package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

const dateLayout = "2006-01-02 15:04:05"

type silence struct {
	Matchers  []matcher `json:"matchers"`
	StartsAt  string    `json:"startsAt"`
	EndsAt    string    `json:"endsAt"`
	CreatedBy string    `json:"createdBy"`
	Comment   string    `json:"comment"`
}

type matcher struct {
	Name    string `json:"name"`
	Value   string `json:"value"`
	IsRegex bool   `json:"isRegex"`
	IsEqual bool   `json:"isEqual"`
}

type silenceBody struct {
	AlertManagerURL string            `json:"alertmanagerURL"`
	Labels          map[string]string `json:"labels"`
}

type silenceResponse struct {
	ID string `json:"silenceID"`
}

func (rcv *receiver) handleSilences(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()

	if r.Method != http.MethodPost {
		http.Error(w, "Only POST allowed", http.StatusMethodNotAllowed)
		rcv.logger.Debugf("silences: illegal HTTP method: expected %q, got %q", "POST", r.Method)
		return
	}

	b, err := io.ReadAll(r.Body)
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	b, err = base64.StdEncoding.DecodeString(string(b))
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	var sb silenceBody
	err = json.Unmarshal(b, &sb)
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	var matchers []matcher
	for key, value := range sb.Labels {
		m := matcher{
			Name:    key,
			Value:   value,
			IsRegex: false,
			IsEqual: true,
		}

		matchers = append(matchers, m)
	}

	silence := &silence{
		StartsAt:  time.Now().UTC().Format(dateLayout),
		EndsAt:    time.Now().Add(rcv.cfg.am.SilenceDuration).UTC().Format(dateLayout),
		CreatedBy: "ntfy-alertmanager",
		Comment:   "",
		Matchers:  matchers,
	}

	b, err = json.Marshal(silence)
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	client := &http.Client{Timeout: time.Second * 3}

	url := sb.AlertManagerURL
	if rcv.cfg.am.URL != "" {
		url = rcv.cfg.am.URL
	}
	url += "/api/v2/silences"

	req, err := http.NewRequest(http.MethodPost, url, bytes.NewBuffer(b))
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	// Basic auth
	if rcv.cfg.am.User != "" && rcv.cfg.am.Password != "" {
		auth := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", rcv.cfg.am.User, rcv.cfg.am.Password)))
		req.Header.Set("Authorization", fmt.Sprintf("Basic %s", auth))
	}

	req.Header.Add("Content-Type", "application/json")
	resp, err := client.Do(req)
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}
	defer resp.Body.Close()

	b, err = io.ReadAll(resp.Body)
	if err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	if resp.StatusCode != http.StatusOK {
		rcv.logger.Debugf("silences: received status code %d", resp.StatusCode)
		return
	}

	var id silenceResponse
	if err := json.Unmarshal(b, &id); err != nil {
		rcv.logger.Debugf("silences: %v", err)
		return
	}

	rcv.logger.Debugf("silences: created new silence %s", id.ID)
}