// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later

package input

import (
	"strings"
	"sync"
	"time"
)

// Intent records only the kind of input, never the text the user typed.
type Intent uint8

const (
	NoIntent Intent = iota
	TypingIntent
	LineIntent
	WordIntent
	CharacterIntent
	DeleteIntent
	OtherIntent
)

type Activity struct {
	Selecting bool
	Intent    Intent
	Sequence  uint64
	Clipboard ClipboardAction
}

type ClipboardAction uint8

const (
	NoClipboardAction ClipboardAction = iota
	CopyAction
	CutAction
	PasteAction
)

type IntentTracker struct {
	sequence  uint64
	mutex     sync.Mutex
	held      map[string]bool
	intent    Intent
	clipboard ClipboardAction
	selecting bool
	at        time.Time
}

func (tracker *IntentTracker) Observe(event Event) {
	tracker.mutex.Lock()
	defer tracker.mutex.Unlock()
	if event.Pressed {
		tracker.sequence++
	}
	if tracker.held == nil {
		tracker.held = make(map[string]bool)
	}
	if event.Kind == KeyModifier {
		tracker.held[event.Name] = event.Pressed
		if event.Pressed {
			tracker.intent, tracker.at = OtherIntent, time.Now()
			tracker.clipboard = NoClipboardAction
			tracker.selecting = false
		}
		return
	}
	if !event.Pressed {
		return
	}
	ctrl := tracker.held["Control_L"] || tracker.held["Control_R"]
	shift := tracker.held["Shift_L"] || tracker.held["Shift_R"]
	alt := tracker.held["Alt_L"] || tracker.held["Alt_R"] || tracker.held["Meta_L"] || tracker.held["Meta_R"]
	intent := OtherIntent
	tracker.clipboard = NoClipboardAction
	name := strings.TrimPrefix(event.Name, "KP_")
	if !alt {
		if ctrl && !shift {
			switch strings.ToLower(name) {
			case "c":
				tracker.clipboard = CopyAction
			case "x":
				tracker.clipboard = CutAction
			case "v":
				tracker.clipboard = PasteAction
			}
		}
		switch name {
		case "Up", "Down", "Page_Up", "Page_Down", "Prior", "Next":
			intent = LineIntent
		case "Left", "Right":
			intent = CharacterIntent
			if ctrl {
				intent = WordIntent
			}
		case "Home", "End":
			intent = CharacterIntent
			if ctrl {
				intent = LineIntent
			}
		case "Insert", "Caps_Lock", "Num_Lock", "Scroll_Lock", "Super_L", "Super_R":
			intent = OtherIntent
		case "BackSpace", "Delete":
			intent = DeleteIntent
		default:
			if !ctrl && (event.Name != "" && event.Kind == KeyUnknown) {
				intent = TypingIntent
			}
		}
	}
	tracker.selecting = shift && (intent == CharacterIntent || intent == WordIntent || intent == LineIntent)
	tracker.intent, tracker.at = intent, time.Now()
}

func (tracker *IntentTracker) RecentIntent() Intent { return tracker.RecentInput().Intent }

// Reset retires held modifiers and presentation intent across secure input.
func (tracker *IntentTracker) Reset() {
	tracker.mutex.Lock()
	defer tracker.mutex.Unlock()
	clear(tracker.held)
	tracker.intent, tracker.at = OtherIntent, time.Time{}
	tracker.clipboard, tracker.selecting = NoClipboardAction, false
}

func (tracker *IntentTracker) RecentInput() Activity {
	tracker.mutex.Lock()
	defer tracker.mutex.Unlock()
	if time.Since(tracker.at) > time.Second {
		return Activity{}
	}
	return Activity{Intent: tracker.intent, Sequence: tracker.sequence, Clipboard: tracker.clipboard, Selecting: tracker.selecting}
}