func buildGoPackage(ctx blueprint.ModuleContext, pkgRoot string,
	pkgPath string, archiveFile string, srcs []string, genSrcs []string, orderDeps []string) {

	srcDir := moduleSrcDir(ctx)
	srcFiles := pathtools.PrefixPaths(srcs, srcDir)
	srcFiles = append(srcFiles, genSrcs...)

	var incFlags []string
	deps := []string{"$compileCmd"}
	ctx.VisitDepsDepthFirstIf(isGoPackageProducer,
		func(module blueprint.Module) {
			dep := module.(goPackageProducer)
			incDir := dep.GoPkgRoot()
			target := dep.GoPackageTarget()
			incFlags = append(incFlags, "-I "+incDir)
			deps = append(deps, target)
		})

	compileArgs := map[string]string{
		"pkgPath": pkgPath,
	}

	if len(incFlags) > 0 {
		compileArgs["incFlags"] = strings.Join(incFlags, " ")
	}

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      compile,
		Outputs:   []string{archiveFile},
		Inputs:    srcFiles,
		OrderOnly: orderDeps,
		Implicits: deps,
		Args:      compileArgs,
	})
}

func buildGoPluginLoader(ctx blueprint.ModuleContext, pkgPath, pluginSrc string, stage Stage) bool {
	ret := true
	name := ctx.ModuleName()

	var pluginPaths []string
	ctx.VisitDepsDepthFirstIf(isGoPluginFor(name),
		func(module blueprint.Module) {
			plugin := module.(goPluginProvider)
			pluginPaths = append(pluginPaths, plugin.GoPkgPath())
			if stage == StageBootstrap {
				ctx.OtherModuleErrorf(module, "plugin %q may not be included in core module %q",
					ctx.OtherModuleName(module), name)
				ret = false
			}
		})

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      pluginGenSrc,
		Outputs:   []string{pluginSrc},
		Implicits: []string{"$pluginGenSrcCmd"},
		Args: map[string]string{
			"pkg":     pkgPath,
			"plugins": strings.Join(pluginPaths, " "),
		},
	})

	return ret
}

func phonyGoTarget(ctx blueprint.ModuleContext, target string, srcs []string,
	gensrcs []string, intermediates []string) {

	var depTargets []string
	ctx.VisitDepsDepthFirstIf(isGoPackageProducer,
		func(module blueprint.Module) {
			dep := module.(goPackageProducer)
			target := dep.GoPackageTarget()
			depTargets = append(depTargets, target)
		})

	moduleDir := ctx.ModuleDir()
	srcs = pathtools.PrefixPaths(srcs, filepath.Join("$srcDir", moduleDir))
	srcs = append(srcs, gensrcs...)

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      phony,
		Outputs:   []string{target},
		Inputs:    srcs,
		Implicits: depTargets,
	})

	// If one of the source files gets deleted or renamed that will prevent the
	// re-bootstrapping happening because it depends on the missing source file.
	// To get around this we add a build statement using the built-in phony rule
	// for each source file, which will cause Ninja to treat it as dirty if its
	// missing.
	for _, src := range srcs {
		ctx.Build(pctx, blueprint.BuildParams{
			Rule:    blueprint.Phony,
			Outputs: []string{src},
		})
	}

	// If there is no rule to build the intermediate files of a bootstrap go package
	// the cleanup phase of the primary builder will delete the intermediate files,
	// forcing an unnecessary rebuild.  Add phony rules for all of them.
	for _, intermediate := range intermediates {
		ctx.Build(pctx, blueprint.BuildParams{
			Rule:    blueprint.Phony,
			Outputs: []string{intermediate},
		})
	}

}

func (g *goPackage) GenerateBuildActions(ctx blueprint.ModuleContext) {
	name := ctx.ModuleName()

	if g.properties.PkgPath == "" {
		ctx.ModuleErrorf("module %s did not specify a valid pkgPath", name)
		return
	}

	g.pkgRoot = packageRoot(ctx)
	g.archiveFile = filepath.Join(g.pkgRoot,
		filepath.FromSlash(g.properties.PkgPath)+".a")
	if len(g.properties.TestSrcs) > 0 && g.config.runGoTests {
		g.testArchiveFile = filepath.Join(testRoot(ctx),
			filepath.FromSlash(g.properties.PkgPath)+".a")
	}

	// We only actually want to build the builder modules if we're running as
	// minibp (i.e. we're generating a bootstrap Ninja file).  This is to break
	// the circular dependence that occurs when the builder requires a new Ninja
	// file to be built, but building a new ninja file requires the builder to
	// be built.
	if g.config.generatingBootstrapper {
		var deps []string

		if g.config.runGoTests {
			deps = buildGoTest(ctx, testRoot(ctx), g.testArchiveFile,
				g.properties.PkgPath, g.properties.Srcs,
				g.properties.TestSrcs)
		}

		buildGoPackage(ctx, g.pkgRoot, g.properties.PkgPath, g.archiveFile,
			g.properties.Srcs, deps)
	} else {
		if len(g.properties.TestSrcs) > 0 && g.config.runGoTests {
			phonyGoTarget(ctx, g.testArchiveFile, g.properties.TestSrcs, nil)
		}
		phonyGoTarget(ctx, g.archiveFile, g.properties.Srcs, nil)
	}
}

func (g *goPackage) GenerateBuildActions(ctx blueprint.ModuleContext) {
	var (
		name       = ctx.ModuleName()
		hasPlugins = false
		pluginSrc  = ""
		genSrcs    = []string{}
	)

	if g.properties.PkgPath == "" {
		ctx.ModuleErrorf("module %s did not specify a valid pkgPath", name)
		return
	}

	g.pkgRoot = packageRoot(ctx)
	g.archiveFile = filepath.Join(g.pkgRoot,
		filepath.FromSlash(g.properties.PkgPath)+".a")
	if len(g.properties.TestSrcs) > 0 && g.config.runGoTests {
		g.testArchiveFile = filepath.Join(testRoot(ctx),
			filepath.FromSlash(g.properties.PkgPath)+".a")
	}

	ctx.VisitDepsDepthFirstIf(isGoPluginFor(name),
		func(module blueprint.Module) { hasPlugins = true })
	if hasPlugins {
		pluginSrc = filepath.Join(moduleGenSrcDir(ctx), "plugin.go")
		genSrcs = append(genSrcs, pluginSrc)
	}

	// We only actually want to build the builder modules if we're running as
	// minibp (i.e. we're generating a bootstrap Ninja file).  This is to break
	// the circular dependence that occurs when the builder requires a new Ninja
	// file to be built, but building a new ninja file requires the builder to
	// be built.
	if g.config.stage == g.BuildStage() {
		var deps []string

		if hasPlugins && !buildGoPluginLoader(ctx, g.properties.PkgPath, pluginSrc, g.config.stage) {
			return
		}

		if g.config.runGoTests {
			deps = buildGoTest(ctx, testRoot(ctx), g.testArchiveFile,
				g.properties.PkgPath, g.properties.Srcs, genSrcs,
				g.properties.TestSrcs)
		}

		buildGoPackage(ctx, g.pkgRoot, g.properties.PkgPath, g.archiveFile,
			g.properties.Srcs, genSrcs, deps)
	} else if g.config.stage != StageBootstrap {
		if len(g.properties.TestSrcs) > 0 && g.config.runGoTests {
			phonyGoTarget(ctx, g.testArchiveFile, g.properties.TestSrcs, nil, nil)
		}
		phonyGoTarget(ctx, g.archiveFile, g.properties.Srcs, genSrcs, nil)
	}
}

// moduleGenSrcDir returns the module-specific generated sources path.
func moduleGenSrcDir(ctx blueprint.ModuleContext) string {
	return filepath.Join(bootstrapDir, ctx.ModuleName(), "gen")
}

// moduleObjDir returns the module-specific object directory path.
func moduleObjDir(ctx blueprint.ModuleContext) string {
	return filepath.Join(bootstrapDir, ctx.ModuleName(), "obj")
}

// moduleSrcDir returns the path of the directory that all source file paths are
// specified relative to.
func moduleSrcDir(ctx blueprint.ModuleContext) string {
	return filepath.Join("$srcDir", ctx.ModuleDir())
}

// testRoot returns the module-specific package root directory path used for
// building tests. The .a files generated here will include everything from
// packageRoot, plus the test-only code.
func testRoot(ctx blueprint.ModuleContext) string {
	return filepath.Join(bootstrapDir, ctx.ModuleName(), "test")
}

// packageRoot returns the module-specific package root directory path.  This
// directory is where the final package .a files are output and where dependant
// modules search for this package via -I arguments.
func packageRoot(ctx blueprint.ModuleContext) string {
	return filepath.Join(bootstrapDir, ctx.ModuleName(), "pkg")
}

func buildGoTest(ctx blueprint.ModuleContext, testRoot, testPkgArchive,
	pkgPath string, srcs, genSrcs, testSrcs []string) []string {

	if len(testSrcs) == 0 {
		return nil
	}

	srcDir := moduleSrcDir(ctx)
	testFiles := pathtools.PrefixPaths(testSrcs, srcDir)

	mainFile := filepath.Join(testRoot, "test.go")
	testArchive := filepath.Join(testRoot, "test.a")
	testFile := filepath.Join(testRoot, "test")
	testPassed := filepath.Join(testRoot, "test.passed")

	buildGoPackage(ctx, testRoot, pkgPath, testPkgArchive,
		append(srcs, testSrcs...), genSrcs, nil)

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      goTestMain,
		Outputs:   []string{mainFile},
		Inputs:    testFiles,
		Implicits: []string{"$goTestMainCmd"},
		Args: map[string]string{
			"pkg": pkgPath,
		},
	})

	libDirFlags := []string{"-L " + testRoot}
	ctx.VisitDepsDepthFirstIf(isGoPackageProducer,
		func(module blueprint.Module) {
			dep := module.(goPackageProducer)
			libDir := dep.GoPkgRoot()
			libDirFlags = append(libDirFlags, "-L "+libDir)
		})

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      compile,
		Outputs:   []string{testArchive},
		Inputs:    []string{mainFile},
		Implicits: []string{"$compileCmd", testPkgArchive},
		Args: map[string]string{
			"pkgPath":  "main",
			"incFlags": "-I " + testRoot,
		},
	})

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:      link,
		Outputs:   []string{testFile},
		Inputs:    []string{testArchive},
		Implicits: []string{"$linkCmd"},
		Args: map[string]string{
			"libDirFlags": strings.Join(libDirFlags, " "),
		},
	})

	ctx.Build(pctx, blueprint.BuildParams{
		Rule:    test,
		Outputs: []string{testPassed},
		Inputs:  []string{testFile},
		Args: map[string]string{
			"pkg":       pkgPath,
			"pkgSrcDir": filepath.Dir(testFiles[0]),
		},
	})

	return []string{testPassed}
}