" attribute to specify another platform that they will inherit
  constraint values from. Although the "parents" attribute takes a list, no more than a single value
  is currently supported, and specifying multiple parents is an error.
</p>

<p>
  When checking for the value of a constraint setting in a platform, first the values directly set
  (via the "constraint_values" attribute) are checked, and then the constraint values on the parent.
  This continues recursively up the chain of parent platforms. In this manner, any values set
  directly on a platform will override the values set on the parent.
</p>

<p>
  Platforms can also inherit the "remote_execution_properties" attribute from the parent platform.
  The logic for setting the "remote_execution_platform" is as follows when there is a parent
  platform:

  <ol>
    <li>
      If "remote_execution_property" is not set on the child platform, the parent's
      "remote_execution_properties" will be used.
    </li>
    <li>
      If "remote_execution_property" is set on the child platform, and contains the literal string
      "{PARENT_REMOTE_EXECUTION_PROPERTIES}", that macro will be replaced with the contents of the
      parent's "remote_execution_property" attribute.
    </li>
    <li>
      If "remote_execution_property" is set on the child platform, and does not contain the macro,
      the child's "remote_execution_property" will be used unchanged.
    </li>
  </ol>
</p>

<h4 id="platform_inheritance_examples">Example</h4>
<pre class="code">
platform(
    name = "parent",
    constraint_values = [
        "@bazel_tools//platforms:linux",
        "@bazel_tools//platforms:arm",
    ],
    remote_execution_properties = """
      parent properties
    """,
)
platform(
    name = "child_a",
    parents = [":parent"],
    constraint_values = [
        "@bazel_tools//platforms:x86_64",
    ],
    remote_execution_properties = """
      child a properties
    """,
)
platform(
    name = "child_b",
    parents = [":parent"],
    remote_execution_properties = """
      child b properties
      {PARENT_REMOTE_EXECUTION_PROPERTIES}
      more child b properties
    """,
)
</pre>

<p>
  In these examples, the child platforms have the following properties:

  <ul>
    <li>
      "child_a" has the constraint values "@bazel_tools//platforms:linux" (inherited from the
      parent) and "@bazel_tools//platforms:x86_64" (set directly on the platform). It has the
      "remote_execution_properties" set to "child a properties"
    </li>
    <li>
      "child_b" inherits all constraint values from the parent, and doesn't set any of its own.
      It has the "remote_execution_properties" set to:
<pre>
child b properties
parent properties
more child b properties
</pre>
    </li>
  </ul>
</p>
<!-- #END_BLAZE_RULE -->*/