/*
   GoToSocial
   Copyright (C) 2021-2022 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 text

import (
	"bytes"
	"context"
	"html"
	"strings"
	"unicode"

	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
	"github.com/superseriousbusiness/gotosocial/internal/log"
	"github.com/superseriousbusiness/gotosocial/internal/regexes"
)

// preformat contains some common logic for making a string ready for formatting, which should be used for all user-input text.
func preformat(in string) string {
	// do some preformatting of the text

	// 1. unescape everything that might be html escaped
	s := html.UnescapeString(in)

	// 2. trim leading or trailing whitespace
	s = strings.TrimSpace(s)
	return s
}

// postformat contains some common logic for html sanitization of text, wrapping elements, and trimming newlines and whitespace
func postformat(in string) string {
	// do some postformatting of the text

	// 1. sanitize html to remove potentially dangerous elements
	s := SanitizeHTML(in)

	// 2. the sanitize step tends to escape characters inside codeblocks, which is behavior we don't want, so unescape everything again
	s = html.UnescapeString(s)

	// 3. minify html to remove any trailing newlines, spaces, unnecessary elements, etc etc
	mini, err := MinifyHTML(s)
	if err != nil {
		// if the minify failed, just return what we have
		return s
	}
	// return minified version of the html
	return mini
}

func (f *formatter) ReplaceTags(ctx context.Context, in string, tags []*gtsmodel.Tag) string {
	return regexes.ReplaceAllStringFunc(regexes.HashtagFinder, in, func(match string, buf *bytes.Buffer) string {
		// we have a match
		matchTrimmed := strings.TrimSpace(match)
		tagAsEntered := matchTrimmed[1:]

		// check through the tags to find what we're matching
		for _, tag := range tags {
			if strings.EqualFold(tagAsEntered, tag.Name) {
				// Add any dropped space from match
				if unicode.IsSpace(rune(match[0])) {
					buf.WriteByte(match[0])
				}

				// replace the #tag with the formatted tag content
				// `<a href="tag.URL" class="mention hashtag" rel="tag">#<span>tagAsEntered</span></a>
				buf.WriteString(`<a href="`)
				buf.WriteString(tag.URL)
				buf.WriteString(`" class="mention hashtag" rel="tag">#<span>`)
				buf.WriteString(tagAsEntered)
				buf.WriteString(`</span></a>`)
				return buf.String()
			}
		}

		// the match wasn't in the list of tags for whatever reason, so just return the match as we found it so nothing changes
		return match
	})
}

func (f *formatter) ReplaceMentions(ctx context.Context, in string, mentions []*gtsmodel.Mention) string {
	return regexes.ReplaceAllStringFunc(regexes.MentionFinder, in, func(match string, buf *bytes.Buffer) string {
		// we have a match, trim any spaces
		matchTrimmed := strings.TrimSpace(match)

		// check through mentions to find what we're matching
		for _, menchie := range mentions {
			if strings.EqualFold(matchTrimmed, menchie.NameString) {
				// make sure we have an account attached to this mention
				if menchie.TargetAccount == nil {
					a, err := f.db.GetAccountByID(ctx, menchie.TargetAccountID)
					if err != nil {
						log.Errorf("error getting account with id %s from the db: %s", menchie.TargetAccountID, err)
						return match
					}
					menchie.TargetAccount = a
				}

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

				// Add any dropped space from match
				if unicode.IsSpace(rune(match[0])) {
					buf.WriteByte(match[0])
				}

				// 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>
				buf.WriteString(`<span class="h-card"><a href="`)
				buf.WriteString(targetAccount.URL)
				buf.WriteString(`" class="u-url mention">@<span>`)
				buf.WriteString(targetAccount.Username)
				buf.WriteString(`</span></a></span>`)
				return buf.String()
			}
		}

		// the match wasn't in the list of mentions for whatever reason, so just return the match as we found it so nothing changes
		return match
	})
}