package command

import (
	"fmt"
	"strings"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/pluginapi"
)

const cleanupCommandTrigger = "cleanup-channel"

type Handler struct {
	client *pluginapi.Client
	cleanup func(userID, channelID string) (int, error)
}

type Command interface {
	Handle(args *model.CommandArgs) (*model.CommandResponse, error)
}

func NewCommandHandler(client *pluginapi.Client, cleanup func(userID, channelID string) (int, error)) Command {
	err := client.SlashCommand.Register(&model.Command{
		Trigger:          cleanupCommandTrigger,
		AutoComplete:     false,
		AutoCompleteDesc: "Remove all messages from the current channel (system admins only)",
	})
	if err != nil {
		client.Log.Error("Failed to register command", "error", err)
	}

	return &Handler{
		client:  client,
		cleanup: cleanup,
	}
}

func (c *Handler) Handle(args *model.CommandArgs) (*model.CommandResponse, error) {
	fields := strings.Fields(args.Command)
	if len(fields) == 0 {
		return ephemeralResponse("Empty command"), nil
	}

	trigger := strings.TrimPrefix(fields[0], "/")
	if trigger != cleanupCommandTrigger {
		return ephemeralResponse(fmt.Sprintf("Unknown command: %s", args.Command)), nil
	}

	if !c.client.User.HasPermissionTo(args.UserId, model.PermissionManageSystem) {
		return ephemeralResponse("This command is only available to system administrators."), nil
	}

	deleted, err := c.cleanup(args.UserId, args.ChannelId)
	if err != nil {
		c.client.Log.Error("Failed to cleanup channel via slash command", "channel_id", args.ChannelId, "error", err)
		return ephemeralResponse("Failed to remove messages from this channel."), nil
	}

	return ephemeralResponse(fmt.Sprintf("Removed %d message(s) from this channel.", deleted)), nil
}

func ephemeralResponse(text string) *model.CommandResponse {
	return &model.CommandResponse{
		ResponseType: model.CommandResponseTypeEphemeral,
		Text:         text,
	}
}