package router

import (
	"net"
	"net/http"
	"sync"
	"time"

	"golang.org/x/time/rate"
)

type Limit struct {
	rpm   int
	spm   int
	burst int
	mpr   int

	request map[string]*rate.Limiter
	size    map[string]*rate.Limiter
	mx      sync.Mutex
}

func NewLimit(requestPerMinute, sizePerMinute, burstSize, memPerRequest int) *Limit {
	return &Limit{
		rpm:     requestPerMinute,
		spm:     sizePerMinute,
		burst:   burstSize,
		mpr:     memPerRequest,
		request: make(map[string]*rate.Limiter),
		size:    make(map[string]*rate.Limiter),
		mx:      sync.Mutex{},
	}
}

func (l *Limit) file(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if l.hasHitRequestLimit(r.RemoteAddr) {
			http.Error(w, "Too many requests", http.StatusTooManyRequests)
			return
		}

		if err := r.ParseMultipartForm(int64(l.mpr)); err != nil {
			http.Error(w, "Invalid multipart form", http.StatusBadRequest)
			return
		}

		files := r.MultipartForm.File["file"]
		if len(files) != 1 {
			http.Error(w, "Expected exactly one file", http.StatusBadRequest)
			return
		}

		if l.hasHitSizeLimit(r.RemoteAddr, files[0].Size) {
			http.Error(w, "File too big", http.StatusTooManyRequests)
			return
		}

		next.ServeHTTP(w, r)
	})
}

func (l *Limit) redirect(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if l.hasHitRequestLimit(r.RemoteAddr) {
			http.Error(w, "Too many requests", http.StatusTooManyRequests)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// hasHitRequestLimit returns if the requested remote address has reached the request limit.
func (l *Limit) hasHitRequestLimit(remoteAddr string) bool {
	ip, _, err := net.SplitHostPort(remoteAddr)
	if err != nil {
		return true
	}

	l.mx.Lock()
	defer l.mx.Unlock()

	if l.request[ip] == nil {
		l.request[ip] = rate.NewLimiter(rate.Limit(l.rpm/60), l.rpm)
		l.size[ip] = rate.NewLimiter(rate.Limit(l.spm/60), l.burst)
	}

	return !l.request[ip].Allow()
}

// hasHitSizeLimit returns if the requested remote address has reached the size limit.
func (l *Limit) hasHitSizeLimit(remoteAddr string, size int64) bool {
	ip, _, err := net.SplitHostPort(remoteAddr)
	if err != nil {
		return true
	}

	l.mx.Lock()
	defer l.mx.Unlock()

	return !l.size[ip].AllowN(time.Now(), int(size))
}