package kjv

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"net"
	"net/http"
	"os"
	"os/signal"
	"runtime"
	"strconv"
	"syscall"
	"time"
)

// localOnly insists on a loopback address: the program is meant to sit behind
// a reverse proxy on the same machine and never face the network itself.
func localOnly(addr string) (string, error) {
	host, port, err := net.SplitHostPort(addr)
	if err != nil {
		return "", fmt.Errorf("bad listen address %q: %w", addr, err)
	}
	switch host {
	case "", "localhost":
		host = "127.0.0.1"
	default:
		if ip := net.ParseIP(host); ip == nil || !ip.IsLoopback() {
			return "", fmt.Errorf("refusing to listen on %q: only localhost addresses (127.0.0.1, ::1) are allowed; put a reverse proxy in front", host)
		}
	}
	return net.JoinHostPort(host, port), nil
}

// Run serves the application from the companion database until interrupted.
func Run(dbPath, addr string) error {
	addr, err := localOnly(addr)
	if err != nil {
		return err
	}
	if _, err := os.Stat(dbPath); err != nil {
		return fmt.Errorf("database not found: %s (use -db or KJV_DB)", dbPath)
	}
	store, err := OpenStore(dbPath)
	if err != nil {
		return err
	}
	defer store.Close()
	if store.stateOK {
		lg.Attach(store.db, 90)
	} else {
		fmt.Fprintln(os.Stderr, "WARN: database is read-only: logs go to stderr; reading plans and shortcodes are disabled")
	}
	defer lg.Close()

	app, err := NewApp(store)
	if err != nil {
		return err
	}
	app.secretKey = os.Getenv("KJV_SECRET_API_KEY")
	app.semantic = envOr("KJV_SEMANTIC_ADDR", "localhost:1613")
	if p := os.Getenv("KJV_SERMON_DB"); p != "" {
		if st, err := os.Stat(p); err == nil && st.Size() > 0 {
			if db, err := sql.Open("sqlite", "file:"+p+"?mode=ro&_pragma=busy_timeout(5000)"); err == nil {
				app.sermonDB = db
			}
		} else {
			lg.Warn("sermon database %s not available", p)
		}
	}

	srv := &http.Server{
		Addr:              addr,
		Handler:           app.Routes(),
		MaxHeaderBytes:    16 << 10,
		ReadHeaderTimeout: 10 * time.Second,
		ReadTimeout:       30 * time.Second,
		WriteTimeout:      60 * time.Second,
		IdleTimeout:       120 * time.Second,
	}
	go app.maintain()
	lg.Info("Started %s: db=%s addr=%s verses=%d state=%v sermons=%v", runtime.Version(), dbPath, addr, len(store.verses), store.stateOK, app.sermonDB != nil)
	fmt.Printf("kjv-api listening on %s (database %s)\n", addr, dbPath)

	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}
	errc := make(chan error, 1)
	go func() { errc <- srv.Serve(ln) }()
	sig := make(chan os.Signal, 1)
	signal.Notify(sig, os.Interrupt, syscall.SIGTERM)
	select {
	case err := <-errc:
		return err
	case s := <-sig:
		lg.Info("Stopping on %v", s)
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		if err := srv.Shutdown(ctx); err != nil && !errors.Is(err, http.ErrServerClosed) {
			return err
		}
	}
	return nil
}

// ---------------------------------------------------------------------------
// routes

type statusWriter struct {
	http.ResponseWriter
	status int
}

func (w *statusWriter) WriteHeader(code int) { w.status = code; w.ResponseWriter.WriteHeader(code) }

func (a *App) Routes() http.Handler {
	mux := http.NewServeMux()
	get := func(pattern string, h func(r *http.Request) Resp) {
		mux.HandleFunc("GET "+pattern, func(w http.ResponseWriter, r *http.Request) { h(r).write(w) })
	}

	get("/{$}", func(r *http.Request) Resp { return htmlR(a.indexHTML) })
	get("/{shortcode}", func(r *http.Request) Resp { return a.handleShortcode(r.PathValue("shortcode")) })
	get("/fe", func(r *http.Request) Resp { return a.staticPage("kjv_fe.html") })
	get("/salvation", func(r *http.Request) Resp { return a.staticPage("html/heaven.html") })
	get("/saved", func(r *http.Request) Resp { return a.staticPage("html/saved.html") })
	get("/plan", func(r *http.Request) Resp { return a.staticPage("html/plan.html") })

	get("/show", func(r *http.Request) Resp { return a.handleShow(r.URL.Query()) })
	get("/find", func(r *http.Request) Resp { return a.handleFind(r.URL.Query()) })
	get("/search", func(r *http.Request) Resp {
		v := r.URL.Query()
		return a.handleSearch(v.Get("kw"), viewOf(v, "rich"))
	})
	get("/define", func(r *http.Request) Resp { return a.handleDefine(r.URL.Query()) })
	get("/defs", func(r *http.Request) Resp { return a.handleDefs(r.URL.Query()) })
	get("/random", func(r *http.Request) Resp { return a.handleRandom(r.URL.Query(), "json") })
	get("/t/random", func(r *http.Request) Resp { return a.handleRandom(r.URL.Query(), "plain") })
	get("/votd", func(r *http.Request) Resp { return a.handleVotd(r.URL.Query(), "json") })
	get("/t/votd", func(r *http.Request) Resp { return a.handleVotd(r.URL.Query(), "plain") })
	get("/seq", func(r *http.Request) Resp {
		if r.URL.Query().Get("getuid") != "" && !creations.allow(clientAddr(r)) {
			return tooMany()
		}
		return a.handleSeq(r.URL.Query())
	})
	get("/mksc/{query}", func(r *http.Request) Resp {
		if !creations.allow(clientAddr(r)) {
			return tooMany()
		}
		return a.handleMakeShortcode(r.PathValue("query"))
	})
	get("/ref/{ref}", func(r *http.Request) Resp { return a.handleRef(r.PathValue("ref")) })
	get("/verse_id/{id}", func(r *http.Request) Resp {
		id := cleanInput(r.PathValue("id"), "0123456789")
		n, err := strconv.ParseInt(id, 10, 64)
		if err != nil {
			return errJSON(http.StatusBadRequest, "Invalid verse id")
		}
		v := a.store.Range(n, 0)
		if len(v) == 0 {
			return errJSON(http.StatusNotFound, "No such verse")
		}
		return jsonR([]any{v[0].ID, v[0].Book, v[0].Chapter, v[0].Verse, v[0].Text})
	})
	get("/xref/{id}", func(r *http.Request) Resp { return a.handleXref(r.PathValue("id")) })
	get("/browse", func(r *http.Request) Resp {
		body := "<h2>Books</h2><div class=\"table-wrap\"><table id=\"Books\">"
		for _, n := range a.store.bookNames {
			body += fmt.Sprintf("<tr><td><a href=\"/find?kw=%s&view=rich\">%s</a></td></tr>", urlQuery(n), htmlEsc(n))
		}
		return htmlR(a.staticHTMLDoc("Books", body+"</table></div>"))
	})
	get("/status", func(r *http.Request) Resp {
		var m runtime.MemStats
		runtime.ReadMemStats(&m)
		return htmlR(a.staticHTMLDoc("Status", fmt.Sprintf("<h2>Status</h2><p>Sanity: %v</p><p>Uptime: %s</p><p>Memory: %d KB</p>",
			a.store.stateOK, time.Since(a.started).Round(time.Second), m.Sys/1024)))
	})
	get("/seqreport", func(r *http.Request) Resp {
		if resp, ok := a.adminOnly(r); !ok {
			return resp
		}
		return a.tableReport("Sequence Report", "seq_report", "SELECT uid, verse, last_used FROM reading_tracker", false)
	})
	get("/screport", func(r *http.Request) Resp {
		if resp, ok := a.adminOnly(r); !ok {
			return resp
		}
		return a.tableReport("Shortcode Report", "shortcode_report", "SELECT shortcode, query, creation_date FROM shortcodes", true)
	})
	get("/natural", func(r *http.Request) Resp {
		return htmlR("Submit a POST request to this endpoint with the following params in the body:\n{\"token\": \"mytokenstring\", \"query\" : \"myquerystring\"}")
	})
	mux.HandleFunc("POST /natural", func(w http.ResponseWriter, r *http.Request) { a.handleNaturalPost(r.Body).write(w) })
	mux.HandleFunc("POST /plan/new", func(w http.ResponseWriter, r *http.Request) {
		if !creations.allow(clientAddr(r)) {
			tooMany().write(w)
			return
		}
		r.Body = http.MaxBytesReader(w, r.Body, 16<<10)
		if r.ParseForm() != nil {
			errJSON(http.StatusRequestEntityTooLarge, "Request too large").write(w)
			return
		}
		a.handlePlanNew(r.PostForm).write(w)
	})
	mux.HandleFunc("POST /plan/{uid}/move", func(w http.ResponseWriter, r *http.Request) {
		r.Body = http.MaxBytesReader(w, r.Body, 16<<10)
		if r.ParseForm() != nil {
			errJSON(http.StatusRequestEntityTooLarge, "Request too large").write(w)
			return
		}
		a.handlePlanMove(r.PathValue("uid"), r.PostForm).write(w)
	})
	get("/plan/{uid}", func(r *http.Request) Resp { return a.handlePlanView(r.PathValue("uid"), r.URL.Query()) })

	for _, p := range []string{"/sermons", "/sermons/{rest...}", "/sermon/{rest...}"} {
		get(p, func(r *http.Request) Resp { return a.handleSermons(r.URL.Path) })
	}
	for _, p := range []string{"/preachers", "/churches", "/denominations"} {
		cols := map[string]string{"/preachers": "denomination,preacher,church_name", "/churches": "denomination,church_name", "/denominations": "denomination"}[p]
		get(p, func(r *http.Request) Resp { return a.sermonQuery("select distinct " + cols + " from verse_refs") })
	}

	for u := range servedPaths {
		u := u
		mux.HandleFunc("GET "+u, func(w http.ResponseWriter, r *http.Request) { a.serveAsset(w, r, u) })
	}
	favicon := func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "image/svg+xml")
		w.Header().Set("Cache-Control", "public, max-age=86400")
		w.Write(a.favicon)
	}
	mux.HandleFunc("GET /favicon.ico", favicon)
	mux.HandleFunc("GET /favicon.svg", favicon)
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { a.notFound().write(w) })

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		sw := &statusWriter{ResponseWriter: w, status: 200}
		defer func() {
			if rec := recover(); rec != nil {
				lg.Error("panic serving %s: %v", r.URL.String(), rec)
				sw.status = 500
				errJSON(500, "Internal error").write(w)
			}
			lg.Info("%s %s %d %s", r.Method, r.URL.RequestURI(), sw.status, time.Since(start).Round(time.Microsecond))
		}()
		h := w.Header()
		h.Set("X-Content-Type-Options", "nosniff")
		h.Set("X-Frame-Options", "DENY")
		h.Set("Referrer-Policy", "same-origin")
		mux.ServeHTTP(sw, r)
	})
}

// serveAsset: a URL whose ?v= hash matches the file is immutable for a year;
// any other URL for it is revalidated every time.
func (a *App) serveAsset(w http.ResponseWriter, r *http.Request, u string) {
	as := a.served[u]
	h := w.Header()
	h.Set("Content-Type", as.mime)
	h.Set("ETag", as.etag)
	if r.URL.Query().Get("v") == as.version {
		h.Set("Cache-Control", "public, max-age=31536000, immutable")
	} else {
		h.Set("Cache-Control", "no-cache")
	}
	if r.Header.Get("If-None-Match") == as.etag {
		w.WriteHeader(http.StatusNotModified)
		return
	}
	w.Write(as.body)
}

func (a *App) handleXref(raw string) Resp {
	id, err := strconv.ParseInt(raw, 10, 64)
	if err != nil {
		return a.notFound()
	}
	refs, err := a.store.CrossReferences(id)
	if err != nil {
		lg.Error("xref: %v", err)
		return errJSON(http.StatusInternalServerError, "Database error")
	}
	out := []map[string]any{}
	for _, c := range refs {
		ref := a.store.FormatRef(c.Start)
		var verses []Verse
		if c.End > c.Start {
			if c.Start/1000 == c.End/1000 { // "John 3:16-18" when the range stays in one chapter
				ref += fmt.Sprintf("-%d", c.End%1000)
			} else {
				ref += "-" + a.store.FormatRef(c.End)
			}
			verses = a.store.Range(c.Start, c.End)
		} else {
			verses = a.store.Range(c.Start, 0)
		}
		text := ""
		for i, v := range verses {
			if i > 0 {
				text += " "
			}
			text += v.Text
		}
		out = append(out, map[string]any{"ref": ref, "verse_id": c.Start, "text": text})
	}
	return jsonR(out)
}