package skate

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

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

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. Some examples: XXX
type PartialDoc struct {
	ContainerName string `json:"container_name"`
	Contribs      []struct {
		// XXX: Need a way to sensibly compare sets of author names.
		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 serializes the result of a field mapper as TSV. This is a slim
// adapter, e.g. to parallel.Processor, which expects this function signature.
// A newline will be appended, if not there already.
func (f Mapper) AsTSV(p []byte) ([]byte, error) {
	var (
		fields [][]byte
		err    error
		b      []byte
	)
	if fields, err = f(p); err != nil {
		return nil, err
	}
	if len(fields) == 0 {
		return nil, nil
	}
	b = bytes.Join(fields, bTab)
	if len(b) > 0 && !bytes.HasSuffix(b, bNewline) {
		b = append(b, bNewline...)
	}
	return b, nil
}

// WithPrefix is a "mapper middleware", adding a given prefix to the first field.
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
	}
}

// WithBestEffort will not fail on an error.
func WithBestEffort(f Mapper) Mapper {
	return func(p []byte) ([][]byte, error) {
		if fields, err := f(p); err != nil {
			return nil, nil
		} else {
			return fields, err
		}
	}
}

// WithSkipOnEmpty ignores results where the value at a given field is empty.
// One indexed.
func WithSkipOnEmpty(f Mapper, index int) Mapper {
	return func(p []byte) ([][]byte, error) {
		fields, err := f(p)
		if err != nil {
			return nil, err
		}
		if index < len(fields) && len(fields[index]) == 0 {
			return nil, nil
		}
		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 json key, e.g.
// "biblio.doi" and the like. Returns a function that maps doc to (value, doc).
func CreateFixedMapper(field string) Mapper {
	if len(field) > 0 && field[0] == '.' {
		// gjson is not jq, we do not use a leading dot, so remove it, if
		// accidentally used here
		field = field[1:]
	}
	f := func(p []byte) ([][]byte, error) {
		result := gjson.GetBytes(p, field)
		// A subtle bug can emerge here: By default we use tab as separator. If
		// the value extracted ends with the separator (e.g. tab), then we get
		// an invalid row. Hence, trim all space.
		key := []byte(strings.TrimSpace(result.String()))
		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
}

// MapperURLFromRef extracts the (work ident, release ident, url, doc).
// Previously: parallel -j 16 --block 100M --pipe "jq -rc '[.work_ident,
// .release_ident, .biblio.url?] | @tsv'" ...
// This implementation seems slightly faster that jq and parallel.
func MapperURLFromRef(p []byte) (fields [][]byte, err error) {
	var ref Ref
	if err = json.Unmarshal(p, &ref); err != nil {
		return nil, err
	}
	fields = [][]byte{
		[]byte(ref.WorkIdent),
		[]byte(ref.ReleaseIdent),
		[]byte(ref.Biblio.Url),
		p,
	}
	return fields, nil
}

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