/*
   GoToSocial
   Copyright (C) 2021-2023 GoToSocial Authors admin@gotosocial.org

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package instance

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

	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
	"github.com/superseriousbusiness/gotosocial/internal/config"
	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
	"github.com/superseriousbusiness/gotosocial/internal/oauth"

	"github.com/gin-gonic/gin"
)

// InstancePeersGETHandler swagger:operation GET /api/v1/instance/peers instancePeersGet
//
//	---
//	tags:
//	- instance
//
//	produces:
//	- application/json
//
//	parameters:
//	-
//		name: filter
//		type: string
//		description: |-
//			Comma-separated list of filters to apply to results. Recognized filters are:
//				- `open` -- include peers that are not suspended or silenced
//				- `suspended` -- include peers that have been suspended.
//
//			If filter is `open`, only instances that haven't been suspended or silenced will be returned.
//
//			If filter is `suspended`, only suspended instances will be shown.
//
//			If filter is `open,suspended`, then all known instances will be returned.
//
//			If filter is an empty string or not set, then `open` will be assumed as the default.
//		in: query
//		required: false
//		default: "open"
//
//	responses:
//		'200':
//			description: >-
//				If no filter parameter is provided, or filter is empty, then a legacy,
//				Mastodon-API compatible response will be returned. This will consist of
//				just a 'flat' array of strings like `["example.com", "example.org"]`,
//				which corresponds to domains this instance peers with.
//
//
//				If a filter parameter is provided, then an array of objects with at least
//				a `domain` key set on each object will be returned.
//
//
//				Domains that are silenced or suspended will also have a key
//				`suspended_at` or `silenced_at` that contains an iso8601 date string.
//				If one of these keys is not present on the domain object, it is open.
//				Suspended instances may in some cases be obfuscated, which means they
//				will have some letters replaced by `*` to make it more difficult for
//				bad actors to target instances with harassment.
//
//
//				Whether a flat response or a more detailed response is returned, domains
//				will be sorted alphabetically by hostname.
//			schema:
//				type: array
//				items:
//					"$ref": "#/definitions/domain"
//		'400':
//			description: bad request
//		'401':
//			description: unauthorized
//		'403':
//			description: forbidden
//		'404':
//			description: not found
//		'406':
//			description: not acceptable
//		'500':
//			description: internal server error
func (m *Module) InstancePeersGETHandler(c *gin.Context) {
	authed, err := oauth.Authed(c, false, false, false, false)
	if err != nil {
		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGet)
		return
	}

	var isUnauthenticated = authed.Account == nil || authed.User == nil

	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGet)
		return
	}

	var includeSuspended bool
	var includeOpen bool
	var flat bool
	if filterParam := c.Query(PeersFilterKey); filterParam != "" {
		filters := strings.Split(filterParam, ",")
		for _, f := range filters {
			trimmed := strings.TrimSpace(f)
			switch {
			case strings.EqualFold(trimmed, "suspended"):
				includeSuspended = true
			case strings.EqualFold(trimmed, "open"):
				includeOpen = true
			default:
				err := fmt.Errorf("filter %s not recognized; accepted values are 'open', 'suspended'", trimmed)
				apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
				return
			}
		}
	} else {
		// default is to only include open domains, and present
		// them in a 'flat' manner (just an array of strings),
		// to maintain compatibility with mastodon API
		includeOpen = true
		flat = true
	}

	if includeOpen && !config.GetInstanceExposePeers() && isUnauthenticated {
		err := fmt.Errorf("peers open query requires an authenticated account/user")
		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGet)
		return
	}

	if includeSuspended && !config.GetInstanceExposeSuspended() && isUnauthenticated {
		err := fmt.Errorf("peers suspended query requires an authenticated account/user")
		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGet)
		return
	}

	data, errWithCode := m.processor.InstancePeersGet(c.Request.Context(), includeSuspended, includeOpen, flat)
	if errWithCode != nil {
		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
		return
	}

	c.JSON(http.StatusOK, data)
}