package skate

import (
	"bytes"
	"errors"
	"reflect"
	"runtime"
	"strconv"
	"strings"

	json "github.com/segmentio/encoding/json"
)

var (
	bTab     = []byte("\t")
	bNewline = []byte("\n")

	ErrZeroFields       = errors.New("zero fields")
	ErrMissingFieldName = errors.New("missing field name")
)

// Title is a document with a title.
type TitleDoc struct {
	Title string `json:"title"`
}

// PartialDoc for docs, that do not have DOI or title. E.g. we found 49701699
// (NCVY), 36401044 (NCVYU), 29668363 (NCUY), and so on.
type PartialDoc struct {
	ContainerName string `json:"container_name"`
	Contribs      []struct {
		RawName string `json:"raw_name"`
	} `json:"contribs"`
	Volume       string `json:"volume"`
	Unstructured string `json:"unstructured"`
	Year         string `json:"release_year"`
}

// Mapper maps a blob to an arbitrary number of fields, e.g. for (key,
// doc). We want fields, but we do not want to bake in TSV into each function.
type Mapper func([]byte) ([][]byte, error)

// AsTSV serialized the result of a field mapper as AsTSV. This is a slim adapter,
// e.g. to parallel.Processor, which expects this function signature.
func (f Mapper) AsTSV(p []byte) ([]byte, error) {
	fields, err := f(p)
	if err != nil {
		return nil, err
	}
	return append(bytes.Join(fields, bTab), bNewline...), nil
}

// WithPrefix adds a given prefix to the first element.
func WithPrefix(f Mapper, prefix string) Mapper {
	return func(p []byte) ([][]byte, error) {
		fields, err := f(p)
		if err != nil {
			return fields, err
		}
		if len(fields) == 0 {
			return nil, ErrZeroFields
		}
		fields[0] = append([]byte(prefix+":"), fields[0]...)
		return fields, err
	}
}

// NameOf returns name of value, e.g. the name of a function.
func NameOf(f interface{}) string {
	v := reflect.ValueOf(f)
	if v.Kind() == reflect.Func {
		if rf := runtime.FuncForPC(v.Pointer()); rf != nil {
			return rf.Name()
		}
	}
	return v.String()
}

// Identifier returns just the input again.
func Identity(p []byte) ([][]byte, error) {
	return [][]byte{p}, nil
}

// CreateFixedMapper extract the value from a given fixed top level json key.
// Returns a function that maps doc to (v, doc).
func CreateFixedMapper(field string) Mapper {
	if field == "" {
		return func(p []byte) ([][]byte, error) {
			return nil, ErrMissingFieldName
		}
	}
	f := func(p []byte) ([][]byte, error) {
		var (
			doc map[string]interface{}
			v   interface{}
			ok  bool
			key []byte
		)
		if err := json.Unmarshal(p, &doc); err != nil {
			return nil, err
		}
		if v, ok = doc[field]; !ok {
			return nil, nil
		}
		switch w := v.(type) {
		case string:
			key = []byte(w)
		case int:
			key = []byte(strconv.Itoa(w))
		case int64:
			key = []byte(strconv.Itoa(int(w)))
		case float64:
			key = []byte(strconv.FormatFloat(w, 'f', 52, 64))
		default:
			return nil, nil
		}
		return [][]byte{key, p}, nil
	}
	return f
}

// MapperTitle extracts (title, doc).
func MapperTitle(p []byte) ([][]byte, error) {
	var (
		doc TitleDoc
		key []byte
	)
	if err := json.Unmarshal(p, &doc); err != nil {
		return nil, err
	} else {
		key = []byte(wsReplacer.Replace(strings.TrimSpace(doc.Title)))
	}
	return [][]byte{key, p}, nil
}

// MapperTitleNormalized extracts (title normalized, doc).
func MapperTitleNormalized(p []byte) (fields [][]byte, err error) {
	if fields, err = MapperTitle(p); err != nil {
		return nil, err
	}
	key := string(fields[0])
	key = wsReplacer.Replace(strings.TrimSpace(key))
	key = strings.ToLower(key)
	key = repeatedWs.ReplaceAllString(key, " ")
	key = nonWord.ReplaceAllString(key, "")
	fields[0] = []byte(key)
	return fields, nil
}

// MapperTitleNormalized extracts (title nysiis, doc).
func MapperTitleNysiis(p []byte) (fields [][]byte, err error) {
	if fields, err = MapperTitle(p); err != nil {
		return nil, err
	}
	key := string(fields[0])
	key = wsReplacer.Replace(strings.TrimSpace(key))
	key = NYSIIS(key)
	fields[0] = []byte(key)
	return fields, nil
}

// MapperTitleSandcrawler extracts (title sandcrawler, doc).
func MapperTitleSandcrawler(p []byte) (fields [][]byte, err error) {
	if fields, err = MapperTitle(p); err != nil {
		return nil, err
	}
	key := string(fields[0])
	key = sandcrawlerSlugify(wsReplacer.Replace(strings.TrimSpace(key)))
	fields[0] = []byte(key)
	return fields, nil
}

// MapperPartial works on partial documents.
func MapperPartial(p []byte) (fields [][]byte, err error) {
	// XXX: slugify authors, how to compare two author strings? How do these
	// things look like?
	return nil, nil
}