package db

import (
	"context"
	"errors"
	"fmt"
	"os"
	"strings"
	"sync"
	"th7/data/config"
	"th7/data/core"
	"th7/data/thermocouple"
	"time"

	"github.com/InfluxCommunity/influxdb3-go/influxdb3"
)

var (
	ErrNoToken  = errors.New("InfluxDB requires a secret token field")
	ErrNoBucket = errors.New("InfluxDB requires a bucket field (database name)")
	ErrNoHost   = errors.New("InfluxDB requires a host field (http://example-influxdb-host.com)")
)

const (
	INFLUXDB_MAX_INIT_DUR = 5000 * time.Millisecond
	INFLUXDB_MAX_SAVE_DUR = 2000 * time.Millisecond
)

type InfluxDBAdapter struct {
	mu     sync.Mutex
	client *influxdb3.Client
	cfg    config.Config
}

func NewInfluxDBAdapter(config config.Config) (*InfluxDBAdapter, error) {
	var adapter InfluxDBAdapter
	var err error

	// if `token' is not present in the DB map, check env
	if _, ok := config.DB["token"]; !ok {
		if token := os.Getenv("INFLUXDB_TOKEN"); len(token) > 0 {
			config.DB["token"] = token
		} else {
			return &adapter, ErrNoToken
		}
	}

	// if `bucket' is not present in the DB map, check env
	if _, ok := config.DB["bucket"]; !ok {
		if bucket := os.Getenv("INFLUXDB_BUCKET"); len(bucket) > 0 {
			config.DB["bucket"] = bucket
		} else {
			return &adapter, ErrNoBucket
		}
	}

	// if `host' is not present in the DB map, check env
	if _, ok := config.DB["host"]; !ok {
		if host := os.Getenv("INFLUXDB_HOST"); len(host) > 0 {
			config.DB["host"] = host
		} else {
			return &adapter, ErrNoHost
		}
	}

	adapter.cfg = config

	adapter.client, err = influxdb3.New(influxdb3.ClientConfig{
		Host:     config.DB["host"].(string),
		Token:    config.DB["token"].(string),
		Database: config.DB["bucket"].(string),
	})

	if err != nil {
		return &adapter, err
	}

	initContext, cancel := context.WithTimeout(context.Background(), INFLUXDB_MAX_INIT_DUR)
	defer cancel()

	// Test database connection/auth
	query := `
		SELECT 1;
		`
	_, err = adapter.client.Query(initContext, query)
	if err != nil {
		fmt.Println("Error initialising InfluxDB. Check details/network connection.")
		return &adapter, err
	}

	return &adapter, nil
}

func (ad *InfluxDBAdapter) Close() {
	ad.client.Close()
}

func (ad *InfluxDBAdapter) Save(channels []core.Channel) error {
	ad.mu.Lock()
	defer ad.mu.Unlock()

	var sb strings.Builder
	var err error
	logged := 0

	// influx does timestamping when data arrives to server
	for c := range channels {

		if !ad.cfg.Channels[c].Log {
			continue
		}

		id := channels[c].Id
		value := channels[c].Value
		gain := ad.cfg.Channels[c].Gain
		offset := ad.cfg.Channels[c].Offset
		thermo := thermocouple.ThermoStringLookup[ad.cfg.Channels[c].Thermo]

		sb.WriteString(fmt.Sprintf("TH7,channel=%d,thermocouple=%s gain=%g,offset=%g,value=%g\n",
			id, thermo, gain, offset, value))

		logged++
	}

	// need at least 1 iteration to bother sending data to influx server
	if logged == 0 {
		fmt.Printf("[%s] InfluxDB: nothing to do.\n", time.Now().Format(time.DateTime))
		return nil
	}

	saveContext, cancel := context.WithTimeout(context.Background(), INFLUXDB_MAX_SAVE_DUR)
	defer cancel()

	err = ad.client.Write(saveContext, []byte(sb.String()))
	if err != nil {
		return err
	}

	fmt.Printf("[%s] InfluxDB: logged %d channels OK\n", time.Now().Format(time.DateTime), logged)

	return nil
}