// Copyright 2023 The Forgejo Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package activitypub

import (
	"context"
	"fmt"
	"io"
	"net/http"

	"code.gitea.io/gitea/models/auth"
	"code.gitea.io/gitea/models/db"
	user_model "code.gitea.io/gitea/models/user"
	"code.gitea.io/gitea/modules/forgefed"
	"code.gitea.io/gitea/modules/httplib"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"

	ap "github.com/go-ap/activitypub"
	"github.com/go-ap/jsonld"
)

// Fetch a URL as binary
func Fetch(iri string) (b []byte, err error) {
	req := httplib.NewRequest(iri, http.MethodGet)
	req.Header("Accept", ActivityStreamsContentType)
	req.Header("User-Agent", "Gitea/"+setting.AppVer)
	resp, err := req.Response()
	if err != nil {
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		err = fmt.Errorf("url IRI fetch [%s] failed with status (%d): %s", iri, resp.StatusCode, resp.Status)
		return
	}
	b, err = io.ReadAll(io.LimitReader(resp.Body, setting.Federation.MaxSize))
	return b, err
}

// Fetch a remote ActivityStreams object as an object
func FetchObject(iri string) (ap.ObjectOrLink, error) {
	resp, err := Fetch(iri)
	if err != nil {
		return nil, err
	}
	ap.ItemTyperFunc = forgefed.GetItemByType
	ap.JSONItemUnmarshal = forgefed.JSONUnmarshalerFn
	ap.IsNotEmpty = forgefed.NotEmpty
	return ap.UnmarshalJSON(resp)
}

// Send an activity
func Send(ctx context.Context, user *user_model.User, activity *ap.Activity) error {
	binary, err := jsonld.WithContext(
		jsonld.IRI(ap.ActivityBaseURI),
		jsonld.IRI(ap.SecurityContextURI),
		jsonld.IRI(forgefed.ForgeFedNamespaceURI),
	).Marshal(activity)
	if err != nil {
		return err
	}

	// Construt list of recipients
	recipients := []string{}
	for _, to := range activity.To {
		if to.GetLink().String() == user.GetIRI()+"/followers" {
			followers, count, err := user_model.GetUserFollowers(ctx, user, user, db.ListOptions{})
			if err != nil {
				return err
			}
			for i := int64(0); i < count; i++ {
				if followers[i].LoginType == auth.Federated {
					recipients = append(recipients, followers[i].GetIRI())
				}
			}
		} else {
			recipients = append(recipients, to.GetLink().String()+"/inbox")
		}
	}

	// Send out activity to recipients
	for _, recipient := range recipients {
		client, err := NewClient(user, user.GetIRI()+"#main-key")
		if err != nil {
			return err
		}
		resp, err := client.Post(binary, recipient)
		if err != nil {
			return err
		}
		respBody, err := io.ReadAll(io.LimitReader(resp.Body, setting.Federation.MaxSize))
		if err != nil {
			return err
		}
		log.Trace("Response from sending activity", string(respBody))
	}
	return nil
}