package wellknown

import (
	"fmt"
	"net/http"
	"net/url"
	"strings"

	"git.sleepycat.moe/sam/mercury/internal/database/sql"
	"git.sleepycat.moe/sam/mercury/web/api"
	"github.com/rs/zerolog/log"
)

func (app *App) WebFinger(w http.ResponseWriter, r *http.Request) (any, error) {
	ctx := r.Context()
	validDomains := app.AppConfig.Web.WebFingerDomains()

	resource, err := url.QueryUnescape(r.FormValue("resource"))
	if err != nil {
		return nil, api.Error{Code: api.ErrBadRequest}
	}

	if !strings.HasPrefix(resource, "acct:") {
		return nil, api.Error{Code: api.ErrBadRequest, Details: "WebFinger only supports `acct:` queries"}
	}
	resource = strings.TrimPrefix(resource, "acct:")
	username, domain, ok := strings.Cut(resource, "@")
	if !ok {
		return nil, api.Error{Code: api.ErrBadRequest}
	}
	if !anyMatches(validDomains, domain) {
		return nil, api.Error{Code: api.ErrBadRequest, Details: "Not a local user on this instance"}
	}

	blog, err := app.Blog().ByName(ctx, username, "")
	if err != nil {
		if err == sql.ErrNotFound {
			return nil, api.Error{Code: api.ErrNotFound}
		}

		log.Err(err).Str("username", username).Msg("looking up user for webfinger request")
		return nil, err
	}

	webFingerHref := fmt.Sprintf("%s/@%s", app.AppConfig.Web.Domain, blog.Name)

	return WebFinger{
		Subject: fmt.Sprintf("acct:%s@%s", blog.Name, validDomains[0]),
		Aliases: []string{webFingerHref},
		Links: []WebFingerLink{
			{
				Rel:  "http://webfinger.net/rel/profile-page",
				Type: "text/html",
				Href: webFingerHref,
			},
			{
				Rel:  "self",
				Type: "application/activity+json",
				Href: webFingerHref,
			},
		},
	}, nil
}

type WebFinger struct {
	Subject string          `json:"subject"`
	Aliases []string        `json:"aliases"`
	Links   []WebFingerLink `json:"links"`
}

type WebFingerLink struct {
	Rel  string `json:"rel"`
	Type string `json:"type"`
	Href string `json:"href"`
}

func anyMatches[T comparable](slice []T, t T) bool {
	for _, entry := range slice {
		if entry == t {
			return true
		}
	}
	return false
}