package web

import (
	"context"
	"encoding/json"
	"net/http"
	"path"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/agentapi"
	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
)

// Intermediary-mount model (controller side). Post-migration a drive is visible in the guest ONLY at its
// STABLE path /mnt/felhom-drives/<name> (the host swaps the backing drive underneath it; see the agent's
// internal/localapi/intermediary.go + SPIKE-intermediary-mount). So:
//   - the REGISTERED storage path + every app's HDD_PATH + FileBrowser source = the STABLE path;
//   - the AGENT still operates on the RAW /mnt/<name> host PVE mount (assign/attach/eject/decommission),
//     so controller→agent `where` is mapped back to raw via agentWhere().
// The drive-absent GATE stops + blocks apps when their drive vanishes and auto-restarts them when it
// returns (host-side, no guest reboot).

// StableParentDir is the permanent in-guest parent the agent binds drives under (mirrors
// localapi.StableParentDir).
const StableParentDir = "/mnt/felhom-drives"

// stablePathForName maps a drive name to its registered stable in-guest path.
func stablePathForName(name string) string { return StableParentDir + "/" + name }

// agentWhere maps a registered storage path — stable /mnt/felhom-drives/<name> OR a legacy raw /mnt/<name>
// — to the RAW /mnt/<name> host mount the agent operates on. Idempotent for an already-raw path
// (path.Base drops the directory either way).
func agentWhere(registeredPath string) string {
	name := path.Base(strings.TrimRight(registeredPath, "/"))
	if name == "" || name == "." || name == "/" {
		return registeredPath
	}
	return "/mnt/" + name
}

// stackStartedRecently heuristically reports whether the stack's containers started within ~5 minutes
// (i.e. a fresh guest boot, not a long-running app across a controller-only restart) — read from docker's
// human "Up X …" status string. Used to limit the startup boot-stale recreate to the guest-reboot case.
func (s *Server) stackStartedRecently(name string, _ time.Duration) bool {
	st, ok := s.stackMgr.GetStack(name)
	if !ok {
		return false
	}
	for _, c := range st.Containers {
		status := strings.ToLower(c.Status)
		if strings.Contains(status, "second") || strings.Contains(status, "about a minute") {
			return true
		}
		for _, m := range []string{"up 1 minute", "up 2 minute", "up 3 minute", "up 4 minute"} {
			if strings.Contains(status, m) {
				return true
			}
		}
	}
	return false
}

// appsOnStoragePath returns the deployed stack names whose HDD_PATH equals the given (stable) storage
// path — the apps that depend on that drive.
func (s *Server) appsOnStoragePath(storagePath string) []string {
	var names []string
	for _, st := range s.stackMgr.GetStacks() {
		if cfg := s.stackMgr.LoadAppConfigByName(st.Name); cfg != nil && cfg.Env["HDD_PATH"] == storagePath {
			names = append(names, st.Name)
		}
	}
	return names
}

// stopAppsOnPath stops every deployed app on the given storage path and returns their names (the
// gate-stopped set — distinct from a user stop, which never enters this set). Best-effort per app.
func (s *Server) stopAppsOnPath(storagePath string) []string {
	var stopped []string
	for _, name := range s.appsOnStoragePath(storagePath) {
		if err := s.stackMgr.StopStack(name); err != nil {
			s.logger.Printf("[WARN] [gate] stop %s on absent %s: %v", name, storagePath, err)
			continue
		}
		stopped = append(stopped, name)
	}
	return stopped
}

// restartStacks starts each named stack (the gate-stopped set on drive return). Best-effort per app.
func (s *Server) restartStacks(names []string) {
	for _, name := range names {
		if err := s.stackMgr.StartStack(name); err != nil {
			s.logger.Printf("[WARN] [gate] restart %s: %v", name, err)
		}
	}
}

// gateAction is the reconcile's decision for one registered storage path.
type gateAction struct {
	Path   string
	Stop   bool   // drive ABSENT + not yet marked → stop apps, mark disconnected
	Return bool   // drive RETURNED (present + currently disconnected) → re-attach, restart, clear
	Raw    string // raw /mnt/<name> for the re-attach
}

// planDriveGates is the PURE decision core: given the registry + the agent's disk list, decide per path
// whether to gate (stop) or un-gate (return). A drive is "present" iff a disk with a matching GuestPath
// (stable) or MountPath (legacy raw) is State=="attached". Decommissioned paths are skipped (handled by
// the decommission flow, not the transient gate). No side effects → unit-testable.
func planDriveGates(paths []settings.StoragePath, disks []agentapi.DiskInfo) []gateAction {
	present := map[string]bool{}
	rawByPath := map[string]string{}
	for _, d := range disks {
		// A STABLE path is usable only when the drive's felhom-data is actually BOUND UNDER THE PARENT
		// (BoundUnderParent) — NOT merely when the raw drive is host-mounted (State==attached). This is
		// what makes the gate converge a reboot correctly: at boot the raw drive mounts early but the
		// agent binds it under the parent slightly later; until then the apps' stable-path binds are empty,
		// so the gate keeps them stopped and restarts (recreates) them once the bind is live.
		if d.GuestPath != "" {
			present[d.GuestPath] = present[d.GuestPath] || d.BoundUnderParent
			rawByPath[d.GuestPath] = d.MountPath
		}
		if d.MountPath != "" { // legacy raw path registered directly — host mount is the usable signal
			present[d.MountPath] = present[d.MountPath] || d.State == "attached"
			rawByPath[d.MountPath] = d.MountPath
		}
	}
	var actions []gateAction
	for _, sp := range paths {
		if sp.Decommissioned {
			continue
		}
		// ONLY gate EXTERNAL drives — those registered under the stable parent /mnt/felhom-drives/<name>.
		// Internal SSD / system paths (e.g. /mnt/sys_drive/felhom-data) are always-present locals the agent
		// never reports as drives; gating them on "absence" would falsely stop/block their apps. (Legacy
		// raw /mnt/<name> external paths are present via the agent's MountPath during the transition and get
		// repointed under the parent by the migration.)
		if !strings.HasPrefix(sp.Path, StableParentDir+"/") {
			continue
		}
		switch {
		case !present[sp.Path] && !sp.Disconnected:
			actions = append(actions, gateAction{Path: sp.Path, Stop: true})
		case present[sp.Path] && sp.Disconnected:
			actions = append(actions, gateAction{Path: sp.Path, Return: true, Raw: rawByPath[sp.Path]})
		}
	}
	return actions
}

// ReconcileDriveGates enforces the drive-absent gate: an ABSENT registered drive gets its apps STOPPED +
// recorded (disconnected); a RETURNED drive gets re-bound under the parent and its gate-stopped apps
// restarted. Best-effort + idempotent — safe to call on a timer and on demand.
func (s *Server) ReconcileDriveGates() {
	if s.settings == nil || s.stackMgr == nil {
		return
	}
	agent, err := s.agentClient()
	if err != nil {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()
	resp, err := agent.Disks(ctx)
	if err != nil {
		return
	}
	for _, a := range planDriveGates(s.settings.GetStoragePaths(), resp.Disks) {
		switch {
		case a.Stop:
			stopped := s.stopAppsOnPath(a.Path)
			if err := s.settings.SetDisconnected(a.Path, true, stopped); err != nil {
				s.logger.Printf("[WARN] [gate] mark disconnected %s: %v", a.Path, err)
			}
			s.logger.Printf("[WARN] [gate] drive ABSENT %s — stopped+blocked %d app(s): %v", a.Path, len(stopped), stopped)
			go s.SyncFileBrowserMounts()
		case a.Return:
			if a.Raw != "" {
				if err := agent.GuestAttach(ctx, a.Raw); err != nil {
					s.logger.Printf("[WARN] [gate] re-attach %s (raw %s): %v", a.Path, a.Raw, err)
				}
			}
			var stopped []string
			for _, sp := range s.settings.GetStoragePaths() {
				if sp.Path == a.Path {
					stopped = sp.StoppedStacks
				}
			}
			s.restartStacks(stopped)
			if err := s.settings.ClearDisconnected(a.Path); err != nil {
				s.logger.Printf("[WARN] [gate] clear disconnected %s: %v", a.Path, err)
			}
			s.logger.Printf("[INFO] [gate] drive RETURNED %s — re-attached + restarted gate-stopped apps", a.Path)
			go s.SyncFileBrowserMounts()
		}
	}
}

// driveGateLoop runs ReconcileDriveGates on a timer (the periodic absent/return detector — the slice-8C
// watchdog was retired). Started as a goroutine at server startup. The FIRST action is a one-time
// startup recreate (see recreateBootStaleApps) to converge a guest reboot deterministically, then the
// periodic gate.
func (s *Server) driveGateLoop() {
	// Wait for the stack scan to complete (GetStacks empty at NewServer time) and the agent to come up,
	// so the one-time boot-stale recreate sees the real deployed apps + drive state. Bounded poll.
	for i := 0; i < 30; i++ {
		if s.stackMgr != nil && len(s.stackMgr.GetStacks()) > 0 {
			break
		}
		time.Sleep(time.Second)
	}
	s.recreateBootStaleApps()
	s.ReconcileDriveGates()
	t := time.NewTicker(30 * time.Second)
	defer t.Stop()
	for range t.C {
		s.ReconcileDriveGates()
	}
}

// recreateBootStaleApps converges a GUEST REBOOT deterministically. On a guest reboot docker auto-starts
// the app containers (restart:unless-stopped) potentially BEFORE the agent has re-propagated the drive
// under the parent — so those containers bind the empty fail-closed stable dir (and the non-recursive
// parent bind + leaf-bind pinning means they never pick up the later propagation in their own ns). This
// runs ONCE at controller startup (the controller itself restarts with the guest): for every deployed
// drive-backed app whose drive is NOW present (BoundUnderParent) AND whose containers started recently
// (a fresh guest boot, not a long-running app across a controller-only restart), it recreates the app
// (Stop=down + Start=up) so it binds the populated path. Apps whose drive is still absent are left to the
// normal gate (stop→return→restart). Best-effort.
func (s *Server) recreateBootStaleApps() {
	if s.settings == nil || s.stackMgr == nil {
		return
	}
	agent, err := s.agentClient()
	if err != nil {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	resp, derr := agent.Disks(ctx)
	cancel()
	if derr != nil {
		return
	}
	presentStable := map[string]bool{}
	for _, d := range resp.Disks {
		if d.GuestPath != "" && d.BoundUnderParent {
			presentStable[d.GuestPath] = true
		}
	}
	for _, st := range s.stackMgr.GetStacks() {
		cfg := s.stackMgr.LoadAppConfigByName(st.Name)
		if cfg == nil {
			continue
		}
		hdd := cfg.Env["HDD_PATH"]
		if hdd == "" || !strings.HasPrefix(hdd, StableParentDir+"/") || !presentStable[hdd] {
			continue
		}
		// Recreate when the app is boot-stale or not cleanly running: recently-started (it likely came up
		// on the empty bind before the drive was re-propagated) OR currently exited/restarting/unhealthy
		// (came up wrong and bailed). SKIP a healthy long-running app (no bounce on a controller-only
		// restart) and a cleanly user-Stopped app (respect the user's intent).
		needs := s.stackStartedRecently(st.Name, 5*time.Minute) ||
			st.State == stacks.StateExited || st.State == stacks.StateRestarting || st.State == stacks.StateUnhealthy
		if !needs {
			continue
		}
		s.logger.Printf("[INFO] [gate] startup: recreating drive-backed app %s (state=%s) onto its drive %s", st.Name, st.State, hdd)
		_ = s.stackMgr.StopStack(st.Name)
		if serr := s.stackMgr.StartStack(st.Name); serr != nil {
			s.logger.Printf("[WARN] [gate] startup recreate %s: %v", st.Name, serr)
		}
	}
}

// ---- H1 endpoints (the UI's settings.js calls these; previously 404/unrouted) -----------------

// handleStorageDisconnect EJECTS a drive without restart: stop its apps (gate-stopped), agent-detach the
// felhom-data bind from under the parent (live, fail-closed), and mark it disconnected. The drive is then
// safely removable. POST {where} where = the registered (stable) path.
func (s *Server) handleStorageDisconnect(w http.ResponseWriter, r *http.Request) {
	where, ok := s.gateWhere(w, r)
	if !ok {
		return
	}
	stopped := s.stopAppsOnPath(where)
	agent, err := s.agentClient()
	if err == nil {
		if _, derr := agent.EjectDisk(r.Context(), agentWhere(where)); derr != nil {
			s.logger.Printf("[WARN] [web] disconnect: agent detach %s failed: %v", where, derr)
		}
	}
	if err := s.settings.SetDisconnected(where, true, stopped); err != nil {
		writeDiskJSON(w, http.StatusInternalServerError, false, err.Error(), nil)
		return
	}
	go s.SyncFileBrowserMounts()
	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"where": where, "stopped": stopped})
}

// handleStorageReconnect re-attaches a returned drive without restart: agent-attach the felhom-data bind
// under the parent (live), restart the gate-stopped apps, clear the disconnected mark.
func (s *Server) handleStorageReconnect(w http.ResponseWriter, r *http.Request) {
	where, ok := s.gateWhere(w, r)
	if !ok {
		return
	}
	var stopped []string
	for _, sp := range s.settings.GetStoragePaths() {
		if sp.Path == where {
			stopped = sp.StoppedStacks
		}
	}
	agent, err := s.agentClient()
	if err != nil {
		writeDiskJSON(w, http.StatusServiceUnavailable, false, err.Error(), nil)
		return
	}
	if aerr := agent.GuestAttach(r.Context(), agentWhere(where)); aerr != nil {
		writeDiskJSON(w, http.StatusBadGateway, false, "újracsatolás sikertelen: "+aerr.Error(), nil)
		return
	}
	s.restartStacks(stopped)
	if err := s.settings.ClearDisconnected(where); err != nil {
		writeDiskJSON(w, http.StatusInternalServerError, false, err.Error(), nil)
		return
	}
	go s.SyncFileBrowserMounts()
	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"where": where, "restarted": stopped})
}

// handleStorageRestartApps restarts the gate-stopped apps on a path (without changing connection state) —
// the manual "restart the apps that were stopped" action.
func (s *Server) handleStorageRestartApps(w http.ResponseWriter, r *http.Request) {
	where, ok := s.gateWhere(w, r)
	if !ok {
		return
	}
	var stopped []string
	for _, sp := range s.settings.GetStoragePaths() {
		if sp.Path == where {
			stopped = sp.StoppedStacks
		}
	}
	s.restartStacks(stopped)
	writeDiskJSON(w, http.StatusOK, true, "", map[string]any{"where": where, "restarted": stopped})
}

// gateWhere decodes + validates the {where} body shared by the H1 endpoints.
func (s *Server) gateWhere(w http.ResponseWriter, r *http.Request) (string, bool) {
	var req struct {
		Where string `json:"where"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeDiskJSON(w, http.StatusBadRequest, false, "érvénytelen kérés", nil)
		return "", false
	}
	where := path.Clean(strings.TrimSpace(req.Where))
	if where == "" || where == "." || !strings.HasPrefix(where, "/mnt/") {
		writeDiskJSON(w, http.StatusBadRequest, false, "érvénytelen csatlakoztatási pont", nil)
		return "", false
	}
	return where, true
}