// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// 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 text

import (
	"errors"
	"strings"

	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/gotosocial/internal/util"
	"golang.org/x/text/unicode/norm"
)

const (
	maximumHashtagLength = 30
)

// given a mention or a hashtag string, the methods in this file will attempt to parse it,
// add it to the database, and render it as HTML. If any of these steps fails, the method
// will just return the original string and log an error.

// replaceMention takes a string in the form @username@domain.com or @localusername
func (r *customRenderer) replaceMention(text string) string {
	mention, err := r.parseMention(r.ctx, text, r.accountID, r.statusID)
	if err != nil {
		log.Errorf(r.ctx, "error parsing mention %s from status: %s", text, err)
		return text
	}

	if r.statusID != "" {
		if err := r.f.db.PutMention(r.ctx, mention); err != nil {
			log.Errorf(r.ctx, "error putting mention in db: %s", err)
			return text
		}
	}

	// only append if it's not been listed yet
	listed := false
	for _, m := range r.result.Mentions {
		if mention.ID == m.ID {
			listed = true
			break
		}
	}
	if !listed {
		r.result.Mentions = append(r.result.Mentions, mention)
	}

	if mention.TargetAccount == nil {
		// Fetch mention target account if not yet populated.
		mention.TargetAccount, err = r.f.db.GetAccountByID(
			gtscontext.SetBarebones(r.ctx),
			mention.TargetAccountID,
		)
		if err != nil {
			log.Errorf(r.ctx, "error populating mention target account: %v", err)
			return text
		}
	}

	// The mention's target is our target
	targetAccount := mention.TargetAccount

	var b strings.Builder

	// replace the mention with the formatted mention content
	// <span class="h-card"><a href="targetAccount.URL" class="u-url mention">@<span>targetAccount.Username</span></a></span>
	b.WriteString(`<span class="h-card"><a href="`)
	b.WriteString(targetAccount.URL)
	b.WriteString(`" class="u-url mention">@<span>`)
	b.WriteString(targetAccount.Username)
	b.WriteString(`</span></a></span>`)
	return b.String()
}

// replaceMention takes a string in the form #HashedTag, and will normalize it before
// adding it to the db and turning it into HTML.
func (r *customRenderer) replaceHashtag(text string) string {
	// this normalization is specifically to avoid cases where visually-identical
	// hashtags are stored with different unicode representations (e.g. with combining
	// diacritics). It allows a tasteful number of combining diacritics to be used,
	// as long as they can be combined with parent characters to form regular letter
	// symbols.
	normalized := norm.NFC.String(text[1:])

	for i, r := range normalized {
		if i >= maximumHashtagLength || !util.IsPermittedInHashtag(r) {
			return text
		}
	}

	tag, err := r.f.db.TagStringToTag(r.ctx, normalized, r.accountID)
	if err != nil {
		log.Errorf(r.ctx, "error generating hashtags from status: %s", err)
		return text
	}

	// only append if it's not been listed yet
	listed := false
	for _, t := range r.result.Tags {
		if tag.ID == t.ID {
			listed = true
			break
		}
	}
	if !listed {
		err = r.f.db.Put(r.ctx, tag)
		if err != nil {
			if !errors.Is(err, db.ErrAlreadyExists) {
				log.Errorf(r.ctx, "error putting tags in db: %s", err)
				return text
			}
		}
		r.result.Tags = append(r.result.Tags, tag)
	}

	var b strings.Builder
	// replace the #tag with the formatted tag content
	// `<a href="tag.URL" class="mention hashtag" rel="tag">#<span>tagAsEntered</span></a>
	b.WriteString(`<a href="`)
	b.WriteString(tag.URL)
	b.WriteString(`" class="mention hashtag" rel="tag">#<span>`)
	b.WriteString(normalized)
	b.WriteString(`</span></a>`)

	return b.String()
}