// Copyright (c) 2024 Mattermost Community Enterprise
// Message Export Implementation

package message_export

import (
	"net/http"
	"time"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
	"github.com/mattermost/mattermost/server/v8/channels/store"
)

// MessageExportConfig holds configuration for the message export interface
type MessageExportConfig struct {
	Store  store.Store
	Config func() *model.Config
	Logger mlog.LoggerIFace
}

// MessageExportImpl implements the MessageExportInterface
type MessageExportImpl struct {
	store  store.Store
	config func() *model.Config
	logger mlog.LoggerIFace
}

// NewMessageExportInterface creates a new message export interface
func NewMessageExportInterface(cfg *MessageExportConfig) *MessageExportImpl {
	return &MessageExportImpl{
		store:  cfg.Store,
		config: cfg.Config,
		logger: cfg.Logger,
	}
}

// StartSynchronizeJob starts a new message export synchronization job
func (me *MessageExportImpl) StartSynchronizeJob(rctx request.CTX, exportFromTimestamp int64) (*model.Job, *model.AppError) {
	cfg := me.config()

	// Check if message export is enabled
	if cfg.MessageExportSettings.EnableExport == nil || !*cfg.MessageExportSettings.EnableExport {
		return nil, model.NewAppError("StartSynchronizeJob", "message_export.not_enabled", nil, "Message export is not enabled", http.StatusNotImplemented)
	}

	// Create job data
	jobData := map[string]string{
		"export_from_timestamp": time.Unix(0, exportFromTimestamp*int64(time.Millisecond)).Format(time.RFC3339),
	}

	// Add export format to job data
	if cfg.MessageExportSettings.ExportFormat != nil {
		jobData["export_format"] = *cfg.MessageExportSettings.ExportFormat
	} else {
		jobData["export_format"] = model.ComplianceExportTypeActiance
	}

	// Create the job
	job := &model.Job{
		Id:       model.NewId(),
		Type:     model.JobTypeMessageExport,
		Status:   model.JobStatusPending,
		Data:     jobData,
		CreateAt: model.GetMillis(),
	}

	// In a real implementation, we would save the job to the store
	// and let the job scheduler pick it up
	if me.store != nil {
		savedJob, err := me.store.Job().Save(job)
		if err != nil {
			return nil, model.NewAppError("StartSynchronizeJob", "message_export.save_job_failed", nil, err.Error(), http.StatusInternalServerError)
		}
		job = savedJob
	}

	me.logger.Info("Started message export synchronization job",
		mlog.String("job_id", job.Id),
		mlog.String("export_from_timestamp", jobData["export_from_timestamp"]),
		mlog.String("export_format", jobData["export_format"]),
	)

	return job, nil
}

// Export formats supported
const (
	ExportFormatActiance         = "actiance"
	ExportFormatGlobalrelay      = "globalrelay"
	ExportFormatGlobalrelayZip   = "globalrelay-zip"
	ExportFormatCSV              = "csv"
)

// MessageExportRecord represents an exported message
type MessageExportRecord struct {
	PostId          string
	TeamId          string
	TeamName        string
	TeamDisplayName string
	ChannelId       string
	ChannelName     string
	ChannelType     string
	UserId          string
	UserEmail       string
	Username        string
	PostCreateAt    int64
	PostMessage     string
	PostType        string
	PostFileIds     []string
}

// FormatMessage formats a message for export based on the export format
func (me *MessageExportImpl) FormatMessage(record *MessageExportRecord, format string) ([]byte, error) {
	switch format {
	case ExportFormatActiance:
		return me.formatActiance(record)
	case ExportFormatGlobalrelay, ExportFormatGlobalrelayZip:
		return me.formatGlobalrelay(record)
	case ExportFormatCSV:
		return me.formatCSV(record)
	default:
		return me.formatActiance(record)
	}
}

func (me *MessageExportImpl) formatActiance(record *MessageExportRecord) ([]byte, error) {
	// Actiance XML format
	xml := `<?xml version="1.0" encoding="UTF-8"?>
<Message>
  <MessageId>` + record.PostId + `</MessageId>
  <ConversationId>` + record.ChannelId + `</ConversationId>
  <SenderId>` + record.UserId + `</SenderId>
  <SenderEmail>` + record.UserEmail + `</SenderEmail>
  <DateTime>` + time.Unix(0, record.PostCreateAt*int64(time.Millisecond)).Format(time.RFC3339) + `</DateTime>
  <Body>` + escapeXML(record.PostMessage) + `</Body>
</Message>`
	return []byte(xml), nil
}

func (me *MessageExportImpl) formatGlobalrelay(record *MessageExportRecord) ([]byte, error) {
	// GlobalRelay EML format (simplified)
	eml := `From: ` + record.UserEmail + `
To: ` + record.ChannelName + `@mattermost.local
Date: ` + time.Unix(0, record.PostCreateAt*int64(time.Millisecond)).Format(time.RFC1123Z) + `
Subject: Message in ` + record.ChannelName + `
Message-ID: <` + record.PostId + `@mattermost.local>
Content-Type: text/plain; charset="UTF-8"

` + record.PostMessage
	return []byte(eml), nil
}

func (me *MessageExportImpl) formatCSV(record *MessageExportRecord) ([]byte, error) {
	// CSV row
	createTime := time.Unix(0, record.PostCreateAt*int64(time.Millisecond)).Format(time.RFC3339)
	csv := escapeCSV(record.PostId) + "," +
		escapeCSV(record.TeamName) + "," +
		escapeCSV(record.ChannelName) + "," +
		escapeCSV(record.Username) + "," +
		escapeCSV(record.UserEmail) + "," +
		escapeCSV(createTime) + "," +
		escapeCSV(record.PostMessage) + "\n"
	return []byte(csv), nil
}

func escapeXML(s string) string {
	result := ""
	for _, c := range s {
		switch c {
		case '<':
			result += "&lt;"
		case '>':
			result += "&gt;"
		case '&':
			result += "&amp;"
		case '"':
			result += "&quot;"
		case '\'':
			result += "&apos;"
		default:
			result += string(c)
		}
	}
	return result
}

func escapeCSV(s string) string {
	needsQuotes := false
	for _, c := range s {
		if c == '"' || c == ',' || c == '\n' || c == '\r' {
			needsQuotes = true
			break
		}
	}

	if !needsQuotes {
		return s
	}

	result := "\""
	for _, c := range s {
		if c == '"' {
			result += "\"\""
		} else {
			result += string(c)
		}
	}
	result += "\""
	return result
}