// Package api implements the REST API handlers for uopi.
package api

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
	"strings"

	"github.com/uopi/uopi/internal/access"
	"github.com/uopi/uopi/internal/broker"
	"github.com/uopi/uopi/internal/datasource"
	"github.com/uopi/uopi/internal/datasource/synthetic"
	"github.com/uopi/uopi/internal/panelacl"
	"github.com/uopi/uopi/internal/storage"
)

// Handler holds the dependencies shared across all API endpoints.
type Handler struct {
	broker           *broker.Broker
	synthetic        *synthetic.Synthetic // nil if not enabled
	store            *storage.Store
	policy           *access.Policy
	acl              *panelacl.Store
	channelFinderURL string // empty if not configured
	archiverURL      string // empty if not configured
	log              *slog.Logger
}

// New creates an API Handler. synth may be nil if the synthetic DS is disabled.
func New(b *broker.Broker, synth *synthetic.Synthetic, store *storage.Store, policy *access.Policy, acl *panelacl.Store, channelFinderURL, archiverURL string, log *slog.Logger) *Handler {
	return &Handler{
		broker:           b,
		synthetic:        synth,
		store:            store,
		policy:           policy,
		acl:              acl,
		channelFinderURL: channelFinderURL,
		archiverURL:      archiverURL,
		log:              log,
	}
}

// Register mounts all API routes onto mux under the given prefix.
// Requires Go 1.22+ for method+path routing.
func (h *Handler) Register(mux *http.ServeMux, prefix string) {
	mux.HandleFunc("GET "+prefix+"/me", h.getMe)
	mux.HandleFunc("GET "+prefix+"/datasources", h.listDataSources)
	mux.HandleFunc("GET "+prefix+"/signals", h.listSignals)
	mux.HandleFunc("GET "+prefix+"/signals/search", h.searchSignals)
	mux.HandleFunc("GET "+prefix+"/channel-finder", h.channelFinder)
	mux.HandleFunc("GET "+prefix+"/archiver/search", h.archiverSearch)
	mux.HandleFunc("GET "+prefix+"/interfaces", h.listInterfaces)
	mux.HandleFunc("POST "+prefix+"/interfaces", h.createInterface)
	mux.HandleFunc("POST "+prefix+"/interfaces/reorder", h.reorderInterfaces)
	mux.HandleFunc("GET "+prefix+"/interfaces/{id}", h.getInterface)
	mux.HandleFunc("PUT "+prefix+"/interfaces/{id}", h.updateInterface)
	mux.HandleFunc("DELETE "+prefix+"/interfaces/{id}", h.deleteInterface)
	mux.HandleFunc("POST "+prefix+"/interfaces/{id}/clone", h.cloneInterface)
	mux.HandleFunc("GET "+prefix+"/interfaces/{id}/versions", h.listVersions)
	mux.HandleFunc("GET "+prefix+"/interfaces/{id}/versions/{version}", h.getVersion)
	mux.HandleFunc("PUT "+prefix+"/interfaces/{id}/versions/{version}/tag", h.setVersionTag)
	mux.HandleFunc("POST "+prefix+"/interfaces/{id}/versions/{version}/promote", h.promoteVersion)
	mux.HandleFunc("POST "+prefix+"/interfaces/{id}/versions/{version}/fork", h.forkVersion)
	// Per-panel ownership / sharing (Phase 2)
	mux.HandleFunc("GET "+prefix+"/interfaces/{id}/acl", h.getPanelACL)
	mux.HandleFunc("PUT "+prefix+"/interfaces/{id}/acl", h.putPanelACL)
	// Panel folders / hierarchy (Phase 3)
	mux.HandleFunc("GET "+prefix+"/folders", h.listFolders)
	mux.HandleFunc("POST "+prefix+"/folders", h.createFolder)
	mux.HandleFunc("PUT "+prefix+"/folders/{id}", h.updateFolder)
	mux.HandleFunc("DELETE "+prefix+"/folders/{id}", h.deleteFolder)
	// User groups defined in config (read-only; for the sharing UI)
	mux.HandleFunc("GET "+prefix+"/usergroups", h.listUserGroups)
	// Signal group tree
	mux.HandleFunc("GET "+prefix+"/groups", h.getGroups)
	mux.HandleFunc("PUT "+prefix+"/groups", h.putGroups)
	// Synthetic signal CRUD
	mux.HandleFunc("GET "+prefix+"/synthetic", h.listSynthetic)
	mux.HandleFunc("POST "+prefix+"/synthetic", h.createSynthetic)
	mux.HandleFunc("GET "+prefix+"/synthetic/{name}", h.getSynthetic)
	mux.HandleFunc("PUT "+prefix+"/synthetic/{name}", h.updateSynthetic)
	mux.HandleFunc("DELETE "+prefix+"/synthetic/{name}", h.deleteSynthetic)
}

// ── /me ─────────────────────────────────────────────────────────────────────

// getMe reports the caller's resolved identity, global access level, and group
// memberships. The frontend uses this to tailor the UI (hide edit affordances
// for read-only users, block no-access users). Always reachable, even for
// no-access users, so the UI can render an appropriate blocked state.
func (h *Handler) getMe(w http.ResponseWriter, r *http.Request) {
	user := access.UserFrom(r.Context())
	groups := h.policy.GroupsOf(user)
	if groups == nil {
		groups = []string{}
	}
	jsonOK(w, map[string]any{
		"user":   user,
		"level":  h.policy.Level(user).String(),
		"groups": groups,
	})
}

// ── access helpers ────────────────────────────────────────────────────────────

// caller returns the resolved end-user identity for the request (set by the
// access middleware).
func caller(r *http.Request) string { return access.UserFrom(r.Context()) }

// capByGlobal lowers a per-panel/folder permission to what the user's global
// access level allows: read-only users can never exceed read, no-access users
// get nothing.
func (h *Handler) capByGlobal(user string, p panelacl.Perm) panelacl.Perm {
	switch h.policy.Level(user) {
	case access.LevelNone:
		return panelacl.PermNone
	case access.LevelRead:
		if p > panelacl.PermRead {
			return panelacl.PermRead
		}
	}
	return p
}

// panelPerm returns the caller's effective permission on a panel. A request
// with no resolved identity (no proxy header and no default_user) is a trusted
// LAN deployment with no per-user enforcement, so it gets full write.
func (h *Handler) panelPerm(r *http.Request, id string) panelacl.Perm {
	user := caller(r)
	if user == "" {
		return panelacl.PermWrite
	}
	return h.capByGlobal(user, h.acl.PanelPerm(id, user, h.policy.GroupsOf(user)))
}

// folderPerm returns the caller's effective permission on a folder. As with
// panelPerm, an unidentified caller is trusted with full write.
func (h *Handler) folderPerm(r *http.Request, id string) panelacl.Perm {
	user := caller(r)
	if user == "" {
		return panelacl.PermWrite
	}
	return h.capByGlobal(user, h.acl.FolderPerm(id, user, h.policy.GroupsOf(user)))
}

// ── /datasources ──────────────────────────────────────────────────────────────

type dsInfo struct {
	Name   string `json:"name"`
	Status string `json:"status"`
}

func (h *Handler) listDataSources(w http.ResponseWriter, r *http.Request) {
	sources := h.broker.DataSources()
	out := make([]dsInfo, len(sources))
	for i, ds := range sources {
		out[i] = dsInfo{Name: ds.Name(), Status: "connected"}
	}
	jsonOK(w, out)
}

// ── /signals ──────────────────────────────────────────────────────────────────

type signalInfo struct {
	Name        string            `json:"name"`
	Type        string            `json:"type"`
	Unit        string            `json:"unit,omitempty"`
	Description string            `json:"description,omitempty"`
	DisplayLow  float64           `json:"displayLow"`
	DisplayHigh float64           `json:"displayHigh"`
	Writable    bool              `json:"writable"`
	EnumStrings []string          `json:"enumStrings,omitempty"`
	Properties  map[string]string `json:"properties,omitempty"`
	Tags        []string          `json:"tags,omitempty"`
}

func (h *Handler) listSignals(w http.ResponseWriter, r *http.Request) {
	dsName := r.URL.Query().Get("ds")
	if dsName == "" {
		jsonError(w, http.StatusBadRequest, "query parameter 'ds' is required")
		return
	}

	// Synthetic signals carry per-caller visibility rules, so build their list
	// from the definitions (filtered) rather than the generic metadata path.
	if dsName == "synthetic" && h.synthetic != nil {
		user := caller(r)
		panel := r.URL.Query().Get("panel")
		metas := h.synthetic.FilteredMetadata(func(d synthetic.SignalDef) bool {
			return synVisible(d, user, panel)
		})
		out := make([]signalInfo, len(metas))
		for i, m := range metas {
			out[i] = metaToSignalInfo(m)
		}
		jsonOK(w, out)
		return
	}

	ds, ok := h.broker.Source(dsName)
	if !ok {
		jsonError(w, http.StatusNotFound, "unknown data source: "+dsName)
		return
	}

	metas, err := ds.ListSignals(r.Context())
	if err != nil {
		h.log.Error("list signals", "ds", dsName, "err", err)
		jsonError(w, http.StatusInternalServerError, err.Error())
		return
	}

	out := make([]signalInfo, len(metas))
	for i, m := range metas {
		out[i] = metaToSignalInfo(m)
	}
	jsonOK(w, out)
}

// synVisible reports whether a synthetic signal should be listed for the given
// caller while editing the given panel. An empty Visibility is treated as
// "global" so legacy definitions remain visible everywhere.
func synVisible(d synthetic.SignalDef, user, panel string) bool {
	switch d.Visibility {
	case "user":
		return user != "" && d.Owner == user
	case "panel":
		return panel != "" && d.Panel == panel
	default: // "global" or legacy empty
		return true
	}
}

// ── /signals/search ───────────────────────────────────────────────────────────

func (h *Handler) searchSignals(w http.ResponseWriter, r *http.Request) {
	q := strings.ToLower(r.URL.Query().Get("q"))
	dsName := r.URL.Query().Get("ds")

	var sources []datasource.DataSource
	if dsName != "" {
		ds, ok := h.broker.Source(dsName)
		if !ok {
			jsonError(w, http.StatusNotFound, "unknown data source: "+dsName)
			return
		}
		sources = []datasource.DataSource{ds}
	} else {
		sources = h.broker.DataSources()
	}

	user := caller(r)
	panel := r.URL.Query().Get("panel")

	var out []signalInfo
	for _, ds := range sources {
		var metas []datasource.Metadata
		if ds.Name() == "synthetic" && h.synthetic != nil {
			metas = h.synthetic.FilteredMetadata(func(d synthetic.SignalDef) bool {
				return synVisible(d, user, panel)
			})
		} else {
			var err error
			metas, err = ds.ListSignals(r.Context())
			if err != nil {
				continue
			}
		}
		for _, m := range metas {
			if q == "" || strings.Contains(strings.ToLower(m.Name), q) || strings.Contains(strings.ToLower(m.Description), q) {
				si := metaToSignalInfo(m)
				out = append(out, si)
			}
		}
	}
	if out == nil {
		out = []signalInfo{}
	}
	jsonOK(w, out)
}

// ── /channel-finder ───────────────────────────────────────────────────────────

// channelFinder proxies a query to the EPICS Channel Finder service when one
// is configured, returning a flat list of PV names. Returns 501 otherwise.
func (h *Handler) channelFinder(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query().Get("q")

	// Empty-query availability probe (used by the signal tree to decide whether
	// to surface Channel Finder UI). Always respond 200 so an unconfigured CFS
	// is not logged as a failed request in the browser console.
	if q == "" && (r.URL.RawQuery == "" || r.URL.RawQuery == "q=") {
		jsonOK(w, map[string]bool{"available": h.channelFinderURL != ""})
		return
	}

	if h.channelFinderURL == "" {
		jsonError(w, http.StatusNotImplemented, "Channel Finder not configured (set channel_finder_url in config)")
		return
	}

	cfURL := strings.TrimRight(h.channelFinderURL, "/") + "/resources/channels"
	if q != "" {
		cfURL += "?~name=*" + q + "*"
	} else {
		// Structured query (e.g. ~name=, ~tag=, property filters) passed through.
		cfURL += "?" + r.URL.RawQuery
	}

	resp, err := http.Get(cfURL) //nolint:noctx
	if err != nil {
		jsonError(w, http.StatusBadGateway, "Channel Finder request failed: "+err.Error())
		return
	}
	defer resp.Body.Close()

	// Channel Finder returns JSON array of channel objects; extract names.
	var channels []struct {
		Name string `json:"name"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&channels); err != nil {
		jsonError(w, http.StatusBadGateway, "Channel Finder response parse error: "+err.Error())
		return
	}

	names := make([]string, 0, len(channels))
	for _, ch := range channels {
		if ch.Name != "" {
			names = append(names, ch.Name)
		}
	}
	jsonOK(w, names)
}

// ── /archiver/search ──────────────────────────────────────────────────────────

// archiverSearch proxies a search query to the EPICS Archive Appliance
// management API when configured. Returns 501 otherwise.
func (h *Handler) archiverSearch(w http.ResponseWriter, r *http.Request) {
	if h.archiverURL == "" {
		jsonError(w, http.StatusNotImplemented, "Archiver not configured (set archive_url in config)")
		return
	}

	pattern := r.URL.Query().Get("q")
	if pattern == "" {
		pattern = "*"
	}
	// AA expects glob patterns. If no glob characters, wrap in stars.
	if !strings.ContainsAny(pattern, "*?[]") {
		pattern = "*" + pattern + "*"
	}

	searchURL := strings.TrimRight(h.archiverURL, "/") + "/mgmt/bpl/getAllPVs?pv=" + url.QueryEscape(pattern)
	resp, err := http.Get(searchURL) //nolint:noctx
	if err != nil {
		jsonError(w, http.StatusBadGateway, "Archiver request failed: "+err.Error())
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		jsonError(w, http.StatusBadGateway, "Archiver returned status "+resp.Status)
		return
	}

	var pvs []string
	if err := json.NewDecoder(resp.Body).Decode(&pvs); err != nil {
		jsonError(w, http.StatusBadGateway, "Archiver response parse error: "+err.Error())
		return
	}

	jsonOK(w, pvs)
}

// ── /groups ───────────────────────────────────────────────────────────────────

// getGroups returns the workspace group tree as a JSON array.
func (h *Handler) getGroups(w http.ResponseWriter, r *http.Request) {
	data, err := h.store.ReadGroups()
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_, _ = w.Write(data)
}

// putGroups replaces the workspace group tree. The body must be a JSON array.
func (h *Handler) putGroups(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20)) // 1 MB max
	if err != nil {
		http.Error(w, "read error", http.StatusBadRequest)
		return
	}
	// Validate it is a JSON array (basic sanity check).
	var raw []json.RawMessage
	if err := json.Unmarshal(body, &raw); err != nil {
		http.Error(w, "body must be a JSON array", http.StatusBadRequest)
		return
	}
	if err := h.store.WriteGroups(body); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ── /interfaces ───────────────────────────────────────────────────────────────

// interfaceListItem enriches the stored metadata with the panel's owner,
// containing folder, and the caller's effective permission, so the frontend can
// render sharing affordances and filter the visible set.
type interfaceListItem struct {
	storage.InterfaceMeta
	Owner  string `json:"owner,omitempty"`
	Folder string `json:"folder,omitempty"`
	Perm   string `json:"perm"`
}

func (h *Handler) listInterfaces(w http.ResponseWriter, r *http.Request) {
	list, err := h.store.List()
	if err != nil {
		h.log.Error("list interfaces", "err", err)
		jsonError(w, http.StatusInternalServerError, err.Error())
		return
	}
	out := make([]interfaceListItem, 0, len(list))
	for _, m := range list {
		perm := h.panelPerm(r, m.ID)
		if perm < panelacl.PermRead {
			continue // hide panels the caller cannot see
		}
		item := interfaceListItem{InterfaceMeta: m, Perm: perm.String()}
		if acl := h.acl.GetPanel(m.ID); acl != nil {
			item.Owner = acl.Owner
			item.Folder = acl.Folder
		}
		out = append(out, item)
	}
	h.log.Info("list interfaces", "count", len(out))
	jsonOK(w, out)
}

func (h *Handler) createInterface(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, 4<<20))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "read body: "+err.Error())
		return
	}
	id, err := h.store.Create(body, r.URL.Query().Get("tag"))
	if err != nil {
		h.log.Error("create interface", "err", err)
		jsonError(w, http.StatusBadRequest, err.Error())
		return
	}
	// Record ownership so the new panel defaults to private (owner-only). Skip
	// for unidentified callers (trusted LAN): an owner-less record would make the
	// panel invisible to everyone.
	if user := caller(r); user != "" {
		if err := h.acl.CreatePanel(id, user); err != nil {
			h.log.Error("record panel ownership", "id", id, "err", err)
		}
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(map[string]string{"id": id})
}

func (h *Handler) getInterface(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	data, err := h.store.Get(id)
	if err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.Header().Set("Content-Type", "application/xml")
	_, _ = w.Write(data)
}

func (h *Handler) updateInterface(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this panel")
		return
	}
	body, err := io.ReadAll(io.LimitReader(r.Body, 4<<20))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "read body: "+err.Error())
		return
	}
	if err := h.store.Update(id, body, r.URL.Query().Get("tag")); err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			h.log.Error("update interface", "id", id, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handler) listVersions(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	versions, err := h.store.Versions(id)
	if err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			h.log.Error("list versions", "id", id, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	jsonOK(w, versions)
}

func (h *Handler) getVersion(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	version, err := strconv.Atoi(r.PathValue("version"))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
		return
	}
	data, err := h.store.GetVersion(id, version)
	if err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "version not found")
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.Header().Set("Content-Type", "application/xml")
	_, _ = w.Write(data)
}

func (h *Handler) setVersionTag(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this panel")
		return
	}
	version, err := strconv.Atoi(r.PathValue("version"))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
		return
	}
	if err := h.store.SetVersionTag(id, version, r.URL.Query().Get("tag")); err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "version not found")
		} else {
			h.log.Error("set version tag", "id", id, "version", version, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handler) promoteVersion(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this panel")
		return
	}
	version, err := strconv.Atoi(r.PathValue("version"))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
		return
	}
	if err := h.store.Promote(id, version); err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "version not found")
		} else {
			h.log.Error("promote version", "id", id, "version", version, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handler) forkVersion(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	version, err := strconv.Atoi(r.PathValue("version"))
	if err != nil {
		jsonError(w, http.StatusBadRequest, "invalid version: "+r.PathValue("version"))
		return
	}
	newID, err := h.store.Fork(id, version)
	if err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "version not found")
		} else {
			h.log.Error("fork version", "id", id, "version", version, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	// The fork is a brand-new panel owned by the caller.
	if user := caller(r); user != "" {
		if err := h.acl.CreatePanel(newID, user); err != nil {
			h.log.Error("record fork ownership", "id", newID, "err", err)
		}
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(map[string]string{"id": newID})
}

func (h *Handler) deleteInterface(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this panel")
		return
	}
	if err := h.store.Delete(id); err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	if err := h.acl.DeletePanel(id); err != nil {
		h.log.Error("delete panel ACL", "id", id, "err", err)
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *Handler) cloneInterface(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.panelPerm(r, id) < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	newID, err := h.store.Clone(id)
	if err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			h.log.Error("clone interface", "id", id, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	// The clone is a brand-new panel owned by the caller.
	if user := caller(r); user != "" {
		if err := h.acl.CreatePanel(newID, user); err != nil {
			h.log.Error("record clone ownership", "id", newID, "err", err)
		}
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(map[string]string{"id": newID})
}

// ── /interfaces/{id}/acl (Phase 2) ──────────────────────────────────────────

// panelACLRequest is the body accepted by putPanelACL: the panel's folder,
// public level, and explicit user/group grants. Owner is immutable here.
type panelACLRequest struct {
	Folder string           `json:"folder"`
	Public string           `json:"public"`
	Grants []panelacl.Grant `json:"grants"`
}

// panelACLResponse is the sharing record returned to the frontend, enriched
// with the caller's own effective permission.
type panelACLResponse struct {
	Owner  string           `json:"owner"`
	Folder string           `json:"folder"`
	Public string           `json:"public"`
	Grants []panelacl.Grant `json:"grants"`
	Perm   string           `json:"perm"`
}

// getPanelACL returns the sharing settings for a panel. Any user who can see
// the panel (read) may inspect them.
func (h *Handler) getPanelACL(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	perm := h.panelPerm(r, id)
	if perm < panelacl.PermRead {
		jsonError(w, http.StatusNotFound, "interface not found: "+id)
		return
	}
	resp := panelACLResponse{Grants: []panelacl.Grant{}, Perm: perm.String()}
	if acl := h.acl.GetPanel(id); acl != nil {
		resp.Owner = acl.Owner
		resp.Folder = acl.Folder
		resp.Public = acl.Public
		if acl.Grants != nil {
			resp.Grants = acl.Grants
		}
	}
	jsonOK(w, resp)
}

// putPanelACL replaces a panel's sharing settings. Only the panel owner may do
// this (an unmanaged legacy panel is adopted by the first writer to set an ACL).
func (h *Handler) putPanelACL(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	user := caller(r)
	// The panel must exist in storage.
	if _, err := h.store.Get(id); err != nil {
		if errors.Is(err, storage.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "interface not found: "+id)
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	// Read-only / no-access users can never change sharing.
	if h.policy.Level(user) < access.LevelWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access")
		return
	}
	owner := user
	if acl := h.acl.GetPanel(id); acl != nil && acl.Owner != "" {
		if acl.Owner != user {
			jsonError(w, http.StatusForbidden, "only the owner can change sharing")
			return
		}
		owner = acl.Owner
	}
	var req panelACLRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	// A referenced folder must exist.
	if req.Folder != "" {
		if _, err := h.acl.GetFolder(req.Folder); err != nil {
			jsonError(w, http.StatusBadRequest, "unknown folder: "+req.Folder)
			return
		}
	}
	if err := h.acl.SetPanel(id, owner, req.Folder, req.Public, req.Grants); err != nil {
		h.log.Error("set panel ACL", "id", id, "err", err)
		jsonError(w, http.StatusInternalServerError, err.Error())
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ── /folders (Phase 3) ──────────────────────────────────────────────────────

// folderItem is a folder enriched with the caller's effective permission.
type folderItem struct {
	panelacl.Folder
	Perm string `json:"perm"`
}

// folderRequest is the body accepted by create/updateFolder.
type folderRequest struct {
	Name   string           `json:"name"`
	Parent string           `json:"parent"`
	Public string           `json:"public"`
	Grants []panelacl.Grant `json:"grants"`
}

// listFolders returns every folder the caller can at least read.
func (h *Handler) listFolders(w http.ResponseWriter, r *http.Request) {
	folders := h.acl.Folders()
	out := make([]folderItem, 0, len(folders))
	for id, f := range folders {
		perm := h.folderPerm(r, id)
		if perm < panelacl.PermRead {
			continue
		}
		if f.Grants == nil {
			f.Grants = []panelacl.Grant{}
		}
		out = append(out, folderItem{Folder: f, Perm: perm.String()})
	}
	jsonOK(w, out)
}

// createFolder creates a new folder owned by the caller. Creating a subfolder
// requires write access on the parent.
func (h *Handler) createFolder(w http.ResponseWriter, r *http.Request) {
	user := caller(r)
	if h.policy.Level(user) < access.LevelWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access")
		return
	}
	var req folderRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	if strings.TrimSpace(req.Name) == "" {
		jsonError(w, http.StatusBadRequest, "folder name is required")
		return
	}
	if req.Parent != "" && h.folderPerm(r, req.Parent) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to the parent folder")
		return
	}
	f, err := h.acl.CreateFolder(genID("fld"), req.Name, req.Parent, user)
	if err != nil {
		if errors.Is(err, panelacl.ErrNotFound) {
			jsonError(w, http.StatusBadRequest, "unknown parent folder: "+req.Parent)
		} else {
			h.log.Error("create folder", "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(f)
}

// updateFolder replaces a folder's mutable fields. Requires write access on the
// folder (owners always have it).
func (h *Handler) updateFolder(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.folderPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this folder")
		return
	}
	var req folderRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	if strings.TrimSpace(req.Name) == "" {
		jsonError(w, http.StatusBadRequest, "folder name is required")
		return
	}
	if err := h.acl.UpdateFolder(id, req.Name, req.Parent, req.Public, req.Grants); err != nil {
		switch {
		case errors.Is(err, panelacl.ErrNotFound):
			jsonError(w, http.StatusNotFound, "folder not found: "+id)
		default:
			jsonError(w, http.StatusBadRequest, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// deleteFolder removes a folder, reparenting its contents. Requires write
// access on the folder.
func (h *Handler) deleteFolder(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if h.folderPerm(r, id) < panelacl.PermWrite {
		jsonError(w, http.StatusForbidden, "you do not have write access to this folder")
		return
	}
	if err := h.acl.DeleteFolder(id); err != nil {
		if errors.Is(err, panelacl.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "folder not found: "+id)
		} else {
			h.log.Error("delete folder", "id", id, "err", err)
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ── /usergroups ─────────────────────────────────────────────────────────────

// listUserGroups returns the names of the user-groups defined in config, for
// populating the sharing UI's group picker.
func (h *Handler) listUserGroups(w http.ResponseWriter, _ *http.Request) {
	names := h.policy.GroupNames()
	if names == nil {
		names = []string{}
	}
	jsonOK(w, names)
}

// genID returns a short unique id with the given prefix (e.g. "fld-1a2b3c4d").
func genID(prefix string) string {
	var b [8]byte
	_, _ = rand.Read(b[:])
	return prefix + "-" + hex.EncodeToString(b[:])
}

// ── /synthetic ────────────────────────────────────────────────────────────────

func (h *Handler) listSynthetic(w http.ResponseWriter, _ *http.Request) {
	if h.synthetic == nil {
		jsonOK(w, []any{})
		return
	}
	jsonOK(w, h.synthetic.GetDefs())
}

func (h *Handler) createSynthetic(w http.ResponseWriter, r *http.Request) {
	if h.synthetic == nil {
		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
		return
	}
	var def synthetic.SignalDef
	if err := json.NewDecoder(r.Body).Decode(&def); err != nil {
		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	// Stamp ownership from the trusted identity; clients cannot spoof it.
	def.Owner = caller(r)
	if def.Visibility == "" {
		def.Visibility = "panel"
	}
	if err := h.synthetic.AddSignal(def); err != nil {
		if errors.Is(err, datasource.ErrNotFound) {
			jsonError(w, http.StatusConflict, err.Error())
		} else {
			jsonError(w, http.StatusBadRequest, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusCreated)
	jsonOK(w, def)
}

func (h *Handler) getSynthetic(w http.ResponseWriter, r *http.Request) {
	if h.synthetic == nil {
		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
		return
	}
	name := r.PathValue("name")
	def, err := h.synthetic.GetSignal(name)
	if err != nil {
		if errors.Is(err, datasource.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "synthetic signal not found: "+name)
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	jsonOK(w, def)
}

func (h *Handler) updateSynthetic(w http.ResponseWriter, r *http.Request) {
	if h.synthetic == nil {
		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
		return
	}
	name := r.PathValue("name")
	var def synthetic.SignalDef
	if err := json.NewDecoder(r.Body).Decode(&def); err != nil {
		jsonError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	// Ensure the name in the URL matches the body (or fill it in).
	def.Name = name
	// Preserve the original owner across edits; never trust a client-supplied one.
	if existing, err := h.synthetic.GetSignal(name); err == nil {
		def.Owner = existing.Owner
	}
	if err := h.synthetic.UpdateSignal(def); err != nil {
		if errors.Is(err, datasource.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "synthetic signal not found: "+name)
		} else {
			jsonError(w, http.StatusBadRequest, err.Error())
		}
		return
	}
	jsonOK(w, def)
}

func (h *Handler) deleteSynthetic(w http.ResponseWriter, r *http.Request) {
	if h.synthetic == nil {
		jsonError(w, http.StatusServiceUnavailable, "synthetic data source not enabled")
		return
	}
	name := r.PathValue("name")
	if err := h.synthetic.RemoveSignal(name); err != nil {
		if errors.Is(err, datasource.ErrNotFound) {
			jsonError(w, http.StatusNotFound, "synthetic signal not found: "+name)
		} else {
			jsonError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ── Helpers ───────────────────────────────────────────────────────────────────

func metaToSignalInfo(m datasource.Metadata) signalInfo {
	return signalInfo{
		Name:        m.Name,
		Type:        dataTypeName(m.Type),
		Unit:        m.Unit,
		Description: m.Description,
		DisplayLow:  m.DisplayLow,
		DisplayHigh: m.DisplayHigh,
		Writable:    m.Writable,
		EnumStrings: m.EnumStrings,
		Properties:  m.Properties,
		Tags:        m.Tags,
	}
}

func dataTypeName(t datasource.DataType) string {
	switch t {
	case datasource.TypeFloat64:
		return "float64"
	case datasource.TypeFloat64Array:
		return "float64[]"
	case datasource.TypeString:
		return "string"
	case datasource.TypeInt64:
		return "int64"
	case datasource.TypeBool:
		return "bool"
	case datasource.TypeEnum:
		return "enum"
	default:
		return "unknown"
	}
}

func jsonOK(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(v)
}

func jsonError(w http.ResponseWriter, code int, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(map[string]string{"error": message})
}