package tsdb

import (
	"container/list"
	"context"
	"database/sql"
	"fmt"
	"math"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/grafana/grafana/pkg/log"

	"github.com/grafana/grafana/pkg/components/null"

	"github.com/go-xorm/core"
	"github.com/go-xorm/xorm"
	"github.com/grafana/grafana/pkg/components/simplejson"
	"github.com/grafana/grafana/pkg/models"
)

// SqlMacroEngine interpolates macros into sql. It takes in the Query to have access to query context and
// timeRange to be able to generate queries that use from and to.
type SqlMacroEngine interface {
	Interpolate(query *Query, timeRange *TimeRange, sql string) (string, error)
}

// SqlTableRowTransformer transforms a query result row to RowValues with proper types.
type SqlTableRowTransformer interface {
	Transform(columnTypes []*sql.ColumnType, rows *core.Rows) (RowValues, error)
}

type engineCacheType struct {
	cache    map[int64]*xorm.Engine
	versions map[int64]int
	sync.Mutex
}

var engineCache = engineCacheType{
	cache:    make(map[int64]*xorm.Engine),
	versions: make(map[int64]int),
}

var NewXormEngine = func(driverName string, connectionString string) (*xorm.Engine, error) {
	return xorm.NewEngine(driverName, connectionString)
}

type sqlQueryEndpoint struct {
	macroEngine       SqlMacroEngine
	rowTransformer    SqlTableRowTransformer
	engine            *xorm.Engine
	timeColumnNames   []string
	metricColumnTypes []string
	log               log.Logger
}

type SqlQueryEndpointConfiguration struct {
	DriverName        string
	Datasource        *models.DataSource
	ConnectionString  string
	TimeColumnNames   []string
	MetricColumnTypes []string
}

var NewSqlQueryEndpoint = func(config *SqlQueryEndpointConfiguration, rowTransformer SqlTableRowTransformer, macroEngine SqlMacroEngine, log log.Logger) (TsdbQueryEndpoint, error) {
	queryEndpoint := sqlQueryEndpoint{
		rowTransformer:  rowTransformer,
		macroEngine:     macroEngine,
		timeColumnNames: []string{"time"},
		log:             log,
	}

	if len(config.TimeColumnNames) > 0 {
		queryEndpoint.timeColumnNames = config.TimeColumnNames
	}

	if len(config.MetricColumnTypes) > 0 {
		queryEndpoint.metricColumnTypes = config.MetricColumnTypes
	}

	engineCache.Lock()
	defer engineCache.Unlock()

	if engine, present := engineCache.cache[config.Datasource.Id]; present {
		if version := engineCache.versions[config.Datasource.Id]; version == config.Datasource.Version {
			queryEndpoint.engine = engine
			return &queryEndpoint, nil
		}
	}

	engine, err := NewXormEngine(config.DriverName, config.ConnectionString)
	if err != nil {
		return nil, err
	}

	engine.SetMaxOpenConns(10)
	engine.SetMaxIdleConns(10)

	engineCache.versions[config.Datasource.Id] = config.Datasource.Version
	engineCache.cache[config.Datasource.Id] = engine
	queryEndpoint.engine = engine

	return &queryEndpoint, nil
}

const rowLimit = 1000000

// Query is the main function for the SqlQueryEndpoint
func (e *sqlQueryEndpoint) Query(ctx context.Context, dsInfo *models.DataSource, tsdbQuery *TsdbQuery) (*Response, error) {
	result := &Response{
		Results: make(map[string]*QueryResult),
	}

	session := e.engine.NewSession()
	defer session.Close()
	db := session.DB()

	for _, query := range tsdbQuery.Queries {
		rawSQL := query.Model.Get("rawSql").MustString()
		if rawSQL == "" {
			continue
		}

		queryResult := &QueryResult{Meta: simplejson.New(), RefId: query.RefId}
		result.Results[query.RefId] = queryResult

		rawSQL, err := e.macroEngine.Interpolate(query, tsdbQuery.TimeRange, rawSQL)
		if err != nil {
			queryResult.Error = err
			continue
		}

		queryResult.Meta.Set("sql", rawSQL)

		rows, err := db.Query(rawSQL)
		if err != nil {
			queryResult.Error = err
			continue
		}

		defer rows.Close()

		format := query.Model.Get("format").MustString("time_series")

		switch format {
		case "time_series":
			err := e.transformToTimeSeries(query, rows, queryResult, tsdbQuery)
			if err != nil {
				queryResult.Error = err
				continue
			}
		case "table":
			err := e.transformToTable(query, rows, queryResult, tsdbQuery)
			if err != nil {
				queryResult.Error = err
				continue
			}
		}
	}

	return result, nil
}

func (e *sqlQueryEndpoint) transformToTable(query *Query, rows *core.Rows, result *QueryResult, tsdbQuery *TsdbQuery) error {
	columnNames, err := rows.Columns()
	columnCount := len(columnNames)

	if err != nil {
		return err
	}

	rowCount := 0
	timeIndex := -1

	table := &Table{
		Columns: make([]TableColumn, columnCount),
		Rows:    make([]RowValues, 0),
	}

	for i, name := range columnNames {
		table.Columns[i].Text = name

		for _, tc := range e.timeColumnNames {
			if name == tc {
				timeIndex = i
				break
			}
		}
	}

	columnTypes, err := rows.ColumnTypes()
	if err != nil {
		return err
	}

	for ; rows.Next(); rowCount++ {
		if rowCount > rowLimit {
			return fmt.Errorf("query row limit exceeded, limit %d", rowLimit)
		}

		values, err := e.rowTransformer.Transform(columnTypes, rows)
		if err != nil {
			return err
		}

		// converts column named time to unix timestamp in milliseconds
		// to make native mssql datetime types and epoch dates work in
		// annotation and table queries.
		ConvertSqlTimeColumnToEpochMs(values, timeIndex)
		table.Rows = append(table.Rows, values)
	}

	result.Tables = append(result.Tables, table)
	result.Meta.Set("rowCount", rowCount)
	return nil
}

func (e *sqlQueryEndpoint) transformToTimeSeries(query *Query, rows *core.Rows, result *QueryResult, tsdbQuery *TsdbQuery) error {
	pointsBySeries := make(map[string]*TimeSeries)
	seriesByQueryOrder := list.New()

	columnNames, err := rows.Columns()
	if err != nil {
		return err
	}

	columnTypes, err := rows.ColumnTypes()
	if err != nil {
		return err
	}

	rowCount := 0
	timeIndex := -1
	metricIndex := -1
	metricPrefix := false
	var metricPrefixValue string

	// check columns of resultset: a column named time is mandatory
	// the first text column is treated as metric name unless a column named metric is present
	for i, col := range columnNames {
		for _, tc := range e.timeColumnNames {
			if col == tc {
				timeIndex = i
				continue
			}
		}
		switch col {
		case "metric":
			metricIndex = i
		default:
			if metricIndex == -1 {
				columnType := columnTypes[i].DatabaseTypeName()

				for _, mct := range e.metricColumnTypes {
					if columnType == mct {
						metricIndex = i
						continue
					}
				}
			}
		}
	}

	// use metric column as prefix with multiple value columns
	if metricIndex != -1 && len(columnNames) > 3 {
		metricPrefix = true
	}

	if timeIndex == -1 {
		return fmt.Errorf("Found no column named %s", strings.Join(e.timeColumnNames, " or "))
	}

	fillMissing := query.Model.Get("fill").MustBool(false)
	var fillInterval float64
	fillValue := null.Float{}
	fillPrevious := false

	if fillMissing {
		fillInterval = query.Model.Get("fillInterval").MustFloat64() * 1000
		switch query.Model.Get("fillMode").MustString() {
		case "null":
		case "previous":
			fillPrevious = true
		case "value":
			fillValue.Float64 = query.Model.Get("fillValue").MustFloat64()
			fillValue.Valid = true
		}
	}

	for rows.Next() {
		var timestamp float64
		var value null.Float
		var metric string

		if rowCount > rowLimit {
			return fmt.Errorf("query row limit exceeded, limit %d", rowLimit)
		}

		values, err := e.rowTransformer.Transform(columnTypes, rows)
		if err != nil {
			return err
		}

		// converts column named time to unix timestamp in milliseconds to make
		// native mysql datetime types and epoch dates work in
		// annotation and table queries.
		ConvertSqlTimeColumnToEpochMs(values, timeIndex)

		switch columnValue := values[timeIndex].(type) {
		case int64:
			timestamp = float64(columnValue)
		case float64:
			timestamp = columnValue
		default:
			return fmt.Errorf("Invalid type for column time, must be of type timestamp or unix timestamp, got: %T %v", columnValue, columnValue)
		}

		if metricIndex >= 0 {
			if columnValue, ok := values[metricIndex].(string); ok {
				if metricPrefix {
					metricPrefixValue = columnValue
				} else {
					metric = columnValue
				}
			} else {
				return fmt.Errorf("Column metric must be of type %s. metric column name: %s type: %s but datatype is %T", strings.Join(e.metricColumnTypes, ", "), columnNames[metricIndex], columnTypes[metricIndex].DatabaseTypeName(), values[metricIndex])
			}
		}

		for i, col := range columnNames {
			if i == timeIndex || i == metricIndex {
				continue
			}

			if value, err = ConvertSqlValueColumnToFloat(col, values[i]); err != nil {
				return err
			}

			if metricIndex == -1 {
				metric = col
			} else if metricPrefix {
				metric = metricPrefixValue + " " + col
			}

			series, exist := pointsBySeries[metric]
			if !exist {
				series = &TimeSeries{Name: metric}
				pointsBySeries[metric] = series
				seriesByQueryOrder.PushBack(metric)
			}

			if fillMissing {
				var intervalStart float64
				if !exist {
					intervalStart = float64(tsdbQuery.TimeRange.MustGetFrom().UnixNano() / 1e6)
				} else {
					intervalStart = series.Points[len(series.Points)-1][1].Float64 + fillInterval
				}

				if fillPrevious {
					if len(series.Points) > 0 {
						fillValue = series.Points[len(series.Points)-1][0]
					} else {
						fillValue.Valid = false
					}
				}

				// align interval start
				intervalStart = math.Floor(intervalStart/fillInterval) * fillInterval

				for i := intervalStart; i < timestamp; i += fillInterval {
					series.Points = append(series.Points, TimePoint{fillValue, null.FloatFrom(i)})
					rowCount++
				}
			}

			series.Points = append(series.Points, TimePoint{value, null.FloatFrom(timestamp)})

			e.log.Debug("Rows", "metric", metric, "time", timestamp, "value", value)
		}
	}

	for elem := seriesByQueryOrder.Front(); elem != nil; elem = elem.Next() {
		key := elem.Value.(string)
		result.Series = append(result.Series, pointsBySeries[key])

		if fillMissing {
			series := pointsBySeries[key]
			// fill in values from last fetched value till interval end
			intervalStart := series.Points[len(series.Points)-1][1].Float64
			intervalEnd := float64(tsdbQuery.TimeRange.MustGetTo().UnixNano() / 1e6)

			if fillPrevious {
				if len(series.Points) > 0 {
					fillValue = series.Points[len(series.Points)-1][0]
				} else {
					fillValue.Valid = false
				}
			}

			// align interval start
			intervalStart = math.Floor(intervalStart/fillInterval) * fillInterval
			for i := intervalStart + fillInterval; i < intervalEnd; i += fillInterval {
				series.Points = append(series.Points, TimePoint{fillValue, null.FloatFrom(i)})
				rowCount++
			}
		}
	}

	result.Meta.Set("rowCount", rowCount)
	return nil
}

// ConvertSqlTimeColumnToEpochMs converts column named time to unix timestamp in milliseconds
// to make native datetime types and epoch dates work in annotation and table queries.
func ConvertSqlTimeColumnToEpochMs(values RowValues, timeIndex int) {
	if timeIndex >= 0 {
		switch value := values[timeIndex].(type) {
		case time.Time:
			values[timeIndex] = float64(value.UnixNano()) / float64(time.Millisecond)
		case *time.Time:
			if value != nil {
				values[timeIndex] = float64((*value).UnixNano()) / float64(time.Millisecond)
			}
		case int64:
			values[timeIndex] = int64(EpochPrecisionToMs(float64(value)))
		case *int64:
			if value != nil {
				values[timeIndex] = int64(EpochPrecisionToMs(float64(*value)))
			}
		case uint64:
			values[timeIndex] = int64(EpochPrecisionToMs(float64(value)))
		case *uint64:
			if value != nil {
				values[timeIndex] = int64(EpochPrecisionToMs(float64(*value)))
			}
		case int32:
			values[timeIndex] = int64(EpochPrecisionToMs(float64(value)))
		case *int32:
			if value != nil {
				values[timeIndex] = int64(EpochPrecisionToMs(float64(*value)))
			}
		case uint32:
			values[timeIndex] = int64(EpochPrecisionToMs(float64(value)))
		case *uint32:
			if value != nil {
				values[timeIndex] = int64(EpochPrecisionToMs(float64(*value)))
			}
		case float64:
			values[timeIndex] = EpochPrecisionToMs(value)
		case *float64:
			if value != nil {
				values[timeIndex] = EpochPrecisionToMs(*value)
			}
		case float32:
			values[timeIndex] = EpochPrecisionToMs(float64(value))
		case *float32:
			if value != nil {
				values[timeIndex] = EpochPrecisionToMs(float64(*value))
			}
		}
	}
}

// ConvertSqlValueColumnToFloat converts timeseries value column to float.
func ConvertSqlValueColumnToFloat(columnName string, columnValue interface{}) (null.Float, error) {
	var value null.Float

	switch typedValue := columnValue.(type) {
	case int:
		value = null.FloatFrom(float64(typedValue))
	case *int:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case int64:
		value = null.FloatFrom(float64(typedValue))
	case *int64:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case int32:
		value = null.FloatFrom(float64(typedValue))
	case *int32:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case int16:
		value = null.FloatFrom(float64(typedValue))
	case *int16:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case int8:
		value = null.FloatFrom(float64(typedValue))
	case *int8:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case uint:
		value = null.FloatFrom(float64(typedValue))
	case *uint:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case uint64:
		value = null.FloatFrom(float64(typedValue))
	case *uint64:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case uint32:
		value = null.FloatFrom(float64(typedValue))
	case *uint32:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case uint16:
		value = null.FloatFrom(float64(typedValue))
	case *uint16:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case uint8:
		value = null.FloatFrom(float64(typedValue))
	case *uint8:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case float64:
		value = null.FloatFrom(typedValue)
	case *float64:
		value = null.FloatFromPtr(typedValue)
	case float32:
		value = null.FloatFrom(float64(typedValue))
	case *float32:
		if typedValue == nil {
			value.Valid = false
		} else {
			value = null.FloatFrom(float64(*typedValue))
		}
	case nil:
		value.Valid = false
	default:
		return null.NewFloat(0, false), fmt.Errorf("Value column must have numeric datatype, column: %s type: %T value: %v", columnName, typedValue, typedValue)
	}

	return value, nil
}

func SetupFillmode(query *Query, interval time.Duration, fillmode string) error {
	query.Model.Set("fill", true)
	query.Model.Set("fillInterval", interval.Seconds())
	switch fillmode {
	case "NULL":
		query.Model.Set("fillMode", "null")
	case "previous":
		query.Model.Set("fillMode", "previous")
	default:
		query.Model.Set("fillMode", "value")
		floatVal, err := strconv.ParseFloat(fillmode, 64)
		if err != nil {
			return fmt.Errorf("error parsing fill value %v", fillmode)
		}
		query.Model.Set("fillValue", floatVal)
	}

	return nil
}