package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"net/http/fcgi"
	"time"

	"blitiri.com.ar/go/systemd"
	"github.com/jackc/pgx/v4"
	"github.com/jackc/pgx/v4/pgxpool"
)

type Event struct {
	Created_ts int64
	Kind       string
	Details    string
}

func getListener() (net.Listener, error) {
	listeners, err := systemd.Listeners()
	if err != nil {
		return nil, fmt.Errorf("unable to get systemd listeners: %w", err)
	}
	count := 0
	for _, listeners := range listeners {
		count += len(listeners)
		if count == 1 {
			return listeners[0], nil
		}
	}
	return nil, fmt.Errorf("expected 1 systemd fd passed, got %v", count)
}

func httpEnd(w http.ResponseWriter, r *http.Request, content string, code int) {
	log.Printf("%v %d %d %s", r.RemoteAddr, r.ContentLength, code, content)
	http.Error(w, content, code)
}

func main() {
	conn, err := pgxpool.Connect(context.Background(), "")
	if err != nil {
		log.Fatal("Unable to connect to database: ", err)
	}
	defer conn.Close()

	http.HandleFunc("/analytics", func(w http.ResponseWriter, r *http.Request) {
		if r.Method == "GET" {
			if url, ok := r.URL.Query()["url"]; ok {
				if len(url) > 1 {
					httpEnd(w, r, "too many urls", 400)
				} else {
					http.Redirect(w, r, url[0], 303)
					_, err = conn.Exec(context.Background(), "insert into events(created_ts, ip_addr, kind, details) values ($1, $2, $3, $4)", time.Now(), r.RemoteAddr, "r", url[0])
					if err != nil {
						log.Printf("%v 0 303 db error: %s", r.RemoteAddr, err)
						return
					}
					log.Printf("%v 0 303 ok", r.RemoteAddr)
				}
			} else {
				httpEnd(w, r, "missing url for GET", 400)
			}
			return
		}
		if r.Method != "POST" {
			httpEnd(w, r, "method not allowed: "+r.Method, 405)
			return
		}
		if r.ContentLength <= 0 {
			httpEnd(w, r, "length required", 411)
			return
		}
		if r.ContentLength > 1048576 {
			httpEnd(w, r, "too much data", 413)
			return
		}

		data, err := io.ReadAll(r.Body)
		if err != nil {
			httpEnd(w, r, "read error", 400)
			return
		}
		var events []Event
		if err := json.Unmarshal(data, &events); err != nil {
			log.Print(err)
			httpEnd(w, r, "bad json", 400)
			return
		}

		_, err = conn.CopyFrom(
			r.Context(),
			pgx.Identifier{"events"},
			[]string{"created_ts", "ip_addr", "kind", "details"},
			pgx.CopyFromSlice(len(events), func(i int) ([]interface{}, error) {
				return []interface{}{time.Unix(events[i].Created_ts/1000, events[i].Created_ts%1000*1000000), r.RemoteAddr, events[i].Kind, events[i].Details}, nil
			}),
		)
		if err != nil {
			log.Printf("%v %d 500 db error: %s", r.RemoteAddr, r.ContentLength, err)
			http.Error(w, "db error", 500)
		} else {
			httpEnd(w, r, "ok", 200)
		}
	})

	l, err := getListener()
	if err != nil {
		log.Fatal(err)
	}
	fcgi.Serve(l, nil)
}