/*
Copyright 2015 The Kubernetes Authors.

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 args has common command-line flags for generation programs.
package args

import (
	"bytes"
	goflag "flag"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"k8s.io/gengo/generator"
	"k8s.io/gengo/namer"
	"k8s.io/gengo/parser"

	"github.com/spf13/pflag"
)

// Default returns a defaulted GeneratorArgs. You may change the defaults
// before calling AddFlags.
func Default() *GeneratorArgs {
	return &GeneratorArgs{
		OutputBase:                 DefaultSourceTree(),
		GoHeaderFilePath:           filepath.Join(DefaultSourceTree(), "k8s.io/gengo/boilerplate/boilerplate.go.txt"),
		GeneratedBuildTag:          "ignore_autogenerated",
		GeneratedByCommentTemplate: "// Code generated by GENERATOR_NAME. DO NOT EDIT.",
		defaultCommandLineFlags:    true,
	}
}

// GeneratorArgs has arguments that are passed to generators.
type GeneratorArgs struct {
	// Which directories to parse.
	InputDirs []string

	// Source tree to write results to.
	OutputBase string

	// Package path within the source tree.
	OutputPackagePath string

	// Output file name.
	OutputFileBaseName string

	// Where to get copyright header text.
	GoHeaderFilePath string

	// If GeneratedByCommentTemplate is set, generate a "Code generated by" comment
	// below the bloilerplate, of the format defined by this string.
	// Any instances of "GENERATOR_NAME" will be replaced with the name of the code generator.
	GeneratedByCommentTemplate string

	// If true, only verify, don't write anything.
	VerifyOnly bool

	// If true, include *_test.go files
	IncludeTestFiles bool

	// GeneratedBuildTag is the tag used to identify code generated by execution
	// of this type. Each generator should use a different tag, and different
	// groups of generators (external API that depends on Kube generations) should
	// keep tags distinct as well.
	GeneratedBuildTag string

	// Any custom arguments go here
	CustomArgs interface{}

	// If specified, trim the prefix from OutputPackagePath before writing files.
	TrimPathPrefix string

	// Whether to use default command line flags
	defaultCommandLineFlags bool
}

// WithoutDefaultFlagParsing disables implicit addition of command line flags and parsing.
func (g *GeneratorArgs) WithoutDefaultFlagParsing() *GeneratorArgs {
	g.defaultCommandLineFlags = false
	return g
}

func (g *GeneratorArgs) AddFlags(fs *pflag.FlagSet) {
	fs.StringSliceVarP(&g.InputDirs, "input-dirs", "i", g.InputDirs, "Comma-separated list of import paths to get input types from.")
	fs.StringVarP(&g.OutputBase, "output-base", "o", g.OutputBase, "Output base; defaults to $GOPATH/src/ or ./ if $GOPATH is not set.")
	fs.StringVarP(&g.OutputPackagePath, "output-package", "p", g.OutputPackagePath, "Base package path.")
	fs.StringVarP(&g.OutputFileBaseName, "output-file-base", "O", g.OutputFileBaseName, "Base name (without .go suffix) for output files.")
	fs.StringVarP(&g.GoHeaderFilePath, "go-header-file", "h", g.GoHeaderFilePath, "File containing boilerplate header text. The string YEAR will be replaced with the current 4-digit year.")
	fs.BoolVar(&g.VerifyOnly, "verify-only", g.VerifyOnly, "If true, only verify existing output, do not write anything.")
	fs.StringVar(&g.GeneratedBuildTag, "build-tag", g.GeneratedBuildTag, "A Go build tag to use to identify files generated by this command. Should be unique.")
	fs.StringVar(&g.TrimPathPrefix, "trim-path-prefix", g.TrimPathPrefix, "If set, trim the specified prefix from --output-package when generating files.")
}

// LoadGoBoilerplate loads the boilerplate file passed to --go-header-file.
func (g *GeneratorArgs) LoadGoBoilerplate() ([]byte, error) {
	b, err := ioutil.ReadFile(g.GoHeaderFilePath)
	if err != nil {
		return nil, err
	}
	b = bytes.Replace(b, []byte("YEAR"), []byte(strconv.Itoa(time.Now().UTC().Year())), -1)

	if g.GeneratedByCommentTemplate != "" {
		if len(b) != 0 {
			b = append(b, byte('\n'))
		}
		generatorName := filepath.Base(os.Args[0])
		// Strip the extension from the name to normalize output between *nix and Windows.
		generatorName = generatorName[:len(generatorName)-len(filepath.Ext(generatorName))]
		generatedByComment := strings.Replace(g.GeneratedByCommentTemplate, "GENERATOR_NAME", generatorName, -1)
		s := fmt.Sprintf("%s\n\n", generatedByComment)
		b = append(b, []byte(s)...)
	}
	return b, nil
}

// NewBuilder makes a new parser.Builder and populates it with the input
// directories.
func (g *GeneratorArgs) NewBuilder() (*parser.Builder, error) {
	b := parser.New()

	// flag for including *_test.go
	b.IncludeTestFiles = g.IncludeTestFiles

	// Ignore all auto-generated files.
	b.AddBuildTags(g.GeneratedBuildTag)

	for _, d := range g.InputDirs {
		var err error
		if strings.HasSuffix(d, "/...") {
			err = b.AddDirRecursive(strings.TrimSuffix(d, "/..."))
		} else {
			err = b.AddDir(d)
		}
		if err != nil {
			return nil, fmt.Errorf("unable to add directory %q: %v", d, err)
		}
	}
	return b, nil
}

// DefaultSourceTree returns the /src directory of the first entry in $GOPATH.
// If $GOPATH is empty, it returns "./". Useful as a default output location.
func DefaultSourceTree() string {
	paths := strings.Split(os.Getenv("GOPATH"), string(filepath.ListSeparator))
	if len(paths) > 0 && len(paths[0]) > 0 {
		return filepath.Join(paths[0], "src")
	}
	return "./"
}

// Execute implements main().
// If you don't need any non-default behavior, use as:
// args.Default().Execute(...)
func (g *GeneratorArgs) Execute(nameSystems namer.NameSystems, defaultSystem string, pkgs func(*generator.Context, *GeneratorArgs) generator.Packages) error {
	if g.defaultCommandLineFlags {
		g.AddFlags(pflag.CommandLine)
		pflag.CommandLine.AddGoFlagSet(goflag.CommandLine)
		pflag.Parse()
	}

	b, err := g.NewBuilder()
	if err != nil {
		return fmt.Errorf("Failed making a parser: %v", err)
	}

	// pass through the flag on whether to include *_test.go files
	b.IncludeTestFiles = g.IncludeTestFiles

	c, err := generator.NewContext(b, nameSystems, defaultSystem)
	if err != nil {
		return fmt.Errorf("Failed making a context: %v", err)
	}

	c.TrimPathPrefix = g.TrimPathPrefix

	c.Verify = g.VerifyOnly
	packages := pkgs(c, g)
	if err := c.ExecutePackages(g.OutputBase, packages); err != nil {
		return fmt.Errorf("Failed executing generator: %v", err)
	}

	return nil
}