package openlibrary

import (
	"encoding/json"
	"fmt"
	"strings"
)

type OpenLibraryBookResult struct {
	Title       string `json:"title"`
	Description string `json:"description"`
	AuthorID    string `json:"author_id"`
}

type openLibraryParsedBook struct {
	Title       string                        `json:"title"`
	Description string                        `json:"description"`
	AuthorInfo  []openLibraryBookAuthorResult `json:"authors"`
}

type openLibraryBookAuthorResult struct {
	AuthorOLID string
	Type       string
	Key        string
}

type keyContainer struct {
	Key string `json:"key"`
}

func (r *openLibraryBookAuthorResult) UnmarshalJSON(data []byte) error {

	var parentAuthor struct {
		AuthorKey keyContainer `json:"author"`
		TypeKey   keyContainer `json:"type"`
		Key       string       `json:"key"`
	}

	if err := json.Unmarshal(data, &parentAuthor); err != nil {
		return err
	}
	r.AuthorOLID = parseUrlPathToField(parentAuthor.AuthorKey.Key)
	r.Type = parseUrlPathToField(parentAuthor.TypeKey.Key)
	r.Key = parseUrlPathToField(parentAuthor.Key)
	return nil
}

// some fields follow this format "/authors/OL274606A"
// this method extracts the last part "OL274606A"
func parseUrlPathToField(urlpath string) string {
	splittedPath := strings.Split(urlpath, "/")
	if len(splittedPath) > 2 {
		return splittedPath[2]
	} else {
		return urlpath
	}
}

func CallOpenLibraryBook(openLibraryId string) (OpenLibraryBookResult, error) {
	var response OpenLibraryBookResult
	u, err := computeOpenLibraryUrl("works", fmt.Sprintf("%s.json", openLibraryId))
	if err != nil {
		return response, err
	}
	var queryResult openLibraryParsedBook
	err = fetchAndParseResult(u, &queryResult)
	if err != nil {
		return response, err
	}
	author := computeAuthorFromParsedBook(&queryResult)
	response = OpenLibraryBookResult{
		Title:       queryResult.Title,
		Description: queryResult.Description,
		AuthorID:    author,
	}
	return response, err
}

func computeAuthorFromParsedBook(parsedBook *openLibraryParsedBook) string {
	authors := parsedBook.AuthorInfo
	for _, author := range authors {
		if author.Key != "" {
			return author.Key
		}
		if author.Type == "author_role" {
			return author.AuthorOLID
		}
	}
	if len(authors) > 0 {
		return authors[0].AuthorOLID
	}
	return ""
}