package main

import (
	"bytes"
	"context"
	"encoding/binary"
	"encoding/json"
	"example/minio-into-stck/util"
	"fmt"
	"log"
	"math"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/ClickHouse/clickhouse-go/v2"
	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"
	"github.com/fsnotify/fsnotify"
	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
	"github.com/minio/minio-go/v7/pkg/notification"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
	// "github.com/natefinch/lumberjack"
	// "github.com/sirupsen/logrus"
	"github.com/spf13/viper"
)

// AppInitConfig is the initial configuration of the application, loaded from the config file.
type AppInitConfig struct {
	Mysql struct {
		User     string `mapstructure:"user"`
		Password string `mapstructure:"password"`
		Host     string `mapstructure:"host"`
		Database string `mapstructure:"database"`
	} `mapstructure:"mysql"`
	Minio struct {
		AccessKey string `mapstructure:"accessKey"`
		Secret    string `mapstructure:"secret"`
		Bucket    string `mapstructure:"bucket"`
		Host      string `mapstructure:"host"`
	} `mapstructure:"minio"`
	Stck struct {
		Host  string `mapstructure:"host"`
		Table string `mapstructure:"table"`
	} `mapstructure:"stck"`
}

type AppConfig struct {
	// List of name regex patterns to exclude from import.
	ImportBlacklist []string
}

type AppConfigDbEntry struct {
	Key   string `gorm:"primaryKey"`
	Value string
}

// TODO: 插入时先创建行，插入完后更新插入耗时

// UploadRecord Represents a record of an uploaded stream. (A major upload task.)
type UploadRecord struct {
	Key       string `gorm:"primaryKey"`
	CreatedAt time.Time
}

// PartUploadRecord Represents a record of an uploaded part of a stream. (A minor upload task.)
type PartUploadRecord struct {
	StreamName string `gorm:"primaryKey"`
	PartName   string `gorm:"primaryKey"`
	CreatedAt  time.Time
}

type StreamMetadata struct {
	Name            string `json:"name"`
	TimestampOffset int64  `json:"timestamp_offset"`
	Interval        int64  `json:"interval"`
	PartsCount      int    `json:"parts_count"`
	PointsPerPart   int    `json:"points_per_part"`
	TotalPoints     int    `json:"total_points"`
}

var appInitCfg *AppInitConfig = &AppInitConfig{}

func initLoadConfig() {
	viper.SetConfigFile("./config/application.yaml")
	viper.WatchConfig()
	viper.OnConfigChange(func(e fsnotify.Event) {
		log.Println("Config file changed:", e.Name)
		var newAppInitConfig AppInitConfig
		err := viper.Unmarshal(&newAppInitConfig)
		if err != nil {
			log.Println("Failed to unmarshal config:", err)
		}
		appInitCfg = &newAppInitConfig
	})
	err := viper.ReadInConfig()
	if err != nil {
		log.Fatalf("Failed to read config file: %v", err)
	}
	err = viper.Unmarshal(appInitCfg)
	if err != nil {
		log.Printf("Failed to unmarshal config: %v\n", err)
	}
}

func main() {
	var err error

	log.Println("Starting application...")

	// Load configuration from file
	initLoadConfig()

	// Connect to MySQL
	dsn := fmt.Sprintf("%s:%s@tcp(%s)/%s?charset=utf8mb4&parseTime=True&loc=Local",
		appInitCfg.Mysql.User, appInitCfg.Mysql.Password, appInitCfg.Mysql.Host, appInitCfg.Mysql.Database)
	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
	if err != nil {
		log.Fatalf("Failed to connect to MySQL: %v", err)
	}
	// Disable logging
	db.Logger = logger.Discard
	// Get the underlying sql.DB object to close the connection later
	sqlDB, err := db.DB()
	if err != nil {
		log.Fatalf("Failed to get MySQL DB: %v", err)
	}
	defer sqlDB.Close()
	// Ping the database to check if the connection is successful
	err = sqlDB.Ping()
	if err != nil {
		log.Printf("ping db error: %v", err)
		return
	}
	log.Println("Database connection successful")
	// Perform auto migration
	err = db.AutoMigrate(&AppConfigDbEntry{}, &UploadRecord{}, &PartUploadRecord{})
	if err != nil {
		log.Printf("auto migrate error: %v", err)
		return
	}
	log.Println("Auto migration completed")

	// Connect to MinIO
	minioClient, err := minio.New(util.ExpandShellStringInfallible(appInitCfg.Minio.Host), &minio.Options{
		Creds:  credentials.NewStaticV4(appInitCfg.Minio.AccessKey, appInitCfg.Minio.Secret, ""),
		Secure: false,
	})
	if err == nil {
		bucketExists, err := minioClient.BucketExists(context.Background(), appInitCfg.Minio.Bucket)
		if err != nil {
			log.Fatalf("Failed to check if bucket %s exists: %v", appInitCfg.Minio.Bucket, err)
		}
		if !bucketExists {
			log.Fatalf("Bucket %s does not exist", appInitCfg.Minio.Bucket)
		}
	}
	if err != nil {
		log.Fatalf("Failed to connect to MinIO: %v", err)
	}
	log.Println("Connected to MinIO")

	// Connect to ClickHouse
	ckConn, err := clickhouse.Open(&clickhouse.Options{
		Addr: []string{appInitCfg.Stck.Host},
	})
	if err == nil {
		err = ckConn.Ping(context.Background())
	}
	if err != nil {
		log.Fatalf("Failed to connect to ClickHouse: %v", err)
	}
	log.Println("Connected to ClickHouse")

	// Start the main work
	log.Println("Starting main worker...")
	main_worker(AppCtx{db, minioClient, ckConn})
}

type AppCtx struct {
	db          *gorm.DB
	minioClient *minio.Client
	ckConn      driver.Conn
}

/** Design notes:
 * The main worker will first load the app config from the database. Then it will pull the
 * list of objects from MinIO to build a local mirrored list (which gets rebuilt on every startup).
 * A bucket notification will be registered to listen for new objects at the same time.
 * For each new (stream) object, the worker will check if it's in the blacklist or if it's already
 * uploaded. If not, it will start the upload process by putting parts of the stream into parts table.
 * When all parts are uploaded, the worker will mark the stream as uploaded (insert into uploads table).
 */

var gAppCfg *AppConfig

type PartUploadArgs struct {
	StreamInfo *StreamMetadata
	StreamName string
	PartName   string
}

func main_worker(app AppCtx) {
	ctx := context.Background()

	objUploadChan := make(chan string)
	partUploadChan := make(chan PartUploadArgs)

	// Load config from DB
	appCfg, err := load_app_cfg_from_db(app.db)
	if err != nil {
		log.Fatalf("Failed to load app config from DB: %v", err)
	}
	gAppCfg = &appCfg

	// Register bucket notification
	notifys := app.minioClient.ListenBucketNotification(
		ctx, appInitCfg.Minio.Bucket, "", "", []string{string(notification.ObjectCreatedAll)})

	// Start the notification listener
	go func() {
		for notifyInfo := range notifys {
			for _, record := range notifyInfo.Records {
				key := record.S3.Object.Key
				log.Println("New object notification:", key)
				// Only process root folders
				key = strings.Split(key, "/")[0]
				objUploadChan <- key
			}
		}
	}()

	// Start the full upload trigger
	go trigger_full_upload(app, objUploadChan)

	// Start the parts upload worker
	go upload_parts_worker(app, partUploadChan)

	// Start the main loop (streams upload worker)
	for objToUpload := range objUploadChan {
		log.Println("Checking stream object:", objToUpload)
		if object_is_blacklisted(objToUpload) {
			log.Printf("Object %s is blacklisted, skipping\n", objToUpload)
			continue
		}

		fullyUploaded, err := upload_one_stream(app, objToUpload, partUploadChan)
		if err != nil {
			// Queue the object for retry
			log.Printf("Failed to upload stream %s: `%v`, retrying\n", objToUpload, err)
			go func() {
				time.Sleep(5 * time.Second)
				objUploadChan <- objToUpload
			}()
			continue
		}

		if fullyUploaded {
			// Mark the stream as fully uploaded
			//err = app.db.Create(&UploadRecord{Key: objToUpload}).Error
			err = app.db.Where(UploadRecord{Key: objToUpload}).FirstOrCreate(&UploadRecord{}).Error
			if err != nil {
				log.Printf("Failed to mark stream %s as uploaded: %v\n", objToUpload, err)
			} else {
				// We can now remove the stream parts from the parts table
				err = app.db.Where("stream_name = ?", objToUpload).Delete(&PartUploadRecord{}).Error
				if err != nil {
					log.Printf("Failed to remove parts of stream %s from parts table: %v\n", objToUpload, err)
				}
			}
		} else {
			// Queue the object for retry
			log.Printf("Stream %s is not fully uploaded, retrying\n", objToUpload)
			go func() {
				time.Sleep(60 * time.Second)
				objUploadChan <- objToUpload
			}()
		}
	}
}

// Polls the parts table for not-yet-uploaded parts and uploads them.
func upload_parts_worker(app AppCtx, partUploadChan chan PartUploadArgs) {
	for partInfo := range partUploadChan {
		log.Printf("Uploading part %s of stream %s\n", partInfo.PartName, partInfo.StreamName)

		err := upload_one_part(app, partInfo.StreamInfo, partInfo.StreamName, partInfo.PartName)
		if err != nil {
			log.Printf("Failed to upload part %s of stream %s: %v\n", partInfo.PartName, partInfo.StreamName, err)
			// Queue the part for retry
			go func() {
				time.Sleep(5 * time.Second)
				partUploadChan <- partInfo
			}()
			continue
		}

		// Mark the part as uploaded
		//err = app.db.Create(&PartUploadRecord{StreamName: partInfo.StreamName, PartName: partInfo.PartName}).Error
		part := PartUploadRecord{StreamName: partInfo.StreamName, PartName: partInfo.PartName}
		err = app.db.Where(part).FirstOrCreate(&PartUploadRecord{}).Error
		if err != nil {
			log.Printf("Failed to mark part %s of stream %s as uploaded: %v\n", partInfo.PartName, partInfo.StreamName, err)
		}
	}
}

func trigger_full_upload(app AppCtx, objToUploadChan chan<- string) {
	// Upload all files in the directory
	options := minio.ListObjectsOptions{
		Recursive: false,
	}
	objectsCh := app.minioClient.ListObjects(context.Background(), appInitCfg.Minio.Bucket, options)
	for objInfo := range objectsCh {
		if objInfo.Err != nil {
			log.Printf("Error listing objects: %v\n", objInfo.Err)
			break
		}
		key := objInfo.Key
		if strings.HasSuffix(key, "/") {
			objToUploadChan <- strings.Split(key, "/")[0]
		}
	}
}

func upload_one_stream(app AppCtx, streamName string, partUploadChan chan PartUploadArgs) (fullyUploaded bool, err error) {
	if object_already_uploaded(app, streamName) {
		return true, nil
	}

	fullyUploaded = true

	// Get stream metadata
	streamInfo, err := get_stream_metadata(app, streamName)
	if err != nil {
		return false, err
	}
	if streamInfo.PartsCount == 0 {
		// Edge device didn't finish uploading the stream yet
		fullyUploaded = false
	}

	// Upload parts
	streamObjPath := streamName + "/"
	options := minio.ListObjectsOptions{
		Prefix:    streamObjPath,
		Recursive: false,
	}
	for objInfo := range app.minioClient.ListObjects(context.Background(), appInitCfg.Minio.Bucket, options) {
		if objInfo.Err != nil {
			return false, objInfo.Err
		}
		if strings.HasSuffix(objInfo.Key, "/") {
			continue
		}
		if objInfo.Key == streamObjPath+"metadata.json" {
			continue
		}

		if part_already_uploaded(app, streamName, objInfo.Key) {
			continue
		}
		fullyUploaded = false
		partUploadChan <- PartUploadArgs{StreamInfo: streamInfo, StreamName: streamName, PartName: objInfo.Key}
	}

	return fullyUploaded, nil
}

func upload_one_part(app AppCtx, streamInfo *StreamMetadata, streamName string, partName string) (err error) {
	if part_already_uploaded(app, streamName, partName) {
		return nil
	}

	dryRun := false
	if !dryRun {
		// Get the part data from MinIO
		obj, err := app.minioClient.GetObject(context.Background(), appInitCfg.Minio.Bucket, partName, minio.GetObjectOptions{})
		if err != nil {
			return fmt.Errorf("failed to get part data: %w", err)
		}
		defer obj.Close()

		// Read the part data
		var partDataBuf = new(bytes.Buffer)
		_, err = partDataBuf.ReadFrom(obj)
		if err != nil {
			return fmt.Errorf("failed to read part data: %w", err)
		}

		// Process the part data
		partData, err := util.DecompressZstdBuffer(partDataBuf.Bytes())
		if err != nil {
			return fmt.Errorf("failed to decompress part data: %w", err)
		}

		// Use regex to extract the part index from the part name
		partIndex := 0
		{
			re := regexp.MustCompile(`part_(\d+)\.zst`)
			matches := re.FindStringSubmatch(partName)
			if len(matches) != 2 {
				return fmt.Errorf("failed to extract part index from part name: %s", partName)
			}
			partIndex, err = strconv.Atoi(matches[1])
			if err != nil {
				return fmt.Errorf("failed to convert part index to integer: %w", err)
			}

			// Check if the part index is correct
			if partIndex < 0 || (streamInfo.PartsCount != 0 && partIndex >= streamInfo.PartsCount) {
				return fmt.Errorf("part index out of bounds: %d / %d", partIndex, streamInfo.PartsCount)
			}

			// Check if the part data size is correct
			if streamInfo.PartsCount != 0 {
				if partIndex < streamInfo.PartsCount-1 {
					if len(partData) != streamInfo.PointsPerPart*8 {
						return fmt.Errorf("part data size mismatch: %d", len(partData))
					}
				} else if partIndex == streamInfo.PartsCount-1 {
					if len(partData) != (streamInfo.TotalPoints%streamInfo.PointsPerPart)*8 {
						return fmt.Errorf("part data size mismatch: %d", len(partData))
					}
				} else {
					return fmt.Errorf("part index out of bounds: %d", partIndex)
				}
			}
		}
		partPointsCount := len(partData) / 8

		// Insert the part data into ClickHouse
		batch, err := app.ckConn.PrepareBatch(context.Background(), "INSERT INTO "+appInitCfg.Stck.Table)
		if err != nil {
			return fmt.Errorf("failed to insert part data into ClickHouse: %w", err)
		}
		/*
			┌─name────────┬─type────────────────────────────────────────────────┬─default_type─┬─default_expression─┬─comment───────────────────┬─codec_expression─┬─ttl_expression─┐
			│ metric_name │ LowCardinality(String)                              │              │                    │ Metric name               │                  │                │
			│ point_name  │ LowCardinality(String)                              │              │                    │ Point name                │                  │                │
			│ tags        │ Map(LowCardinality(String), LowCardinality(String)) │              │                    │ Point tags                │                  │                │
			│ value       │ Float64                                             │              │                    │ Point value               │                  │                │
			│ nanoseconds │ Int64                                               │              │                    │ Point time in nanoseconds │ DoubleDelta, LZ4 │                │
			└─────────────┴─────────────────────────────────────────────────────┴──────────────┴────────────────────┴───────────────────────────┴──────────────────┴────────────────┘
		*/
		for i := 0; i < partPointsCount; i++ {
			metricName := ""
			pointName := streamInfo.Name
			tags := map[string]string{}
			value := math.Float64frombits(binary.LittleEndian.Uint64(partData[i*8 : (i+1)*8]))
			// NOTE: TimestampOffset is in milliseconds, need to convert to nanoseconds
			nanoseconds := streamInfo.TimestampOffset * 1e6
			nanoseconds += int64(partIndex) * int64(streamInfo.PointsPerPart) * streamInfo.Interval
			nanoseconds += int64(i) * streamInfo.Interval
			err := batch.Append(metricName, pointName, tags, value, nanoseconds)
			if err != nil {
				return err
			}
		}
		err = batch.Send()
		if err != nil {
			return err
		}
	}

	return nil
}

func load_app_cfg_from_db(db *gorm.DB) (AppConfig, error) {
	var cfg AppConfig

	err := db.AutoMigrate(&AppConfigDbEntry{})
	if err != nil {
		return cfg, err
	}
	//db.Create(&AppConfigDbEntry{Key: "ImportBlacklist", Value: `[]`})

	var dbEntry AppConfigDbEntry
	result := db.Where(AppConfigDbEntry{Key: "ImportBlacklist"}).Attrs(AppConfigDbEntry{Value: `[]`}).FirstOrCreate(&dbEntry)
	if result.Error != nil {
		//if errors.Is(result.Error, gorm.ErrRecordNotFound) {
		//	dbEntry.Value = `[]`
		//} else {
		//	return cfg, result.Error
		//}
		return cfg, result.Error
	}
	err = json.Unmarshal([]byte(dbEntry.Value), &cfg.ImportBlacklist)
	if err != nil {
		return cfg, err
	}
	return cfg, nil
}

func object_already_uploaded(app AppCtx, key string) bool {
	var record UploadRecord
	result := app.db.First(&record, "key", key)
	return result.Error == nil
}

func object_is_blacklisted(key string) bool {
	for _, regexPattern := range gAppCfg.ImportBlacklist {
		// TODO: Cache compiled regex patterns
		if matched, _ := regexp.MatchString(regexPattern, key); matched {
			return true
		}
	}
	return false
}

func part_already_uploaded(app AppCtx, streamName string, partName string) bool {
	var record PartUploadRecord
	result := app.db.First(&record, "stream_name = ? AND part_name = ?", streamName, partName)
	return result.Error == nil
}

func get_stream_metadata(app AppCtx, streamName string) (*StreamMetadata, error) {
	// Get the stream metadata from MinIO
	metadataObjPath := streamName + "/metadata.json"
	obj, err := app.minioClient.GetObject(context.Background(), appInitCfg.Minio.Bucket,
		metadataObjPath, minio.GetObjectOptions{})
	if err != nil {
		return nil, fmt.Errorf("failed to get stream metadata: %w", err)
	}
	defer obj.Close()

	var streamInfo StreamMetadata
	err = json.NewDecoder(obj).Decode(&streamInfo)
	if err != nil {
		return nil, fmt.Errorf("failed to decode stream metadata: %w", err)
	}

	return &streamInfo, nil
}