package main

import (
	"bytes"
	"fmt"
	"go/format"
	"io/ioutil"
	"path/filepath"
	"runtime"
	"strings"
	"text/template"
)

type opType struct {
	Op                    string
	Code                  string
	HeadToPtrHead         func() string
	HeadToOmitEmptyHead   func() string
	HeadToStringTagHead   func() string
	PtrHeadToHead         func() string
	FieldToEnd            func() string
	FieldToOmitEmptyField func() string
	FieldToStringTagField func() string
}

func (t opType) IsHeadToPtrHead() bool {
	return t.Op != t.HeadToPtrHead()
}

func (t opType) IsHeadToOmitEmptyHead() bool {
	return t.Op != t.HeadToOmitEmptyHead()
}

func (t opType) IsHeadToStringTagHead() bool {
	return t.Op != t.HeadToStringTagHead()
}

func (t opType) IsPtrHeadToHead() bool {
	return t.Op != t.PtrHeadToHead()
}

func (t opType) IsFieldToEnd() bool {
	return t.Op != t.FieldToEnd()
}

func (t opType) IsFieldToOmitEmptyField() bool {
	return t.Op != t.FieldToOmitEmptyField()
}

func (t opType) IsFieldToStringTagField() bool {
	return t.Op != t.FieldToStringTagField()
}

func createOpType(op, code string) opType {
	return opType{
		Op:                    op,
		Code:                  code,
		HeadToPtrHead:         func() string { return op },
		HeadToOmitEmptyHead:   func() string { return op },
		HeadToStringTagHead:   func() string { return op },
		PtrHeadToHead:         func() string { return op },
		FieldToEnd:            func() string { return op },
		FieldToOmitEmptyField: func() string { return op },
		FieldToStringTagField: func() string { return op },
	}
}

func _main() error {
	tmpl, err := template.New("").Parse(`// Code generated by cmd/generator. DO NOT EDIT!
package json

import (
  "strings"
)

type codeType int

const (
{{- range $index, $type := .CodeTypes }}
  code{{ $type }} codeType = {{ $index }}
{{- end }}
)

var opTypeStrings = [{{ .OpLen }}]string{
{{- range $type := .OpTypes }}
    "{{ $type.Op }}",
{{- end }}
}

type opType int

const (
{{- range $index, $type := .OpTypes }}
  op{{ $type.Op }} opType = {{ $index }}
{{- end }}
)

func (t opType) String() string {
  if int(t) >= {{ .OpLen }} {
    return ""
  }
  return opTypeStrings[int(t)]
}

func (t opType) codeType() codeType {
  if strings.Contains(t.String(), "Struct") {
    if strings.Contains(t.String(), "End") {
      return codeStructEnd
    }
    return codeStructField
  }
  if t.String() == "Array" || t.String() == "ArrayPtr" {
    return codeArrayHead
  }
  if strings.Contains(t.String(), "ArrayElem") {
    return codeArrayElem
  }
  if t.String() == "Slice" || t.String() == "SlicePtr" {
    return codeSliceHead
  }
  if strings.Contains(t.String(), "SliceElem") {
    return codeSliceElem
  }
  if t.String() == "Map" || t.String() == "MapPtr" {
    return codeMapHead
  }
  if strings.Contains(t.String(), "MapKey") {
    return codeMapKey
  }
  if strings.Contains(t.String(), "MapValue") {
    return codeMapValue
  }
  if strings.Contains(t.String(), "MapEnd") {
    return codeMapEnd
  }

  return codeOp
}

func (t opType) headToPtrHead() opType {
  if strings.Index(t.String(), "PtrHead") > 0 {
    return t
  }

  idx := strings.Index(t.String(), "Field")
  if idx == -1 {
    return t
  }
  suffix := "Ptr"+t.String()[idx+len("Field"):]

  const toPtrOffset = 3
  if strings.Contains(opType(int(t) + toPtrOffset).String(), suffix) {
    return opType(int(t) + toPtrOffset)
  }
  return t
}

func (t opType) headToOmitEmptyHead() opType {
  const toOmitEmptyOffset = 1
  if strings.Contains(opType(int(t) + toOmitEmptyOffset).String(), "OmitEmpty") {
    return opType(int(t) + toOmitEmptyOffset)
  }

  return t
}

func (t opType) headToStringTagHead() opType {
  const toStringTagOffset = 2
  if strings.Contains(opType(int(t) + toStringTagOffset).String(), "StringTag") {
    return opType(int(t) + toStringTagOffset)
  }
  return t
}

func (t opType) ptrHeadToHead() opType {
  idx := strings.Index(t.String(), "Ptr")
  if idx == -1 {
    return t
  }
  suffix := t.String()[idx+len("Ptr"):]

  const toPtrOffset = 3
  if strings.Contains(opType(int(t) - toPtrOffset).String(), suffix) {
    return opType(int(t) - toPtrOffset)
  }
  return t
}

func (t opType) fieldToEnd() opType {
  switch t {
{{- range $type := .OpTypes }}
{{- if $type.IsFieldToEnd }}
  case op{{ $type.Op }}:
    return op{{ call $type.FieldToEnd }}
{{- end }}
{{- end }}
  }
  return t
}

func (t opType) fieldToOmitEmptyField() opType {
  const toOmitEmptyOffset = 1
  if strings.Contains(opType(int(t) + toOmitEmptyOffset).String(), "OmitEmpty") {
    return opType(int(t) + toOmitEmptyOffset)
  }
  return t
}

func (t opType) fieldToStringTagField() opType {
  const toStringTagOffset = 2
  if strings.Contains(opType(int(t) + toStringTagOffset).String(), "StringTag") {
    return opType(int(t) + toStringTagOffset)
  }
  return t
}

`)
	if err != nil {
		return err
	}
	codeTypes := []string{
		"Op",
		"ArrayHead",
		"ArrayElem",
		"SliceHead",
		"SliceElem",
		"MapHead",
		"MapKey",
		"MapValue",
		"MapEnd",
		"StructFieldRecursive",
		"StructField",
		"StructEnd",
	}
	primitiveTypes := []string{
		"int", "uint", "float32", "float64", "bool", "string", "bytes",
		"array", "map", "slice", "struct", "MarshalJSON", "MarshalText", "recursive",
		"intString", "uintString",
		"intPtr", "uintPtr", "float32Ptr", "float64Ptr", "boolPtr", "stringPtr", "bytesPtr",
		"arrayPtr", "slicePtr", "mapPtr", "marshalJSONPtr", "marshalTextPtr", "interfacePtr",
	}
	primitiveTypesUpper := []string{}
	for _, typ := range primitiveTypes {
		primitiveTypesUpper = append(primitiveTypesUpper, strings.ToUpper(string(typ[0]))+typ[1:])
	}
	opTypes := []opType{
		createOpType("End", "Op"),
		createOpType("Interface", "Op"),
		createOpType("Ptr", "Op"),
		createOpType("RootSliceHead", "SliceHead"),
		createOpType("SliceElem", "SliceElem"),
		createOpType("RootSliceElem", "SliceElem"),
		createOpType("SliceEnd", "Op"),
		createOpType("ArrayElem", "ArrayElem"),
		createOpType("ArrayEnd", "Op"),
		createOpType("MapKey", "MapKey"),
		createOpType("MapValue", "MapValue"),
		createOpType("MapEnd", "Op"),
		createOpType("StructFieldRecursiveEnd", "Op"),
		createOpType("StructAnonymousEnd", "StructEnd"),
	}
	for _, typ := range primitiveTypesUpper {
		typ := typ
		opTypes = append(opTypes, createOpType(typ, "Op"))
	}
	for _, typ := range append(primitiveTypesUpper, "") {
		for _, ptrOrNot := range []string{"", "Ptr"} {
			for _, opt := range []string{"", "OmitEmpty", "StringTag"} {
				ptrOrNot := ptrOrNot
				opt := opt
				typ := typ

				op := fmt.Sprintf(
					"StructField%sHead%s%s",
					ptrOrNot,
					opt,
					typ,
				)
				opTypes = append(opTypes, opType{
					Op:   op,
					Code: "StructField",
					HeadToPtrHead: func() string {
						return fmt.Sprintf(
							"StructFieldPtrHead%s%s",
							opt,
							typ,
						)
					},
					HeadToOmitEmptyHead: func() string {
						return fmt.Sprintf(
							"StructField%sHeadOmitEmpty%s",
							ptrOrNot,
							typ,
						)
					},
					HeadToStringTagHead: func() string {
						return fmt.Sprintf(
							"StructField%sHeadStringTag%s",
							ptrOrNot,
							typ,
						)
					},
					PtrHeadToHead: func() string {
						return fmt.Sprintf(
							"StructFieldHead%s%s",
							opt,
							typ,
						)
					},
					FieldToEnd:            func() string { return op },
					FieldToOmitEmptyField: func() string { return op },
					FieldToStringTagField: func() string { return op },
				})
			}
		}
	}
	for _, typ := range append(primitiveTypesUpper, "") {
		for _, opt := range []string{"", "OmitEmpty", "StringTag"} {
			opt := opt
			typ := typ

			op := fmt.Sprintf(
				"StructField%s%s",
				opt,
				typ,
			)
			opTypes = append(opTypes, opType{
				Op:                  op,
				Code:                "StructField",
				HeadToPtrHead:       func() string { return op },
				HeadToOmitEmptyHead: func() string { return op },
				HeadToStringTagHead: func() string { return op },
				PtrHeadToHead:       func() string { return op },
				FieldToEnd: func() string {
					switch typ {
					case "", "Array", "Map", "Slice", "Struct", "Recursive":
						return op
					}
					return fmt.Sprintf(
						"StructEnd%s%s",
						opt,
						typ,
					)
				},
				FieldToOmitEmptyField: func() string {
					return fmt.Sprintf(
						"StructFieldOmitEmpty%s",
						typ,
					)
				},
				FieldToStringTagField: func() string {
					return fmt.Sprintf(
						"StructFieldStringTag%s",
						typ,
					)
				},
			})
		}
	}
	for _, typ := range append(primitiveTypesUpper, "") {
		for _, opt := range []string{"", "OmitEmpty", "StringTag"} {
			opt := opt
			typ := typ

			op := fmt.Sprintf(
				"StructEnd%s%s",
				opt,
				typ,
			)
			opTypes = append(opTypes, opType{
				Op:                    op,
				Code:                  "StructEnd",
				HeadToPtrHead:         func() string { return op },
				HeadToOmitEmptyHead:   func() string { return op },
				HeadToStringTagHead:   func() string { return op },
				PtrHeadToHead:         func() string { return op },
				FieldToEnd:            func() string { return op },
				FieldToOmitEmptyField: func() string { return op },
				FieldToStringTagField: func() string { return op },
			})
		}
	}
	var b bytes.Buffer
	if err := tmpl.Execute(&b, struct {
		CodeTypes []string
		OpTypes   []opType
		OpLen     int
	}{
		CodeTypes: codeTypes,
		OpTypes:   opTypes,
		OpLen:     len(opTypes),
	}); err != nil {
		return err
	}
	path := filepath.Join(repoRoot(), "encode_optype.go")
	buf, err := format.Source(b.Bytes())
	if err != nil {
		return err
	}
	return ioutil.WriteFile(path, buf, 0644)
}

func repoRoot() string {
	_, file, _, _ := runtime.Caller(0)
	relativePathFromRepoRoot := filepath.Join("cmd", "generator")
	return strings.TrimSuffix(filepath.Dir(file), relativePathFromRepoRoot)
}

func main() {
	if err := _main(); err != nil {
		panic(err)
	}
}