// Copyright 2018 The CUE 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 cmd

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"unicode"

	"cuelang.org/go/cue"
	"cuelang.org/go/cue/ast"
	"cuelang.org/go/cue/encoding"
	"cuelang.org/go/cue/format"
	"cuelang.org/go/cue/literal"
	"cuelang.org/go/cue/load"
	"cuelang.org/go/cue/parser"
	"cuelang.org/go/cue/token"
	"cuelang.org/go/internal"
	"cuelang.org/go/internal/third_party/yaml"
	"github.com/spf13/cobra"
	"golang.org/x/sync/errgroup"
)

// importCmd represents the import command
var importCmd = &cobra.Command{
	Use:   "import",
	Short: "convert other data formats to CUE files",
	Long: `import converts other data formats, like JSON and YAML to CUE files

The following file formats are currently supported:

  Format     Extensions
    JSON       .json .jsonl .ndjson
    YAML       .yaml .yml

Files can either be specified explicitly, or inferred from the specified
packages. In either case, the file extension is replaced with .cue. It will
fail if the file already exists by default. The -f flag overrides this.

Examples:

  # Convert individual files:
  $ cue import foo.json bar.json  # create foo.yaml and bar.yaml

  # Convert all json files in the indicated directories:
  $ cue import ./... -type=json


The -path flag

By default the parsed files are included as emit values. This default can be
overridden by specifying a sequence of labels as you would in a CUE file.
An identifier or string label are interpreted as usual. A label expression is
evaluated within the context of the imported file. label expressions may also
refer to builtin packages, which will be implicitly imported.


Handling multiple documents or streams

To handle Multi-document files, such as concatenated JSON objects or
YAML files with document separators (---) the user must specify either the
-path, -list, or -files flag. The -path flag assign each element to a path
(identical paths are treated as usual); -list concatenates the entries, and
-files causes each entry to be written to a different file. The -files flag
may only be used if files are explicitly imported. The -list flag may be
used in combination with the -path flag, concatenating each entry to the
mapped location.


Examples:

  $ cat <<EOF > foo.yaml
  kind: Service
  name: booster
  EOF

  # include the parsed file as an emit value:
  $ cue import foo.yaml
  $ cat foo.cue
  {
      kind: Service
      name: booster
  }

  # include the parsed file at the root of the CUE file:
  $ cue import -f -l "" foo.yaml
  $ cat foo.cue
  kind: Service
  name: booster

  # include the import config at the mystuff path
  $ cue import -f -l mystuff foo.yaml
  $ cat foo.cue
  myStuff: {
      kind: Service
      name: booster
  }

  # append another object to the input file
  $ cat <<EOF >> foo.yaml
  ---
  kind: Deployment
  name: booster
  replicas: 1

  # base the path values on th input
  $ cue import -f -l '"\(strings.ToLower(kind))" "\(x.name)"' foo.yaml
  $ cat foo.cue
  service booster: {
      kind: "Service"
      name: "booster"
  }

  deployment booster: {
      kind:     "Deployment"
      name:     "booster
      replicas: 1
  }

  # base the path values on th input
  $ cue import -f -list -foo.yaml
  $ cat foo.cue
  [{
      kind: "Service"
      name: "booster"
  }, {
      kind:     "Deployment"
      name:     "booster
      replicas: 1
  }]

  # base the path values on th input
  $ cue import -f -list -l '"\(strings.ToLower(kind))"' foo.yaml
  $ cat foo.cue
  service: [{
      kind: "Service"
      name: "booster"
  }
  deployment: [{
      kind:     "Deployment"
      name:     "booster
      replicas: 1
  }]


Embedded data files

The --recursive or -R flag enables the parsing of fields that are string
representations of data formats themselves. A field that can be parsed is
replaced with a call encoding the data from a structured form that is placed
in a sibling field.

It is also possible to recursively hoist data formats:

Example:
  $ cat <<EOF > example.json
  "a": {
      "data": '{ "foo": 1, "bar": 2 }',
  }
  EOF

  $ cue import -R example.json
  $ cat example.cue
  import "encode/json"

  a: {
      data: json.Encode(_data),
      _data: {
          foo: 1
          bar: 2
      }
  }
`,
	RunE: runImport,
}

func init() {
	rootCmd.AddCommand(importCmd)

	out = importCmd.Flags().StringP("out", "o", "", "alternative output or - for stdout")
	name = importCmd.Flags().StringP("name", "n", "", "glob filter for file names")
	typ = importCmd.Flags().String("type", "", "only apply to files of this type")
	force = importCmd.Flags().BoolP("force", "f", false, "force overwriting existing files")
	dryrun = importCmd.Flags().Bool("dryrun", false, "force overwriting existing files")

	node = importCmd.Flags().StringP("path", "l", "", "path to include root")
	list = importCmd.Flags().Bool("list", false, "concatenate multiple objects into a list")
	files = importCmd.Flags().Bool("files", false, "split multiple entries into different files")
	parseStrings = importCmd.Flags().BoolP("recursive", "R", false, "recursively parse string values")

	importCmd.Flags().String("fix", "", "apply given fix")
}

var (
	force        *bool
	name         *string
	typ          *string
	node         *string
	out          *string
	dryrun       *bool
	list         *bool
	files        *bool
	parseStrings *bool
)

type importFunc func(path string, r io.Reader) ([]ast.Expr, error)

type encodingInfo struct {
	fn  importFunc
	typ string
}

var (
	jsonEnc = &encodingInfo{handleJSON, "json"}
	yamlEnc = &encodingInfo{handleYAML, "yaml"}
)

func getExtInfo(ext string) *encodingInfo {
	enc := encoding.MapExtension(ext)
	if enc == nil {
		return nil
	}
	switch enc.Name() {
	case "json":
		return jsonEnc
	case "yaml":
		return yamlEnc
	}
	return nil
}

func runImport(cmd *cobra.Command, args []string) error {
	log.SetOutput(cmd.OutOrStderr())

	var group errgroup.Group

	group.Go(func() error {
		if len(args) > 0 && len(filepath.Ext(args[0])) > len(".") {
			for _, a := range args {
				group.Go(func() error { return handleFile(cmd, *fPackage, a) })
			}
			return nil
		}

		done := map[string]bool{}

		inst := load.Instances(args, &load.Config{DataFiles: true})
		for _, pkg := range inst {
			pkgName := *fPackage
			if pkgName == "" {
				pkgName = pkg.PkgName
			}
			if pkgName == "" && len(inst) > 1 {
				return fmt.Errorf("must specify package name with the -p flag")
			}
			dir := pkg.Dir
			if err := pkg.Err; err != nil {
				return err
			}
			if done[dir] {
				continue
			}
			done[dir] = true

			files, err := ioutil.ReadDir(dir)
			if err != nil {
				return err
			}
			for _, file := range files {
				ext := filepath.Ext(file.Name())
				if enc := getExtInfo(ext); enc == nil || (*typ != "" && *typ != enc.typ) {
					continue
				}
				path := filepath.Join(dir, file.Name())
				group.Go(func() error { return handleFile(cmd, pkgName, path) })
			}
		}
		return nil
	})

	err := group.Wait()
	if err != nil {
		return fmt.Errorf("Import failed: %v", err)
	}
	return nil
}

func handleFile(cmd *cobra.Command, pkg, filename string) error {
	re, err := regexp.Compile(*name)
	if err != nil {
		return err
	}
	if !re.MatchString(filepath.Base(filename)) {
		return nil
	}
	f, err := os.Open(filename)
	if err != nil {
		return fmt.Errorf("error opening file: %v", err)
	}
	defer f.Close()

	ext := filepath.Ext(filename)
	handler := getExtInfo(ext)

	if handler == nil {
		return fmt.Errorf("unsupported extension %q", ext)
	}
	objs, err := handler.fn(filename, f)
	if err != nil {
		return err
	}

	if *files {
		for i, f := range objs {
			err := combineExpressions(cmd, pkg, newName(filename, i), f)
			if err != nil {
				return err
			}
		}
		return nil
	} else if len(objs) > 1 {
		if !*list && *node == "" && !*files {
			return fmt.Errorf("list, flag, or files flag needed to handle multiple objects in file %q", filename)
		}
	}
	return combineExpressions(cmd, pkg, newName(filename, 0), objs...)
}

func combineExpressions(cmd *cobra.Command, pkg, cueFile string, objs ...ast.Expr) error {
	if *out != "" {
		cueFile = *out
	}
	if cueFile != "-" {
		switch _, err := os.Stat(cueFile); {
		case os.IsNotExist(err):
		case err == nil:
			if !*force {
				log.Printf("skipping file %q: already exists", cueFile)
				return nil
			}
		default:
			return fmt.Errorf("error creating file: %v", err)
		}
	}

	f := &ast.File{}
	if pkg != "" {
		f.Name = ast.NewIdent(pkg)
	}

	h := hoister{
		fields:   map[string]bool{},
		altNames: map[string]*ast.Ident{},
	}

	index := newIndex()
	for _, expr := range objs {
		if *parseStrings {
			h.hoist(expr)
		}

		// Compute a path different from root.
		var pathElems []ast.Label

		switch {
		case *node != "":
			inst, err := cue.FromExpr(nil, expr)
			if err != nil {
				return err
			}

			labels, err := parsePath(*node)
			if err != nil {
				return err
			}
			for _, l := range labels {
				switch x := l.(type) {
				case *ast.Interpolation:
					v := inst.Eval(x)
					if v.Kind() == cue.BottomKind {
						return v.Err()
					}
					pathElems = append(pathElems, v.Syntax().(ast.Label))

				case *ast.Ident, *ast.BasicLit:
					pathElems = append(pathElems, x)

				case *ast.TemplateLabel:
					return fmt.Errorf("template labels not supported in path flag")
				}
			}
		}

		if *list {
			idx := index
			for _, e := range pathElems {
				idx = idx.label(e)
			}
			if idx.field.Value == nil {
				idx.field.Value = &ast.ListLit{
					Lbrack: token.Pos(token.NoSpace),
					Rbrack: token.Pos(token.NoSpace),
				}
			}
			list := idx.field.Value.(*ast.ListLit)
			list.Elts = append(list.Elts, expr)
		} else if len(pathElems) == 0 {
			obj, ok := expr.(*ast.StructLit)
			if !ok {
				return fmt.Errorf("cannot map non-struct to object root")
			}
			f.Decls = append(f.Decls, obj.Elts...)
		} else {
			field := &ast.Field{Label: pathElems[0]}
			f.Decls = append(f.Decls, field)
			for _, e := range pathElems[1:] {
				newField := &ast.Field{Label: e}
				newVal := &ast.StructLit{Elts: []ast.Decl{newField}}
				field.Value = newVal
				field = newField
			}
			field.Value = expr
		}
	}

	if len(h.altNames) > 0 {
		imports := &ast.ImportDecl{}

		for _, enc := range encoding.All() {
			if ident, ok := h.altNames[enc.Name()]; ok {
				short := enc.Name()
				name := h.uniqueName(short, "", "")
				ident.Name = name
				if name == short {
					ident = nil
				}

				path := fmt.Sprintf(`"encoding/%s"`, short)
				imports.Specs = append(imports.Specs, &ast.ImportSpec{
					Name: ident,
					Path: &ast.BasicLit{Kind: token.STRING, Value: path},
				})
			}
		}
		f.Decls = append([]ast.Decl{imports}, f.Decls...)
	}

	if *list {
		switch x := index.field.Value.(type) {
		case *ast.StructLit:
			f.Decls = append(f.Decls, x.Elts...)
		case *ast.ListLit:
			f.Decls = append(f.Decls, &ast.EmitDecl{Expr: x})
		default:
			panic("unreachable")
		}
	}

	var buf bytes.Buffer
	err := format.Node(&buf, f, format.Simplify())
	if err != nil {
		return fmt.Errorf("error formatting file: %v", err)
	}

	if cueFile == "-" {
		_, err := io.Copy(cmd.OutOrStdout(), &buf)
		return err
	}
	return ioutil.WriteFile(cueFile, buf.Bytes(), 0644)
}

type listIndex struct {
	index map[string]*listIndex
	file  *ast.File // top-level only
	field *ast.Field
}

func newIndex() *listIndex {
	return &listIndex{
		index: map[string]*listIndex{},
		field: &ast.Field{},
	}
}

func newString(s string) *ast.BasicLit {
	return &ast.BasicLit{Kind: token.STRING, Value: strconv.Quote(s)}
}

func (x *listIndex) label(label ast.Label) *listIndex {
	key := internal.DebugStr(label)
	idx := x.index[key]
	if idx == nil {
		if x.field.Value == nil {
			x.field.Value = &ast.StructLit{}
		}
		obj := x.field.Value.(*ast.StructLit)
		newField := &ast.Field{Label: label}
		obj.Elts = append(obj.Elts, newField)
		idx = &listIndex{
			index: map[string]*listIndex{},
			field: newField,
		}
		x.index[key] = idx
	}
	return idx
}

func parsePath(exprs string) (p []ast.Label, err error) {
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "<path flag>", exprs+": _")
	if err != nil {
		return nil, fmt.Errorf("parser error in path %q: %v", exprs, err)
	}

	if len(f.Decls) != 1 {
		return nil, errors.New("path flag must be a space-separated sequence of labels")
	}

	for d := f.Decls[0]; ; {
		field, ok := d.(*ast.Field)
		if !ok {
			// This should never happen
			return nil, errors.New("%q not a sequence of labels")
		}

		p = append(p, field.Label)

		v, ok := field.Value.(*ast.StructLit)
		if !ok {
			break
		}

		if len(v.Elts) != 1 {
			// This should never happen
			return nil, errors.New("path value may not contain a struct")
		}

		d = v.Elts[0]
	}
	return p, nil
}

func newName(filename string, i int) string {
	ext := filepath.Ext(filename)
	filename = filename[:len(filename)-len(ext)]
	if i > 0 {
		filename += fmt.Sprintf("-%d", i)
	}
	filename += ".cue"
	return filename
}

var fset = token.NewFileSet()

func handleJSON(path string, r io.Reader) (objects []ast.Expr, err error) {
	d := json.NewDecoder(r)

	for {
		var raw json.RawMessage
		err := d.Decode(&raw)
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("could not parse JSON: %v", err)
		}
		expr, err := parser.ParseExpr(fset, path, []byte(raw))
		if err != nil {
			return nil, fmt.Errorf("invalid input: %v %q", err, raw)
		}
		objects = append(objects, expr)
	}
	return objects, nil
}

func handleYAML(path string, r io.Reader) (objects []ast.Expr, err error) {
	d, err := yaml.NewDecoder(fset, path, r)
	if err != nil {
		return nil, err
	}
	for i := 0; ; i++ {
		expr, err := d.Decode()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, err
		}
		objects = append(objects, expr)
	}
	return objects, nil
}

type hoister struct {
	fields   map[string]bool
	altNames map[string]*ast.Ident
}

func (h *hoister) hoist(expr ast.Expr) {
	ast.Walk(expr, nil, func(n ast.Node) {
		name := ""
		switch x := n.(type) {
		case *ast.Field:
			name, _ = ast.LabelName(x.Label)
		case *ast.Alias:
			name = x.Ident.Name
		}
		if name != "" {
			h.fields[name] = true
		}
	})

	ast.Walk(expr, func(n ast.Node) bool {
		switch n.(type) {
		case *ast.ComprehensionDecl:
			return false
		}
		return true

	}, func(n ast.Node) {
		obj, ok := n.(*ast.StructLit)
		if !ok {
			return
		}
		for i := 0; i < len(obj.Elts); i++ {
			f, ok := obj.Elts[i].(*ast.Field)
			if !ok {
				continue
			}

			name, ident := ast.LabelName(f.Label)
			if name == "" || !ident {
				continue
			}

			lit, ok := f.Value.(*ast.BasicLit)
			if !ok || lit.Kind != token.STRING {
				continue
			}

			str, err := literal.Unquote(lit.Value)
			if err != nil {
				continue
			}

			expr, enc := tryParse(str)
			if expr == nil {
				continue
			}

			if h.altNames[enc.typ] == nil {
				h.altNames[enc.typ] = &ast.Ident{Name: "_cue"} // set name later
			}

			// found a replacable string
			dataField := h.uniqueName(name, "_", "cue_")

			f.Value = &ast.CallExpr{
				Fun: &ast.SelectorExpr{
					X:   h.altNames[enc.typ],
					Sel: ast.NewIdent("Marshal"),
				},
				Args: []ast.Expr{
					ast.NewIdent(dataField),
				},
			}

			obj.Elts = append(obj.Elts, nil)
			copy(obj.Elts[i+1:], obj.Elts[i:])

			obj.Elts[i+1] = &ast.Alias{
				Ident: ast.NewIdent(dataField),
				Expr:  expr,
			}

			h.hoist(expr)
		}
	})
}

func tryParse(str string) (s ast.Expr, format *encodingInfo) {
	b := []byte(str)
	fset := token.NewFileSet()
	if json.Valid(b) {
		expr, err := parser.ParseExpr(fset, "", b)
		if err != nil {
			// TODO: report error
			return nil, nil
		}
		switch expr.(type) {
		case *ast.StructLit, *ast.ListLit:
		default:
			return nil, nil
		}
		return expr, jsonEnc
	}

	if expr, err := yaml.Unmarshal(fset, "", b); err == nil {
		switch expr.(type) {
		case *ast.StructLit, *ast.ListLit:
		default:
			return nil, nil
		}
		return expr, yamlEnc
	}

	return nil, nil
}

func (h *hoister) uniqueName(base, prefix, typ string) string {
	base = strings.Map(func(r rune) rune {
		if unicode.In(r, unicode.L, unicode.N) {
			return r
		}
		return '_'
	}, base)

	name := prefix + typ + base
	for {
		if !h.fields[name] {
			h.fields[name] = true
			return name
		}
		name = prefix + typ + base
		typ += "x"
	}
}