package main

import (
	"fmt"
	"strconv"
	"strings"

	intdevice "netdome.biz/paul/qmk-rgb/internal/device"
)

// selectDevice resolves the --device selector against the discovered
// keyboards. An empty selector picks the only keyboard when exactly one is
// connected and fails otherwise, so commands never silently target the wrong
// keyboard.
func selectDevice(devices []intdevice.Device, selector string) (intdevice.Device, error) {
	if len(devices) == 0 {
		return intdevice.Device{}, fmt.Errorf("no QMK keyboard found")
	}

	if selector == "" {
		if len(devices) > 1 {
			return intdevice.Device{}, fmt.Errorf(
				"multiple QMK keyboards found, use --device to select:\n%s",
				formatDeviceList(devices))
		}
		return devices[0], nil
	}

	invalid := fmt.Errorf("invalid --device %q: expected a keyboard number\n%s",
		selector, formatDeviceList(devices))

	index, err := strconv.Atoi(selector)
	if err != nil {
		return intdevice.Device{}, invalid
	}

	if index < 1 || index > len(devices) {
		return intdevice.Device{}, invalid
	}

	return devices[index-1], nil
}

// formatDeviceList renders the selectable keyboards with the numbers that
// --device accepts.
func formatDeviceList(devices []intdevice.Device) string {
	var b strings.Builder
	for _, d := range devices {
		name := d.Name
		if name == "" {
			name = "Unknown QMK keyboard"
		}
		fmt.Fprintf(&b, "  %d  %s  VID=0x%04x PID=0x%04x  %s\n",
			d.Index, name, d.VendorID, d.ProductID, d.Path)
	}
	return b.String()
}