package searchutils

import (
	"flag"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httputils"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/storage"
	"github.com/VictoriaMetrics/metricsql"
)

var (
	maxExportDuration        = flag.Duration("search.maxExportDuration", time.Hour*24*30, "The maximum duration for /api/v1/export call")
	maxQueryDuration         = flag.Duration("search.maxQueryDuration", time.Second*30, "The maximum duration for query execution. It can be overridden to a smaller value on a per-query basis via 'timeout' query arg")
	maxStatusRequestDuration = flag.Duration("search.maxStatusRequestDuration", time.Minute*5, "The maximum duration for /api/v1/status/* requests")
	maxLabelsAPIDuration     = flag.Duration("search.maxLabelsAPIDuration", time.Second*5, "The maximum duration for /api/v1/labels, /api/v1/label/.../values and /api/v1/series requests. "+
		"See also -search.maxLabelsAPISeries and -search.ignoreExtraFiltersAtLabelsAPI")
)

// GetMaxQueryDuration returns the maximum duration for query from r.
func GetMaxQueryDuration(r *http.Request) time.Duration {
	dms, err := httputils.GetDuration(r, "timeout", 0)
	if err != nil {
		dms = 0
	}
	d := time.Duration(dms) * time.Millisecond
	if d <= 0 || d > *maxQueryDuration {
		d = *maxQueryDuration
	}
	return d
}

// GetDeadlineForQuery returns deadline for the given query r.
func GetDeadlineForQuery(r *http.Request, startTime time.Time) Deadline {
	dMax := maxQueryDuration.Milliseconds()
	return getDeadlineWithMaxDuration(r, startTime, dMax, "-search.maxQueryDuration")
}

// GetDeadlineForStatusRequest returns deadline for the given request to /api/v1/status/*.
func GetDeadlineForStatusRequest(r *http.Request, startTime time.Time) Deadline {
	dMax := maxStatusRequestDuration.Milliseconds()
	return getDeadlineWithMaxDuration(r, startTime, dMax, "-search.maxStatusRequestDuration")
}

// GetDeadlineForExport returns deadline for the given request to /api/v1/export.
func GetDeadlineForExport(r *http.Request, startTime time.Time) Deadline {
	dMax := maxExportDuration.Milliseconds()
	return getDeadlineWithMaxDuration(r, startTime, dMax, "-search.maxExportDuration")
}

// GetDeadlineForLabelsAPI returns deadline for the given request to /api/v1/labels, /api/v1/label/.../values or /api/v1/series
func GetDeadlineForLabelsAPI(r *http.Request, startTime time.Time) Deadline {
	dMax := maxLabelsAPIDuration.Milliseconds()
	return getDeadlineWithMaxDuration(r, startTime, dMax, "-search.maxLabelsAPIDuration")
}

func getDeadlineWithMaxDuration(r *http.Request, startTime time.Time, dMax int64, flagHint string) Deadline {
	d, err := httputils.GetDuration(r, "timeout", 0)
	if err != nil {
		d = 0
	}
	if d <= 0 || d > dMax {
		d = dMax
	}
	timeout := time.Duration(d) * time.Millisecond
	return NewDeadline(startTime, timeout, flagHint)
}

// Deadline contains deadline with the corresponding timeout for pretty error messages.
type Deadline struct {
	deadline uint64

	timeout  time.Duration
	flagHint string
}

// NewDeadline returns deadline for the given timeout.
//
// flagHint must contain a hit for command-line flag, which could be used
// in order to increase timeout.
func NewDeadline(startTime time.Time, timeout time.Duration, flagHint string) Deadline {
	return Deadline{
		deadline: uint64(startTime.Add(timeout).Unix()),
		timeout:  timeout,
		flagHint: flagHint,
	}
}

// Exceeded returns true if deadline is exceeded.
func (d *Deadline) Exceeded() bool {
	return fasttime.UnixTimestamp() > d.deadline
}

// Deadline returns deadline in unix timestamp seconds.
func (d *Deadline) Deadline() uint64 {
	return d.deadline
}

// String returns human-readable string representation for d.
func (d *Deadline) String() string {
	startTime := time.Unix(int64(d.deadline), 0).Add(-d.timeout)
	elapsed := time.Since(startTime)
	msg := fmt.Sprintf("%.3f seconds (elapsed %.3f seconds)", d.timeout.Seconds(), elapsed.Seconds())
	if float64(elapsed)/float64(d.timeout) > 0.9 && d.flagHint != "" {
		msg += fmt.Sprintf("; the timeout can be adjusted with `%s` command-line flag", d.flagHint)
	}
	return msg
}

// GetExtraTagFilters returns additional label filters from request.
//
// Label filters can be present in extra_label and extra_filters[] query args.
// They are combined. For example, the following query args:
//
//	extra_label=t1=v1&extra_label=t2=v2&extra_filters[]={env="prod",team="devops"}&extra_filters={env=~"dev|staging",team!="devops"}
//
// should be translated to the following filters joined with "or":
//
//	{env="prod",team="devops",t1="v1",t2="v2"}
//	{env=~"dev|staging",team!="devops",t1="v1",t2="v2"}
func GetExtraTagFilters(r *http.Request) ([][]storage.TagFilter, error) {
	var tagFilters []storage.TagFilter
	for _, match := range r.Form["extra_label"] {
		tmp := strings.SplitN(match, "=", 2)
		if len(tmp) != 2 {
			return nil, fmt.Errorf("`extra_label` query arg must have the format `name=value`; got %q", match)
		}
		if tmp[0] == "__name__" {
			// This is required for storage.Search.
			tmp[0] = ""
		}
		tagFilters = append(tagFilters, storage.TagFilter{
			Key:   []byte(tmp[0]),
			Value: []byte(tmp[1]),
		})
	}
	extraFilters := append([]string{}, r.Form["extra_filters"]...)
	extraFilters = append(extraFilters, r.Form["extra_filters[]"]...)
	if len(extraFilters) == 0 {
		if len(tagFilters) == 0 {
			return nil, nil
		}
		return [][]storage.TagFilter{tagFilters}, nil
	}
	var etfs [][]storage.TagFilter
	for _, extraFilter := range extraFilters {
		tfss, err := ParseMetricSelector(extraFilter)
		if err != nil {
			return nil, fmt.Errorf("cannot parse extra_filters=%s: %w", extraFilter, err)
		}
		for i := range tfss {
			tfss[i] = append(tfss[i], tagFilters...)
		}
		etfs = append(etfs, tfss...)
	}
	return etfs, nil
}

// JoinTagFilterss adds etfs to every src filter and returns the result.
func JoinTagFilterss(src, etfs [][]storage.TagFilter) [][]storage.TagFilter {
	if len(src) == 0 {
		return etfs
	}
	if len(etfs) == 0 {
		return src
	}
	var dst [][]storage.TagFilter
	for _, tf := range src {
		for _, etf := range etfs {
			tfs := append([]storage.TagFilter{}, tf...)
			tfs = append(tfs, etf...)
			dst = append(dst, tfs)
		}
	}
	return dst
}

// ParseMetricSelector parses s containing PromQL metric selector and returns the corresponding LabelFilters.
func ParseMetricSelector(s string) ([][]storage.TagFilter, error) {
	expr, err := metricsql.Parse(s)
	if err != nil {
		return nil, err
	}
	me, ok := expr.(*metricsql.MetricExpr)
	if !ok {
		return nil, fmt.Errorf("expecting metricSelector; got %q", expr.AppendString(nil))
	}
	if len(me.LabelFilterss) == 0 {
		return nil, fmt.Errorf("labelFilterss cannot be empty")
	}
	tfss := ToTagFilterss(me.LabelFilterss)
	return tfss, nil
}

// ToTagFilterss converts lfss to or-delimited slices of storage.TagFilter
func ToTagFilterss(lfss [][]metricsql.LabelFilter) [][]storage.TagFilter {
	tfss := make([][]storage.TagFilter, len(lfss))
	for i, lfs := range lfss {
		tfs := make([]storage.TagFilter, len(lfs))
		for j := range lfs {
			toTagFilter(&tfs[j], &lfs[j])
		}
		tfss[i] = tfs
	}
	return tfss
}

func toTagFilter(dst *storage.TagFilter, src *metricsql.LabelFilter) {
	if src.Label != "__name__" {
		dst.Key = []byte(src.Label)
	} else {
		// This is required for storage.Search.
		dst.Key = nil
	}
	dst.Value = []byte(src.Value)
	dst.IsRegexp = src.IsRegexp
	dst.IsNegative = src.IsNegative
}