package api

import (
	"database/sql"
	"encoding/json"
	"log"
	"net/http"
	"time"
)

// amPayload mirrors the Alertmanager webhook v4 payload.
type amPayload struct {
	Version string    `json:"version"`
	Status  string    `json:"status"`
	Alerts  []amAlert `json:"alerts"`
}

type amAlert struct {
	Status       string            `json:"status"`
	Labels       map[string]string `json:"labels"`
	Annotations  map[string]string `json:"annotations"`
	StartsAt     time.Time         `json:"startsAt"`
	EndsAt       time.Time         `json:"endsAt"`
	GeneratorURL string            `json:"generatorURL"`
	Fingerprint  string            `json:"fingerprint"`
}

func handleAlertmanagerWebhook(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var payload amPayload
		if err := decodeJSON(r, &payload); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid payload"))
			return
		}

		now := time.Now().Unix()
		for _, a := range payload.Alerts {
			name := a.Labels["alertname"]
			labelsJSON, _ := json.Marshal(a.Labels)
			annotationsJSON, _ := json.Marshal(a.Annotations)

			// Alertmanager uses zero time ("0001-01-01T00:00:00Z") to mean "still firing".
			var endsAtUnix *int64
			if a.EndsAt.Year() > 1 {
				t := a.EndsAt.Unix()
				endsAtUnix = &t
			}

			_, err := db.ExecContext(r.Context(), `
				INSERT INTO alerts
					(fingerprint, name, status, labels, annotations, starts_at, ends_at, generator_url, received_at)
				VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
				ON CONFLICT(fingerprint) DO UPDATE SET
					status        = excluded.status,
					labels        = excluded.labels,
					annotations   = excluded.annotations,
					ends_at       = excluded.ends_at,
					generator_url = excluded.generator_url,
					received_at   = excluded.received_at`,
				a.Fingerprint, name, a.Status,
				string(labelsJSON), string(annotationsJSON),
				a.StartsAt.Unix(), endsAtUnix,
				a.GeneratorURL, now,
			)
			if err != nil {
				log.Printf("upsert alert %s: %v", a.Fingerprint, err)
			}
		}

		w.WriteHeader(http.StatusOK)
	}
}