package main

import (
	"fmt"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"
)

var macAddress = regexp.MustCompile(`^[0-9A-Fa-f]{2}(:[0-9A-Fa-f]{2}){5}$`)

func addressOf(args map[string]any) (string, error) {
	a, err := text(args, "address")
	if err != nil {
		return "", err
	}
	if !macAddress.MatchString(a) {
		return "", fmt.Errorf("%q is not a Bluetooth address (six hex pairs separated by colons)", a)
	}
	return strings.ToUpper(a), nil
}

var ansi = regexp.MustCompile(`\x1b\[[0-9;]*[A-Za-z]|\x01|\x02`)

// btFailed are the words bluetoothctl uses for an act that did not happen, whatever its exit status.
var btFailed = regexp.MustCompile(`(?m)(Failed to \w+|not available|org\.bluez\.Error\.\w+|No default controller available)`)

// bt runs bluetoothctl once, non-interactively, as the account; bluez's bus policy lets the
// account act, and if it refuses, the act is run through sudo -n.
func bt(timeout time.Duration, args ...string) (string, error) {
	c := Cmd{Name: "bluetoothctl", Args: args, Timeout: timeout}
	r := run(c)
	if strings.Contains(r.Stdout+r.Stderr, "AccessDenied") || strings.Contains(r.Stdout+r.Stderr, "Not authorized") {
		c.Root = true
		r = run(c)
	}
	out := ansi.ReplaceAllString(r.Stdout+"\n"+r.Stderr, "")
	if r.Error != "" {
		return out, failure(c, r)
	}
	if strings.Contains(out, "No default controller available") {
		return out, fmt.Errorf("this machine has no Bluetooth controller bluez can use: none is present, it is blocked (rfkill), or bluetooth.service is not running")
	}
	if m := btFailed.FindString(out); m != "" || r.Status != 0 {
		said := strings.TrimSpace(out)
		if said == "" {
			said = fmt.Sprintf("exit status %d", r.Status)
		}
		return out, fmt.Errorf("bluetoothctl %s: %s", strings.Join(args, " "), tail(said, 1000))
	}
	return out, nil
}

// fields reads bluetoothctl's "\tKey: value" lines; a key seen twice keeps its first value.
func fields(s string) map[string]string {
	out := map[string]string{}
	for _, l := range strings.Split(s, "\n") {
		if !strings.HasPrefix(l, "\t") {
			continue
		}
		k, v, ok := strings.Cut(strings.TrimSpace(l), ":")
		if !ok {
			continue
		}
		if _, seen := out[k]; !seen {
			out[k] = strings.TrimSpace(v)
		}
	}
	return out
}

func yes(v string) bool { return v == "yes" }

// ControllerAnswer is what bluetooth_controller answers.
type ControllerAnswer struct {
	Address      string `json:"address"`
	Name         string `json:"name"`
	Alias        string `json:"alias"`
	Powered      bool   `json:"powered"`
	PowerState   string `json:"power_state,omitempty"`
	Discoverable bool   `json:"discoverable"`
	Pairable     bool   `json:"pairable"`
	Discovering  bool   `json:"discovering"`
}

// Controller answers the default controller.
func Controller() (ControllerAnswer, error) {
	out, err := bt(CallTimeout, "show")
	if err != nil {
		return ControllerAnswer{}, err
	}
	c := ControllerAnswer{}
	for _, l := range strings.Split(out, "\n") {
		if f := strings.Fields(l); len(f) >= 2 && f[0] == "Controller" {
			c.Address = f[1]
			break
		}
	}
	if c.Address == "" {
		return ControllerAnswer{}, fmt.Errorf("bluetoothctl show answered no controller: %s", tail(strings.TrimSpace(out), 500))
	}
	f := fields(out)
	c.Name, c.Alias, c.PowerState = f["Name"], f["Alias"], f["PowerState"]
	c.Powered, c.Discoverable, c.Pairable, c.Discovering = yes(f["Powered"]), yes(f["Discoverable"]), yes(f["Pairable"]), yes(f["Discovering"])
	return c, nil
}

// Power switches the controller on or off.
func Power(on bool) (map[string]any, error) {
	word := "off"
	if on {
		word = "on"
	}
	if _, err := bt(CallTimeout, "power", word); err != nil {
		return nil, err
	}
	c, err := Controller()
	if err != nil {
		return nil, err
	}
	return map[string]any{"powered": c.Powered, "asked": word}, nil
}

// Device is one device bluez knows.
type Device struct {
	Address   string `json:"address"`
	Name      string `json:"name"`
	Icon      string `json:"kind,omitempty"`
	Paired    bool   `json:"paired"`
	Bonded    bool   `json:"bonded"`
	Trusted   bool   `json:"trusted"`
	Blocked   bool   `json:"blocked"`
	Connected bool   `json:"connected"`
	Battery   *int   `json:"battery_percent,omitempty"`
	RSSI      *int   `json:"rssi,omitempty"`
}

var inParens = regexp.MustCompile(`\((-?[0-9]+)\)`)

// number reads "0x50 (80)" or "-62" as a number.
func number(v string) *int {
	if m := inParens.FindStringSubmatch(v); m != nil {
		v = m[1]
	}
	n, err := strconv.Atoi(strings.TrimSpace(v))
	if err != nil {
		return nil
	}
	return &n
}

// deviceInfo asks bluez for one device.
func deviceInfo(address string) (Device, error) {
	out, err := bt(CallTimeout, "info", address)
	if err != nil {
		return Device{}, err
	}
	f := fields(out)
	d := Device{Address: address, Name: f["Name"], Icon: f["Icon"], Paired: yes(f["Paired"]), Bonded: yes(f["Bonded"]),
		Trusted: yes(f["Trusted"]), Blocked: yes(f["Blocked"]), Connected: yes(f["Connected"])}
	if d.Name == "" {
		d.Name = f["Alias"]
	}
	if v, ok := f["Battery Percentage"]; ok {
		d.Battery = number(v)
	}
	if v, ok := f["RSSI"]; ok {
		d.RSSI = number(v)
	}
	return d, nil
}

// listed reads "Device <address> <name>" lines.
func listed(out string) []string {
	seen := map[string]bool{}
	addrs := []string{}
	for _, l := range strings.Split(out, "\n") {
		f := strings.Fields(strings.TrimSpace(l))
		if len(f) >= 2 && f[0] == "Device" && macAddress.MatchString(f[1]) && !seen[f[1]] {
			seen[f[1]] = true
			addrs = append(addrs, f[1])
		}
	}
	return addrs
}

// Devices answers the devices bluez knows, with each one's state.
func Devices(which string) (map[string]any, error) {
	if err := oneOf("which", which, "all", "paired", "connected", "trusted"); err != nil {
		return nil, err
	}
	args := []string{"devices"}
	if which != "all" {
		args = append(args, strings.ToUpper(which[:1])+which[1:])
	}
	out, err := bt(CallTimeout, args...)
	if err != nil {
		return nil, err
	}
	devices := []Device{}
	for _, a := range listed(out) {
		d, err := deviceInfo(a)
		if err != nil {
			return nil, err
		}
		devices = append(devices, d)
	}
	sort.SliceStable(devices, func(i, k int) bool {
		if devices[i].Connected != devices[k].Connected {
			return devices[i].Connected
		}
		return devices[i].Name < devices[k].Name
	})
	return map[string]any{"which": which, "count": len(devices), "devices": devices}, nil
}

// Scan discovers for a while and answers the devices found that are not paired.
func Scan(seconds int) (map[string]any, error) {
	// bluetoothctl's own --timeout ends the scan; the command's bound is a little longer.
	limit := time.Duration(seconds+4) * time.Second
	if _, err := bt(limit, "--timeout", strconv.Itoa(seconds), "scan", "on"); err != nil {
		return nil, err
	}
	out, err := bt(CallTimeout, "devices")
	if err != nil {
		return nil, err
	}
	found := []Device{}
	for _, a := range listed(out) {
		// A device seen a moment ago may have gone out of reach: it is skipped, not a failure.
		d, err := deviceInfo(a)
		if err != nil {
			continue
		}
		if !d.Paired {
			found = append(found, d)
		}
	}
	sort.SliceStable(found, func(i, k int) bool {
		ri, rk := -1000, -1000
		if found[i].RSSI != nil {
			ri = *found[i].RSSI
		}
		if found[k].RSSI != nil {
			rk = *found[k].RSSI
		}
		return ri > rk
	})
	return map[string]any{"seconds": seconds, "count": len(found), "found": found}, nil
}

// Act runs one act on a device and answers the device's state afterwards.
func Act(verb, address string) (map[string]any, error) {
	limit := CallTimeout
	if verb == "connect" {
		// A connect waits for the device; bluetoothctl's own timeout ends it first.
		if _, err := bt(limit, "--timeout", "15", verb, address); err != nil {
			return nil, err
		}
	} else if _, err := bt(limit, verb, address); err != nil {
		return nil, err
	}
	if verb == "remove" {
		return map[string]any{"act": verb, "address": address, "removed": true}, nil
	}
	d, err := deviceInfo(address)
	if err != nil {
		return nil, err
	}
	return map[string]any{"act": verb, "device": d}, nil
}

// Pair pairs a device with an agent that confirms nothing, then trusts it.
func Pair(address string) (map[string]any, error) {
	if _, err := bt(CallTimeout, "--agent", "NoInputNoOutput", "--timeout", "15", "pair", address); err != nil {
		return nil, err
	}
	return Act("trust", address)
}