// Copyright (c) 2024 Mattermost Community Enterprise
// Open source implementation of Mattermost Enterprise Compliance

package compliance

import (
	"archive/zip"
	"encoding/csv"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"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"
	"github.com/mattermost/mattermost/server/v8/einterfaces"
)

const (
	ExportBatchSize = 10000
)

type ComplianceImpl struct {
	store     store.Store
	config    func() *model.Config
	logger    mlog.LoggerIFace
	stopChan  chan struct{}
	isRunning bool
}

type ComplianceConfig struct {
	Store  store.Store
	Config func() *model.Config
	Logger mlog.LoggerIFace
}

func NewComplianceInterface(cfg *ComplianceConfig) einterfaces.ComplianceInterface {
	return &ComplianceImpl{
		store:    cfg.Store,
		config:   cfg.Config,
		logger:   cfg.Logger,
		stopChan: make(chan struct{}),
	}
}

// StartComplianceDailyJob starts the daily compliance job
func (c *ComplianceImpl) StartComplianceDailyJob() {
	if c.isRunning {
		return
	}

	c.isRunning = true
	c.logger.Info("Starting compliance daily job scheduler")

	go func() {
		ticker := time.NewTicker(24 * time.Hour)
		defer ticker.Stop()

		// Run once at startup if enabled
		c.runDailyExport()

		for {
			select {
			case <-c.stopChan:
				c.logger.Info("Stopping compliance daily job scheduler")
				return
			case <-ticker.C:
				c.runDailyExport()
			}
		}
	}()
}

func (c *ComplianceImpl) runDailyExport() {
	config := c.config()
	if !*config.ComplianceSettings.Enable || !*config.ComplianceSettings.EnableDaily {
		return
	}

	c.logger.Info("Running daily compliance export")

	now := time.Now()
	startOfYesterday := time.Date(now.Year(), now.Month(), now.Day()-1, 0, 0, 0, 0, now.Location())
	endOfYesterday := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())

	job := &model.Compliance{
		Desc:    "Daily Export",
		Type:    model.ComplianceTypeDaily,
		StartAt: startOfYesterday.UnixMilli(),
		EndAt:   endOfYesterday.UnixMilli(),
	}
	job.PreSave()

	// Save the job
	savedJob, err := c.store.Compliance().Save(job)
	if err != nil {
		c.logger.Error("Failed to save daily compliance job", mlog.Err(err))
		return
	}

	// Run the export
	rctx := request.EmptyContext(c.logger)
	if appErr := c.RunComplianceJob(rctx, savedJob); appErr != nil {
		c.logger.Error("Failed to run daily compliance job", mlog.Err(appErr))
	}
}

// RunComplianceJob runs a compliance export job
func (c *ComplianceImpl) RunComplianceJob(rctx request.CTX, job *model.Compliance) *model.AppError {
	config := c.config()

	// Update job status to running
	job.Status = model.ComplianceStatusRunning
	if _, err := c.store.Compliance().Update(job); err != nil {
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.update.app_error", nil, "", 500).Wrap(err)
	}

	rctx.Logger().Info("Starting compliance export job",
		mlog.String("job_id", job.Id),
		mlog.String("job_type", job.Type),
	)

	// Ensure compliance directory exists
	complianceDir := *config.ComplianceSettings.Directory
	if complianceDir == "" {
		complianceDir = "./data/"
	}
	complianceDir = filepath.Join(complianceDir, "compliance")

	if err := os.MkdirAll(complianceDir, 0750); err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.mkdir.app_error", nil, "", 500).Wrap(err)
	}

	// Create the zip file
	zipFilePath := filepath.Join(complianceDir, job.JobName()+".zip")
	zipFile, err := os.Create(zipFilePath)
	if err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.create_zip.app_error", nil, "", 500).Wrap(err)
	}
	defer zipFile.Close()

	zipWriter := zip.NewWriter(zipFile)
	defer zipWriter.Close()

	// Create CSV file inside zip
	csvWriter, err := zipWriter.Create("posts.csv")
	if err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.create_csv.app_error", nil, "", 500).Wrap(err)
	}

	writer := csv.NewWriter(csvWriter)

	// Write header
	if err := writer.Write(model.CompliancePostHeader()); err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.write_header.app_error", nil, "", 500).Wrap(err)
	}

	// Export posts in batches
	cursor := model.ComplianceExportCursor{}
	totalCount := 0

	for {
		posts, newCursor, err := c.store.Compliance().ComplianceExport(job, cursor, ExportBatchSize)
		if err != nil {
			c.updateJobStatus(job, model.ComplianceStatusFailed)
			return model.NewAppError("RunComplianceJob", "ent.compliance.run.export.app_error", nil, "", 500).Wrap(err)
		}

		for _, post := range posts {
			if err := writer.Write(post.Row()); err != nil {
				c.updateJobStatus(job, model.ComplianceStatusFailed)
				return model.NewAppError("RunComplianceJob", "ent.compliance.run.write_row.app_error", nil, "", 500).Wrap(err)
			}
			totalCount++
		}

		cursor = newCursor

		// Check if we're done
		if cursor.ChannelsQueryCompleted && cursor.DirectMessagesQueryCompleted {
			break
		}

		// Check if we got fewer posts than requested (means we're done)
		if len(posts) < ExportBatchSize {
			break
		}
	}

	writer.Flush()
	if err := writer.Error(); err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.flush.app_error", nil, "", 500).Wrap(err)
	}

	// Create metadata file
	metaWriter, err := zipWriter.Create("metadata.txt")
	if err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.create_meta.app_error", nil, "", 500).Wrap(err)
	}

	metadata := c.generateMetadata(job, totalCount)
	if _, err := metaWriter.Write([]byte(metadata)); err != nil {
		c.updateJobStatus(job, model.ComplianceStatusFailed)
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.write_meta.app_error", nil, "", 500).Wrap(err)
	}

	// Update job status to finished
	job.Status = model.ComplianceStatusFinished
	job.Count = totalCount
	if _, err := c.store.Compliance().Update(job); err != nil {
		return model.NewAppError("RunComplianceJob", "ent.compliance.run.update_final.app_error", nil, "", 500).Wrap(err)
	}

	rctx.Logger().Info("Compliance export job completed",
		mlog.String("job_id", job.Id),
		mlog.Int("count", totalCount),
	)

	return nil
}

func (c *ComplianceImpl) updateJobStatus(job *model.Compliance, status string) {
	job.Status = status
	if _, err := c.store.Compliance().Update(job); err != nil {
		c.logger.Error("Failed to update compliance job status",
			mlog.String("job_id", job.Id),
			mlog.String("status", status),
			mlog.Err(err),
		)
	}
}

func (c *ComplianceImpl) generateMetadata(job *model.Compliance, count int) string {
	var sb strings.Builder

	sb.WriteString("Mattermost Compliance Export\n")
	sb.WriteString("============================\n\n")
	sb.WriteString(fmt.Sprintf("Job ID: %s\n", job.Id))
	sb.WriteString(fmt.Sprintf("Job Type: %s\n", job.Type))
	sb.WriteString(fmt.Sprintf("Description: %s\n", job.Desc))
	sb.WriteString(fmt.Sprintf("Created At: %s\n", time.UnixMilli(job.CreateAt).Format(time.RFC3339)))
	sb.WriteString(fmt.Sprintf("Start Time: %s\n", time.UnixMilli(job.StartAt).Format(time.RFC3339)))
	sb.WriteString(fmt.Sprintf("End Time: %s\n", time.UnixMilli(job.EndAt).Format(time.RFC3339)))
	sb.WriteString(fmt.Sprintf("Total Posts: %d\n", count))

	if job.Keywords != "" {
		sb.WriteString(fmt.Sprintf("Keywords Filter: %s\n", job.Keywords))
	}
	if job.Emails != "" {
		sb.WriteString(fmt.Sprintf("Emails Filter: %s\n", job.Emails))
	}

	sb.WriteString(fmt.Sprintf("\nGenerated At: %s\n", time.Now().Format(time.RFC3339)))
	sb.WriteString("Generated By: Mattermost Community Enterprise\n")

	return sb.String()
}

// Stop stops the compliance service
func (c *ComplianceImpl) Stop() {
	if c.isRunning {
		close(c.stopChan)
		c.isRunning = false
	}
}