package serve

import (
	"context"
	"net/http"
	"net/netip"
	"strings"

	"github.com/google/uuid"

	"git.sunturtle.xyz/studio/shotgun/player"
)

// WithPlayerID is a middleware that adds a player ID to the request context
// based on the X-Forwarded-For header. If there is no such header, or the
// originator addr otherwise cannot be parsed from it, the request fails with
// a 500 error.
func WithPlayerID(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ff := r.Header.Get("X-Forwarded-For")
		addr, err := originator(ff)
		if err != nil {
			http.Error(w, "missing or invalid X-Forwarded-For header; check server configuration", http.StatusInternalServerError)
			return
		}
		id := player.ID{UUID: uuid.UUID(addr.As16())}
		ctx := ctxWith(r.Context(), id)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

// Player returns the player ID set by WithPlayerID in the request context.
func PlayerID(ctx context.Context) player.ID {
	return ctxValue[player.ID](ctx)
}

// originator parses the IP of the client that originated a request from the
// content of its X-Forwarded-For header.
func originator(ff string) (netip.Addr, error) {
	ff, _, _ = strings.Cut(ff, ",")
	return netip.ParseAddr(ff)
}

type ctxKey[T any] struct{}

func ctxValue[T any](ctx context.Context) T {
	r, _ := ctx.Value(ctxKey[T]{}).(T)
	return r
}

func ctxWith[T any](ctx context.Context, v T) context.Context {
	return context.WithValue(ctx, ctxKey[T]{}, v)
}