package metadata

import (
	"fmt"
	"git.gammaspectra.live/S.O.N.G/METANOIA/utilities"
	"net/http"
	"runtime"
	"time"
)

//DefaultUserAgent Follows most identification rules (Like for Musicbrainz, or Discogs)
var DefaultUserAgent = fmt.Sprintf("Mozilla/5.0 (compatible; METANOIA/%s; +https://git.gammaspectra.live/S.O.N.G/METANOIA) golang/%s (%s; %s; net/http; %s)", utilities.Version, runtime.Version(), runtime.GOOS, runtime.GOARCH, runtime.Compiler)

var defaultCacheStore CacheStore

type CachingClient struct {
	context   string
	client    *http.Client
	throttler <-chan time.Time
}

type CacheStore interface {
	Get(request *http.Request) (*http.Response, error)
	Set(request *http.Request, response *http.Response) (*http.Response, error)
}

func SetCacheStore(store CacheStore) {
	defaultCacheStore = store
}

func NewCachingClient(context string, rateLimit time.Duration) *CachingClient {
	return &CachingClient{
		context:   context,
		client:    http.DefaultClient,
		throttler: time.Tick(rateLimit),
	}
}

func (c *CachingClient) Request(req *http.Request, lifetime time.Duration) (*http.Response, error) {
	if req.Header == nil || req.UserAgent() == "" {
		if req.Header == nil {
			req.Header = make(http.Header)
		}
		req.Header.Set("User-Agent", DefaultUserAgent)
	}

	if defaultCacheStore != nil {
		response, err := defaultCacheStore.Get(req)
		if err == nil && response != nil {
			timestamp, _ := time.ParseInLocation(time.UnixDate, response.Request.Header.Get("X-Fetched-At"), time.UTC)

			if timestamp.Add(lifetime).After(time.Now()) {
				return response, nil
			}
		}
	}

	<-c.throttler
	response, err := c.client.Do(req)
	if defaultCacheStore != nil && err == nil {
		req.Header.Set("X-Fetched-At", time.Now().UTC().Format(time.UnixDate))
		response, err = defaultCacheStore.Set(req, response)
	}

	return response, err
}