// A simple Go wrapper around the OpenLibrary.org Books API
package client

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
)

var (
	defaultAPI = "https://openlibrary.org/api/books"
)

var (
	// FormatError marks errors with provided book identifers
	FormatError = fmt.Errorf("identifier in wrong format")
	// NetworkError marks errors with the connection to the OpenLibrary API
	NetworkError = fmt.Errorf("network error")
	// NotFoundError marks an empty response from the OpenLibrary API
	NotFoundError = fmt.Errorf("book not found")
)

// Client provides OpenLibrary Books API query methods
type Client struct {
	httpClient http.Client
	apipath    string
}

// SetHTTPClient updates the httpClient on the client with a manually-configured one.
// If unset, the client will fall back to using http.DefaultClient.
func (c *Client) SetHTTPClient(h http.Client) {
	c.httpClient = h
}

// SetAPIPath updates the hostname and path to the API; the default is "https://openlibrary.org/api/books".
// If APIPath is set to an empty string, the client will fall back to the default option.
func (c *Client) SetAPIPath(p string) {
	c.apipath = p
}

// GetByISBN fetches details for a book based on its ISBN10 or ISBN13.
func (c *Client) GetByISBN(k string) (*BookDetails, error) {
	if k == "" {
		return nil, fmt.Errorf("%w: ISBN cannot be empty", FormatError)
	} else if len(k) != 10 && len(k) != 13 {
		return nil, fmt.Errorf("%w: ISBN must be either 10 or 13 digits", FormatError)
	}
	key := "ISBN:" + k
	return c.fetch(key)
}

// GetByOCLC fetches details for a book based on its WorldCat OCLC number.
func (c *Client) GetByOCLC(k string) (*BookDetails, error) {
	if k == "" {
		return nil, fmt.Errorf("%w: OCLC cannot be empty", FormatError)
	}
	key := "OCLC:" + k
	return c.fetch(key)
}

// GetByLCCN fetches details for a book based on its Library of Congress Control Number.
func (c *Client) GetByLCCN(k string) (*BookDetails, error) {
	if k == "" {
		return nil, fmt.Errorf("%w: LCCN cannot be empty", FormatError)
	}
	key := "LCCN:" + k
	return c.fetch(key)
}

// GetByOLID fetches details for a book based on its OpenLibrary ID number.
func (c *Client) GetByOLID(k string) (*BookDetails, error) {
	if k == "" {
		return nil, fmt.Errorf("%w: OLID cannot be empty", FormatError)
	}
	key := "OLID:" + k
	return c.fetch(key)
}

// GetByRawKey fetches details for a book based on an arbitrary key; this method is provided
// as a future-proof fallback in case the OpenLibrary API adds more "bibkey" request types in the future.
// Most users should use one of the other lookup functions.
func (c *Client) GetByRawKey(k string) (*BookDetails, error) {
	return c.fetch(k)
}

func (c *Client) fetch(key string) (*BookDetails, error) {
	h := c.apipath
	if h == "" {
		h = defaultAPI
	}
	u, err := url.Parse(h)
	if err != nil {
		return nil, fmt.Errorf("%w: %v", NetworkError, err)
	}
	u.RawQuery = url.Values{
		"bibkeys": []string{key},
		"jscmd":   []string{"data"},
		"format":  []string{"json"},
	}.Encode()

	resp, err := c.httpClient.Get(u.String())
	if err != nil {
		return nil, fmt.Errorf("%w: %v", NetworkError, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("%w: received non-200 status code: %d", NetworkError, resp.StatusCode)
	}

	var result response
	b, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("%w: %v", NetworkError, err)
	}
	if err = json.Unmarshal(b, &result); err != nil {
		return nil, fmt.Errorf("%w: %v", NetworkError, err)
	}

	details, ok := result[key]
	if !ok {
		return nil, NotFoundError
	}

	return &details, nil
}