// Package yaml implements YAML support for the Go language.
//
// Source code and other details for the project are available at GitHub:
//
//   https://github.com/go-yaml/yaml
//
package yaml // import "cuelang.org/go/internal/third_party/yaml"

import (
	"errors"
	"fmt"
	"io"
	"reflect"
	"strconv"
	"strings"
	"sync"

	"cuelang.org/go/cue/ast"
)

// MapSlice encodes and decodes as a YAML map.
// The order of keys is preserved when encoding and decoding.
type MapSlice []MapItem

// MapItem is an item in a MapSlice.
type MapItem struct {
	Key, Value interface{}
}

// The Unmarshaler interface may be implemented by types to customize their
// behavior when being unmarshaled from a YAML document. The UnmarshalYAML
// method receives a function that may be called to unmarshal the original
// YAML value into a field or variable. It is safe to call the unmarshal
// function parameter more than once if necessary.
type Unmarshaler interface {
	UnmarshalYAML(unmarshal func(interface{}) error) error
}

// The Marshaler interface may be implemented by types to customize their
// behavior when being marshaled into a YAML document. The returned value
// is marshaled in place of the original value implementing Marshaler.
//
// If an error is returned by MarshalYAML, the marshaling procedure stops
// and returns with the provided error.
type Marshaler interface {
	MarshalYAML() (interface{}, error)
}

// Unmarshal decodes the first document found within the in byte slice
// and assigns decoded values into the out value.
//
// Maps and pointers (to a struct, string, int, etc) are accepted as out
// values. If an internal pointer within a struct is not initialized,
// the yaml package will initialize it if necessary for unmarshalling
// the provided data. The out parameter must not be nil.
//
// The type of the decoded values should be compatible with the respective
// values in out. If one or more values cannot be decoded due to a type
// mismatches, decoding continues partially until the end of the YAML
// content, and a *yaml.TypeError is returned with details for all
// missed values.
//
// Struct fields are only unmarshalled if they are exported (have an
// upper case first letter), and are unmarshalled using the field name
// lowercased as the default key. Custom keys may be defined via the
// "yaml" name in the field tag: the content preceding the first comma
// is used as the key, and the following comma-separated options are
// used to tweak the marshalling process (see Marshal).
// Conflicting names result in a runtime error.
//
// For example:
//
//     type T struct {
//         F int `yaml:"a,omitempty"`
//         B int
//     }
//     var t T
//     yaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
//
// See the documentation of Marshal for the format of tags and a list of
// supported tag options.
//
func Unmarshal(filename string, in []byte) (expr ast.Expr, err error) {
	return unmarshal(filename, in)
}

// A Decorder reads and decodes YAML values from an input stream.
type Decoder struct {
	strict bool
	parser *parser
}

// NewDecoder returns a new decoder that reads from r.
//
// The decoder introduces its own buffering and may read
// data from r beyond the YAML values requested.
func NewDecoder(filename string, src interface{}) (*Decoder, error) {
	d, err := newParser(filename, src)
	if err != nil {
		return nil, err
	}
	return &Decoder{parser: d}, nil
}

// Decode reads the next YAML-encoded value from its input and stores it in the
// value pointed to by v. It returns io.EOF if there are no more value in the
// stream.
//
// See the documentation for Unmarshal for details about the conversion of YAML
// into a Go value.
func (dec *Decoder) Decode() (expr ast.Expr, err error) {
	d := newDecoder(dec.parser)
	defer handleErr(&err)
	node := dec.parser.parse()
	if node == nil {
		return nil, io.EOF
	}
	expr = d.unmarshal(node)
	if len(d.terrors) > 0 {
		return nil, &TypeError{d.terrors}
	}
	return expr, nil
}

func unmarshal(filename string, in []byte) (expr ast.Expr, err error) {
	defer handleErr(&err)
	p, err := newParser(filename, in)
	if err != nil {
		return nil, err
	}
	defer p.destroy()
	node := p.parse()
	d := newDecoder(p)
	if node != nil {
		expr = d.unmarshal(node)
	}
	if len(d.terrors) > 0 {
		return nil, &TypeError{d.terrors}
	}
	return expr, nil
}

func handleErr(err *error) {
	if v := recover(); v != nil {
		if e, ok := v.(yamlError); ok {
			*err = e.err
		} else {
			panic(v)
		}
	}
}

type yamlError struct {
	err error
}

func (p *parser) failf(line int, format string, args ...interface{}) {
	where := p.parser.filename + ":"
	line++
	where += strconv.Itoa(line) + ": "
	panic(yamlError{fmt.Errorf(where+format, args...)})
}

// A TypeError is returned by Unmarshal when one or more fields in
// the YAML document cannot be properly decoded into the requested
// types. When this error is returned, the value is still
// unmarshaled partially.
type TypeError struct {
	Errors []string
}

func (e *TypeError) Error() string {
	return fmt.Sprintf("yaml: unmarshal errors:\n  %s", strings.Join(e.Errors, "\n  "))
}

// --------------------------------------------------------------------------
// Maintain a mapping of keys to structure field indexes

// The code in this section was copied from mgo/bson.

// structInfo holds details for the serialization of fields of
// a given struct.
type structInfo struct {
	FieldsMap  map[string]fieldInfo
	FieldsList []fieldInfo

	// InlineMap is the number of the field in the struct that
	// contains an ,inline map, or -1 if there's none.
	InlineMap int
}

type fieldInfo struct {
	Key       string
	Num       int
	OmitEmpty bool
	Flow      bool
	// Id holds the unique field identifier, so we can cheaply
	// check for field duplicates without maintaining an extra map.
	Id int

	// Inline holds the field index if the field is part of an inlined struct.
	Inline []int
}

var structMap = make(map[reflect.Type]*structInfo)
var fieldMapMutex sync.RWMutex

func getStructInfo(st reflect.Type) (*structInfo, error) {
	fieldMapMutex.RLock()
	sinfo, found := structMap[st]
	fieldMapMutex.RUnlock()
	if found {
		return sinfo, nil
	}

	n := st.NumField()
	fieldsMap := make(map[string]fieldInfo)
	fieldsList := make([]fieldInfo, 0, n)
	inlineMap := -1
	for i := 0; i != n; i++ {
		field := st.Field(i)
		if field.PkgPath != "" && !field.Anonymous {
			continue // Private field
		}

		info := fieldInfo{Num: i}

		tag := field.Tag.Get("yaml")
		if tag == "" && strings.Index(string(field.Tag), ":") < 0 {
			tag = string(field.Tag)
		}
		if tag == "-" {
			continue
		}

		inline := false
		fields := strings.Split(tag, ",")
		if len(fields) > 1 {
			for _, flag := range fields[1:] {
				switch flag {
				case "omitempty":
					info.OmitEmpty = true
				case "flow":
					info.Flow = true
				case "inline":
					inline = true
				default:
					return nil, errors.New(fmt.Sprintf("Unsupported flag %q in tag %q of type %s", flag, tag, st))
				}
			}
			tag = fields[0]
		}

		if inline {
			switch field.Type.Kind() {
			case reflect.Map:
				if inlineMap >= 0 {
					return nil, errors.New("Multiple ,inline maps in struct " + st.String())
				}
				if field.Type.Key() != reflect.TypeOf("") {
					return nil, errors.New("Option ,inline needs a map with string keys in struct " + st.String())
				}
				inlineMap = info.Num
			case reflect.Struct:
				sinfo, err := getStructInfo(field.Type)
				if err != nil {
					return nil, err
				}
				for _, finfo := range sinfo.FieldsList {
					if _, found := fieldsMap[finfo.Key]; found {
						msg := "Duplicated key '" + finfo.Key + "' in struct " + st.String()
						return nil, errors.New(msg)
					}
					if finfo.Inline == nil {
						finfo.Inline = []int{i, finfo.Num}
					} else {
						finfo.Inline = append([]int{i}, finfo.Inline...)
					}
					finfo.Id = len(fieldsList)
					fieldsMap[finfo.Key] = finfo
					fieldsList = append(fieldsList, finfo)
				}
			default:
				//return nil, errors.New("Option ,inline needs a struct value or map field")
				return nil, errors.New("Option ,inline needs a struct value field")
			}
			continue
		}

		if tag != "" {
			info.Key = tag
		} else {
			info.Key = strings.ToLower(field.Name)
		}

		if _, found = fieldsMap[info.Key]; found {
			msg := "Duplicated key '" + info.Key + "' in struct " + st.String()
			return nil, errors.New(msg)
		}

		info.Id = len(fieldsList)
		fieldsList = append(fieldsList, info)
		fieldsMap[info.Key] = info
	}

	sinfo = &structInfo{
		FieldsMap:  fieldsMap,
		FieldsList: fieldsList,
		InlineMap:  inlineMap,
	}

	fieldMapMutex.Lock()
	structMap[st] = sinfo
	fieldMapMutex.Unlock()
	return sinfo, nil
}

// IsZeroer is used to check whether an object is zero to
// determine whether it should be omitted when marshaling
// with the omitempty flag. One notable implementation
// is time.Time.
type IsZeroer interface {
	IsZero() bool
}

func isZero(v reflect.Value) bool {
	kind := v.Kind()
	if z, ok := v.Interface().(IsZeroer); ok {
		if (kind == reflect.Ptr || kind == reflect.Interface) && v.IsNil() {
			return true
		}
		return z.IsZero()
	}
	switch kind {
	case reflect.String:
		return len(v.String()) == 0
	case reflect.Interface, reflect.Ptr:
		return v.IsNil()
	case reflect.Slice:
		return v.Len() == 0
	case reflect.Map:
		return v.Len() == 0
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return v.Int() == 0
	case reflect.Float32, reflect.Float64:
		return v.Float() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return v.Uint() == 0
	case reflect.Bool:
		return !v.Bool()
	case reflect.Struct:
		vt := v.Type()
		for i := v.NumField() - 1; i >= 0; i-- {
			if vt.Field(i).PkgPath != "" {
				continue // Private field
			}
			if !isZero(v.Field(i)) {
				return false
			}
		}
		return true
	}
	return false
}