package querier

import (
	"fmt"
	"math"
	"reflect"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"
	qbtypes "github.com/SigNoz/signoz/pkg/types/querybuildertypes/querybuildertypesv5"
	"github.com/SigNoz/signoz/pkg/types/telemetrytypes"
)

var (
	aggRe = regexp.MustCompile(`^__result_(\d+)$`)
)

// consume reads every row and shapes it into the payload expected for the
// given request type.
//
// * Time-series - []*qbtypes.TimeSeriesData
// * Scalar      - []*qbtypes.ScalarData
// * Raw         - []*qbtypes.RawData
// * Distribution- []*qbtypes.DistributionData
func consume(rows driver.Rows, kind qbtypes.RequestType) (any, error) {
	var (
		payload any
		err     error
	)

	switch kind {
	case qbtypes.RequestTypeTimeSeries:
		payload, err = readAsTimeSeries(rows)
	case qbtypes.RequestTypeScalar:
		payload, err = readAsScalar(rows)
	case qbtypes.RequestTypeRaw:
		payload, err = readAsRaw(rows)
		// TODO: add support for other request types
	}

	return payload, err
}

func readAsTimeSeries(rows driver.Rows) ([]*qbtypes.TimeSeriesData, error) {

	colTypes := rows.ColumnTypes()
	colNames := rows.Columns()

	slots := make([]any, len(colTypes))
	numericColsCount := 0
	for i, ct := range colTypes {
		slots[i] = reflect.New(ct.ScanType()).Interface()
		if numericKind(ct.ScanType().Kind()) {
			numericColsCount++
		}
	}

	type sKey struct {
		agg int
		key string // deterministic join of label values
	}
	seriesMap := map[sKey]*qbtypes.TimeSeries{}

	for rows.Next() {
		if err := rows.Scan(slots...); err != nil {
			return nil, err
		}

		var (
			ts            int64
			lblVals       []string
			lblObjs       []*qbtypes.Label
			aggValues     = map[int]float64{} // all __result_N in this row
			fallbackValue float64             // value when NO __result_N columns exist
			fallbackSeen  bool
		)

		for idx, ptr := range slots {
			name := colNames[idx]

			switch v := ptr.(type) {
			case *time.Time:
				ts = v.UnixMilli()

			case *float64, *float32, *int64, *int32, *uint64, *uint32:
				val := numericAsFloat(reflect.ValueOf(ptr).Elem().Interface())
				if m := aggRe.FindStringSubmatch(name); m != nil {
					id, _ := strconv.Atoi(m[1])
					aggValues[id] = val
				} else if numericColsCount == 1 { // classic single-value query
					fallbackValue = val
					fallbackSeen = true
				} else {
					// numeric label
					lblVals = append(lblVals, fmt.Sprint(val))
					lblObjs = append(lblObjs, &qbtypes.Label{
						Key:   telemetrytypes.TelemetryFieldKey{Name: name},
						Value: val,
					})
				}

			case **float64, **float32, **int64, **int32, **uint64, **uint32:
				tempVal := reflect.ValueOf(ptr)
				if tempVal.IsValid() && !tempVal.IsNil() && !tempVal.Elem().IsNil() {
					val := numericAsFloat(tempVal.Elem().Elem().Interface())
					if m := aggRe.FindStringSubmatch(name); m != nil {
						id, _ := strconv.Atoi(m[1])
						aggValues[id] = val
					} else if numericColsCount == 1 { // classic single-value query
						fallbackValue = val
						fallbackSeen = true
					} else {
						// numeric label
						lblVals = append(lblVals, fmt.Sprint(val))
						lblObjs = append(lblObjs, &qbtypes.Label{
							Key:   telemetrytypes.TelemetryFieldKey{Name: name},
							Value: val,
						})
					}
				}

			case *string:
				lblVals = append(lblVals, *v)
				lblObjs = append(lblObjs, &qbtypes.Label{
					Key:   telemetrytypes.TelemetryFieldKey{Name: name},
					Value: *v,
				})

			case **string:
				val := *v
				if val == nil {
					var empty string
					val = &empty
				}
				lblVals = append(lblVals, *val)
				lblObjs = append(lblObjs, &qbtypes.Label{
					Key:   telemetrytypes.TelemetryFieldKey{Name: name},
					Value: val,
				})

			default:
				continue
			}
		}

		// Edge-case: no __result_N columns, but a single numeric column present
		if len(aggValues) == 0 && fallbackSeen {
			aggValues[0] = fallbackValue
		}

		if ts == 0 || len(aggValues) == 0 {
			continue // nothing useful
		}

		sort.Strings(lblVals)
		labelsKey := strings.Join(lblVals, ",")

		// one point per aggregation in this row
		for aggIdx, val := range aggValues {
			if math.IsNaN(val) || math.IsInf(val, 0) {
				continue
			}

			key := sKey{agg: aggIdx, key: labelsKey}

			series, ok := seriesMap[key]
			if !ok {
				series = &qbtypes.TimeSeries{Labels: lblObjs}
				seriesMap[key] = series
			}
			series.Values = append(series.Values, &qbtypes.TimeSeriesValue{
				Timestamp: ts,
				Value:     val,
			})
		}
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	maxAgg := -1
	for k := range seriesMap {
		if k.agg > maxAgg {
			maxAgg = k.agg
		}
	}
	if maxAgg < 0 {
		return nil, nil // empty result-set
	}

	buckets := make([]*qbtypes.AggregationBucket, maxAgg+1)
	for i := range buckets {
		buckets[i] = &qbtypes.AggregationBucket{
			Index: i,
			Alias: "__result_" + strconv.Itoa(i),
		}
	}
	for k, s := range seriesMap {
		buckets[k.agg].Series = append(buckets[k.agg].Series, s)
	}

	var nonEmpty []*qbtypes.AggregationBucket
	for _, b := range buckets {
		if len(b.Series) > 0 {
			nonEmpty = append(nonEmpty, b)
		}
	}

	return []*qbtypes.TimeSeriesData{{
		Aggregations: nonEmpty,
	}}, nil
}

func numericKind(k reflect.Kind) bool {
	switch k {
	case reflect.Float32, reflect.Float64,
		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return true
	default:
		return false
	}
}

func readAsScalar(rows driver.Rows) (*qbtypes.ScalarData, error) {
	colNames := rows.Columns()
	colTypes := rows.ColumnTypes()

	cd := make([]*qbtypes.ColumnDescriptor, len(colNames))

	for i, name := range colNames {
		colType := qbtypes.ColumnTypeGroup
		if aggRe.MatchString(name) {
			colType = qbtypes.ColumnTypeAggregation
		}
		cd[i] = &qbtypes.ColumnDescriptor{
			TelemetryFieldKey: telemetrytypes.TelemetryFieldKey{Name: name},
			AggregationIndex:  int64(i),
			Type:              colType,
		}
	}

	var data [][]any

	for rows.Next() {
		scan := make([]any, len(colTypes))
		for i := range scan {
			scan[i] = reflect.New(colTypes[i].ScanType()).Interface()
		}
		if err := rows.Scan(scan...); err != nil {
			return nil, err
		}

		// 2. deref each slot into the output row
		row := make([]any, len(scan))
		for i, cell := range scan {
			valPtr := reflect.ValueOf(cell)
			if valPtr.Kind() == reflect.Pointer && !valPtr.IsNil() {
				row[i] = valPtr.Elem().Interface()
			} else {
				row[i] = nil // Nullable columns come back as nil pointers
			}
		}
		data = append(data, row)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	return &qbtypes.ScalarData{
		Columns: cd,
		Data:    data,
	}, nil
}

func readAsRaw(rows driver.Rows) (*qbtypes.RawData, error) {

	colNames := rows.Columns()
	colTypes := rows.ColumnTypes()
	colCnt := len(colNames)

	// Build a template slice of correctly-typed pointers once
	scanTpl := make([]any, colCnt)
	for i, ct := range colTypes {
		scanTpl[i] = reflect.New(ct.ScanType()).Interface()
	}

	var outRows []*qbtypes.RawRow

	for rows.Next() {
		// fresh copy of the scan slice (otherwise the driver reuses pointers)
		scan := make([]any, colCnt)
		for i := range scanTpl {
			scan[i] = reflect.New(colTypes[i].ScanType()).Interface()
		}

		if err := rows.Scan(scan...); err != nil {
			return nil, err
		}

		rr := qbtypes.RawRow{
			Data: make(map[string]*any, colCnt),
		}

		for i, cellPtr := range scan {
			name := colNames[i]

			// de-reference the typed pointer to any
			val := reflect.ValueOf(cellPtr).Elem().Interface()

			// special-case: timestamp column
			if name == "timestamp" || name == "timestamp_datetime" {
				switch t := val.(type) {
				case time.Time:
					rr.Timestamp = t
				case uint64: // epoch-ns stored as integer
					rr.Timestamp = time.Unix(0, int64(t))
				case int64:
					rr.Timestamp = time.Unix(0, t)
				default:
					// leave zero time if unrecognised
				}
			}

			// store value in map as *any, to match the schema
			v := any(val)
			rr.Data[name] = &v
		}
		outRows = append(outRows, &rr)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	return &qbtypes.RawData{
		Rows: outRows,
	}, nil
}

func numericAsFloat(v any) float64 {
	switch x := v.(type) {
	case float64:
		return x
	case float32:
		return float64(x)
	case int64:
		return float64(x)
	case int32:
		return float64(x)
	case int16:
		return float64(x)
	case int8:
		return float64(x)
	case int:
		return float64(x)
	case uint64:
		return float64(x)
	case uint32:
		return float64(x)
	case uint16:
		return float64(x)
	case uint8:
		return float64(x)
	case uint:
		return float64(x)
	default:
		return math.NaN()
	}
}