package main

import (
	"errors"

	"github.com/mattermost/mattermost/server/public/model"
	pkgerrors "github.com/pkg/errors"
)

var errPermissionDenied = errors.New("permission denied: system admin required")

const postsPerPage = 200

func (p *Plugin) isSystemAdmin(userID string) bool {
	return p.client.User.HasPermissionTo(userID, model.PermissionManageSystem)
}

func (p *Plugin) cleanupChannel(userID, channelID string) (int, error) {
	if !p.isSystemAdmin(userID) {
		return 0, errPermissionDenied
	}

	if _, err := p.client.Channel.Get(channelID); err != nil {
		return 0, pkgerrors.Wrap(err, "failed to get channel")
	}

	deleted := 0
	for {
		postList, err := p.client.Post.GetPostsForChannel(channelID, 0, postsPerPage)
		if err != nil {
			return deleted, pkgerrors.Wrap(err, "failed to get channel posts")
		}
		if len(postList.Order) == 0 {
			break
		}

		for _, postID := range postList.Order {
			if err := p.client.Post.DeletePost(postID); err != nil {
				p.client.Log.Warn("Failed to delete post", "post_id", postID, "error", err)
				continue
			}
			deleted++
		}
	}

	return deleted, nil
}