// SPDX-License-Identifier: Unlicense OR MIT

package router

import (
	"gioui.org/io/event"
	"gioui.org/io/key"
)

type TextInputState uint8

type keyQueue struct {
	focus    event.Tag
	handlers map[event.Tag]*keyHandler
	state    TextInputState
	hint     key.InputHint
}

type keyHandler struct {
	// visible will be true if the InputOp is present
	// in the current frame.
	visible bool
	new     bool
	hint    key.InputHint
}

// keyCollector tracks state required to update a keyQueue
// from key ops.
type keyCollector struct {
	q       *keyQueue
	focus   event.Tag
	changed bool
}

const (
	TextInputKeep TextInputState = iota
	TextInputClose
	TextInputOpen
)

// InputState returns the last text input state as
// determined in Frame.
func (q *keyQueue) InputState() TextInputState {
	return q.state
}

// InputHint returns the input mode from the most recent key.InputOp.
func (q *keyQueue) InputHint() (key.InputHint, bool) {
	if q.focus == nil {
		return q.hint, false
	}
	focused, ok := q.handlers[q.focus]
	if !ok {
		return q.hint, false
	}
	old := q.hint
	q.hint = focused.hint
	return q.hint, old != q.hint
}

func (q *keyQueue) Reset() {
	if q.handlers == nil {
		q.handlers = make(map[event.Tag]*keyHandler)
	}
	for _, h := range q.handlers {
		h.visible, h.new = false, false
	}
	q.state = TextInputKeep
}

func (q *keyQueue) Frame(events *handlerEvents, collector keyCollector) {
	for k, h := range q.handlers {
		if !h.visible {
			delete(q.handlers, k)
			if q.focus == k {
				// Remove the focus from the handler that is no longer visible.
				q.focus = nil
				q.state = TextInputClose
			}
		} else if h.new && k != collector.focus {
			// Reset the handler on (each) first appearance, but don't trigger redraw.
			events.AddNoRedraw(k, key.FocusEvent{Focus: false})
		}
	}
	if collector.changed && collector.focus != nil {
		if _, exists := q.handlers[collector.focus]; !exists {
			collector.focus = nil
		}
	}
	if collector.changed && collector.focus != q.focus {
		if q.focus != nil {
			events.Add(q.focus, key.FocusEvent{Focus: false})
		}
		q.focus = collector.focus
		if q.focus != nil {
			events.Add(q.focus, key.FocusEvent{Focus: true})
		} else {
			q.state = TextInputClose
		}
	}
}

func (q *keyQueue) Push(e event.Event, events *handlerEvents) {
	if q.focus != nil {
		events.Add(q.focus, e)
	}
}

func (k *keyCollector) focusOp(tag event.Tag) {
	k.focus = tag
	k.changed = true
}

func (k *keyCollector) softKeyboard(show bool) {
	if show {
		k.q.state = TextInputOpen
	} else {
		k.q.state = TextInputClose
	}
}

func (k *keyCollector) inputOp(op key.InputOp) {
	h, ok := k.q.handlers[op.Tag]
	if !ok {
		h = &keyHandler{new: true}
		k.q.handlers[op.Tag] = h
	}
	h.visible = true
	h.hint = op.Hint
}

func (t TextInputState) String() string {
	switch t {
	case TextInputKeep:
		return "Keep"
	case TextInputClose:
		return "Close"
	case TextInputOpen:
		return "Open"
	default:
		panic("unexpected value")
	}
}