package app

import (
	"encoding/json"
	"io"
	"net/http"
	"time"
)

func handleTransportNetnsToggle(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	var body TransportNetnsToggleRequest
	if r.Body != nil {
		defer r.Body.Close()
		if err := json.NewDecoder(io.LimitReader(r.Body, 1<<20)).Decode(&body); err != nil && err != io.EOF {
			http.Error(w, "bad json", http.StatusBadRequest)
			return
		}
	}

	lockIDs := resolveTransportNetnsToggleLockIDs(body)
	resp := TransportNetnsToggleResponse{}
	withTransportIfaceLocks(lockIDs, func() {
		resp = executeTransportNetnsToggleLocked(body, time.Now().UTC())
	})
	if resp.SuccessCount > 0 {
		publishTransportRuntimeObservabilitySnapshotChanged("transport_netns_toggled", nil, lockIDs)
	}
	writeJSON(w, http.StatusOK, resp)
}

func resolveTransportNetnsToggleLockIDs(req TransportNetnsToggleRequest) []string {
	now := time.Now().UTC()
	transportMu.Lock()
	clientsState := loadTransportClientsState()
	ifacesState := loadTransportInterfacesState()
	ifacesSnapshot := captureTransportInterfacesStateSnapshot(clientsState, ifacesState)
	transportMu.Unlock()

	normIfaces, changed := normalizeTransportInterfacesState(ifacesState, clientsState.Items)
	if changed {
		_ = saveTransportInterfacesIfSnapshotCurrent(ifacesSnapshot, normIfaces)
	}

	indexes, _ := resolveTransportNetnsToggleTargets(clientsState.Items, req.ClientIDs)
	lockIDs := make([]string, 0, len(indexes))
	targetEnabled := transportNetnsToggleTarget(req.Enabled, clientsState.Items, indexes)
	provisionEnabled := true
	if req.Provision != nil {
		provisionEnabled = *req.Provision
	}
	restartRunning := true
	if req.RestartRunning != nil {
		restartRunning = *req.RestartRunning
	}
	if !provisionEnabled {
		restartRunning = false
	}

	plannedItems := make([]TransportClient, len(clientsState.Items))
	copy(plannedItems, clientsState.Items)
	for _, idx := range indexes {
		if idx < 0 || idx >= len(clientsState.Items) {
			continue
		}
		lockIDs = append(lockIDs, clientsState.Items[idx].IfaceID)
		_, updated := prepareTransportNetnsToggleClientLocked(plannedItems[idx], normIfaces, targetEnabled, now)
		plannedItems[idx] = updated
		lockIDs = append(lockIDs, updated.IfaceID)
	}
	if restartRunning {
		for _, idx := range indexes {
			if idx < 0 || idx >= len(plannedItems) {
				continue
			}
			if normalizeTransportStatus(clientsState.Items[idx].Status) != TransportClientUp {
				continue
			}
			_, peers := matchTransportSingBoxPeersInSameNetnsForLock(plannedItems, idx, normIfaces)
			for _, peer := range peers {
				lockIDs = append(lockIDs, peer.Binding.IfaceID)
			}
		}
	}
	return lockIDs
}

func executeTransportNetnsToggleLocked(req TransportNetnsToggleRequest, now time.Time) TransportNetnsToggleResponse {
	transportMu.Lock()
	st := loadTransportClientsState()
	rawIfaces := loadTransportInterfacesState()
	ifacesSnapshot := captureTransportInterfacesOnlySnapshot(rawIfaces)
	ifaces, ifacesChanged := normalizeTransportInterfacesState(rawIfaces, st.Items)
	resp := TransportNetnsToggleResponse{}
	var plans []transportNetnsToggleClientPlan
	var missing []string

	indexes, missing := resolveTransportNetnsToggleTargets(st.Items, req.ClientIDs)
	targetEnabled := transportNetnsToggleTarget(req.Enabled, st.Items, indexes)
	provisionEnabled := true
	if req.Provision != nil {
		provisionEnabled = *req.Provision
	}
	restartRunning := true
	if req.RestartRunning != nil {
		restartRunning = *req.RestartRunning
	}
	if !provisionEnabled {
		restartRunning = false
	}

	resp = TransportNetnsToggleResponse{
		OK:      true,
		Enabled: targetEnabled,
		Items:   make([]TransportNetnsToggleItem, 0, len(indexes)+len(missing)),
	}
	plans = make([]transportNetnsToggleClientPlan, 0, len(indexes))
	for _, idx := range indexes {
		if idx < 0 || idx >= len(st.Items) {
			continue
		}
		item, updated := prepareTransportNetnsToggleClientLocked(st.Items[idx], ifaces, targetEnabled, now)
		st.Items[idx] = updated
		plans = append(plans, transportNetnsToggleClientPlan{
			Item:           item,
			NeedsProvision: item.OK && provisionEnabled,
			NeedsRestart:   item.OK && restartRunning && item.StatusBefore == TransportClientUp,
		})
	}
	if len(indexes) > 0 {
		if err := saveTransportClientsState(st); err != nil {
			transportMu.Unlock()
			resp.Items = append(resp.Items, markTransportNetnsTogglePlansSaveFailed(plans, "save failed: "+err.Error())...)
			for _, missingID := range missing {
				resp.Items = append(resp.Items, TransportNetnsToggleItem{
					OK:           false,
					ClientID:     missingID,
					Code:         "TRANSPORT_CLIENT_NOT_FOUND",
					Message:      "not found",
					NetnsEnabled: targetEnabled,
				})
			}
			return finalizeTransportNetnsToggleResponse(resp)
		}
	}
	transportMu.Unlock()

	if ifacesChanged {
		_ = saveTransportInterfacesIfUnchanged(ifacesSnapshot, ifaces)
	}

	for _, plan := range plans {
		resp.Items = append(resp.Items, applyTransportNetnsToggleClientPlanLocked(plan))
	}
	for _, missingID := range missing {
		resp.Items = append(resp.Items, TransportNetnsToggleItem{
			OK:           false,
			ClientID:     missingID,
			Code:         "TRANSPORT_CLIENT_NOT_FOUND",
			Message:      "not found",
			NetnsEnabled: targetEnabled,
		})
	}
	refreshTransportNetnsToggleFinalStatuses(&resp)
	return finalizeTransportNetnsToggleResponse(resp)
}

func resolveTransportNetnsToggleTargets(items []TransportClient, clientIDs []string) ([]int, []string) {
	if len(clientIDs) == 0 {
		out := make([]int, 0, len(items))
		for i := range items {
			if items[i].Kind == TransportClientSingBox {
				out = append(out, i)
			}
		}
		return out, nil
	}
	out := make([]int, 0, len(clientIDs))
	missing := make([]string, 0, 2)
	seen := make(map[int]struct{}, len(clientIDs))
	for _, raw := range clientIDs {
		id := sanitizeID(raw)
		if id == "" {
			continue
		}
		idx := findTransportClientIndex(items, id)
		if idx < 0 {
			missing = append(missing, id)
			continue
		}
		if _, ok := seen[idx]; ok {
			continue
		}
		seen[idx] = struct{}{}
		out = append(out, idx)
	}
	return out, missing
}

func transportNetnsToggleTarget(enabled *bool, items []TransportClient, indexes []int) bool {
	if enabled != nil {
		return *enabled
	}
	any := false
	allEnabled := true
	for _, idx := range indexes {
		if idx < 0 || idx >= len(items) {
			continue
		}
		it := items[idx]
		if it.Kind != TransportClientSingBox {
			continue
		}
		any = true
		if !transportNetnsEnabled(it) {
			allEnabled = false
		}
	}
	if !any {
		return false
	}
	return !allEnabled
}