// Package jsonschema uses reflection to generate JSON Schemas from Go types [1].
//
// If json tags are present on struct fields, they will be used to infer
// property names and if a property is required (omitempty is present).
//
// [1] http://json-schema.org/latest/json-schema-validation.html
package jsonschema

import (
	"encoding/json"
	"net"
	"net/url"
	"reflect"
	"strconv"
	"strings"
	"time"

	"github.com/iancoleman/orderedmap"
)

// Version is the JSON Schema version.
// If extending JSON Schema with custom values use a custom URI.
// RFC draft-wright-json-schema-00, section 6
var Version = "http://json-schema.org/draft-04/schema#"

// Schema is the root schema.
// RFC draft-wright-json-schema-00, section 4.5
type Schema struct {
	*Type
	Definitions Definitions
}

// Type represents a JSON Schema object type.
type Type struct {
	// RFC draft-wright-json-schema-00
	Version string `json:"$schema,omitempty"` // section 6.1
	Ref     string `json:"$ref,omitempty"`    // section 7
	// RFC draft-wright-json-schema-validation-00, section 5
	MultipleOf           int                    `json:"multipleOf,omitempty"`           // section 5.1
	Maximum              int                    `json:"maximum,omitempty"`              // section 5.2
	ExclusiveMaximum     bool                   `json:"exclusiveMaximum,omitempty"`     // section 5.3
	Minimum              int                    `json:"minimum,omitempty"`              // section 5.4
	ExclusiveMinimum     bool                   `json:"exclusiveMinimum,omitempty"`     // section 5.5
	MaxLength            int                    `json:"maxLength,omitempty"`            // section 5.6
	MinLength            int                    `json:"minLength,omitempty"`            // section 5.7
	Pattern              string                 `json:"pattern,omitempty"`              // section 5.8
	AdditionalItems      *Type                  `json:"additionalItems,omitempty"`      // section 5.9
	Items                *Type                  `json:"items,omitempty"`                // section 5.9
	MaxItems             int                    `json:"maxItems,omitempty"`             // section 5.10
	MinItems             int                    `json:"minItems,omitempty"`             // section 5.11
	UniqueItems          bool                   `json:"uniqueItems,omitempty"`          // section 5.12
	MaxProperties        int                    `json:"maxProperties,omitempty"`        // section 5.13
	MinProperties        int                    `json:"minProperties,omitempty"`        // section 5.14
	Required             []string               `json:"required,omitempty"`             // section 5.15
	Properties           *orderedmap.OrderedMap `json:"properties,omitempty"`           // section 5.16
	PatternProperties    map[string]*Type       `json:"patternProperties,omitempty"`    // section 5.17
	AdditionalProperties json.RawMessage        `json:"additionalProperties,omitempty"` // section 5.18
	Dependencies         map[string]*Type       `json:"dependencies,omitempty"`         // section 5.19
	Enum                 []interface{}          `json:"enum,omitempty"`                 // section 5.20
	Type                 string                 `json:"type,omitempty"`                 // section 5.21
	AllOf                []*Type                `json:"allOf,omitempty"`                // section 5.22
	AnyOf                []*Type                `json:"anyOf,omitempty"`                // section 5.23
	OneOf                []*Type                `json:"oneOf,omitempty"`                // section 5.24
	Not                  *Type                  `json:"not,omitempty"`                  // section 5.25
	Definitions          Definitions            `json:"definitions,omitempty"`          // section 5.26
	// RFC draft-wright-json-schema-validation-00, section 6, 7
	Title       string        `json:"title,omitempty"`       // section 6.1
	Description string        `json:"description,omitempty"` // section 6.1
	Default     interface{}   `json:"default,omitempty"`     // section 6.2
	Format      string        `json:"format,omitempty"`      // section 7
	Examples    []interface{} `json:"examples,omitempty"`    // section 7.4
	// RFC draft-wright-json-schema-hyperschema-00, section 4
	Media          *Type  `json:"media,omitempty"`          // section 4.3
	BinaryEncoding string `json:"binaryEncoding,omitempty"` // section 4.3

	Extras map[string]interface{} `json:"-"`
}

// Reflect reflects to Schema from a value using the default Reflector
func Reflect(v interface{}) *Schema {
	return ReflectFromType(reflect.TypeOf(v))
}

// ReflectFromType generates root schema using the default Reflector
func ReflectFromType(t reflect.Type) *Schema {
	r := &Reflector{}
	return r.ReflectFromType(t)
}

// A Reflector reflects values into a Schema.
type Reflector struct {
	// AllowAdditionalProperties will cause the Reflector to generate a schema
	// with additionalProperties to 'true' for all struct types. This means
	// the presence of additional keys in JSON objects will not cause validation
	// to fail. Note said additional keys will simply be dropped when the
	// validated JSON is unmarshaled.
	AllowAdditionalProperties bool

	// RequiredFromJSONSchemaTags will cause the Reflector to generate a schema
	// that requires any key tagged with `jsonschema:required`, overriding the
	// default of requiring any key *not* tagged with `json:,omitempty`.
	RequiredFromJSONSchemaTags bool

	// YAMLEmbeddedStructs will cause the Reflector to generate a schema that does
	// not inline embedded structs. This should be enabled if the JSON schemas are
	// used with yaml.Marshal/Unmarshal.
	YAMLEmbeddedStructs bool

	// ExpandedStruct will cause the toplevel definitions of the schema not
	// be referenced itself to a definition.
	ExpandedStruct bool

	// Do not reference definitions.
	// All types are still registered under the "definitions" top-level object,
	// but instead of $ref fields in containing types, the entire definition
	// of the contained type is inserted.
	// This will cause the entire structure of types to be output in one tree.
	DoNotReference bool

	// Use package paths as well as type names, to avoid conflicts.
	// Without this setting, if two packages contain a type with the same name,
	// and both are present in a schema, they will conflict and overwrite in
	// the definition map and produce bad output.  This is particularly
	// noticeable when using DoNotReference.
	FullyQualifyTypeNames bool

	// IgnoredTypes defines a slice of types that should be ignored in the schema,
	// switching to just allowing additional properties instead.
	IgnoredTypes []interface{}

	// TypeMapper is a function that can be used to map custom Go types to jsconschema types.
	TypeMapper func(reflect.Type) *Type
}

// Reflect reflects to Schema from a value.
func (r *Reflector) Reflect(v interface{}) *Schema {
	return r.ReflectFromType(reflect.TypeOf(v))
}

// ReflectFromType generates root schema
func (r *Reflector) ReflectFromType(t reflect.Type) *Schema {
	definitions := Definitions{}
	if r.ExpandedStruct {
		st := &Type{
			Version:              Version,
			Type:                 "object",
			Properties:           orderedmap.New(),
			AdditionalProperties: []byte("false"),
		}
		if r.AllowAdditionalProperties {
			st.AdditionalProperties = []byte("true")
		}
		r.reflectStructFields(st, definitions, t)
		r.reflectStruct(definitions, t)
		delete(definitions, r.typeName(t))
		return &Schema{Type: st, Definitions: definitions}
	}

	s := &Schema{
		Type:        r.reflectTypeToSchema(definitions, t),
		Definitions: definitions,
	}
	return s
}

// Definitions hold schema definitions.
// http://json-schema.org/latest/json-schema-validation.html#rfc.section.5.26
// RFC draft-wright-json-schema-validation-00, section 5.26
type Definitions map[string]*Type

// Available Go defined types for JSON Schema Validation.
// RFC draft-wright-json-schema-validation-00, section 7.3
var (
	timeType = reflect.TypeOf(time.Time{}) // date-time RFC section 7.3.1
	ipType   = reflect.TypeOf(net.IP{})    // ipv4 and ipv6 RFC section 7.3.4, 7.3.5
	uriType  = reflect.TypeOf(url.URL{})   // uri RFC section 7.3.6
)

// Byte slices will be encoded as base64
var byteSliceType = reflect.TypeOf([]byte(nil))

// Go code generated from protobuf enum types should fulfil this interface.
type protoEnum interface {
	EnumDescriptor() ([]byte, []int)
}

var protoEnumType = reflect.TypeOf((*protoEnum)(nil)).Elem()

func (r *Reflector) reflectTypeToSchema(definitions Definitions, t reflect.Type) *Type {
	// Already added to definitions?
	if _, ok := definitions[r.typeName(t)]; ok && !r.DoNotReference {
		return &Type{Ref: "#/definitions/" + r.typeName(t)}
	}

	// jsonpb will marshal protobuf enum options as either strings or integers.
	// It will unmarshal either.
	if t.Implements(protoEnumType) {
		return &Type{OneOf: []*Type{
			{Type: "string"},
			{Type: "integer"},
		}}
	}

	if r.TypeMapper != nil {
		if t := r.TypeMapper(t); t != nil {
			return t
		}
	}

	// Defined format types for JSON Schema Validation
	// RFC draft-wright-json-schema-validation-00, section 7.3
	// TODO email RFC section 7.3.2, hostname RFC section 7.3.3, uriref RFC section 7.3.7
	switch t {
	case ipType:
		// TODO differentiate ipv4 and ipv6 RFC section 7.3.4, 7.3.5
		return &Type{Type: "string", Format: "ipv4"} // ipv4 RFC section 7.3.4
	}

	switch t.Kind() {
	case reflect.Struct:

		switch t {
		case timeType: // date-time RFC section 7.3.1
			return &Type{Type: "string", Format: "date-time"}
		case uriType: // uri RFC section 7.3.6
			return &Type{Type: "string", Format: "uri"}
		default:
			return r.reflectStruct(definitions, t)
		}

	case reflect.Map:
		rt := &Type{
			Type: "object",
			PatternProperties: map[string]*Type{
				".*": r.reflectTypeToSchema(definitions, t.Elem()),
			},
		}
		delete(rt.PatternProperties, "additionalProperties")
		return rt

	case reflect.Slice, reflect.Array:
		returnType := &Type{}
		if t.Kind() == reflect.Array {
			returnType.MinItems = t.Len()
			returnType.MaxItems = returnType.MinItems
		}
		if t.Kind() == reflect.Slice && t.Elem() == byteSliceType.Elem() {
			returnType.Type = "string"
			returnType.Media = &Type{BinaryEncoding: "base64"}
			return returnType
		}
		returnType.Type = "array"
		returnType.Items = r.reflectTypeToSchema(definitions, t.Elem())
		return returnType

	case reflect.Interface:
		return &Type{
			AdditionalProperties: []byte("true"),
		}

	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return &Type{Type: "integer"}

	case reflect.Float32, reflect.Float64:
		return &Type{Type: "number"}

	case reflect.Bool:
		return &Type{Type: "boolean"}

	case reflect.String:
		return &Type{Type: "string"}

	case reflect.Ptr:
		return r.reflectTypeToSchema(definitions, t.Elem())
	}
	panic("unsupported type " + t.String())
}

// Refects a struct to a JSON Schema type.
func (r *Reflector) reflectStruct(definitions Definitions, t reflect.Type) *Type {
	for _, ignored := range r.IgnoredTypes {
		if reflect.TypeOf(ignored) == t {
			st := &Type{
				Type:                 "object",
				Properties:           orderedmap.New(),
				AdditionalProperties: []byte("true"),
			}
			definitions[r.typeName(t)] = st

			if r.DoNotReference {
				return st
			} else {
				return &Type{
					Version: Version,
					Ref:     "#/definitions/" + r.typeName(t),
				}
			}

		}
	}
	st := &Type{
		Type:                 "object",
		Properties:           orderedmap.New(),
		AdditionalProperties: []byte("false"),
	}
	if r.AllowAdditionalProperties {
		st.AdditionalProperties = []byte("true")
	}
	definitions[r.typeName(t)] = st
	r.reflectStructFields(st, definitions, t)

	if r.DoNotReference {
		return st
	} else {
		return &Type{
			Version: Version,
			Ref:     "#/definitions/" + r.typeName(t),
		}
	}
}

func (r *Reflector) reflectStructFields(st *Type, definitions Definitions, t reflect.Type) {
	if t.Kind() == reflect.Ptr {
		t = t.Elem()
	}
	if t.Kind() != reflect.Struct {
		return
	}
	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		name, exist, required, nullable := r.reflectFieldName(f)
		// if anonymous and exported type should be processed recursively
		// current type should inherit properties of anonymous one
		if name == "" {
			if f.Anonymous && !exist {
				r.reflectStructFields(st, definitions, f.Type)
			}
			continue
		}

		property := r.reflectTypeToSchema(definitions, f.Type)
		property.structKeywordsFromTags(f, st, name)

		if nullable {
			property = &Type{
				OneOf: []*Type{
					property,
					{
						Type: "null",
					},
				},
			}
		}

		st.Properties.Set(name, property)
		if required {
			st.Required = append(st.Required, name)
		}
	}
}

func (t *Type) structKeywordsFromTags(f reflect.StructField, parentType *Type, propertyName string) {
	t.Description = f.Tag.Get("jsonschema_description")
	tags := strings.Split(f.Tag.Get("jsonschema"), ",")
	t.genericKeywords(tags, parentType, propertyName)
	switch t.Type {
	case "string":
		t.stringKeywords(tags)
	case "number":
		t.numbericKeywords(tags)
	case "integer":
		t.numbericKeywords(tags)
	case "array":
		t.arrayKeywords(tags)
	}
	extras := strings.Split(f.Tag.Get("jsonschema_extras"), ",")
	t.extraKeywords(extras)
}

// read struct tags for generic keyworks
func (t *Type) genericKeywords(tags []string, parentType *Type, propertyName string) {
	for _, tag := range tags {
		nameValue := strings.Split(tag, "=")
		if len(nameValue) == 2 {
			name, val := nameValue[0], nameValue[1]
			switch name {
			case "title":
				t.Title = val
			case "description":
				t.Description = val
			case "type":
				t.Type = val
			case "oneof_required":
				var typeFound *Type
				for i := range parentType.OneOf {
					if parentType.OneOf[i].Title == nameValue[1] {
						typeFound = parentType.OneOf[i]
					}
				}
				if typeFound == nil {
					typeFound = &Type{
						Title:    nameValue[1],
						Required: []string{},
					}
					parentType.OneOf = append(parentType.OneOf, typeFound)
				}
				typeFound.Required = append(typeFound.Required, propertyName)
			case "oneof_type":
				if t.OneOf == nil {
					t.OneOf = make([]*Type, 0, 1)
				}
				t.Type = ""
				types := strings.Split(nameValue[1], ";")
				for _, ty := range types {
					t.OneOf = append(t.OneOf, &Type{
						Type: ty,
					})
				}
			case "enum":
				switch t.Type {
				case "string":
					t.Enum = append(t.Enum, val)
				case "integer":
					i, _ := strconv.Atoi(val)
					t.Enum = append(t.Enum, i)
				case "number":
					f, _ := strconv.ParseFloat(val, 64)
					t.Enum = append(t.Enum, f)
				}
			}
		}
	}
}

// read struct tags for string type keyworks
func (t *Type) stringKeywords(tags []string) {
	for _, tag := range tags {
		nameValue := strings.Split(tag, "=")
		if len(nameValue) == 2 {
			name, val := nameValue[0], nameValue[1]
			switch name {
			case "minLength":
				i, _ := strconv.Atoi(val)
				t.MinLength = i
			case "maxLength":
				i, _ := strconv.Atoi(val)
				t.MaxLength = i
			case "pattern":
				t.Pattern = val
			case "format":
				switch val {
				case "date-time", "email", "hostname", "ipv4", "ipv6", "uri":
					t.Format = val
					break
				}
			case "default":
				t.Default = val
			case "example":
				t.Examples = append(t.Examples, val)
			}
		}
	}
}

// read struct tags for numberic type keyworks
func (t *Type) numbericKeywords(tags []string) {
	for _, tag := range tags {
		nameValue := strings.Split(tag, "=")
		if len(nameValue) == 2 {
			name, val := nameValue[0], nameValue[1]
			switch name {
			case "multipleOf":
				i, _ := strconv.Atoi(val)
				t.MultipleOf = i
			case "minimum":
				i, _ := strconv.Atoi(val)
				t.Minimum = i
			case "maximum":
				i, _ := strconv.Atoi(val)
				t.Maximum = i
			case "exclusiveMaximum":
				b, _ := strconv.ParseBool(val)
				t.ExclusiveMaximum = b
			case "exclusiveMinimum":
				b, _ := strconv.ParseBool(val)
				t.ExclusiveMinimum = b
			case "default":
				i, _ := strconv.Atoi(val)
				t.Default = i
			case "example":
				if i, err := strconv.Atoi(val); err == nil {
					t.Examples = append(t.Examples, i)
				}
			}
		}
	}
}

// read struct tags for object type keyworks
// func (t *Type) objectKeywords(tags []string) {
//     for _, tag := range tags{
//         nameValue := strings.Split(tag, "=")
//         name, val := nameValue[0], nameValue[1]
//         switch name{
//             case "dependencies":
//                 t.Dependencies = val
//                 break;
//             case "patternProperties":
//                 t.PatternProperties = val
//                 break;
//         }
//     }
// }

// read struct tags for array type keyworks
func (t *Type) arrayKeywords(tags []string) {
	var defaultValues []interface{}
	for _, tag := range tags {
		nameValue := strings.Split(tag, "=")
		if len(nameValue) == 2 {
			name, val := nameValue[0], nameValue[1]
			switch name {
			case "minItems":
				i, _ := strconv.Atoi(val)
				t.MinItems = i
			case "maxItems":
				i, _ := strconv.Atoi(val)
				t.MaxItems = i
			case "uniqueItems":
				t.UniqueItems = true
			case "default":
				defaultValues = append(defaultValues, val)
			}
		}
	}
	if len(defaultValues) > 0 {
		t.Default = defaultValues
	}
}

func (t *Type) extraKeywords(tags []string) {
	for _, tag := range tags {
		nameValue := strings.Split(tag, "=")
		if len(nameValue) == 2 {
			t.setExtra(nameValue[0], nameValue[1])
		}
	}
}

func (t *Type) setExtra(key, val string) {
	if t.Extras == nil {
		t.Extras = map[string]interface{}{}
	}
	if existingVal, ok := t.Extras[key]; ok {
		switch existingVal.(type) {
		case string:
			t.Extras[key] = []string{existingVal.(string), val}
		case []string:
			t.Extras[key] = append(existingVal.([]string), val)
		}
	} else {
		t.Extras[key] = val
	}
}

func requiredFromJSONTags(tags []string) bool {
	if ignoredByJSONTags(tags) {
		return false
	}

	for _, tag := range tags[1:] {
		if tag == "omitempty" {
			return false
		}
	}
	return true
}

func requiredFromJSONSchemaTags(tags []string) bool {
	if ignoredByJSONSchemaTags(tags) {
		return false
	}
	for _, tag := range tags {
		if tag == "required" {
			return true
		}
	}
	return false
}

func nullableFromJSONSchemaTags(tags []string) bool {
	if ignoredByJSONSchemaTags(tags) {
		return false
	}
	for _, tag := range tags {
		if tag == "nullable" {
			return true
		}
	}
	return false
}

func ignoredByJSONTags(tags []string) bool {
	return tags[0] == "-"
}

func ignoredByJSONSchemaTags(tags []string) bool {
	return tags[0] == "-"
}

func (r *Reflector) reflectFieldName(f reflect.StructField) (string, bool, bool, bool) {
	jsonTags, exist := f.Tag.Lookup("json")
	if !exist {
		jsonTags = f.Tag.Get("yaml")
	}

	jsonTagsList := strings.Split(jsonTags, ",")

	if ignoredByJSONTags(jsonTagsList) {
		return "", exist, false, false
	}

	jsonSchemaTags := strings.Split(f.Tag.Get("jsonschema"), ",")
	if ignoredByJSONSchemaTags(jsonSchemaTags) {
		return "", exist, false, false
	}

	name := f.Name
	required := requiredFromJSONTags(jsonTagsList)

	if r.RequiredFromJSONSchemaTags {
		required = requiredFromJSONSchemaTags(jsonSchemaTags)
	}

	nullable := nullableFromJSONSchemaTags(jsonSchemaTags)

	if jsonTagsList[0] != "" {
		name = jsonTagsList[0]
	}

	// field not anonymous and not export has no export name
	if !f.Anonymous && f.PkgPath != "" {
		name = ""
	}

	// field anonymous but without json tag should be inherited by current type
	if f.Anonymous && !exist {
		if !r.YAMLEmbeddedStructs {
			name = ""
		} else {
			name = strings.ToLower(name)
		}
	}

	return name, exist, required, nullable
}

func (s *Schema) MarshalJSON() ([]byte, error) {
	b, err := json.Marshal(s.Type)
	if err != nil {
		return nil, err
	}
	if s.Definitions == nil || len(s.Definitions) == 0 {
		return b, nil
	}
	d, err := json.Marshal(struct {
		Definitions Definitions `json:"definitions,omitempty"`
	}{s.Definitions})
	if err != nil {
		return nil, err
	}
	if len(b) == 2 {
		return d, nil
	} else {
		b[len(b)-1] = ','
		return append(b, d[1:]...), nil
	}
}

func (t *Type) MarshalJSON() ([]byte, error) {
	type Type_ Type
	b, err := json.Marshal((*Type_)(t))
	if err != nil {
		return nil, err
	}
	if t.Extras == nil || len(t.Extras) == 0 {
		return b, nil
	}
	m, err := json.Marshal(t.Extras)
	if err != nil {
		return nil, err
	}
	if len(b) == 2 {
		return m, nil
	} else {
		b[len(b)-1] = ','
		return append(b, m[1:]...), nil
	}
}

func (r *Reflector) typeName(t reflect.Type) string {
	if r.FullyQualifyTypeNames {
		return t.PkgPath() + "." + t.Name()
	}
	return t.Name()
}