MSE-PI-E2EEDA-Plein-de-eeeeeeeeeee/db/src/mapping.go

package main

import (
	"encoding/json"
	"fmt"
	"os"
)

// mappingFile is the structure of the JSON config file.
// Campus names map to the list of gateway IDs that belong to them.
// Room names map to the list of node IDs that belong to them.
type mappingFile struct {
	Campus map[string][]string `json:"campus"`
	Room   map[string][]string `json:"room"`
}

// MappingConfig holds the reverse lookup maps built from the config file:
//
//	gateway_id -> campus name
//	node_id    -> room name
type MappingConfig struct {
	gatewayToCampus map[string]string
	nodeToRoom      map[string]string
}

// EmptyMapping returns a MappingConfig with no entries.
// GetCampus and GetRoom will return their "unknown_*" fallback values.
func EmptyMapping() *MappingConfig {
	return &MappingConfig{
		gatewayToCampus: make(map[string]string),
		nodeToRoom:      make(map[string]string),
	}
}

// LoadMapping reads the mapping configuration from a JSON file and builds
// the internal reverse-lookup tables.
func LoadMapping(path string) (*MappingConfig, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read mapping file %q: %w", path, err)
	}

	var raw mappingFile
	if err := json.Unmarshal(data, &raw); err != nil {
		return nil, fmt.Errorf("failed to parse mapping JSON: %w", err)
	}

	cfg := &MappingConfig{
		gatewayToCampus: make(map[string]string),
		nodeToRoom:      make(map[string]string),
	}

	for campus, gateways := range raw.Campus {
		for _, gwID := range gateways {
			cfg.gatewayToCampus[gwID] = campus
		}
	}

	for room, nodes := range raw.Room {
		for _, nodeID := range nodes {
			cfg.nodeToRoom[nodeID] = room
		}
	}

	return cfg, nil
}

// GetCampus returns the campus name for a given gateway ID.
// The boolean is false if the gateway ID has no mapping.
func (c *MappingConfig) GetCampus(gatewayID string) (string, bool) {
	campus, ok := c.gatewayToCampus[gatewayID]
	return campus, ok
}

// GetRoom returns the room name for a given node ID.
// The boolean is false if the node ID has no mapping.
func (c *MappingConfig) GetRoom(nodeID string) (string, bool) {
	room, ok := c.nodeToRoom[nodeID]
	return room, ok
}