// Copyright 2017 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package alertmanager defines structures and primitives to support Alertmanager's webhook API.
//
// Shamelessly ripped from github.com/prometheus/alertmanager/template/template.go to avoid a huge dependency tree,
package alertmanager

import (
	"sort"
	"time"
)

const (
	// AlertNameLabel is the name of the label containing the an alert's name.
	AlertNameLabel = "alertname"

	// AlertFiring is the status value for a firing alert.
	AlertFiring = "firing"

	// AlertResolved is the status value for a resolved alert.
	AlertResolved = "resolved"
)

// Pair is a key/value string pair.
type Pair struct {
	Name, Value string
}

// Pairs is a list of key/value string pairs.
type Pairs []Pair

// Names returns a list of names of the pairs.
func (ps Pairs) Names() []string {
	ns := make([]string, 0, len(ps))
	for _, p := range ps {
		ns = append(ns, p.Name)
	}
	return ns
}

// Values returns a list of values of the pairs.
func (ps Pairs) Values() []string {
	vs := make([]string, 0, len(ps))
	for _, p := range ps {
		vs = append(vs, p.Value)
	}
	return vs
}

// KV is a set of key/value string pairs.
type KV map[string]string

// SortedPairs returns a sorted list of key/value pairs.
func (kv KV) SortedPairs() Pairs {
	var (
		pairs     = make([]Pair, 0, len(kv))
		keys      = make([]string, 0, len(kv))
		sortStart = 0
	)
	for k := range kv {
		if k == AlertNameLabel {
			keys = append([]string{k}, keys...)
			sortStart = 1
		} else {
			keys = append(keys, k)
		}
	}
	sort.Strings(keys[sortStart:])

	for _, k := range keys {
		pairs = append(pairs, Pair{k, kv[k]})
	}
	return pairs
}

// Remove returns a copy of the key/value set without the given keys.
func (kv KV) Remove(keys []string) KV {
	keySet := make(map[string]struct{}, len(keys))
	for _, k := range keys {
		keySet[k] = struct{}{}
	}

	res := KV{}
	for k, v := range kv {
		if _, ok := keySet[k]; !ok {
			res[k] = v
		}
	}
	return res
}

// Names returns the names of the label names in the LabelSet.
func (kv KV) Names() []string {
	return kv.SortedPairs().Names()
}

// Values returns a list of the values in the LabelSet.
func (kv KV) Values() []string {
	return kv.SortedPairs().Values()
}

// Data is the data passed to notification templates and webhook pushes.
//
// End-users should not be exposed to Go's type system, as this will confuse them and prevent
// simple things like simple equality checks to fail. Map everything to float64/string.
type Data struct {
	// The protocol version.
	Version  string `json:"version"`
	GroupKey string `json:"groupKey"`

	Receiver string `json:"receiver"`
	Status   string `json:"status"`
	Alerts   Alerts `json:"alerts"`

	GroupLabels       KV `json:"groupLabels"`
	CommonLabels      KV `json:"commonLabels"`
	CommonAnnotations KV `json:"commonAnnotations"`

	ExternalURL string `json:"externalURL"`
}

// Alert holds one alert for notification templates.
type Alert struct {
	Status       string    `json:"status"`
	Labels       KV        `json:"labels"`
	Annotations  KV        `json:"annotations"`
	StartsAt     time.Time `json:"startsAt"`
	EndsAt       time.Time `json:"endsAt"`
	GeneratorURL string    `json:"generatorURL"`
}

// Alerts is a list of Alert objects.
type Alerts []Alert

// Firing returns the subset of alerts that are firing.
func (as Alerts) Firing() []Alert {
	var res []Alert
	for _, a := range as {
		if a.Status == AlertFiring {
			res = append(res, a)
		}
	}
	return res
}