// Package api holds functions to interact with the artifacts API
package api

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"slices"
)

// custom error codes
var (
	ErrTokenNotProvided = errors.New("make sure to provide a token via the api.SetToken() function, or set it via env variable ARTIFACTS_TOKEN")
)

const (
	baseURL = "https://api.artifactsmmo.com"
)

var token string // the token must be provided for the client to work

type apiResponse struct {
	Data  json.RawMessage `json:"data"`
	Total int             `json:"total"`
	Page  int             `json:"page"`
	Size  int             `json:"size"`
	Pages int             `json:"pages"`
}

// SetToken can be used to set the token, which must be provided before calling any other function.
// It can be provided using this function or via environment variable 'ARTIFACTS_TOKEN'.
func SetToken(t string) {
	token = t
}

func meta[T any](endpoint string, method string, body any, responseCodes map[int]string) (*T, error) {
	// make it possible to set a token via env variable
	if token == "" && os.Getenv("ARTIFACTS_TOKEN") != "" {
		SetToken(os.Getenv("ARTIFACTS_TOKEN"))
	}

	// check for token
	if token == "" {
		return nil, ErrTokenNotProvided
	}

	bodyBytes, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}

	// create a new request to retrieve characters
	request, err := http.NewRequest(method, baseURL+endpoint, bytes.NewReader(bodyBytes))
	if err != nil {
		return nil, err
	}

	// add auth header to the request
	request.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
	request.Header.Set("Content-Type", "application/json")

	// execute this request
	response, err := http.DefaultClient.Do(request)
	if err != nil {
		return nil, err
	}

	// check all additional status codes first
	for code, message := range responseCodes {
		if response.StatusCode != code {
			continue
		}

		// exit the function if a statuscode was found and return it's message
		return nil, fmt.Errorf("%d: %s", code, message)
	}

	// basic error handling
	if response.StatusCode != 200 {
		return nil, fmt.Errorf("%s", response.Status)
	}

	// read in the body of the response
	b, err := io.ReadAll(response.Body)
	if err != nil {
		return nil, err
	}

	// close the body when we are finished
	defer response.Body.Close()

	// convert it to a native go type
	var ar apiResponse
	if err := json.Unmarshal(b, &ar); err != nil {
		return nil, err
	}

	if ar.Page < ar.Pages {
		// parse endpoint
		u, err := url.Parse(endpoint)
		if err != nil {
			return nil, err
		}

		urlValues := u.Query()
		urlValues.Set("page", fmt.Sprintf("%d", ar.Page+1))
		endpoint = u.Path

		nextPage, err := meta[T](fmt.Sprintf("%s?%s", endpoint, urlValues.Encode()), method, body, responseCodes)
		if err != nil {
			return nil, err
		}

		b1, err := ar.Data.MarshalJSON()
		if err != nil {
			return nil, err
		}

		b2, err := json.Marshal(nextPage)
		if err != nil {
			return nil, err
		}

		bCombined := slices.Concat(b1[0:len(b1)-1], []byte(","), b2[1:])

		// copy combined dataset into ar.Data
		ar.Data.UnmarshalJSON(bCombined)

		// combine both things
	}

	d, err := ar.Data.MarshalJSON()
	if err != nil {
		return nil, err
	}

	// no error occurred
	var r T
	if err := json.Unmarshal(d, &r); err != nil {
		return nil, err
	}

	return &r, nil
}

// Post is used to call an endpoint using a POST request, responseCodes contains all possible
// error codes that the API can respond with other than 200 OK
func Post[T any](endpoint string, body any, responseCodes map[int]string) (output T, err error) {
	// use meta function to get a response
	response, err := meta[T](endpoint, http.MethodPost, body, responseCodes)
	if err != nil {
		return output, err
	}

	// return the data alongside any error that might have occurred
	return *response, err
}

// Get is used to call an endpoint using a GET request, responseCodes contains all possible
// error codes that the API can respond with other than 200 OK
func Get[T any](endpoint string, responseCodes map[int]string) (output T, err error) {
	// use meta function to get a response
	response, err := meta[T](endpoint, http.MethodGet, nil, responseCodes)
	if err != nil {
		return output, err
	}

	// return the data alongside any error that might have occurred
	return *response, err
}