golang program to watch for and display nearby BLE devices, their manufacturers, and signal strength. may become a repo in the future if logic gets complex enough

show-ble.go

package main

import (
    "context"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
    "os"
    "sync"
    "time"

    "github.com/go-ble/ble"
    "github.com/go-ble/ble/linux"
    "github.com/gdamore/tcell/v2"
    "github.com/rivo/tview"
)

const (
    apiKeyFilename         = "macvendors_api_key.txt"
    deviceProcessInterval  = time.Second * 5
    manufacturerLookupURL  = "https://api.macvendors.com/v1/lookup/"
)

var (
    seenDevices = make(map[string]struct{})
    mutex       = &sync.Mutex{}
)

func main() {
    device, err := linux.NewDevice()
    if err != nil {
        fmt.Fprintf(os.Stderr, "Failed to create BLE device: %v\n", err)
        return
    }
    ble.SetDefaultDevice(device)

    apiKey, err := ioutil.ReadFile(apiKeyFilename)
    if err != nil {
        fmt.Fprintf(os.Stderr, "Failed to read API key: %v\n", err)
        return
    }

    app := tview.NewApplication()
    table := tview.NewTable().SetBorders(true)
    setupTable(table)

    exitButton := tview.NewButton(`E["underline"]x[""]it`).SetSelectedFunc(func() { app.Stop() })
    flex := setupLayout(table, exitButton)

    setupExitHandler(app, exitButton)

    go scanBLEDevices(app, table, string(apiKey))

    app.SetRoot(flex, true).SetFocus(table)
    if err := app.Run(); err != nil {
        fmt.Fprintf(os.Stderr, "Failed to run application: %v\n", err)
    }
}

func setupTable(table *tview.Table) {
    headers := []string{"MAC Address", "RSSI", "Manufacturer"}
    for i, header := range headers {
        table.SetCell(0, i, tview.NewTableCell(header).SetAlign(tview.AlignCenter))
    }
}

func setupLayout(table *tview.Table, exitButton *tview.Button) *tview.Flex {
    return tview.NewFlex().
        SetDirection(tview.FlexRow).
        AddItem(table, 0, 1, true).
        AddItem(exitButton, 1, 0, false)
}

func setupExitHandler(app *tview.Application, exitButton *tview.Button) {
    app.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
        if event.Key() == tcell.KeyESC || event.Rune() == 'x' || event.Rune() == 'X' {
            app.Stop()
            return nil
        }
        return event
    })

    exitButton.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
        if event.Key() == tcell.KeyEnter {
            app.Stop()
            return nil
        }
        return event
    })
}

func scanBLEDevices(app *tview.Application, table *tview.Table, apiKey string) {
    ctx := ble.WithSigHandler(context.WithTimeout(context.Background(), 10*time.Second))
    ble.Scan(ctx, false, func(a ble.Advertisement) {
        mac := a.Addr().String()
        mutex.Lock()
        if _, seen := seenDevices[mac]; seen {
            mutex.Unlock()
            return
        }
        seenDevices[mac] = struct{}{}
        mutex.Unlock()

        row := table.GetRowCount()
        app.QueueUpdateDraw(func() {
            table.SetCell(row, 0, tview.NewTableCell(mac))
            table.SetCell(row, 1, tview.NewTableCell(fmt.Sprintf("%d", a.RSSI())))
        })

        go fetchManufacturer(mac, apiKey, app, table, row)
    }, nil)
}

func fetchManufacturer(mac, apiKey string, app *tview.Application, table *tview.Table, row int) {
    resp, err := http.Get(manufacturerLookupURL + mac)
    if err != nil {
        updateTableWithManufacturer(app, table, row, "Error fetching manufacturer")
        return
    }
    defer resp.Body.Close()

    var result map[string]interface{}
    if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
        updateTableWithManufacturer(app, table, row, "Error parsing JSON")
        return
    }

    manufacturer := "Unknown Manufacturer"
    if name, ok := result["companyName"].(string); ok {
        manufacturer = name
    }

    updateTableWithManufacturer(app, table, row, manufacturer)
}

func updateTableWithManufacturer(app *tview.Application, table *tview.Table, row int, manufacturer string) {
    app.QueueUpdateDraw(func() {
        table.SetCell(row, 2, tview.NewTableCell(manufacturer))
    })
}