// Command edgeguard-api serves the management REST API on
// 127.0.0.1:9443. HAProxy (or a dev curl) terminates TLS in front of
// it; this process is plain HTTP behind that.
package main

import (
	"context"
	"crypto/rand"
	"log"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/jackc/pgx/v5/pgxpool"

	"git.netcell-it.de/projekte/edgeguard-native/internal/cluster"
	"git.netcell-it.de/projekte/edgeguard-native/internal/database"
	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers"
	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/audit"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/backends"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/domains"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/routingrules"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/session"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/setup"
)

var version = "0.0.1-dev"

func main() {
	addr := os.Getenv("EDGEGUARD_API_ADDR")
	if addr == "" {
		addr = "127.0.0.1:9443"
	}

	dataDir := os.Getenv("EDGEGUARD_DATA_DIR")
	if dataDir == "" {
		dataDir = setup.DefaultDir
	}
	setupStore := setup.NewStore(dataDir)

	signer, err := session.NewSignerFromPath("")
	if err != nil {
		// /var/lib/edgeguard not writable in dev → fall back to a
		// process-local secret so `go run` works without sudo. Tokens
		// won't survive a restart, which is fine for an unprivileged
		// developer machine.
		slog.Warn("session signer: persisted secret unavailable, using ephemeral",
			"error", err)
		signer = session.NewSigner(randomEphemeralSecret(), nil, 0)
	}

	gin.SetMode(gin.ReleaseMode)
	r := gin.New()
	r.Use(handlers.Recover())

	// Health endpoints are mounted *before* SetupGate so they answer
	// 200 even on a virgin box. UI uses /api/v1/system/health for the
	// post-upgrade version-flip poll.
	r.GET("/healthz", func(c *gin.Context) {
		response.OK(c, gin.H{"status": "ok", "version": version})
	})
	r.GET("/api/health", func(c *gin.Context) {
		response.OK(c, gin.H{"status": "ok", "version": version})
	})

	// ACME HTTP-01 webroot — HAProxy proxies these through pre-setup
	// so certbot can issue the first cert. Webroot location matches
	// certbot's default; override via EDGEGUARD_ACME_WEBROOT for
	// dev/tests.
	acmeWebroot := os.Getenv("EDGEGUARD_ACME_WEBROOT")
	handlers.NewACMEHandler(acmeWebroot).Register(r)

	v1 := r.Group("/api/v1")
	v1.Use(handlers.SetupGate(setupStore))

	requireAuth := handlers.RequireAuth(signer)

	handlers.NewSetupHandler(setupStore).Register(v1)
	handlers.NewSystemHandler(version).Register(v1)
	handlers.NewAuthHandler(setupStore, signer).Register(v1, requireAuth)

	// Open the DB pool best-effort. Without a reachable PG, CRUD
	// handlers stay unregistered and only Auth/Setup/System answer —
	// good enough for `go run` on a developer machine that has no
	// postgres-16 yet.
	pool, err := openDBBestEffort()
	if err != nil {
		slog.Warn("DB pool unavailable, CRUD endpoints disabled",
			"error", err)
	} else {
		slog.Info("DB pool open, registering CRUD handlers")

		nodeID, nodeErr := cluster.EnsureNodeID("")
		if nodeErr != nil {
			slog.Warn("node-id not persisted, using ephemeral",
				"id", nodeID, "error", nodeErr)
		}
		clusterStore := cluster.NewStore(pool)

		// Self-register in ha_nodes — only if setup is complete
		// (we want the operator-defined FQDN, not the OS hostname,
		// to land in api_url). Failures are logged but non-fatal.
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		st, _ := setupStore.Load()
		if st != nil && st.Completed {
			if _, err := cluster.EnsureSelfRegistered(ctx, clusterStore, st.FQDN, "primary"); err != nil {
				slog.Warn("self-register in ha_nodes failed", "error", err)
			}
		}
		cancel()

		auditRepo := audit.New(pool)
		domainsRepo := domains.New(pool)
		backendsRepo := backends.New(pool)
		routingRepo := routingrules.New(pool)

		authed := v1.Group("")
		authed.Use(requireAuth)
		handlers.NewDomainsHandler(domainsRepo, routingRepo, auditRepo, nodeID).Register(authed)
		handlers.NewBackendsHandler(backendsRepo, auditRepo, nodeID).Register(authed)
		handlers.NewRoutingRulesHandler(routingRepo, auditRepo, nodeID).Register(authed)
		handlers.NewClusterHandler(clusterStore, nodeID).Register(authed)
	}

	mountUI(r)

	log.Printf("edgeguard-api %s listening on %s", version, addr)
	srv := &http.Server{Addr: addr, Handler: r}
	if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
		log.Fatalf("edgeguard-api: %v", err)
	}
}

// mountUI serves the management UI — Vite-built static assets under
// /usr/share/edgeguard/ui/ — with SPA fallback (any path that isn't
// /api/* or /healthz and isn't a real file → index.html). When the
// dist directory is missing (dev box without `bun run build`), a
// placeholder HTML page is served at /.
func mountUI(r *gin.Engine) {
	uiDir := os.Getenv("EDGEGUARD_UI_DIR")
	if uiDir == "" {
		uiDir = "/usr/share/edgeguard/ui"
	}
	indexPath := filepath.Join(uiDir, "index.html")

	if _, err := os.Stat(indexPath); err != nil {
		slog.Warn("UI dist not found, serving placeholder",
			"ui_dir", uiDir, "error", err)
		r.NoRoute(func(c *gin.Context) {
			path := c.Request.URL.Path
			if isAPIPath(path) {
				c.Status(http.StatusNotFound)
				return
			}
			c.Data(http.StatusOK, "text/html; charset=utf-8", []byte(uiPlaceholder))
		})
		return
	}

	r.NoRoute(func(c *gin.Context) {
		path := c.Request.URL.Path
		if isAPIPath(path) {
			c.Status(http.StatusNotFound)
			return
		}
		// Serve real file when one exists for the requested path.
		// filepath.Clean blocks `..` traversal; the join still pins
		// the result inside uiDir even with shenanigans.
		clean := filepath.Clean(path)
		if !strings.HasPrefix(clean, "/") {
			clean = "/" + clean
		}
		full := filepath.Join(uiDir, clean)
		if !strings.HasPrefix(full, uiDir) {
			c.Status(http.StatusForbidden)
			return
		}
		if info, err := os.Stat(full); err == nil && !info.IsDir() {
			c.File(full)
			return
		}
		// SPA fallback — React Router renders the right page.
		c.File(indexPath)
	})
}

// isAPIPath returns true for paths the API owns; UI serves
// everything else. /healthz and /api/health are technically API
// surfaces but don't need to fall through to index.html either.
func isAPIPath(p string) bool {
	return strings.HasPrefix(p, "/api/") || p == "/healthz" || p == "/api/health"
}

const uiPlaceholder = `<!doctype html>
<html lang="en"><head><meta charset="utf-8"><title>EdgeGuard</title></head>
<body style="font-family: -apple-system, sans-serif; max-width: 640px; margin: 4em auto; line-height: 1.5;">
<h1>EdgeGuard</h1>
<p>The management UI has not been built yet. From the project root, run:</p>
<pre style="background:#f4f4f4;padding:12px;border-radius:4px;">cd management-ui &amp;&amp; bun install &amp;&amp; bun run build</pre>
<p>Then the same URL will serve the React SPA. The REST API is fully functional at
<code>/api/v1/*</code> regardless.</p>
</body></html>`

// openDBBestEffort opens the pool with a 3s timeout. Returns the
// non-nil error so callers can decide whether to register CRUD or
// degrade gracefully.
func openDBBestEffort() (*pgxpoolPool, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	dsn := database.ConnStringFromEnv()
	return database.Open(ctx, dsn)
}

// pgxpoolPool aliases the concrete pool type so we don't import it in
// main.go on every platform — keeps the import block lean.
type pgxpoolPool = pgxpool.Pool

// nodeIDOrHostname returns the node identifier audit_log entries are
// stamped with. v1 just uses /etc/machine-id (or the hostname on dev
// machines without one). Phase 3's cluster store will replace this.
func nodeIDOrHostname() string {
	if b, err := os.ReadFile("/etc/machine-id"); err == nil {
		s := string(b)
		s = stripTrailingNewline(s)
		if s != "" {
			return s
		}
	}
	if h, err := os.Hostname(); err == nil {
		return h
	}
	return "unknown"
}

func stripTrailingNewline(s string) string {
	for len(s) > 0 && (s[len(s)-1] == '\n' || s[len(s)-1] == '\r') {
		s = s[:len(s)-1]
	}
	return s
}

// randomEphemeralSecret is the fallback for dev environments where
// /var/lib/edgeguard isn't writable. Tokens issued with this secret
// die on restart — production reads/writes the persistent file via
// session.NewSignerFromPath.
func randomEphemeralSecret() []byte {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		// Should never happen on a sane Linux box; fall back to a
		// time-based filler so the process can at least start.
		log.Printf("WARN: crypto/rand read failed: %v", err)
	}
	return b
}