// Package hotkey converts between human-readable hotkey strings
// ("Ctrl+Alt+G") and the win32.Hotkey struct the registration syscall
// expects. The mapping is intentionally limited to the keys WinAuth
// users actually configured: letters, digits, F1-F12.
package hotkey

import (
	"errors"
	"fmt"
	"strings"

	"git.wxccs.org/iceking2nd/winauth-go/internal/win32"
)

// ErrEmpty is returned by Parse when the input is empty or whitespace.
// It is *not* a syntax error — callers typically treat it as "no
// hotkey configured" rather than a validation failure.
var ErrEmpty = errors.New("hotkey: empty")

// Parse turns "Ctrl+Alt+G" / "ctrl + shift + f5" into a win32.Hotkey.
// Whitespace and case are ignored. Modifier order is irrelevant.
func Parse(s string) (win32.Hotkey, error) {
	s = strings.TrimSpace(s)
	if s == "" {
		return win32.Hotkey{}, ErrEmpty
	}
	parts := strings.Split(s, "+")
	if len(parts) == 0 {
		return win32.Hotkey{}, fmt.Errorf("hotkey: malformed %q", s)
	}

	var mods uint32
	var key string
	for _, p := range parts {
		token := strings.ToLower(strings.TrimSpace(p))
		switch token {
		case "ctrl", "control":
			mods |= win32.ModCtrl
		case "alt":
			mods |= win32.ModAlt
		case "shift":
			mods |= win32.ModShift
		case "win", "super":
			mods |= win32.ModWin
		case "":
			// tolerate trailing "+"
		default:
			if key != "" {
				return win32.Hotkey{}, fmt.Errorf("hotkey: more than one base key in %q", s)
			}
			key = token
		}
	}
	if key == "" {
		return win32.Hotkey{}, fmt.Errorf("hotkey: no base key in %q", s)
	}
	if mods == 0 {
		return win32.Hotkey{}, fmt.Errorf("hotkey: %q has no modifier (would conflict with normal typing)", s)
	}
	vk, ok := vkFromName(key)
	if !ok {
		return win32.Hotkey{}, fmt.Errorf("hotkey: unsupported key %q", key)
	}
	return win32.Hotkey{Mods: mods | win32.ModNoRepeat, VK: vk}, nil
}

// Format canonicalises h back into a "Ctrl+Alt+G" style string. The
// modifier order is fixed (Ctrl, Alt, Shift, Win) so two equivalent
// hotkeys render identically.
func Format(h win32.Hotkey) string {
	if h.VK == 0 {
		return ""
	}
	parts := make([]string, 0, 4)
	if h.Mods&win32.ModCtrl != 0 {
		parts = append(parts, "Ctrl")
	}
	if h.Mods&win32.ModAlt != 0 {
		parts = append(parts, "Alt")
	}
	if h.Mods&win32.ModShift != 0 {
		parts = append(parts, "Shift")
	}
	if h.Mods&win32.ModWin != 0 {
		parts = append(parts, "Win")
	}
	parts = append(parts, nameFromVK(h.VK))
	return strings.Join(parts, "+")
}

// vkFromName maps the lowercase key name to a Win32 virtual-key code.
// Returns false for anything it doesn't know.
func vkFromName(name string) (uint32, bool) {
	if len(name) == 1 {
		c := name[0]
		switch {
		case c >= 'a' && c <= 'z':
			return uint32(c - 'a' + 'A'), true
		case c >= '0' && c <= '9':
			return uint32(c), true
		}
	}
	if strings.HasPrefix(name, "f") {
		// F1=0x70, F12=0x7B
		var n int
		if _, err := fmt.Sscanf(name, "f%d", &n); err == nil && n >= 1 && n <= 12 {
			return uint32(0x70 + n - 1), true
		}
	}
	switch name {
	case "space":
		return 0x20, true
	case "enter", "return":
		return 0x0D, true
	case "tab":
		return 0x09, true
	}
	return 0, false
}

// nameFromVK is the inverse of vkFromName for the cases Parse accepts.
// Unknown codes render as their hex value so the UI still shows
// something.
func nameFromVK(vk uint32) string {
	switch {
	case vk >= 'A' && vk <= 'Z':
		return string(rune(vk))
	case vk >= '0' && vk <= '9':
		return string(rune(vk))
	case vk >= 0x70 && vk <= 0x7B:
		return fmt.Sprintf("F%d", vk-0x70+1)
	}
	switch vk {
	case 0x20:
		return "Space"
	case 0x0D:
		return "Enter"
	case 0x09:
		return "Tab"
	}
	return fmt.Sprintf("0x%X", vk)
}