// Copyright (C) 2021 The Android Open Source Project
//
// 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 aidl

import (
	"android/soong/android"

	"fmt"
	"io"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/google/blueprint"
	"github.com/google/blueprint/proptools"
)

var (
	aidlDumpApiRule = pctx.StaticRule("aidlDumpApiRule", blueprint.RuleParams{
		Command: `rm -rf "${outDir}" && mkdir -p "${outDir}" && ` +
			`${aidlCmd} --dumpapi --structured ${imports} ${optionalFlags} --out ${outDir} ${in} && ` +
			`${aidlHashGen} ${outDir} ${latestVersion} ${hashFile}`,
		CommandDeps: []string{"${aidlCmd}", "${aidlHashGen}"},
	}, "optionalFlags", "imports", "outDir", "hashFile", "latestVersion")

	aidlCheckApiRule = pctx.StaticRule("aidlCheckApiRule", blueprint.RuleParams{
		Command: `(${aidlCmd} ${optionalFlags} --checkapi=${checkApiLevel} ${imports} ${old} ${new} && touch ${out}) || ` +
			`(cat ${messageFile} && exit 1)`,
		CommandDeps: []string{"${aidlCmd}"},
		Description: "AIDL CHECK API: ${new} against ${old}",
	}, "optionalFlags", "imports", "old", "new", "messageFile", "checkApiLevel")

	aidlVerifyHashRule = pctx.StaticRule("aidlVerifyHashRule", blueprint.RuleParams{
		Command: `if [ $$(cd '${apiDir}' && { find ./ -name "*.aidl" -print0 | LC_ALL=C sort -z | xargs -0 sha1sum && echo ${version}; } | sha1sum | cut -d " " -f 1) = $$(tail -1 '${hashFile}') ]; then ` +
			`touch ${out}; else cat '${messageFile}' && exit 1; fi`,
		Description: "Verify ${apiDir} files have not been modified",
	}, "apiDir", "version", "messageFile", "hashFile")
)

type aidlApiProperties struct {
	BaseName  string
	Srcs      []string `android:"path"`
	AidlRoot  string   // base directory for the input aidl file
	Stability *string
	Imports   []string
	Versions  []string
	Dumpapi   DumpApiProperties
}

type aidlApi struct {
	android.ModuleBase

	properties aidlApiProperties

	// for triggering api check for version X against version X-1
	checkApiTimestamps android.WritablePaths

	// for triggering updating current API
	updateApiTimestamp android.WritablePath

	// for triggering check that files have not been modified
	checkHashTimestamps android.WritablePaths

	// for triggering freezing API as the new version
	freezeApiTimestamp android.WritablePath

	// for checking for active development on unfrozen version
	hasDevelopment android.WritablePath
}

func (m *aidlApi) apiDir() string {
	return filepath.Join(aidlApiDir, m.properties.BaseName)
}

// `m <iface>-freeze-api` will freeze ToT as this version
func (m *aidlApi) nextVersion() string {
	return nextVersion(m.properties.Versions)
}

type apiDump struct {
	version  string
	dir      android.Path
	files    android.Paths
	hashFile android.OptionalPath
}

func (m *aidlApi) getImports(ctx android.ModuleContext, version string) map[string]string {
	iface := ctx.GetDirectDepWithTag(m.properties.BaseName, interfaceDep).(*aidlInterface)
	return iface.getImports(version)
}

func (m *aidlApi) createApiDumpFromSource(ctx android.ModuleContext) apiDump {
	srcs, imports := getPaths(ctx, m.properties.Srcs, m.properties.AidlRoot)

	if ctx.Failed() {
		return apiDump{}
	}

	// dumpapi uses imports for ToT("") version
	deps := getDeps(ctx, m.getImports(ctx, m.nextVersion()))
	imports = append(imports, deps.imports...)

	var apiDir android.WritablePath
	var apiFiles android.WritablePaths
	var hashFile android.WritablePath

	apiDir = android.PathForModuleOut(ctx, "dump")
	for _, src := range srcs {
		outFile := android.PathForModuleOut(ctx, "dump", src.Rel())
		apiFiles = append(apiFiles, outFile)
	}
	hashFile = android.PathForModuleOut(ctx, "dump", ".hash")

	var optionalFlags []string
	if m.properties.Stability != nil {
		optionalFlags = append(optionalFlags, "--stability", *m.properties.Stability)
	}
	if proptools.Bool(m.properties.Dumpapi.No_license) {
		optionalFlags = append(optionalFlags, "--no_license")
	}
	optionalFlags = append(optionalFlags, wrap("-p", deps.preprocessed.Strings(), "")...)

	version := nextVersion(m.properties.Versions)
	ctx.Build(pctx, android.BuildParams{
		Rule:      aidlDumpApiRule,
		Outputs:   append(apiFiles, hashFile),
		Inputs:    srcs,
		Implicits: deps.preprocessed,
		Args: map[string]string{
			"optionalFlags": strings.Join(optionalFlags, " "),
			"imports":       strings.Join(wrap("-I", imports, ""), " "),
			"outDir":        apiDir.String(),
			"hashFile":      hashFile.String(),
			"latestVersion": versionForHashGen(version),
		},
	})
	return apiDump{version, apiDir, apiFiles.Paths(), android.OptionalPathForPath(hashFile)}
}

func wrapWithDiffCheckIfElse(m *aidlApi, rb *android.RuleBuilder, writer func(*android.RuleBuilderCommand), elseBlock func(*android.RuleBuilderCommand)) {
	rbc := rb.Command()
	rbc.Text("if [ \"$(cat ").Input(m.hasDevelopment).Text(")\" = \"1\" ]; then")
	writer(rbc)
	rbc.Text("; else")
	elseBlock(rbc)
	rbc.Text("; fi")
}

func wrapWithDiffCheckIf(m *aidlApi, rb *android.RuleBuilder, writer func(*android.RuleBuilderCommand), needToWrap bool) {
	rbc := rb.Command()
	if needToWrap {
		rbc.Text("if [ \"$(cat ").Input(m.hasDevelopment).Text(")\" = \"1\" ]; then")
	}
	writer(rbc)
	if needToWrap {
		rbc.Text("; fi")
	}
}

// Migrate `versions` into `version_with_info`, and then append a version if it isn't nil
func (m *aidlApi) migrateAndAppendVersion(ctx android.ModuleContext, rb *android.RuleBuilder, version *string, transitive bool) {
	isFreezingApi := version != nil

	// Remove `versions` property which is deprecated.
	wrapWithDiffCheckIf(m, rb, func(rbc *android.RuleBuilderCommand) {
		rbc.BuiltTool("bpmodify").
			Text("-w -m " + m.properties.BaseName).
			Text("-parameter versions -remove-property").
			Text(android.PathForModuleSrc(ctx, "Android.bp").String())
	}, isFreezingApi)

	var iface *aidlInterface
	ctx.VisitDirectDeps(func(dep android.Module) {
		switch ctx.OtherModuleDependencyTag(dep).(type) {
		case interfaceDepTag:
			iface = dep.(*aidlInterface)
		}
	})
	if iface == nil {
		ctx.ModuleErrorf("aidl_interface %s doesn't exist", m.properties.BaseName)
		return
	}
	var versions []string
	if len(iface.properties.Versions_with_info) == 0 {
		versions = append(versions, iface.getVersions()...)
	}
	if isFreezingApi {
		versions = append(versions, *version)
	}
	for _, v := range versions {
		importIfaces := make(map[string]*aidlInterface)
		ctx.VisitDirectDeps(func(dep android.Module) {
			if _, ok := ctx.OtherModuleDependencyTag(dep).(importInterfaceDepTag); ok {
				other := dep.(*aidlInterface)
				importIfaces[other.BaseModuleName()] = other
			}
		})
		imports := make([]string, 0, len(iface.getImportsForVersion(v)))
		needTransitiveFreeze := isFreezingApi && v == *version && transitive

		if needTransitiveFreeze {
			importApis := make(map[string]*aidlApi)
			ctx.WalkDeps(func(child android.Module, parent android.Module) bool {
				if api, ok := child.(*aidlApi); ok {
					moduleName := strings.TrimSuffix(api.Name(), aidlApiSuffix)
					if _, ok := importIfaces[moduleName]; ok {
						importApis[moduleName] = api
						return false
					}
				}
				return true
			})
			wrapWithDiffCheckIf(m, rb, func(rbc *android.RuleBuilderCommand) {
				rbc.BuiltTool("bpmodify").
					Text("-w -m " + m.properties.BaseName).
					Text("-parameter versions_with_info -add-literal '").
					Text(fmt.Sprintf(`{version: "%s", imports: [`, v))

				for _, im := range iface.getImportsForVersion(v) {
					moduleName, version := parseModuleWithVersion(im)

					// Invoke an imported interface's freeze-api only if it depends on ToT version explicitly or implicitly.
					if version == importIfaces[moduleName].nextVersion() || !hasVersionSuffix(im) {
						rb.Command().Text(fmt.Sprintf(`echo "Call %s-freeze-api because %s depends on %s."`, moduleName, m.properties.BaseName, moduleName))
						rbc.Implicit(importApis[moduleName].freezeApiTimestamp)
					}
					if hasVersionSuffix(im) {
						rbc.Text(fmt.Sprintf(`"%s",`, im))
					} else {
						rbc.Text("\"" + im + "-V'" + `$(if [ "$(cat `).
							Input(importApis[im].hasDevelopment).
							Text(`)" = "1" ]; then echo "` + importIfaces[im].nextVersion() +
								`"; else echo "` + importIfaces[im].latestVersion() + `"; fi)'", `)
					}
				}
				rbc.Text("]}' ").
					Text(android.PathForModuleSrc(ctx, "Android.bp").String())
			}, isFreezingApi)
		} else {
			for _, im := range iface.getImportsForVersion(v) {
				if hasVersionSuffix(im) {
					imports = append(imports, im)
				} else {
					imports = append(imports, im+"-V"+importIfaces[im].latestVersion())
				}
			}
			importsStr := strings.Join(wrap(`"`, imports, `"`), ", ")
			data := fmt.Sprintf(`{version: "%s", imports: [%s]}`, v, importsStr)

			// Also modify Android.bp file to add the new version to the 'versions_with_info' property.
			wrapWithDiffCheckIf(m, rb, func(rbc *android.RuleBuilderCommand) {
				rbc.BuiltTool("bpmodify").
					Text("-w -m " + m.properties.BaseName).
					Text("-parameter versions_with_info -add-literal '" + data + "' ").
					Text(android.PathForModuleSrc(ctx, "Android.bp").String())
			}, isFreezingApi)
		}
	}
}

func (m *aidlApi) makeApiDumpAsVersion(ctx android.ModuleContext, dump apiDump, version string, latestVersionDump *apiDump) android.WritablePath {
	creatingNewVersion := version != currentVersion
	moduleDir := android.PathForModuleSrc(ctx).String()
	targetDir := filepath.Join(moduleDir, m.apiDir(), version)
	rb := android.NewRuleBuilder(pctx, ctx)
	transitive := ctx.Config().IsEnvTrue("AIDL_TRANSITIVE_FREEZE")
	var actionWord string
	if creatingNewVersion {
		actionWord = "Making"
		// We are asked to create a new version. But before doing that, check if the given
		// dump is the same as the latest version. If so, don't create a new version,
		// otherwise we will be unnecessarily creating many versions.
		// Copy the given dump to the target directory only when the equality check failed
		// (i.e. `has_development` file contains "1").
		wrapWithDiffCheckIf(m, rb, func(rbc *android.RuleBuilderCommand) {
			rbc.Text("mkdir -p " + targetDir + " && ").
				Text("cp -rf " + dump.dir.String() + "/. " + targetDir).Implicits(dump.files)
		}, true /* needToWrap */)
		wrapWithDiffCheckIfElse(m, rb, func(rbc *android.RuleBuilderCommand) {
			rbc.Text(fmt.Sprintf(`echo "There is change between ToT version and the latest stable version. Freezing %s-V%s."`, m.properties.BaseName, version))
		}, func(rbc *android.RuleBuilderCommand) {
			rbc.Text(fmt.Sprintf(`echo "There is no change from the latest stable version of %s. Nothing happened."`, m.properties.BaseName))
		})
		m.migrateAndAppendVersion(ctx, rb, &version, transitive)
	} else {
		actionWord = "Updating"
		// We are updating the current version. Don't copy .hash to the current dump
		rb.Command().Text("mkdir -p " + targetDir)
		rb.Command().Text("rm -rf " + targetDir + "/*")
		rb.Command().Text("cp -rf " + dump.dir.String() + "/* " + targetDir).Implicits(dump.files)

		m.migrateAndAppendVersion(ctx, rb, nil, false)
	}

	timestampFile := android.PathForModuleOut(ctx, "updateapi_"+version+".timestamp")
	rb.Command().Text("touch").Output(timestampFile)

	rb.Build("dump_aidl_api_"+m.properties.BaseName+"_"+version, actionWord+" AIDL API dump version "+version+" for "+m.properties.BaseName+" (see "+targetDir+")")
	return timestampFile
}

type deps struct {
	preprocessed android.Paths
	implicits    android.Paths
	imports      []string
}

// calculates import flags(-I) from deps.
// When the target is ToT, use ToT of imported interfaces. If not, we use "current" snapshot of
// imported interfaces.
func getDeps(ctx android.ModuleContext, versionedImports map[string]string) deps {
	var deps deps
	ctx.VisitDirectDeps(func(dep android.Module) {
		switch ctx.OtherModuleDependencyTag(dep).(type) {
		case importInterfaceDepTag:
			iface := dep.(*aidlInterface)
			if version, ok := versionedImports[iface.BaseModuleName()]; ok {
				if iface.preprocessed[version] == nil {
					ctx.ModuleErrorf("can't import %v's preprocessed(version=%v)", iface.BaseModuleName(), version)
				}
				deps.preprocessed = append(deps.preprocessed, iface.preprocessed[version])
			}
		case interfaceDepTag:
			iface := dep.(*aidlInterface)
			deps.imports = append(deps.imports, iface.properties.Include_dirs...)
		case apiDepTag:
			api := dep.(*aidlApi)
			// add imported module's checkapiTimestamps as implicits to make sure that imported apiDump is up-to-date
			deps.implicits = append(deps.implicits, api.checkApiTimestamps.Paths()...)
			deps.implicits = append(deps.implicits, api.checkHashTimestamps.Paths()...)
		}
	})
	return deps
}

func (m *aidlApi) checkApi(ctx android.ModuleContext, oldDump, newDump apiDump, checkApiLevel string, messageFile android.Path) android.WritablePath {
	newVersion := newDump.dir.Base()
	timestampFile := android.PathForModuleOut(ctx, "checkapi_"+newVersion+".timestamp")

	// --checkapi(old,new) should use imports for "new"
	deps := getDeps(ctx, m.getImports(ctx, newDump.version))
	var implicits android.Paths
	implicits = append(implicits, deps.implicits...)
	implicits = append(implicits, deps.preprocessed...)
	implicits = append(implicits, oldDump.files...)
	implicits = append(implicits, newDump.files...)
	implicits = append(implicits, messageFile)

	var optionalFlags []string
	if m.properties.Stability != nil {
		optionalFlags = append(optionalFlags, "--stability", *m.properties.Stability)
	}
	optionalFlags = append(optionalFlags, wrap("-p", deps.preprocessed.Strings(), "")...)

	ctx.Build(pctx, android.BuildParams{
		Rule:      aidlCheckApiRule,
		Implicits: implicits,
		Output:    timestampFile,
		Args: map[string]string{
			"optionalFlags": strings.Join(optionalFlags, " "),
			"imports":       strings.Join(wrap("-I", deps.imports, ""), " "),
			"old":           oldDump.dir.String(),
			"new":           newDump.dir.String(),
			"messageFile":   messageFile.String(),
			"checkApiLevel": checkApiLevel,
		},
	})
	return timestampFile
}

func (m *aidlApi) checkCompatibility(ctx android.ModuleContext, oldDump, newDump apiDump) android.WritablePath {
	messageFile := android.PathForSource(ctx, "system/tools/aidl/build/message_check_compatibility.txt")
	return m.checkApi(ctx, oldDump, newDump, "compatible", messageFile)
}

func (m *aidlApi) checkEquality(ctx android.ModuleContext, oldDump apiDump, newDump apiDump) android.WritablePath {
	// Use different messages depending on whether platform SDK is finalized or not.
	// In case when it is finalized, we should never allow updating the already frozen API.
	// If it's not finalized, we let users to update the current version by invoking
	// `m <name>-update-api`.
	messageFile := android.PathForSource(ctx, "system/tools/aidl/build/message_check_equality.txt")
	sdkIsFinal := !ctx.Config().DefaultAppTargetSdk(ctx).IsPreview()
	if sdkIsFinal {
		messageFile = android.PathForSource(ctx, "system/tools/aidl/build/message_check_equality_release.txt")
	}
	formattedMessageFile := android.PathForModuleOut(ctx, "message_check_equality.txt")
	rb := android.NewRuleBuilder(pctx, ctx)
	rb.Command().Text("sed").Flag(" s/%s/" + m.properties.BaseName + "/g ").Input(messageFile).Text(" > ").Output(formattedMessageFile)
	rb.Build("format_message_"+m.properties.BaseName, "")

	return m.checkApi(ctx, oldDump, newDump, "equal", formattedMessageFile)
}

func (m *aidlApi) checkIntegrity(ctx android.ModuleContext, dump apiDump) android.WritablePath {
	version := dump.dir.Base()
	timestampFile := android.PathForModuleOut(ctx, "checkhash_"+version+".timestamp")
	messageFile := android.PathForSource(ctx, "system/tools/aidl/build/message_check_integrity.txt")

	var implicits android.Paths
	implicits = append(implicits, dump.files...)
	implicits = append(implicits, dump.hashFile.Path())
	implicits = append(implicits, messageFile)
	ctx.Build(pctx, android.BuildParams{
		Rule:      aidlVerifyHashRule,
		Implicits: implicits,
		Output:    timestampFile,
		Args: map[string]string{
			"apiDir":      dump.dir.String(),
			"version":     versionForHashGen(version),
			"hashFile":    dump.hashFile.Path().String(),
			"messageFile": messageFile.String(),
		},
	})
	return timestampFile
}

func (m *aidlApi) checkForDevelopment(ctx android.ModuleContext, latestVersionDump *apiDump, totDump apiDump) android.WritablePath {
	hasDevPath := android.PathForModuleOut(ctx, "has_development")
	rb := android.NewRuleBuilder(pctx, ctx)
	rb.Command().Text("rm -f " + hasDevPath.String())
	if latestVersionDump != nil {
		hasDevCommand := rb.Command()
		hasDevCommand.BuiltTool("aidl").FlagWithArg("--checkapi=", "equal")
		if m.properties.Stability != nil {
			hasDevCommand.FlagWithArg("--stability ", *m.properties.Stability)
		}
		// checkapi(latest, tot) should use imports for nextVersion(=tot)
		deps := getDeps(ctx, m.getImports(ctx, m.nextVersion()))
		hasDevCommand.
			FlagForEachArg("-I", deps.imports).Implicits(deps.implicits).
			FlagForEachInput("-p", deps.preprocessed).
			Text(latestVersionDump.dir.String()).Implicits(latestVersionDump.files).
			Text(totDump.dir.String()).Implicits(totDump.files).
			Text("2> /dev/null; echo $? >").Output(hasDevPath)
	} else {
		rb.Command().Text("echo 1 >").Output(hasDevPath)
	}
	rb.Build("check_for_development", "")
	return hasDevPath
}

func (m *aidlApi) GenerateAndroidBuildActions(ctx android.ModuleContext) {
	// An API dump is created from source and it is compared against the API dump of the
	// 'current' (yet-to-be-finalized) version. By checking this we enforce that any change in
	// the AIDL interface is gated by the AIDL API review even before the interface is frozen as
	// a new version.
	totApiDump := m.createApiDumpFromSource(ctx)
	currentApiDir := android.ExistentPathForSource(ctx, ctx.ModuleDir(), m.apiDir(), currentVersion)
	var currentApiDump apiDump
	if currentApiDir.Valid() {
		currentApiDump = apiDump{
			version:  nextVersion(m.properties.Versions),
			dir:      currentApiDir.Path(),
			files:    ctx.Glob(filepath.Join(currentApiDir.Path().String(), "**/*.aidl"), nil),
			hashFile: android.ExistentPathForSource(ctx, ctx.ModuleDir(), m.apiDir(), currentVersion, ".hash"),
		}
		checked := m.checkEquality(ctx, currentApiDump, totApiDump)
		m.checkApiTimestamps = append(m.checkApiTimestamps, checked)
	} else {
		// The "current" directory might not exist, in case when the interface is first created.
		// Instruct user to create one by executing `m <name>-update-api`.
		rb := android.NewRuleBuilder(pctx, ctx)
		ifaceName := m.properties.BaseName
		rb.Command().Text(fmt.Sprintf(`echo "API dump for the current version of AIDL interface %s does not exist."`, ifaceName))
		rb.Command().Text(fmt.Sprintf(`echo Run "m %s-update-api", or add "unstable: true" to the build rule `+
			`for the interface if it does not need to be versioned`, ifaceName))
		// This file will never be created. Otherwise, the build will pass simply by running 'm; m'.
		alwaysChecked := android.PathForModuleOut(ctx, "checkapi_current.timestamp")
		rb.Command().Text("false").ImplicitOutput(alwaysChecked)
		rb.Build("check_current_aidl_api", "")
		m.checkApiTimestamps = append(m.checkApiTimestamps, alwaysChecked)
	}

	// Also check that version X is backwards compatible with version X-1.
	// "current" is checked against the latest version.
	var dumps []apiDump
	for _, ver := range m.properties.Versions {
		apiDir := filepath.Join(ctx.ModuleDir(), m.apiDir(), ver)
		apiDirPath := android.ExistentPathForSource(ctx, apiDir)
		if apiDirPath.Valid() {
			hashFilePath := filepath.Join(apiDir, ".hash")
			dump := apiDump{
				version:  ver,
				dir:      apiDirPath.Path(),
				files:    ctx.Glob(filepath.Join(apiDirPath.String(), "**/*.aidl"), nil),
				hashFile: android.ExistentPathForSource(ctx, hashFilePath),
			}
			if !dump.hashFile.Valid() {
				// We should show the source path of hash_gen because aidl_hash_gen cannot be built due to build error.
				cmd := fmt.Sprintf(`(croot && system/tools/aidl/build/hash_gen.sh %s %s %s)`, apiDir, versionForHashGen(ver), hashFilePath)
				ctx.ModuleErrorf("A frozen aidl_interface must have '.hash' file, but %s-V%s doesn't have it. Use the command below to generate hash.\n%s\n",
					m.properties.BaseName, ver, cmd)
			}
			dumps = append(dumps, dump)
		} else if ctx.Config().AllowMissingDependencies() {
			ctx.AddMissingDependencies([]string{apiDir})
		} else {
			ctx.ModuleErrorf("API version %s path %s does not exist", ver, apiDir)
		}
	}
	var latestVersionDump *apiDump
	if len(dumps) >= 1 {
		latestVersionDump = &dumps[len(dumps)-1]
	}
	if currentApiDir.Valid() {
		dumps = append(dumps, currentApiDump)
	}
	for i, _ := range dumps {
		if dumps[i].hashFile.Valid() {
			checkHashTimestamp := m.checkIntegrity(ctx, dumps[i])
			m.checkHashTimestamps = append(m.checkHashTimestamps, checkHashTimestamp)
		}

		if i == 0 {
			continue
		}
		checked := m.checkCompatibility(ctx, dumps[i-1], dumps[i])
		m.checkApiTimestamps = append(m.checkApiTimestamps, checked)
	}

	// Check for active development on the unfrozen version
	m.hasDevelopment = m.checkForDevelopment(ctx, latestVersionDump, totApiDump)

	// API dump from source is updated to the 'current' version. Triggered by `m <name>-update-api`
	m.updateApiTimestamp = m.makeApiDumpAsVersion(ctx, totApiDump, currentVersion, nil)

	// API dump from source is frozen as the next stable version. Triggered by `m <name>-freeze-api`
	nextVersion := m.nextVersion()
	m.freezeApiTimestamp = m.makeApiDumpAsVersion(ctx, totApiDump, nextVersion, latestVersionDump)
}

func (m *aidlApi) AndroidMk() android.AndroidMkData {
	return android.AndroidMkData{
		Custom: func(w io.Writer, name, prefix, moduleDir string, data android.AndroidMkData) {
			android.WriteAndroidMkData(w, data)
			targetName := m.properties.BaseName + "-freeze-api"
			fmt.Fprintln(w, ".PHONY:", targetName)
			fmt.Fprintln(w, targetName+":", m.freezeApiTimestamp.String())

			targetName = m.properties.BaseName + "-update-api"
			fmt.Fprintln(w, ".PHONY:", targetName)
			fmt.Fprintln(w, targetName+":", m.updateApiTimestamp.String())
		},
	}
}

func (m *aidlApi) DepsMutator(ctx android.BottomUpMutatorContext) {
	ctx.AddReverseDependency(ctx.Module(), nil, aidlMetadataSingletonName)
}

func aidlApiFactory() android.Module {
	m := &aidlApi{}
	m.AddProperties(&m.properties)
	android.InitAndroidModule(m)
	return m
}

func addApiModule(mctx android.LoadHookContext, i *aidlInterface) string {
	apiModule := i.ModuleBase.Name() + aidlApiSuffix
	srcs, aidlRoot := i.srcsForVersion(mctx, i.nextVersion())
	mctx.CreateModule(aidlApiFactory, &nameProperties{
		Name: proptools.StringPtr(apiModule),
	}, &aidlApiProperties{
		BaseName:  i.ModuleBase.Name(),
		Srcs:      srcs,
		AidlRoot:  aidlRoot,
		Stability: i.properties.Stability,
		Imports:   i.properties.Imports,
		Versions:  i.getVersions(),
		Dumpapi:   i.properties.Dumpapi,
	})
	return apiModule
}

func versionForHashGen(ver string) string {
	// aidlHashGen uses the version before current version. If it has never been frozen, return 'latest-version'.
	verInt, _ := strconv.Atoi(ver)
	if verInt > 1 {
		return strconv.Itoa(verInt - 1)
	}
	return "latest-version"
}

func init() {
	android.RegisterSingletonType("aidl-freeze-api", freezeApiSingletonFactory)
}

func freezeApiSingletonFactory() android.Singleton {
	return &freezeApiSingleton{}
}

type freezeApiSingleton struct{}

func (f *freezeApiSingleton) GenerateBuildActions(ctx android.SingletonContext) {
	var files android.Paths
	ctx.VisitAllModules(func(module android.Module) {
		if !module.Enabled() {
			return
		}
		if m, ok := module.(*aidlApi); ok {
			ownersToFreeze := strings.Fields(ctx.Config().Getenv("AIDL_FREEZE_OWNERS"))
			var shouldBeFrozen bool
			if len(ownersToFreeze) > 0 {
				shouldBeFrozen = android.InList(m.Owner(), ownersToFreeze)
			} else {
				shouldBeFrozen = m.Owner() == ""
			}
			if shouldBeFrozen {
				files = append(files, m.freezeApiTimestamp)
			}
		}
	})
	ctx.Phony("aidl-freeze-api", files...)
}