// mautrix-whatsapp - A Matrix-WhatsApp puppeting bridge.
// Copyright (C) 2020 Tulir Asokan
//
// 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 <https://www.gnu.org/licenses/>.

package main

import (
	"fmt"
	"html"
	"regexp"
	"strings"

	"maunium.net/go/mautrix/event"
	"maunium.net/go/mautrix/format"
	"maunium.net/go/mautrix/id"

	"maunium.net/go/mautrix-whatsapp/types"
	"maunium.net/go/mautrix-whatsapp/whatsapp-ext"
)

var italicRegex = regexp.MustCompile("([\\s>~*]|^)_(.+?)_([^a-zA-Z\\d]|$)")
var boldRegex = regexp.MustCompile("([\\s>_~]|^)\\*(.+?)\\*([^a-zA-Z\\d]|$)")
var strikethroughRegex = regexp.MustCompile("([\\s>_*]|^)~(.+?)~([^a-zA-Z\\d]|$)")
var codeBlockRegex = regexp.MustCompile("```(?:.|\n)+?```")
var mentionRegex = regexp.MustCompile("@[0-9]+")

type Formatter struct {
	bridge *Bridge

	matrixHTMLParser *format.HTMLParser

	waReplString   map[*regexp.Regexp]string
	waReplFunc     map[*regexp.Regexp]func(string) string
	waReplFuncText map[*regexp.Regexp]func(string) string
}

func NewFormatter(bridge *Bridge) *Formatter {
	formatter := &Formatter{
		bridge: bridge,
		matrixHTMLParser: &format.HTMLParser{
			TabsToSpaces: 4,
			Newline:      "\n",

			PillConverter: func(mxid, eventID string) string {
				if mxid[0] == '@' {
					puppet := bridge.GetPuppetByMXID(id.UserID(mxid))
					if puppet != nil {
						return "@" + puppet.PhoneNumber()
					}
				}
				return mxid
			},
			BoldConverter: func(text string) string {
				return fmt.Sprintf("*%s*", text)
			},
			ItalicConverter: func(text string) string {
				return fmt.Sprintf("_%s_", text)
			},
			StrikethroughConverter: func(text string) string {
				return fmt.Sprintf("~%s~", text)
			},
			MonospaceConverter: func(text string) string {
				return fmt.Sprintf("```%s```", text)
			},
			MonospaceBlockConverter: func(text, language string) string {
				return fmt.Sprintf("```%s```", text)
			},
		},
		waReplString: map[*regexp.Regexp]string{
			italicRegex:        "$1<em>$2</em>$3",
			boldRegex:          "$1<strong>$2</strong>$3",
			strikethroughRegex: "$1<del>$2</del>$3",
		},
	}
	formatter.waReplFunc = map[*regexp.Regexp]func(string) string{
		codeBlockRegex: func(str string) string {
			str = str[3 : len(str)-3]
			if strings.ContainsRune(str, '\n') {
				return fmt.Sprintf("<pre><code>%s</code></pre>", str)
			}
			return fmt.Sprintf("<code>%s</code>", str)
		},
		mentionRegex: func(str string) string {
			mxid, displayname := formatter.getMatrixInfoByJID(str[1:] + whatsappExt.NewUserSuffix)
			return fmt.Sprintf(`<a href="https://matrix.to/#/%s">%s</a>`, mxid, displayname)
		},
	}
	formatter.waReplFuncText = map[*regexp.Regexp]func(string) string{
		mentionRegex: func(str string) string {
			_, displayname := formatter.getMatrixInfoByJID(str[1:] + whatsappExt.NewUserSuffix)
			return displayname
		},
	}
	return formatter
}

func (formatter *Formatter) getMatrixInfoByJID(jid types.WhatsAppID) (mxid id.UserID, displayname string) {
	if user := formatter.bridge.GetUserByJID(jid); user != nil {
		mxid = user.MXID
		displayname = string(user.MXID)
	} else if puppet := formatter.bridge.GetPuppetByJID(jid); puppet != nil {
		mxid = puppet.MXID
		displayname = puppet.Displayname
	}
	return
}

func (formatter *Formatter) ParseWhatsApp(content *event.MessageEventContent) {
	output := html.EscapeString(content.Body)
	for regex, replacement := range formatter.waReplString {
		output = regex.ReplaceAllString(output, replacement)
	}
	for regex, replacer := range formatter.waReplFunc {
		output = regex.ReplaceAllStringFunc(output, replacer)
	}
	if output != content.Body {
		output = strings.Replace(output, "\n", "<br/>", -1)
		content.FormattedBody = output
		content.Format = event.FormatHTML
		for regex, replacer := range formatter.waReplFuncText {
			content.Body = regex.ReplaceAllStringFunc(content.Body, replacer)
		}
	}
}

func (formatter *Formatter) ParseMatrix(html string) string {
	return formatter.matrixHTMLParser.Parse(html)
}