kaiyan-api: implement api server

cmd/kaiyan-api/main.go

@@ -0,0 +1,167 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log/slog"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"time"
+
+	"github.com/go-json-experiment/json"
+	"zombiezen.com/go/sqlite"
+	"zombiezen.com/go/sqlite/sqlitex"
+
+	"git.sunturtle.xyz/zephyr/kaiyan/emote"
+	"git.sunturtle.xyz/zephyr/kaiyan/emote/sqlitestore"
+)
+
+func main() {
+	var (
+		listen string
+		dburi  string
+	)
+	flag.StringVar(&listen, "listen", ":80", "address to bind")
+	flag.StringVar(&dburi, "db", "", "SQLite database URI")
+	flag.Parse()
+	if dburi == "" {
+		fail("-db is mandatory")
+	}
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	go func() {
+		<-ctx.Done()
+		stop()
+	}()
+
+	opts := sqlitex.PoolOptions{
+		Flags: sqlite.OpenReadWrite | sqlite.OpenURI,
+	}
+	db, err := sqlitex.NewPool(dburi, opts)
+	if err != nil {
+		fail("%v", err)
+	}
+	st, err := sqlitestore.Open(ctx, db)
+	if err != nil {
+		fail("%v", err)
+	}
+
+	mux := http.NewServeMux()
+	mux.Handle("GET /twitch/{channel}", metrics(st))
+	// TODO(branden): GET /metrics
+	l, err := net.Listen("tcp", listen)
+	if err != nil {
+		fail(err.Error())
+	}
+	srv := http.Server{
+		Addr:              listen,
+		Handler:           mux,
+		ReadHeaderTimeout: 3 * time.Second,
+		WriteTimeout:      30 * time.Second,
+		IdleTimeout:       1 * time.Minute,
+		BaseContext:       func(l net.Listener) context.Context { return ctx },
+	}
+	go func() {
+		slog.InfoContext(ctx, "HTTP API", slog.Any("addr", l.Addr()))
+		// TODO(branden): tls? or do we just use caddy/nginx after all?
+		err := srv.Serve(l)
+		if err == http.ErrServerClosed {
+			return
+		}
+		slog.ErrorContext(ctx, "HTTP API closed", slog.Any("err", err))
+	}()
+	<-ctx.Done()
+	stop()
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		slog.ErrorContext(ctx, "HTTP API shutdown", slog.Any("err", err))
+	}
+}
+
+func metrics(st *sqlitestore.Store) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		log := slog.With(slog.Group("request",
+			slog.String("host", r.Host),
+			slog.String("remote", r.RemoteAddr),
+		))
+		channel := r.PathValue("channel")
+		var start, end time.Time
+		if s := r.FormValue("start"); s != "" {
+			t, err := time.Parse(time.RFC3339, s)
+			if err != nil {
+				writerror(w, http.StatusBadRequest, err.Error())
+				return
+			}
+			start = t
+		} else {
+			writerror(w, http.StatusBadRequest, "start time is required")
+			return
+		}
+		if s := r.FormValue("end"); s != "" {
+			t, err := time.Parse(time.RFC3339, s)
+			if err != nil {
+				writerror(w, http.StatusBadRequest, err.Error())
+				return
+			}
+			end = t
+		} else {
+			// We can fill in with the current time.
+			end = time.Now().Truncate(time.Second)
+		}
+		if end.Before(start) {
+			// Be liberal and just swap them.
+			start, end = end, start
+		}
+		if end.Sub(start) > 366*24*time.Hour {
+			writerror(w, http.StatusBadRequest, "timespan is too long")
+			return
+		}
+		log.LogAttrs(r.Context(), slog.LevelInfo, "metrics",
+			slog.String("channel", channel),
+			slog.Time("start", start),
+			slog.Time("end", end),
+		)
+		m, err := st.Metrics(r.Context(), channel, start, end, nil)
+		if err != nil {
+			log.ErrorContext(r.Context(), "metrics", slog.Any("err", err))
+			writerror(w, http.StatusInternalServerError, "data unavailable")
+			return
+		}
+		log.LogAttrs(r.Context(), slog.LevelInfo, "done",
+			slog.String("channel", channel),
+			slog.Time("start", start),
+			slog.Time("end", end),
+		)
+		writedata(w, m)
+	}
+}
+
+func writerror(w http.ResponseWriter, status int, err string) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	v := struct {
+		Error string `json:"error"`
+	}{err}
+	json.MarshalWrite(w, &v)
+}
+
+func writedata(w http.ResponseWriter, data []emote.Metric) {
+	w.Header().Set("Content-Type", "application/json")
+	if len(data) == 0 {
+		w.Write([]byte(`{"data":[]}`))
+		return
+	}
+	v := struct {
+		Data []emote.Metric `json:"data"`
+	}{data}
+	json.MarshalWrite(w, &v)
+}
+
+func fail(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, format+"\n", args...)
+	os.Exit(1)
+}