package cli

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/alecthomas/kingpin"
	"github.com/prometheus/alertmanager/cli/format"
	"github.com/prometheus/alertmanager/dispatch"
	"github.com/prometheus/alertmanager/pkg/parse"
	"github.com/prometheus/alertmanager/types"
	"github.com/prometheus/common/model"
)

type alertmanagerAlertResponse struct {
	Status    string        `json:"status"`
	Data      []*alertGroup `json:"data,omitempty"`
	ErrorType string        `json:"errorType,omitempty"`
	Error     string        `json:"error,omitempty"`
}

type alertGroup struct {
	Labels   model.LabelSet `json:"labels"`
	GroupKey string         `json:"groupKey"`
	Blocks   []*alertBlock  `json:"blocks"`
}

type alertBlock struct {
	RouteOpts interface{}          `json:"routeOpts"`
	Alerts    []*dispatch.APIAlert `json:"alerts"`
}

var (
	alertCmd      = app.Command("alert", "View and search through current alerts")
	alertQueryCmd = alertCmd.Command("query", "View and search through current alerts").Default()
	expired       = alertQueryCmd.Flag("expired", "Show expired alerts as well as active").Bool()
	showSilenced  = alertQueryCmd.Flag("silenced", "Show silenced alerts").Short('s').Bool()
	alertQuery    = alertQueryCmd.Arg("matcher-groups", "Query filter").Strings()
)

func init() {
	alertQueryCmd.Action(queryAlerts)
	longHelpText["alert"] = `View and search through current alerts.

Amtool has a simplified prometheus query syntax, but contains robust support for
bash variable expansions. The non-option section of arguments constructs a list
of "Matcher Groups" that will be used to filter your query. The following
examples will attempt to show this behaviour in action:

amtool alert query alertname=foo node=bar

	This query will match all alerts with the alertname=foo and node=bar label
	value pairs set.

amtool alert query foo node=bar

	If alertname is omitted and the first argument does not contain a '=' or a
	'=~' then it will be assumed to be the value of the alertname pair.

amtool alert query 'alertname=~foo.*'

	As well as direct equality, regex matching is also supported. The '=~' syntax
	(similar to prometheus) is used to represent a regex match. Regex matching
	can be used in combination with a direct match.`
	longHelpText["alert query"] = longHelpText["alert"]
}

func fetchAlerts(filter string) ([]*dispatch.APIAlert, error) {
	alertResponse := alertmanagerAlertResponse{}

	u := GetAlertmanagerURL("/api/v1/alerts/groups")
	u.RawQuery = "filter=" + url.QueryEscape(filter)

	res, err := http.Get(u.String())
	if err != nil {
		return []*dispatch.APIAlert{}, err
	}

	defer res.Body.Close()

	err = json.NewDecoder(res.Body).Decode(&alertResponse)
	if err != nil {
		return []*dispatch.APIAlert{}, fmt.Errorf("unable to decode json response: %s", err)
	}

	if alertResponse.Status != "success" {
		return []*dispatch.APIAlert{}, fmt.Errorf("[%s] %s", alertResponse.ErrorType, alertResponse.Error)
	}

	return flattenAlertOverview(alertResponse.Data), nil
}

func flattenAlertOverview(overview []*alertGroup) []*dispatch.APIAlert {
	alerts := []*dispatch.APIAlert{}
	for _, group := range overview {
		for _, block := range group.Blocks {
			alerts = append(alerts, block.Alerts...)
		}
	}
	return alerts
}

func queryAlerts(element *kingpin.ParseElement, ctx *kingpin.ParseContext) error {
	var filterString = ""
	if len(*alertQuery) == 1 {
		// If we only have one argument then it's possible that the user wants me to assume alertname=<arg>
		// Attempt to use the parser to pare the argument
		// If the parser fails then we likely don't have a (=|=~|!=|!~) so lets prepend `alertname=` to the front
		_, err := parse.Matcher((*alertQuery)[0])
		if err != nil {
			filterString = fmt.Sprintf("{alertname=%s}", (*alertQuery)[0])
		} else {
			filterString = fmt.Sprintf("{%s}", strings.Join(*alertQuery, ","))
		}
	} else if len(*alertQuery) > 1 {
		filterString = fmt.Sprintf("{%s}", strings.Join(*alertQuery, ","))
	}

	fetchedAlerts, err := fetchAlerts(filterString)
	if err != nil {
		return err
	}

	displayAlerts := []*dispatch.APIAlert{}
	for _, alert := range fetchedAlerts {
		// If we are only returning current alerts and this one has already expired skip it
		if !*expired {
			if !alert.EndsAt.IsZero() && alert.EndsAt.Before(time.Now()) {
				continue
			}
		}

		if !*showSilenced {
			// If any silence mutes this alert don't show it
			if alert.Status.State == types.AlertStateSuppressed && len(alert.Status.SilencedBy) > 0 {
				continue
			}
		}

		displayAlerts = append(displayAlerts, alert)
	}

	formatter, found := format.Formatters[*output]
	if !found {
		return errors.New("unknown output formatter")
	}
	return formatter.FormatAlerts(displayAlerts)
}